On 10/31/2014 4:52 PM, Ed Huntress wrote:
On Fri, 31 Oct 2014 15:56:52 -0500, Richard
wrote:

But that's boats.

This project was a lot more fun - and less sweat.
And there was even a little metal-working involved here!

This all came about because I wanted a ray gun.
A real honest to gosh ray gun!
I guess the Buck Rogers weapons were okay - for their day.
But the Bugs Bunny / Marvin the Martian type was the one.
And it really really works! (echoes of Ron Propeil!?!)

The basic design. Kinda spiffy, huh?
http://www.home.earthlink.net/~cave-.../Raygun-01.jpg


The shell is hand laid fiberglass over a foam core using 8 ounce woven
cloth and west 105 epoxy. Both were selected after a detailed study
of what was in the scrap box. Most of the glass was laid on in small
patches because of the curvature, but every lay-up was closed out with a
full sized wrap to help keep loose strings under control and give a
smoother surface. In all three separate lay-ups were done to get the
final shell. Using West 105 with 205 (fast) hardener the resin kicks
and can be handled in half an hour. So it didn't take long to make the
shell.

The core was dissolved out with a little lacquer thinner leaving a the
body hollow, but the insides sharp as 40 grit sandpaper.

The shell was then filed and sanded inside and out to a smooth surface
and finally gelcoated.

This first one has a 15 mw laser pointer installed - because it was
cheap and easy. And it's fun to use as a "kitty prod" to herd cats.


The basic shell with the laser retainer hardware installed.
http://www.home.earthlink.net/~cave-.../Raygun-02.jpg


Laser goes in right about here...
http://www.home.earthlink.net/~cave-.../Raygun-04.jpg

The metal-working part...

It took a few iterations to get the trigger shape right, but I'm happy
with the results. I haven't measured the pull, but it's not heavy.

The trigger was bandsawed from 1/4" aluminum plate and smoothed nicely.
http://www.home.earthlink.net/~cave-.../Raygun-06.jpg

The other part - call it the "loop"(?) - was blacksmithed from .063
steel strap by bending it around the correctly sized deep well socket
and pounding it into submission with a hammer.


The business end.
http://www.home.earthlink.net/~cave-.../Raygun-07.jpg


The pencil laser pointer is held in place with a sort piece of brass
tube bonded in the front end, and a larger diameter piece in the aft
end. The pencil fits over (ie outside) the front one and inside the
aft one. Then a small plastic cap (from a sting-ez insect-sting
stick - hey, it fit perfectly!!) holds the laser firmly in place.

Up and running:
http://www.home.earthlink.net/~cave-.../Raygun-08.jpg


The second one (in the works now) will open up in the middle to allow
for a 450 mw laser to be installed.

Same shape and style, but a seriously more dangerous weapon.


Fiberglass is fun stuff.
All it takes is some imagination.

http://www.instructables.com/id/Maki...erglass-parts/

Very cool, Richard! You should name it "Ronnie." g

I like it. Ronny it is!

Even if that crosses genre - from Bugs Bunny to star wars?
Oops - wrong star wars?

On Fri, 31 Oct 2014 08:45:50 -0400, Ed Huntress
wrote:

On Fri, 31 Oct 2014 08:38:44 +0700, John B. Slocomb
wrote:

On Thu, 30 Oct 2014 09:05:21 -0400, Ed Huntress
wrote:

On Thu, 30 Oct 2014 17:46:39 +0700, John B. Slocomb
wrote:

On Wed, 29 Oct 2014 10:10:39 -0400, Ed Huntress
wrote:

On Wed, 29 Oct 2014 18:46:24 +0700, John B. Slocomb
wrote:

On Wed, 29 Oct 2014 06:37:26 -0400, Ed Huntress
wrote:

snip

Anyway, your sarcasm was misplaced, as was Richard's. I don't know
what the hell he was talking about regarding boat paints. And when you
popped off about PFDs, it was clear that you don't sail where we sail.


I think Richard was probably referring to the fact that most, if not
all, small production fiberglass boats have the hull finished with gel
coat and a boat requiring paint would be one on which the gel coat had
deteriorated to a considerable degree.


Enjoy your sailing in S.E.A., John.

Cheers,

John B.

It's true that failing gel coats on lightly-built fiberglass boats may
reflect fatigue in the hull layup, but I don't see that as a reason to
make a blanket statement about it. Strongly-built boats, like a Boston
Whaler, Black Watch, Cape Dory or Stone Horse, will FAR outlast their
gel coats, and it has nothing to do with fatigue -- because those
boats generally don't fatigue.

In tropical countries it is quite common to see old fiberglass boats
with "chalky" finishes due to UV deterioration.

It's the same here on the mid-Atlantic coast.

While this may or may
not be a serious problem depends on the individual case but the
turning up of the nose at fiberglass boats that need paint is
certainly not a frivolous notion.

It depends. But it's not accurate to make a blanket statement about
it. Eventually, even well-built boats need a new coating of some kind.

Richard's "blanket statement" as I remember it was something like "I
wouldn't buy a boat that had to be painted" or something similar... It
seems like a perfectly legitimate statement.


There's an entire industry dedicated to re-covering those boats. It
satarted with a spray-on replacement gel coat around 1960; progressed
a few years later to sprayed-on two-part epoxy; and, finally,
developed into re-coating with two-part polyurethanes, a lot like the
paint used on high-class custom cars.

Ed, I think in this case you really don't have all the facts. I've got
a good friend in the business and certainly he will re gel-coat your
boat for you, but it costs far more money than a two part polyurethane
paint job

Spray-on polyester get coat is a lot cheaper than two-part
polyurethane -- somewhere around 1/3 the cost. There are quality yards
throughout the Northeast that will replace a gel coat with a new
sprayed-on polyester gel coat.

But then it's a matter of how good you want your finish to be.
As-spraryed, polyurethane is done. You can't rub it out without
ruining its durability, but, if it was done right, you don't have to.
(The one-part acrylic polyurethanes can be rubbed out, but that's a
different material.)

Gel coat, on the other hand, generally looks lousy, as-sprayed. It has
to be levelled and rubbed out. It can require a lot of labor, which
will raise the cost above the cost of a polyurethane finish.


Which, without going into details was pretty much what I said about my
mate "the fiberglass guy". Who is quite willing to do you a re-coating
with gel-coat. If you are willing to pay for it.

All that sanding, rubbing and polishing costs money. Even in a
developing country :-)

, which is not necessarily "similar to paint on high class
cars" as in many cases it is the same stuff. Dupont Imron comes to
mind.

Yeah, it often is the same stuff. Others are similar. I haven't seen a
car painted with Interlux, but then, I've never asked. d8-)


And polyester gel coats are porous; they can get stained, or marked up
badly because of the way they were tied up at a dock.

If "Polyester gel coats" are porous then so is the whole hull as
"gel-coat" is commonly just polyester resin with an added pigment.

It is porous; water enters through diffusion and by capillary action:

http://tinyurl.com/nmxdnlk

And the more styrene there is in the resin, the more porous it becomes
over time. Cheaper boats generally have more styrene in the resin.
Polyester resin is permeable, even without styrene. Epoxy is much less
so. Likewise, polyurethane.

It's not widely appreciated how much this degrades the interlaminar
strength of polyester-resin composites.

I think that statement applies more to people that buy boats rather
then the boating industry as a whole. Certainly blistering, Osmosis it
is usually called, a common fault with polyester boats, seems to be
pretty well known.

It's not just osmosis. It's also diffusion and outright capillary
absorption. The weight gain of a boat that sits in water for a year
can be significant, particularly if the boat is a few years old.

" Osmosis it is usually called" ???

With polyester resin, the capillary action is accelerated by the
breakdown of the resin-to-fiber bonds, which are substantial to begin
with and get worse over time. Polyester resin is a lousy adhesive and
it shrinks quite a bit during curing, which shears the bonds. Then
water makes it worse. You may have noted in that article that the
shear strength of a thin (as in most small boats) laminate typically
falls off by 35% after a year of sitting in water.


But! It is the cheapest resin around :-)

Gel coat is not much protection.

But better then plain old polyester.


Your reference (above) spells out the problem of polyester versus
epoxy - cost. I believe that the better quality boats now incorporate
a layer of vinyl ester (vinylester?) as a water proofing means. (Not
as effective as epoxy but much, much, cheaper :-)

There are more additives in polyester gel coat than just pigment, for
scratch resistance, UV protection, and so on.

That is not necessarily true. I've watched shops building 25 ft. power
boats here and seen how they mix the gel-coat. Just plain polyester
resin and a pigment.

I worked as a bonder at Ranger Yachts in the early '70s. We did not
mix our own gel coat.

But, as I wrote above, some shops do, and the ones I saw simply mixed
the pigment with the polyester and slathered it into the molds. In
fact the pigment is commonly available at shops selling fiberglass
supplies here and you can get it here in various colors.




Gunner is more likely talking about rolling on a coat of house paint
g, but I don't get why Richard was so dismissive about painting a
boat. There are a lot of boats around here right now that are dry
docked or up on stilts, having their topsides painted at the same time
they're getting a new coat of bottom paint, before the weather gets
too cold. Most of them are fiberglass boats.

I suspect that it is because properly painting a deteriorated
gel-coated hull is an expensive proposition as to do a good job you
first need to remove the old gel-coat down to a smooth solid surface
and removing gel-coat is a pain in the butt and pains in the butt tend
to be expensive. Additionally, I suspect, it may well be extra costly
in the U.S. due to your environmental laws. I read somewhere that a
U.S. yard had refused to allow removing old copper bottom paint as
they said it would get them in trouble with the environmental people.

We don't use much copper bottom paint anymore, largely for that
reason. Bottom paints now are usually *very* specific to the regional
waters one will sail in. I got away without bottom paint for a whole
year by sailing my little Cape Dory Typhoon up a freshwater creek once
a week. It killed everything growing on the bottom.

Yes, I know. I once bought a quart of real copper paint - powdered
copper and some sort of binder - local made paint and much cheaper
then the foreign made "bottom paint". I used it on a dinghy and even
there it wasn't really a very good anti-fouling paint.

I asked, sometime later, about "what is this stuff used for" and the
shop told me that most of their sales were to "fishing boats". Which
given their location probably meant the big Thai wooden fishing boats,
say 50 - 70 ft. and they are hauled every year and are under way
probably 75 - 80 percent of the time. Which does make a difference.

But you are correct, bottom paint is like the old English saying,
"Horses for courses". Practical Boat Owner, a British magazine, tried
to do a definitive test of bottom paints and made test panels that
were exposed in all the larger harbors in England (and I think
Scotland) and they determined that "there's no telling" as a paint
that worked well in one location failed in others. They couldn't even
get results that were general - "this paint works well in southern
harbors" - as there seemed to be no correlation between any specifics
that they could discover.

The local yards find out what works from local experience, and stick
with it. It's really amazing how much difference there is from one
location to another.
--
Cheers,

John B.

On Fri, 31 Oct 2014 09:55:37 -0500, Richard
wrote:

On 10/30/2014 8:38 PM, John B. Slocomb wrote:

Richard's "blanket statement" as I remember it was something like "I
wouldn't buy a boat that had to be painted" or something similar... It
seems like a perfectly legitimate statement.

snippage

Thanks, Capt'n.

I think he may have been a bit more adamant about it. Maybe to the point
of a Never Ever! but yeah, that was about the gist of it.


Which, without going into details was pretty much what I said about my
mate "the fiberglass guy". Who is quite willing to do you a re-coating
with gel-coat. If you are willing to pay for it.

All that sanding, rubbing and polishing costs money. Even in a
developing country :-)


It all depends on your personal standards, of course.

Some people think a chalky boat is the epitome of success - because
it takes no effort to maintain. And they are perfectly right -
for them.

Way back in the days of wooden boats I read an article in one of the
U.S. magazines extolling topside paints that chalked easily. The
writer said that they really hade the boot look good, longer, as when
you scrubbed the topsides mid season the chalkiness scrubbed off
taking the dirt and crud with it.

The Maine lobster fishermen usually hauled once during the season and
one chap came up with an ingenious scheme. They, of course, beached
the boats, propped up with sticks and this guy, as soon as the tide
started going out and the sticks started taking some weight started
spraying the hull with Clorox from one of those back mounted spray
tanks. Just walked round and round spraying. When the tide was pretty
well all the way out he'd scrub the hull with a "straw Broom" and all
the weeds and shell fish would fall off. He clamed that as he didn't
have to scrape, the bottom paint wasn't damaged so he didn't have top
re-paint half way through the season :-)

I take a different tack - (or maybe "they" do?) but I adore a nice
shiny hull.

I picked up my technique from a fellow who goes by the handle
Maine Sail. He has written an awful lot about repairing and
maintaining boats, and I have joined the choir there.

The best collection is he
http://forums.hunter.sailboatowners....play.php?f=135


I bought the Ryoby variable speed buffer he recommended - and learned
to use it. I's amazing what you can bring back from the dead that way.
(For various values of dead, of course!)

I started gelcoat craziness with our Capri 18, "Spirit". The surfaces
needed wet sanding first, then polishing. That took a week in all.
Sanding, buffing and waxing. But the finish lasted for years
afterwards, with only an occasional wash and wax.

"Temptress", our Capri 26, was the national fleet flagship for several
years. I didn't need much more incentive to go overboard on her.

But that's a lot more boat. I hired out the buffing part.
Happily!

Here is a link to Maine Sail's article about bringing gelcoat back to
life: http://forums.hunter.sailboatowners....d.php?t=117266

Another phobia picked up from the same source is silicone.
It's perhaps the most misused substance on the planet - or maybe
runs a close second to 3M 4200.

My deck hardware is bedded with high quality Butyl rubber tape.
Now, note: I said High-Quality and Tape (not cheap putty mashed out to
look like tape). The putty-tape is commonly used in RV construction
where it often contributes to hard-to-find leaks. It has no place on a
boat.

I've used Bed-It butyl tape on several boats and guarantee the results.
http://forums.hunter.sailboatowners....d.php?t=117172

And help for cored deck and hull penetrations:
How to keep water out of a balsa or plywood deck core.
http://www.pbase.com/mainecruising/sealing_the_deck

The forty footer I owned, for some reason, had additional jib tracks
added inboard of the original tracks on the gunnels. Apparently done
by the previous owner who simply drilled holes through the deck and
bolted them down. Needless to say, the holes leaked and the plywood
core rutted in two six foot strips down the side decks, toward the
forward end of the cockpit. I finally used a 4" hand grinder and
sliced the fiberglass deck surface and removed two six foot long by
about 18 inch wide sections. The plywood had turned into a black mush.
I cleaned it out back to solid ply thinking that I could simply get
some more plywood of the same thickness to "inlay". It turned out that
the original plywood was some strange dimension that couldn't be
duplicated and I ended up with a horrible job of gluing down a layer
of ply, then building it up with epoxy filler and gluing the original
deck sections back on top. A horrible mess trying to get the whole job
smooth and fair with the old deck.

A lot of work?
Maybe.

But a job that doesn't have to be reworked all the time is worth the
extra expense and effort.
At least that's how I feel.

It all depends on your personal standards...
--
Cheers,

John B.

On Fri, 31 Oct 2014 15:56:52 -0500, Richard
wrote:

But that's boats.

This project was a lot more fun - and less sweat.
And there was even a little metal-working involved here!

This all came about because I wanted a ray gun.
A real honest to gosh ray gun!
I guess the Buck Rogers weapons were okay - for their day.
But the Bugs Bunny / Marvin the Martian type was the one.
And it really really works! (echoes of Ron Propeil!?!)

The basic design. Kinda spiffy, huh?
http://www.home.earthlink.net/~cave-.../Raygun-01.jpg


The shell is hand laid fiberglass over a foam core using 8 ounce woven
cloth and west 105 epoxy. Both were selected after a detailed study
of what was in the scrap box. Most of the glass was laid on in small
patches because of the curvature, but every lay-up was closed out with a
full sized wrap to help keep loose strings under control and give a
smoother surface. In all three separate lay-ups were done to get the
final shell. Using West 105 with 205 (fast) hardener the resin kicks
and can be handled in half an hour. So it didn't take long to make the
shell.

The core was dissolved out with a little lacquer thinner leaving a the
body hollow, but the insides sharp as 40 grit sandpaper.

The shell was then filed and sanded inside and out to a smooth surface
and finally gelcoated.

This first one has a 15 mw laser pointer installed - because it was
cheap and easy. And it's fun to use as a "kitty prod" to herd cats.


Never mind all that fiberglass stuff. If you can actually "herd cats"
you can probably manage a small tribe of wives too :-)

--
Cheers,

John B.

On Sat, 01 Nov 2014 07:41:12 +0700, John B. Slocomb
wrote:

On Fri, 31 Oct 2014 08:45:50 -0400, Ed Huntress
wrote:

On Fri, 31 Oct 2014 08:38:44 +0700, John B. Slocomb
wrote:

On Thu, 30 Oct 2014 09:05:21 -0400, Ed Huntress
wrote:

On Thu, 30 Oct 2014 17:46:39 +0700, John B. Slocomb
wrote:

On Wed, 29 Oct 2014 10:10:39 -0400, Ed Huntress
wrote:

On Wed, 29 Oct 2014 18:46:24 +0700, John B. Slocomb
wrote:

On Wed, 29 Oct 2014 06:37:26 -0400, Ed Huntress
wrote:

snip

Anyway, your sarcasm was misplaced, as was Richard's. I don't know
what the hell he was talking about regarding boat paints. And when you
popped off about PFDs, it was clear that you don't sail where we sail.


I think Richard was probably referring to the fact that most, if not
all, small production fiberglass boats have the hull finished with gel
coat and a boat requiring paint would be one on which the gel coat had
deteriorated to a considerable degree.


Enjoy your sailing in S.E.A., John.

Cheers,

John B.

It's true that failing gel coats on lightly-built fiberglass boats may
reflect fatigue in the hull layup, but I don't see that as a reason to
make a blanket statement about it. Strongly-built boats, like a Boston
Whaler, Black Watch, Cape Dory or Stone Horse, will FAR outlast their
gel coats, and it has nothing to do with fatigue -- because those
boats generally don't fatigue.

In tropical countries it is quite common to see old fiberglass boats
with "chalky" finishes due to UV deterioration.

It's the same here on the mid-Atlantic coast.

While this may or may
not be a serious problem depends on the individual case but the
turning up of the nose at fiberglass boats that need paint is
certainly not a frivolous notion.

It depends. But it's not accurate to make a blanket statement about
it. Eventually, even well-built boats need a new coating of some kind.

Richard's "blanket statement" as I remember it was something like "I
wouldn't buy a boat that had to be painted" or something similar... It
seems like a perfectly legitimate statement.


There's an entire industry dedicated to re-covering those boats. It
satarted with a spray-on replacement gel coat around 1960; progressed
a few years later to sprayed-on two-part epoxy; and, finally,
developed into re-coating with two-part polyurethanes, a lot like the
paint used on high-class custom cars.

Ed, I think in this case you really don't have all the facts. I've got
a good friend in the business and certainly he will re gel-coat your
boat for you, but it costs far more money than a two part polyurethane
paint job

Spray-on polyester get coat is a lot cheaper than two-part
polyurethane -- somewhere around 1/3 the cost. There are quality yards
throughout the Northeast that will replace a gel coat with a new
sprayed-on polyester gel coat.

But then it's a matter of how good you want your finish to be.
As-spraryed, polyurethane is done. You can't rub it out without
ruining its durability, but, if it was done right, you don't have to.
(The one-part acrylic polyurethanes can be rubbed out, but that's a
different material.)

Gel coat, on the other hand, generally looks lousy, as-sprayed. It has
to be levelled and rubbed out. It can require a lot of labor, which
will raise the cost above the cost of a polyurethane finish.


Which, without going into details was pretty much what I said about my
mate "the fiberglass guy". Who is quite willing to do you a re-coating
with gel-coat. If you are willing to pay for it.

All that sanding, rubbing and polishing costs money. Even in a
developing country :-)

, which is not necessarily "similar to paint on high class
cars" as in many cases it is the same stuff. Dupont Imron comes to
mind.

Yeah, it often is the same stuff. Others are similar. I haven't seen a
car painted with Interlux, but then, I've never asked. d8-)


And polyester gel coats are porous; they can get stained, or marked up
badly because of the way they were tied up at a dock.

If "Polyester gel coats" are porous then so is the whole hull as
"gel-coat" is commonly just polyester resin with an added pigment.

It is porous; water enters through diffusion and by capillary action:

http://tinyurl.com/nmxdnlk

And the more styrene there is in the resin, the more porous it becomes
over time. Cheaper boats generally have more styrene in the resin.
Polyester resin is permeable, even without styrene. Epoxy is much less
so. Likewise, polyurethane.

It's not widely appreciated how much this degrades the interlaminar
strength of polyester-resin composites.

I think that statement applies more to people that buy boats rather
then the boating industry as a whole. Certainly blistering, Osmosis it
is usually called, a common fault with polyester boats, seems to be
pretty well known.

It's not just osmosis. It's also diffusion and outright capillary
absorption. The weight gain of a boat that sits in water for a year
can be significant, particularly if the boat is a few years old.

" Osmosis it is usually called" ???

With polyester resin, the capillary action is accelerated by the
breakdown of the resin-to-fiber bonds, which are substantial to begin
with and get worse over time. Polyester resin is a lousy adhesive and
it shrinks quite a bit during curing, which shears the bonds. Then
water makes it worse. You may have noted in that article that the
shear strength of a thin (as in most small boats) laminate typically
falls off by 35% after a year of sitting in water.


But! It is the cheapest resin around :-)

Gel coat is not much protection.

But better then plain old polyester.


Your reference (above) spells out the problem of polyester versus
epoxy - cost. I believe that the better quality boats now incorporate
a layer of vinyl ester (vinylester?) as a water proofing means. (Not
as effective as epoxy but much, much, cheaper :-)

There are more additives in polyester gel coat than just pigment, for
scratch resistance, UV protection, and so on.

That is not necessarily true. I've watched shops building 25 ft. power
boats here and seen how they mix the gel-coat. Just plain polyester
resin and a pigment.

I worked as a bonder at Ranger Yachts in the early '70s. We did not
mix our own gel coat.

But, as I wrote above, some shops do, and the ones I saw simply mixed
the pigment with the polyester and slathered it into the molds. In
fact the pigment is commonly available at shops selling fiberglass
supplies here and you can get it here in various colors.

Well, commercial gel coat is made with a water-clear base, like
casting resin, rather than the purplish or brownish tint that's
common to laminating resin, and it contains plasticizers to reduce
brittleness. If it's to be used in a mold, to build a boat, it doesn't
contain the wax that's in ordinary laminating resin, and it gets a
better bond to the first layup as a result. Of course, it it's a
repair job, and sprayed on the outside, it needs the wax or it won't
cure on the surface. At Ranger, as with most molders, gel coat would
sometimes peel off of the hull, onto the mold, in small chunks, when
the hull was pulled from the mold. Then a specialist would fill the
spot and repair if after the hull had fully cured. They'd use the
regular gel coat for that, with some wax mixed in. It looked like a
colloidal slush and it only took an ounce or so of it per quart of
resin to do the job.

The pigments were used in Ranger boats, and many others, to mix with
the laminating resin used for the initial layer of the layup, as a
color backup for the gel coat. Our gel coats came pre-colored to the
company's color standards.





Gunner is more likely talking about rolling on a coat of house paint
g, but I don't get why Richard was so dismissive about painting a
boat. There are a lot of boats around here right now that are dry
docked or up on stilts, having their topsides painted at the same time
they're getting a new coat of bottom paint, before the weather gets
too cold. Most of them are fiberglass boats.

I suspect that it is because properly painting a deteriorated
gel-coated hull is an expensive proposition as to do a good job you
first need to remove the old gel-coat down to a smooth solid surface
and removing gel-coat is a pain in the butt and pains in the butt tend
to be expensive. Additionally, I suspect, it may well be extra costly
in the U.S. due to your environmental laws. I read somewhere that a
U.S. yard had refused to allow removing old copper bottom paint as
they said it would get them in trouble with the environmental people.

We don't use much copper bottom paint anymore, largely for that
reason. Bottom paints now are usually *very* specific to the regional
waters one will sail in. I got away without bottom paint for a whole
year by sailing my little Cape Dory Typhoon up a freshwater creek once
a week. It killed everything growing on the bottom.

Yes, I know. I once bought a quart of real copper paint - powdered
copper and some sort of binder - local made paint and much cheaper
then the foreign made "bottom paint". I used it on a dinghy and even
there it wasn't really a very good anti-fouling paint.

I asked, sometime later, about "what is this stuff used for" and the
shop told me that most of their sales were to "fishing boats". Which
given their location probably meant the big Thai wooden fishing boats,
say 50 - 70 ft. and they are hauled every year and are under way
probably 75 - 80 percent of the time. Which does make a difference.

But you are correct, bottom paint is like the old English saying,
"Horses for courses". Practical Boat Owner, a British magazine, tried
to do a definitive test of bottom paints and made test panels that
were exposed in all the larger harbors in England (and I think
Scotland) and they determined that "there's no telling" as a paint
that worked well in one location failed in others. They couldn't even
get results that were general - "this paint works well in southern
harbors" - as there seemed to be no correlation between any specifics
that they could discover.

The local yards find out what works from local experience, and stick
with it. It's really amazing how much difference there is from one
location to another.

On 10/31/2014 8:13 PM, John B. Slocomb wrote:
On Fri, 31 Oct 2014 15:56:52 -0500, Richard
wrote:

But that's boats.

This project was a lot more fun - and less sweat.
And there was even a little metal-working involved here!

This all came about because I wanted a ray gun.
A real honest to gosh ray gun!
I guess the Buck Rogers weapons were okay - for their day.
But the Bugs Bunny / Marvin the Martian type was the one.
And it really really works! (echoes of Ron Propeil!?!)

The basic design. Kinda spiffy, huh?
http://www.home.earthlink.net/~cave-.../Raygun-01.jpg


The shell is hand laid fiberglass over a foam core using 8 ounce woven
cloth and west 105 epoxy. Both were selected after a detailed study
of what was in the scrap box. Most of the glass was laid on in small
patches because of the curvature, but every lay-up was closed out with a
full sized wrap to help keep loose strings under control and give a
smoother surface. In all three separate lay-ups were done to get the
final shell. Using West 105 with 205 (fast) hardener the resin kicks
and can be handled in half an hour. So it didn't take long to make the
shell.

The core was dissolved out with a little lacquer thinner leaving a the
body hollow, but the insides sharp as 40 grit sandpaper.

The shell was then filed and sanded inside and out to a smooth surface
and finally gelcoated.

This first one has a 15 mw laser pointer installed - because it was
cheap and easy. And it's fun to use as a "kitty prod" to herd cats.


Never mind all that fiberglass stuff. If you can actually "herd cats"
you can probably manage a small tribe of wives too :-)


Cats are easy.

Women are women.

On 10/31/2014 8:08 PM, John B. Slocomb wrote:

This message has been snipped some - just to show that the technology
still works!

Some people think a chalky boat is the epitome of success - because
it takes no effort to maintain. And they are perfectly right -
for them.

Way back in the days of wooden boats I read an article in one of the
U.S. magazines extolling topside paints that chalked easily. The
writer said that they really hade the boot look good, longer, as when
you scrubbed the topsides mid season the chalkiness scrubbed off
taking the dirt and crud with it.

The Maine lobster fishermen usually hauled once during the season and
one chap came up with an ingenious scheme. They, of course, beached
the boats, propped up with sticks and this guy, as soon as the tide
started going out and the sticks started taking some weight started
spraying the hull with Clorox from one of those back mounted spray
tanks. Just walked round and round spraying. When the tide was pretty
well all the way out he'd scrub the hull with a "straw Broom" and all
the weeds and shell fish would fall off. He clamed that as he didn't
have to scrape, the bottom paint wasn't damaged so he didn't have top
re-paint half way through the season :-)


Now that's a sailor!

Want to know the easiest way to do something?
Put a smart lazy man on the job.

The forty footer I owned, for some reason, had additional jib tracks
added inboard of the original tracks on the gunnels. Apparently done
by the previous owner who simply drilled holes through the deck and
bolted them down. Needless to say, the holes leaked and the plywood
core rutted in two six foot strips down the side decks, toward the
forward end of the cockpit. I finally used a 4" hand grinder and
sliced the fiberglass deck surface and removed two six foot long by
about 18 inch wide sections. The plywood had turned into a black mush.
I cleaned it out back to solid ply thinking that I could simply get
some more plywood of the same thickness to "inlay". It turned out that
the original plywood was some strange dimension that couldn't be
duplicated and I ended up with a horrible job of gluing down a layer
of ply, then building it up with epoxy filler and gluing the original
deck sections back on top. A horrible mess trying to get the whole job
smooth and fair with the old deck.


Oh man. I feel your pain.


A friend is involved with the Sea Scouts and sometimes get boats
donated. One Catalina ancient 27 came in and the entire foredeck was
spongy. He asked what it would cost to have it fixed.
Well, traditional methods - more than the boat was worth - for sure.

We tried something different.
You know how that polyurethane Gorilla Glue foams up from moisture?
We drilled some holes in the under side of the deck, poked plastic
tubing down the length of the deck and squirted in 6 bottles of glue -
one at a time. Squirt a bunch of glue and pull the hose out.
Let it expand for a day or two(!). Then run another tube in as far
as it will go and squirt in more glue.

Didn't plug the holes or anything, just to let it relieve pressure.
Put buckets under the drains and let it cook.

A couple of weeks later the deck was solid as a rock again.
The under side looked like hell.

He didn't want to do anything but trim the foam off flush with a knife.
He didn't want to mislead a buyer as to the condition of the boat.

It sold soon after. Not much, but income for the Scouts.
It's still sailing.


A lot of work?
Maybe.

But a job that doesn't have to be reworked all the time is worth the
extra expense and effort.
At least that's how I feel.

It all depends on your personal standards...

On Sat, 01 Nov 2014 08:08:45 +0700, John B. Slocomb
wrote:

On Fri, 31 Oct 2014 09:55:37 -0500, Richard
wrote:

On 10/30/2014 8:38 PM, John B. Slocomb wrote:

Richard's "blanket statement" as I remember it was something like "I
wouldn't buy a boat that had to be painted" or something similar... It
seems like a perfectly legitimate statement.

snippage

Thanks, Capt'n.

I think he may have been a bit more adamant about it. Maybe to the point
of a Never Ever! but yeah, that was about the gist of it.


Which, without going into details was pretty much what I said about my
mate "the fiberglass guy". Who is quite willing to do you a re-coating
with gel-coat. If you are willing to pay for it.

All that sanding, rubbing and polishing costs money. Even in a
developing country :-)


It all depends on your personal standards, of course.

Some people think a chalky boat is the epitome of success - because
it takes no effort to maintain. And they are perfectly right -
for them.

Way back in the days of wooden boats I read an article in one of the
U.S. magazines extolling topside paints that chalked easily. The
writer said that they really hade the boot look good, longer, as when
you scrubbed the topsides mid season the chalkiness scrubbed off
taking the dirt and crud with it.

Here's one that went for really chalky paint:

http://tinyurl.com/kh59byr

Marty Haines hauled the Sea Pigeon every year, scraped and sanded her
for about a month, and then painted her with regular topsides paint.
He grew tired of that after 20 years and heard that house paint might
be a solution. So in 1981 he did the usual scraping and sanding, and
then painted her with regular latex house paint.

She looked great; chalked off dirt all the next season; and, when he
hauled her the next fall, all he had to do was sand her with an
orbital sander and re-paint. There was no chipping or peeling, and the
wood was in fine shape underneath.

Sea Pigeon was carvel-planked with traditional cotton caulked seams,
but with modern Thiokol caulking compound.

Marty sold her five years later, so I never learned how long it
worked. But it was a revelation to a lot of old-time owners of wooden
working boats in this area.

--
Ed Huntress

On 10/31/2014 10:45 PM, Ed Huntress wrote:
On Sat, 01 Nov 2014 08:08:45 +0700, John B. Slocomb
wrote:

On Fri, 31 Oct 2014 09:55:37 -0500, Richard
wrote:

On 10/30/2014 8:38 PM, John B. Slocomb wrote:

Richard's "blanket statement" as I remember it was something like "I
wouldn't buy a boat that had to be painted" or something similar... It
seems like a perfectly legitimate statement.

snippage

Thanks, Capt'n.

I think he may have been a bit more adamant about it. Maybe to the point
of a Never Ever! but yeah, that was about the gist of it.


Which, without going into details was pretty much what I said about my
mate "the fiberglass guy". Who is quite willing to do you a re-coating
with gel-coat. If you are willing to pay for it.

All that sanding, rubbing and polishing costs money. Even in a
developing country :-)


It all depends on your personal standards, of course.

Some people think a chalky boat is the epitome of success - because
it takes no effort to maintain. And they are perfectly right -
for them.

Way back in the days of wooden boats I read an article in one of the
U.S. magazines extolling topside paints that chalked easily. The
writer said that they really hade the boot look good, longer, as when
you scrubbed the topsides mid season the chalkiness scrubbed off
taking the dirt and crud with it.

Here's one that went for really chalky paint:

http://tinyurl.com/kh59byr

Marty Haines hauled the Sea Pigeon every year, scraped and sanded her
for about a month, and then painted her with regular topsides paint.
He grew tired of that after 20 years and heard that house paint might
be a solution. So in 1981 he did the usual scraping and sanding, and
then painted her with regular latex house paint.

She looked great; chalked off dirt all the next season; and, when he
hauled her the next fall, all he had to do was sand her with an
orbital sander and re-paint. There was no chipping or peeling, and the
wood was in fine shape underneath.

Sea Pigeon was carvel-planked with traditional cotton caulked seams,
but with modern Thiokol caulking compound.

Marty sold her five years later, so I never learned how long it
worked. But it was a revelation to a lot of old-time owners of wooden
working boats in this area.


I was going to say that oakum was "traditional" and cotton would caul.

But then you said Thiokol.
You just KNOW that's gonna leak on a cold day!

On Fri, 31 Oct 2014 23:11:49 -0500, Richard
wrote:

On 10/31/2014 10:45 PM, Ed Huntress wrote:
On Sat, 01 Nov 2014 08:08:45 +0700, John B. Slocomb
wrote:

On Fri, 31 Oct 2014 09:55:37 -0500, Richard
wrote:

On 10/30/2014 8:38 PM, John B. Slocomb wrote:

Richard's "blanket statement" as I remember it was something like "I
wouldn't buy a boat that had to be painted" or something similar... It
seems like a perfectly legitimate statement.

snippage

Thanks, Capt'n.

I think he may have been a bit more adamant about it. Maybe to the point
of a Never Ever! but yeah, that was about the gist of it.


Which, without going into details was pretty much what I said about my
mate "the fiberglass guy". Who is quite willing to do you a re-coating
with gel-coat. If you are willing to pay for it.

All that sanding, rubbing and polishing costs money. Even in a
developing country :-)


It all depends on your personal standards, of course.

Some people think a chalky boat is the epitome of success - because
it takes no effort to maintain. And they are perfectly right -
for them.

Way back in the days of wooden boats I read an article in one of the
U.S. magazines extolling topside paints that chalked easily. The
writer said that they really hade the boot look good, longer, as when
you scrubbed the topsides mid season the chalkiness scrubbed off
taking the dirt and crud with it.

Here's one that went for really chalky paint:

http://tinyurl.com/kh59byr

Marty Haines hauled the Sea Pigeon every year, scraped and sanded her
for about a month, and then painted her with regular topsides paint.
He grew tired of that after 20 years and heard that house paint might
be a solution. So in 1981 he did the usual scraping and sanding, and
then painted her with regular latex house paint.

She looked great; chalked off dirt all the next season; and, when he
hauled her the next fall, all he had to do was sand her with an
orbital sander and re-paint. There was no chipping or peeling, and the
wood was in fine shape underneath.

Sea Pigeon was carvel-planked with traditional cotton caulked seams,
but with modern Thiokol caulking compound.

Marty sold her five years later, so I never learned how long it
worked. But it was a revelation to a lot of old-time owners of wooden
working boats in this area.


I was going to say that oakum was "traditional" and cotton would caul.

But then you said Thiokol.
You just KNOW that's gonna leak on a cold day!

G I caulked my uncle's 42-footer for eight years -- every year after
he turned 70 and couldn't do it himself -- and we used cotton, too.
Actually, with Thiokol, the caulk would last for two or even three
years, and only needed touch-up on an annual basis. I only re-caulked
the whole boat once.

There is some oakum used around here but a tightly-seamed boat
typically is caulked with cotton. My uncle's boat was planked with
African "mahogony," one of the non-mahoganies that have been used
since around 1970, that look good and that have low rates of shrinkage
and expansion.

I would not use cotton and Thiokol on a booster rocket. Maybe they
should have used oakum, white lead, and linseed oil...

--
Ed Huntress

On Wed, 29 Oct 2014 12:53:34 -0500, Richard
wrote:

On 10/29/2014 9:10 AM, Ed Huntress wrote:
On Wed, 29 Oct 2014 18:46:24 +0700, John B. Slocomb
wrote:

On Wed, 29 Oct 2014 06:37:26 -0400, Ed Huntress
wrote:

snip

Anyway, your sarcasm was misplaced, as was Richard's. I don't know
what the hell he was talking about regarding boat paints. And when you
popped off about PFDs, it was clear that you don't sail where we sail.


I think Richard was probably referring to the fact that most, if not
all, small production fiberglass boats have the hull finished with gel
coat and a boat requiring paint would be one on which the gel coat had
deteriorated to a considerable degree.


Enjoy your sailing in S.E.A., John.

Cheers,

John B.

It's true that failing gel coats on lightly-built fiberglass boats may
reflect fatigue in the hull layup, but I don't see that as a reason to
make a blanket statement about it. Strongly-built boats, like a Boston
Whaler, Black Watch, Cape Dory or Stone Horse, will FAR outlast their
gel coats, and it has nothing to do with fatigue -- because those
boats generally don't fatigue.

There's an entire industry dedicated to re-covering those boats. It
satarted with a spray-on replacement gel coat around 1960; progressed
a few years later to sprayed-on two-part epoxy; and, finally,
developed into re-coating with two-part polyurethanes, a lot like the
paint used on high-class custom cars.

And polyester gel coats are porous; they can get stained, or marked up
badly because of the way they were tied up at a dock.

Gunner is more likely talking about rolling on a coat of house paint
g, but I don't get why Richard was so dismissive about painting a
boat. There are a lot of boats around here right now that are dry
docked or up on stilts, having their topsides painted at the same time
they're getting a new coat of bottom paint, before the weather gets
too cold. Most of them are fiberglass boats.


Because once you paint a hull - even with the very best paints - the
maintenance truly begins.

But that's not the real problem here.

The REAL problem is that Gunner is a stalking troll.

Really? Stalking Troll you say?

So posting boat ads is..stalking?

Is that like putting out bait during turkey season?

Then you are saying you are as stupid as a turkey?

Take the bait..take the bait..take the bait!!

Snicker....


"At the core of liberalism is the spoiled child,
miserable, as all spoiled children are, unsatisfied,
demanding, ill-disciplined, despotic and useless.
Liberalism is a philosophy of sniveling brats."
PJ O'Rourke

On Fri, 31 Oct 2014 15:56:52 -0500, Richard
wrote:

But that's boats.

This project was a lot more fun - and less sweat.
And there was even a little metal-working involved here!

This all came about because I wanted a ray gun.
A real honest to gosh ray gun!
I guess the Buck Rogers weapons were okay - for their day.
But the Bugs Bunny / Marvin the Martian type was the one.
And it really really works! (echoes of Ron Propeil!?!)

The basic design. Kinda spiffy, huh?
http://www.home.earthlink.net/~cave-.../Raygun-01.jpg


The shell is hand laid fiberglass over a foam core using 8 ounce woven
cloth and west 105 epoxy. Both were selected after a detailed study
of what was in the scrap box. Most of the glass was laid on in small
patches because of the curvature, but every lay-up was closed out with a
full sized wrap to help keep loose strings under control and give a
smoother surface. In all three separate lay-ups were done to get the
final shell. Using West 105 with 205 (fast) hardener the resin kicks
and can be handled in half an hour. So it didn't take long to make the
shell.

The core was dissolved out with a little lacquer thinner leaving a the
body hollow, but the insides sharp as 40 grit sandpaper.

The shell was then filed and sanded inside and out to a smooth surface
and finally gelcoated.

This first one has a 15 mw laser pointer installed - because it was
cheap and easy. And it's fun to use as a "kitty prod" to herd cats.


The basic shell with the laser retainer hardware installed.
http://www.home.earthlink.net/~cave-.../Raygun-02.jpg


Laser goes in right about here...
http://www.home.earthlink.net/~cave-.../Raygun-04.jpg

The metal-working part...

It took a few iterations to get the trigger shape right, but I'm happy
with the results. I haven't measured the pull, but it's not heavy.

The trigger was bandsawed from 1/4" aluminum plate and smoothed nicely.
http://www.home.earthlink.net/~cave-.../Raygun-06.jpg

The other part - call it the "loop"(?) - was blacksmithed from .063
steel strap by bending it around the correctly sized deep well socket
and pounding it into submission with a hammer.


The business end.
http://www.home.earthlink.net/~cave-.../Raygun-07.jpg


The pencil laser pointer is held in place with a sort piece of brass
tube bonded in the front end, and a larger diameter piece in the aft
end. The pencil fits over (ie outside) the front one and inside the
aft one. Then a small plastic cap (from a sting-ez insect-sting
stick - hey, it fit perfectly!!) holds the laser firmly in place.

Up and running:
http://www.home.earthlink.net/~cave-.../Raygun-08.jpg


The second one (in the works now) will open up in the middle to allow
for a 450 mw laser to be installed.

Same shape and style, but a seriously more dangerous weapon.


Fiberglass is fun stuff.
All it takes is some imagination.

http://www.instructables.com/id/Maki...erglass-parts/

Nicely done!!

Gunner

"At the core of liberalism is the spoiled child,
miserable, as all spoiled children are, unsatisfied,
demanding, ill-disciplined, despotic and useless.
Liberalism is a philosophy of sniveling brats."
PJ O'Rourke

On Fri, 31 Oct 2014 21:15:44 -0500, Richard
wrote:

On 10/31/2014 8:08 PM, John B. Slocomb wrote:

This message has been snipped some - just to show that the technology
still works!

Some people think a chalky boat is the epitome of success - because
it takes no effort to maintain. And they are perfectly right -
for them.

Way back in the days of wooden boats I read an article in one of the
U.S. magazines extolling topside paints that chalked easily. The
writer said that they really hade the boot look good, longer, as when
you scrubbed the topsides mid season the chalkiness scrubbed off
taking the dirt and crud with it.

The Maine lobster fishermen usually hauled once during the season and
one chap came up with an ingenious scheme. They, of course, beached
the boats, propped up with sticks and this guy, as soon as the tide
started going out and the sticks started taking some weight started
spraying the hull with Clorox from one of those back mounted spray
tanks. Just walked round and round spraying. When the tide was pretty
well all the way out he'd scrub the hull with a "straw Broom" and all
the weeds and shell fish would fall off. He clamed that as he didn't
have to scrape, the bottom paint wasn't damaged so he didn't have top
re-paint half way through the season :-)


Now that's a sailor!


Fisherman actually :-) When I met the guy he was pulling 100 pots a
day, so he had 200 lobster pots in the water. I suspect that other
then not liking to scrape barnacles he was also in a hurry to get back
in the water as those lobster pots needed hauling :-)

Want to know the easiest way to do something?
Put a smart lazy man on the job.

The forty footer I owned, for some reason, had additional jib tracks
added inboard of the original tracks on the gunnels. Apparently done
by the previous owner who simply drilled holes through the deck and
bolted them down. Needless to say, the holes leaked and the plywood
core rutted in two six foot strips down the side decks, toward the
forward end of the cockpit. I finally used a 4" hand grinder and
sliced the fiberglass deck surface and removed two six foot long by
about 18 inch wide sections. The plywood had turned into a black mush.
I cleaned it out back to solid ply thinking that I could simply get
some more plywood of the same thickness to "inlay". It turned out that
the original plywood was some strange dimension that couldn't be
duplicated and I ended up with a horrible job of gluing down a layer
of ply, then building it up with epoxy filler and gluing the original
deck sections back on top. A horrible mess trying to get the whole job
smooth and fair with the old deck.


Oh man. I feel your pain.


A friend is involved with the Sea Scouts and sometimes get boats
donated. One Catalina ancient 27 came in and the entire foredeck was
spongy. He asked what it would cost to have it fixed.
Well, traditional methods - more than the boat was worth - for sure.

We tried something different.
You know how that polyurethane Gorilla Glue foams up from moisture?
We drilled some holes in the under side of the deck, poked plastic
tubing down the length of the deck and squirted in 6 bottles of glue -
one at a time. Squirt a bunch of glue and pull the hose out.
Let it expand for a day or two(!). Then run another tube in as far
as it will go and squirt in more glue.

Didn't plug the holes or anything, just to let it relieve pressure.
Put buckets under the drains and let it cook.

I had a friend that tried to the same thing with that two part foam -
mix the two parts and it foams up to ten or 20 times the volume of the
liquid.

He'd decided that his rudder wasn't big enough so he made a new one.
Made a mold and laminated the two sides and glued them together, made
a new shaft and all. Came over to get me to help. The scheme was that
we would assemble the thing, stand it up straight and pour the mix in
the top and it would expand and fill the hollow rudder and he could
trim off the top and Viola! A new rudder.

Unfortunately the stuff doesn't expand smoothly and progressively. It
goes Whoosh and all expands at once and it awful sticky so it sticks
to everything it comes in contact with. We ended up with a rudder that
was half full of foam and twice the size it started.

The next day he told me that after some thought he had decided that a
larger rudder might be detrimental when the wind got up :-)

A couple of weeks later the deck was solid as a rock again.
The under side looked like hell.

He didn't want to do anything but trim the foam off flush with a knife.
He didn't want to mislead a buyer as to the condition of the boat.

It sold soon after. Not much, but income for the Scouts.
It's still sailing.


A lot of work?
Maybe.

But a job that doesn't have to be reworked all the time is worth the
extra expense and effort.
At least that's how I feel.

It all depends on your personal standards...

--
Cheers,

John B.

Hunter 23 sailboat 1987 - $3200 (Lewisville)

http://dallas.craigslist.org/ndf/boa/4736043522.html

Nice, solid Hunter 23 wing keel with trailer and outboard that fits
the budget.
Sails are in good shape.

Below:

V berth
Large overhead opening hatch
Shelves on both sides
Shelf in forepeak
Removable foot boards
12 volt circulation fan

Salon
Ray Jefferson 5000M VHF radio
3 X 12 volt access ports
AM/FM cassette stereo
Interior speakers
Fold up salon table
Bulkheads are solid
12 volt circulation fan
Storage under settees
Settes slide out to form berth

Sliding galley module
Sink
Origo 1500 single burner alcohol stove

Above:
Stainless Steel bow pulpit
Life lines
Anchor locker(very deep)
Mast winch
Reefing mainsail w/ cover
Sliding companionway hatch
Mainsheet traveler
4:1 mainsheet
Maxwell #14 sheet winches
Gas locker to starboard
Storage in port lazarette(very deep)
Kick-up rudder
Game Fisher 9.9hp outboard(haven't tried to start)

Galvanized steel trailer
Swivel tongue jack
15" wheels
Bearing Buddys
Extension tongue


Call, Email or stop by to check her out.
Two halyards, two cushion covers and a want to sail is all you need.
"At the core of liberalism is the spoiled child,
miserable, as all spoiled children are, unsatisfied,
demanding, ill-disciplined, despotic and useless.
Liberalism is a philosophy of sniveling brats."
PJ O'Rourke

John, this has been bugging the heck out of me -- I really hate it
when I don't have a precise answer, so I did some checking to see that
the story is on polyester gelcooat resin.

Quality commercial gelcoats are made from an entirely different resin
than laminating resin. Gelcoats are based on ISO/NPG
(Isophthalic/Neopentyl Glychol) resins, which are much stronger,
clearer, and more scratch-resistant than ordinary laminating resin,
which is orthophthalic resin. In the course of checking this out I
read that high-quality boatbuilders are switching to ISO/NPG resin for
laminating, too, but that wasn't true when I was involved with it, so
I don't know anything about that.

You no doubt know that common plastic laminating resins, particularly
epoxy, have no natural thixotropic properties. Spray or brush them on
a vertical surface, and they drool. Commerical polyester gelcoat
resins are loaded with thixotropic agents so you can lay on a fairly
thick, even coat that doesn't drool. If you cut all the way through
the gelcoat on a cheap boat, you may find that the gelcoat is very
uneven in thickness. Sometimes you can see this as ripples on the
outside surface, because shrinkage upon curing makes the
thick-and-thin stand out. But most builders conquered that problem
decades ago. In the US, they use commercial gelcoat resin from the
start.

FWIW, even ISO/NPG resin, compared to most other resin systems, is
weak and brittle. Without the glass fiber in it for reinforcement, a
good gelcoat resin is mechanically much weaker than the laminate
beneath it. But it does the job acceptably well. And, as you pointed
out, it's cheap. g

--
Ed Huntress

On 11/6/2014 7:28 AM, Ed Huntress wrote:
John, this has been bugging the heck out of me -- I really hate it
when I don't have a precise answer, so I did some checking to see that
the story is on polyester gelcooat resin.

Quality commercial gelcoats are made from an entirely different resin
than laminating resin. Gelcoats are based on ISO/NPG
(Isophthalic/Neopentyl Glychol) resins, which are much stronger,
clearer, and more scratch-resistant than ordinary laminating resin,
which is orthophthalic resin. In the course of checking this out I
read that high-quality boatbuilders are switching to ISO/NPG resin for
laminating, too, but that wasn't true when I was involved with it, so
I don't know anything about that.

You no doubt know that common plastic laminating resins, particularly
epoxy, have no natural thixotropic properties. Spray or brush them on
a vertical surface, and they drool. Commerical polyester gelcoat
resins are loaded with thixotropic agents so you can lay on a fairly
thick, even coat that doesn't drool. If you cut all the way through
the gelcoat on a cheap boat, you may find that the gelcoat is very
uneven in thickness. Sometimes you can see this as ripples on the
outside surface, because shrinkage upon curing makes the
thick-and-thin stand out. But most builders conquered that problem
decades ago. In the US, they use commercial gelcoat resin from the
start.

FWIW, even ISO/NPG resin, compared to most other resin systems, is
weak and brittle. Without the glass fiber in it for reinforcement, a
good gelcoat resin is mechanically much weaker than the laminate
beneath it. But it does the job acceptably well. And, as you pointed
out, it's cheap. g


Excellent research, Ed.

After all this comes the actual mix.

The resin to catalyst ratio is a few drops of MEKP
(methylethelkeytoneperoxide) per pound of resin.
So how big is a drop?
Rule of thumb? Roughly 50 CCs per gallon?
So you can see that a little bit goes a LONG way.

What might be the results from variations in the mix?

Or how well mixed the mix is in the first place?

At what temperature is this all done?

Humidity?

Alignment of the stars and planets?

Lots of possible very small variations that have rather profound
effects in the end product.

On Thu, 06 Nov 2014 08:41:26 -0600, Richard
wrote:

On 11/6/2014 7:28 AM, Ed Huntress wrote:
John, this has been bugging the heck out of me -- I really hate it
when I don't have a precise answer, so I did some checking to see that
the story is on polyester gelcooat resin.

Quality commercial gelcoats are made from an entirely different resin
than laminating resin. Gelcoats are based on ISO/NPG
(Isophthalic/Neopentyl Glychol) resins, which are much stronger,
clearer, and more scratch-resistant than ordinary laminating resin,
which is orthophthalic resin. In the course of checking this out I
read that high-quality boatbuilders are switching to ISO/NPG resin for
laminating, too, but that wasn't true when I was involved with it, so
I don't know anything about that.

You no doubt know that common plastic laminating resins, particularly
epoxy, have no natural thixotropic properties. Spray or brush them on
a vertical surface, and they drool. Commerical polyester gelcoat
resins are loaded with thixotropic agents so you can lay on a fairly
thick, even coat that doesn't drool. If you cut all the way through
the gelcoat on a cheap boat, you may find that the gelcoat is very
uneven in thickness. Sometimes you can see this as ripples on the
outside surface, because shrinkage upon curing makes the
thick-and-thin stand out. But most builders conquered that problem
decades ago. In the US, they use commercial gelcoat resin from the
start.

FWIW, even ISO/NPG resin, compared to most other resin systems, is
weak and brittle. Without the glass fiber in it for reinforcement, a
good gelcoat resin is mechanically much weaker than the laminate
beneath it. But it does the job acceptably well. And, as you pointed
out, it's cheap. g


Excellent research, Ed.

After all this comes the actual mix.

The resin to catalyst ratio is a few drops of MEKP
(methylethelkeytoneperoxide) per pound of resin.
So how big is a drop?
Rule of thumb? Roughly 50 CCs per gallon?
So you can see that a little bit goes a LONG way.

What might be the results from variations in the mix?

Or how well mixed the mix is in the first place?

At what temperature is this all done?

Humidity?

Alignment of the stars and planets?

Lots of possible very small variations that have rather profound
effects in the end product.

It's certainly a lot more complex than we've discussed so far. At
Ranger, laminating resin was mixed, IIRC, 5 gallons at a time. There
was a schedule for desired gel times, and a time/temperature chart
that told you how much MEK would be required to meet those specs. They
used a little graduated cup to measure out the MEK and it was mixed
with a mechanical mixer.

As I mentioned, I started there as a furniture bonder. We mixed much
smaller quantities. We had a rule of thumb, but it was up to us to
make small adjustments. My partner, who spoke no English, liked to get
it over with fast. Some of his mixes actually bubbled and turned
brown. He was overjoyed. The people who bought our boats may not have
been. g

In terms of end properties, polyester resins actually are quite
flexible. You can get away with a pretty wide range of MEK
percentages. The biggest danger, when you're working with large
quantities and going slowly, is to use too little. The resin may never
harden if you do that.

If there's money involved and if that happens, sometimes they'll try
to rescue the job by brushing on some kind of accelerator. Maybe it's
MEK, but I don't think so. Sometimes it works, but it's really
problematic.

--
Ed Huntress

On 11/6/2014 9:01 AM, Ed Huntress wrote:
On Thu, 06 Nov 2014 08:41:26 -0600, Richard
wrote:

On 11/6/2014 7:28 AM, Ed Huntress wrote:
John, this has been bugging the heck out of me -- I really hate it
when I don't have a precise answer, so I did some checking to see that
the story is on polyester gelcooat resin.

Quality commercial gelcoats are made from an entirely different resin
than laminating resin. Gelcoats are based on ISO/NPG
(Isophthalic/Neopentyl Glychol) resins, which are much stronger,
clearer, and more scratch-resistant than ordinary laminating resin,
which is orthophthalic resin. In the course of checking this out I
read that high-quality boatbuilders are switching to ISO/NPG resin for
laminating, too, but that wasn't true when I was involved with it, so
I don't know anything about that.

You no doubt know that common plastic laminating resins, particularly
epoxy, have no natural thixotropic properties. Spray or brush them on
a vertical surface, and they drool. Commerical polyester gelcoat
resins are loaded with thixotropic agents so you can lay on a fairly
thick, even coat that doesn't drool. If you cut all the way through
the gelcoat on a cheap boat, you may find that the gelcoat is very
uneven in thickness. Sometimes you can see this as ripples on the
outside surface, because shrinkage upon curing makes the
thick-and-thin stand out. But most builders conquered that problem
decades ago. In the US, they use commercial gelcoat resin from the
start.

FWIW, even ISO/NPG resin, compared to most other resin systems, is
weak and brittle. Without the glass fiber in it for reinforcement, a
good gelcoat resin is mechanically much weaker than the laminate
beneath it. But it does the job acceptably well. And, as you pointed
out, it's cheap. g


Excellent research, Ed.

After all this comes the actual mix.

The resin to catalyst ratio is a few drops of MEKP
(methylethelkeytoneperoxide) per pound of resin.
So how big is a drop?
Rule of thumb? Roughly 50 CCs per gallon?
So you can see that a little bit goes a LONG way.

What might be the results from variations in the mix?

Or how well mixed the mix is in the first place?

At what temperature is this all done?

Humidity?

Alignment of the stars and planets?

Lots of possible very small variations that have rather profound
effects in the end product.

It's certainly a lot more complex than we've discussed so far. At
Ranger, laminating resin was mixed, IIRC, 5 gallons at a time. There
was a schedule for desired gel times, and a time/temperature chart
that told you how much MEK would be required to meet those specs. They
used a little graduated cup to measure out the MEK and it was mixed
with a mechanical mixer.

As I mentioned, I started there as a furniture bonder. We mixed much
smaller quantities. We had a rule of thumb, but it was up to us to
make small adjustments. My partner, who spoke no English, liked to get
it over with fast. Some of his mixes actually bubbled and turned
brown. He was overjoyed. The people who bought our boats may not have
been. g

In terms of end properties, polyester resins actually are quite
flexible. You can get away with a pretty wide range of MEK
percentages. The biggest danger, when you're working with large
quantities and going slowly, is to use too little. The resin may never
harden if you do that.

If there's money involved and if that happens, sometimes they'll try
to rescue the job by brushing on some kind of accelerator. Maybe it's
MEK, but I don't think so. Sometimes it works, but it's really
problematic.


mek-P
Don't forget the Peroxide!

On Thu, 06 Nov 2014 11:14:16 -0600, Richard
wrote:

On 11/6/2014 9:01 AM, Ed Huntress wrote:
On Thu, 06 Nov 2014 08:41:26 -0600, Richard
wrote:

On 11/6/2014 7:28 AM, Ed Huntress wrote:
John, this has been bugging the heck out of me -- I really hate it
when I don't have a precise answer, so I did some checking to see that
the story is on polyester gelcooat resin.

Quality commercial gelcoats are made from an entirely different resin
than laminating resin. Gelcoats are based on ISO/NPG
(Isophthalic/Neopentyl Glychol) resins, which are much stronger,
clearer, and more scratch-resistant than ordinary laminating resin,
which is orthophthalic resin. In the course of checking this out I
read that high-quality boatbuilders are switching to ISO/NPG resin for
laminating, too, but that wasn't true when I was involved with it, so
I don't know anything about that.

You no doubt know that common plastic laminating resins, particularly
epoxy, have no natural thixotropic properties. Spray or brush them on
a vertical surface, and they drool. Commerical polyester gelcoat
resins are loaded with thixotropic agents so you can lay on a fairly
thick, even coat that doesn't drool. If you cut all the way through
the gelcoat on a cheap boat, you may find that the gelcoat is very
uneven in thickness. Sometimes you can see this as ripples on the
outside surface, because shrinkage upon curing makes the
thick-and-thin stand out. But most builders conquered that problem
decades ago. In the US, they use commercial gelcoat resin from the
start.

FWIW, even ISO/NPG resin, compared to most other resin systems, is
weak and brittle. Without the glass fiber in it for reinforcement, a
good gelcoat resin is mechanically much weaker than the laminate
beneath it. But it does the job acceptably well. And, as you pointed
out, it's cheap. g


Excellent research, Ed.

After all this comes the actual mix.

The resin to catalyst ratio is a few drops of MEKP
(methylethelkeytoneperoxide) per pound of resin.
So how big is a drop?
Rule of thumb? Roughly 50 CCs per gallon?
So you can see that a little bit goes a LONG way.

What might be the results from variations in the mix?

Or how well mixed the mix is in the first place?

At what temperature is this all done?

Humidity?

Alignment of the stars and planets?

Lots of possible very small variations that have rather profound
effects in the end product.

It's certainly a lot more complex than we've discussed so far. At
Ranger, laminating resin was mixed, IIRC, 5 gallons at a time. There
was a schedule for desired gel times, and a time/temperature chart
that told you how much MEK would be required to meet those specs. They
used a little graduated cup to measure out the MEK and it was mixed
with a mechanical mixer.

As I mentioned, I started there as a furniture bonder. We mixed much
smaller quantities. We had a rule of thumb, but it was up to us to
make small adjustments. My partner, who spoke no English, liked to get
it over with fast. Some of his mixes actually bubbled and turned
brown. He was overjoyed. The people who bought our boats may not have
been. g

In terms of end properties, polyester resins actually are quite
flexible. You can get away with a pretty wide range of MEK
percentages. The biggest danger, when you're working with large
quantities and going slowly, is to use too little. The resin may never
harden if you do that.

If there's money involved and if that happens, sometimes they'll try
to rescue the job by brushing on some kind of accelerator. Maybe it's
MEK, but I don't think so. Sometimes it works, but it's really
problematic.


mek-P
Don't forget the Peroxide!

Yeah, I see that they're putting that on the abbreviation now. For
decades, the full name was used, but the abbreviation was just "MEK."

I sometimes wish I knew something about chemistry. It was my weakest
science subject.

--
Ed Huntress

"Ed Huntress" wrote in message
...
On Thu, 06 Nov 2014 11:14:16 -0600, Richard
wrote:

On 11/6/2014 9:01 AM, Ed Huntress wrote:
On Thu, 06 Nov 2014 08:41:26 -0600, Richard

wrote:

On 11/6/2014 7:28 AM, Ed Huntress wrote:
John, this has been bugging the heck out of me -- I really hate
it
when I don't have a precise answer, so I did some checking to
see that
the story is on polyester gelcooat resin.

Quality commercial gelcoats are made from an entirely different
resin
than laminating resin. Gelcoats are based on ISO/NPG
(Isophthalic/Neopentyl Glychol) resins, which are much stronger,
clearer, and more scratch-resistant than ordinary laminating
resin,
which is orthophthalic resin. In the course of checking this out
I
read that high-quality boatbuilders are switching to ISO/NPG
resin for
laminating, too, but that wasn't true when I was involved with
it, so
I don't know anything about that.

You no doubt know that common plastic laminating resins,
particularly
epoxy, have no natural thixotropic properties. Spray or brush
them on
a vertical surface, and they drool. Commerical polyester gelcoat
resins are loaded with thixotropic agents so you can lay on a
fairly
thick, even coat that doesn't drool. If you cut all the way
through
the gelcoat on a cheap boat, you may find that the gelcoat is
very
uneven in thickness. Sometimes you can see this as ripples on
the
outside surface, because shrinkage upon curing makes the
thick-and-thin stand out. But most builders conquered that
problem
decades ago. In the US, they use commercial gelcoat resin from
the
start.

FWIW, even ISO/NPG resin, compared to most other resin systems,
is
weak and brittle. Without the glass fiber in it for
reinforcement, a
good gelcoat resin is mechanically much weaker than the laminate
beneath it. But it does the job acceptably well. And, as you
pointed
out, it's cheap. g


Excellent research, Ed.

After all this comes the actual mix.

The resin to catalyst ratio is a few drops of MEKP
(methylethelkeytoneperoxide) per pound of resin.
So how big is a drop?
Rule of thumb? Roughly 50 CCs per gallon?
So you can see that a little bit goes a LONG way.

What might be the results from variations in the mix?

Or how well mixed the mix is in the first place?

At what temperature is this all done?

Humidity?

Alignment of the stars and planets?

Lots of possible very small variations that have rather profound
effects in the end product.

It's certainly a lot more complex than we've discussed so far. At
Ranger, laminating resin was mixed, IIRC, 5 gallons at a time.
There
was a schedule for desired gel times, and a time/temperature chart
that told you how much MEK would be required to meet those specs.
They
used a little graduated cup to measure out the MEK and it was
mixed
with a mechanical mixer.

As I mentioned, I started there as a furniture bonder. We mixed
much
smaller quantities. We had a rule of thumb, but it was up to us to
make small adjustments. My partner, who spoke no English, liked to
get
it over with fast. Some of his mixes actually bubbled and turned
brown. He was overjoyed. The people who bought our boats may not
have
been. g

In terms of end properties, polyester resins actually are quite
flexible. You can get away with a pretty wide range of MEK
percentages. The biggest danger, when you're working with large
quantities and going slowly, is to use too little. The resin may
never
harden if you do that.

If there's money involved and if that happens, sometimes they'll
try
to rescue the job by brushing on some kind of accelerator. Maybe
it's
MEK, but I don't think so. Sometimes it works, but it's really
problematic.


mek-P
Don't forget the Peroxide!

Yeah, I see that they're putting that on the abbreviation now. For
decades, the full name was used, but the abbreviation was just
"MEK."

I sometimes wish I knew something about chemistry. It was my weakest
science subject.

--
Ed Huntress

"MEK" without the P refers to a common solvent resembling acetone.

On Thu, 6 Nov 2014 13:08:24 -0500, "Jim Wilkins"
wrote:

"Ed Huntress" wrote in message
.. .
On Thu, 06 Nov 2014 11:14:16 -0600, Richard
wrote:

On 11/6/2014 9:01 AM, Ed Huntress wrote:
On Thu, 06 Nov 2014 08:41:26 -0600, Richard

wrote:

On 11/6/2014 7:28 AM, Ed Huntress wrote:
John, this has been bugging the heck out of me -- I really hate
it
when I don't have a precise answer, so I did some checking to
see that
the story is on polyester gelcooat resin.

Quality commercial gelcoats are made from an entirely different
resin
than laminating resin. Gelcoats are based on ISO/NPG
(Isophthalic/Neopentyl Glychol) resins, which are much stronger,
clearer, and more scratch-resistant than ordinary laminating
resin,
which is orthophthalic resin. In the course of checking this out
I
read that high-quality boatbuilders are switching to ISO/NPG
resin for
laminating, too, but that wasn't true when I was involved with
it, so
I don't know anything about that.

You no doubt know that common plastic laminating resins,
particularly
epoxy, have no natural thixotropic properties. Spray or brush
them on
a vertical surface, and they drool. Commerical polyester gelcoat
resins are loaded with thixotropic agents so you can lay on a
fairly
thick, even coat that doesn't drool. If you cut all the way
through
the gelcoat on a cheap boat, you may find that the gelcoat is
very
uneven in thickness. Sometimes you can see this as ripples on
the
outside surface, because shrinkage upon curing makes the
thick-and-thin stand out. But most builders conquered that
problem
decades ago. In the US, they use commercial gelcoat resin from
the
start.

FWIW, even ISO/NPG resin, compared to most other resin systems,
is
weak and brittle. Without the glass fiber in it for
reinforcement, a
good gelcoat resin is mechanically much weaker than the laminate
beneath it. But it does the job acceptably well. And, as you
pointed
out, it's cheap. g


Excellent research, Ed.

After all this comes the actual mix.

The resin to catalyst ratio is a few drops of MEKP
(methylethelkeytoneperoxide) per pound of resin.
So how big is a drop?
Rule of thumb? Roughly 50 CCs per gallon?
So you can see that a little bit goes a LONG way.

What might be the results from variations in the mix?

Or how well mixed the mix is in the first place?

At what temperature is this all done?

Humidity?

Alignment of the stars and planets?

Lots of possible very small variations that have rather profound
effects in the end product.

It's certainly a lot more complex than we've discussed so far. At
Ranger, laminating resin was mixed, IIRC, 5 gallons at a time.
There
was a schedule for desired gel times, and a time/temperature chart
that told you how much MEK would be required to meet those specs.
They
used a little graduated cup to measure out the MEK and it was
mixed
with a mechanical mixer.

As I mentioned, I started there as a furniture bonder. We mixed
much
smaller quantities. We had a rule of thumb, but it was up to us to
make small adjustments. My partner, who spoke no English, liked to
get
it over with fast. Some of his mixes actually bubbled and turned
brown. He was overjoyed. The people who bought our boats may not
have
been. g

In terms of end properties, polyester resins actually are quite
flexible. You can get away with a pretty wide range of MEK
percentages. The biggest danger, when you're working with large
quantities and going slowly, is to use too little. The resin may
never
harden if you do that.

If there's money involved and if that happens, sometimes they'll
try
to rescue the job by brushing on some kind of accelerator. Maybe
it's
MEK, but I don't think so. Sometimes it works, but it's really
problematic.


mek-P
Don't forget the Peroxide!

Yeah, I see that they're putting that on the abbreviation now. For
decades, the full name was used, but the abbreviation was just
"MEK."

I sometimes wish I knew something about chemistry. It was my weakest
science subject.

--
Ed Huntress

"MEK" without the P refers to a common solvent resembling acetone.

Good grief. I see that it's a natural component of chicken, apple
juice, and cheese.

I'm going to get off here, before this gets crazy. Thanks for the
info, Jim...I think. g

--
Ed Huntress

On Thu, 06 Nov 2014 08:28:51 -0500, Ed Huntress
wrote:

John, this has been bugging the heck out of me -- I really hate it
when I don't have a precise answer, so I did some checking to see that
the story is on polyester gelcooat resin.

Quality commercial gelcoats are made from an entirely different resin
than laminating resin. Gelcoats are based on ISO/NPG
(Isophthalic/Neopentyl Glychol) resins, which are much stronger,
clearer, and more scratch-resistant than ordinary laminating resin,
which is orthophthalic resin. In the course of checking this out I
read that high-quality boatbuilders are switching to ISO/NPG resin for
laminating, too, but that wasn't true when I was involved with it, so
I don't know anything about that.

You no doubt know that common plastic laminating resins, particularly
epoxy, have no natural thixotropic properties. Spray or brush them on
a vertical surface, and they drool. Commerical polyester gelcoat
resins are loaded with thixotropic agents so you can lay on a fairly
thick, even coat that doesn't drool. If you cut all the way through
the gelcoat on a cheap boat, you may find that the gelcoat is very
uneven in thickness. Sometimes you can see this as ripples on the
outside surface, because shrinkage upon curing makes the
thick-and-thin stand out. But most builders conquered that problem
decades ago. In the US, they use commercial gelcoat resin from the
start.

FWIW, even ISO/NPG resin, compared to most other resin systems, is
weak and brittle. Without the glass fiber in it for reinforcement, a
good gelcoat resin is mechanically much weaker than the laminate
beneath it. But it does the job acceptably well. And, as you pointed
out, it's cheap. g

Ed, I think I wrote something like "I saw local guys..." or "The way
that they do it here...". I can assure you that people here (however
unlettered) are mixing a color pigment with polyester resin and
slather it in the molds. Just about every "fiberglass shop" carries
the pigments, it is that common.

I think that the reason is that "proper" gel coat is very likely more
expensive and probably not as easily available in local shops so the
local guys don't use it as even with the recent doubling of the
minimum wage here materials are still the most expensive part of job
costs :-0
--
Cheers,

John B.

On Fri, 07 Nov 2014 08:35:49 +0700, John B. Slocomb
wrote:

On Thu, 06 Nov 2014 08:28:51 -0500, Ed Huntress
wrote:

John, this has been bugging the heck out of me -- I really hate it
when I don't have a precise answer, so I did some checking to see that
the story is on polyester gelcooat resin.

Quality commercial gelcoats are made from an entirely different resin
than laminating resin. Gelcoats are based on ISO/NPG
(Isophthalic/Neopentyl Glychol) resins, which are much stronger,
clearer, and more scratch-resistant than ordinary laminating resin,
which is orthophthalic resin. In the course of checking this out I
read that high-quality boatbuilders are switching to ISO/NPG resin for
laminating, too, but that wasn't true when I was involved with it, so
I don't know anything about that.

You no doubt know that common plastic laminating resins, particularly
epoxy, have no natural thixotropic properties. Spray or brush them on
a vertical surface, and they drool. Commerical polyester gelcoat
resins are loaded with thixotropic agents so you can lay on a fairly
thick, even coat that doesn't drool. If you cut all the way through
the gelcoat on a cheap boat, you may find that the gelcoat is very
uneven in thickness. Sometimes you can see this as ripples on the
outside surface, because shrinkage upon curing makes the
thick-and-thin stand out. But most builders conquered that problem
decades ago. In the US, they use commercial gelcoat resin from the
start.

FWIW, even ISO/NPG resin, compared to most other resin systems, is
weak and brittle. Without the glass fiber in it for reinforcement, a
good gelcoat resin is mechanically much weaker than the laminate
beneath it. But it does the job acceptably well. And, as you pointed
out, it's cheap. g

Ed, I think I wrote something like "I saw local guys..." or "The way
that they do it here...". I can assure you that people here (however
unlettered) are mixing a color pigment with polyester resin and
slather it in the molds. Just about every "fiberglass shop" carries
the pigments, it is that common.

Oh, you did, and I don't doubt that they do it.


I think that the reason is that "proper" gel coat is very likely more
expensive and probably not as easily available in local shops so the
local guys don't use it as even with the recent doubling of the
minimum wage here materials are still the most expensive part of job
costs :-0

I don't doubt that, either. But if I recall, somewhere in that
discussion was the statement, or the implication, that gelcoat is
nothing but laminating resin with pigment in it.

I just wanted to clear up that point, in case anyone took that away
from what we were saying.

Mostly, I wanted to check my memory and clear it up for myself. I have
some vivid memories of that work, but it was a *long* time ago.

--
Ed Huntress

On Thu, 06 Nov 2014 10:01:09 -0500, Ed Huntress
wrote:

On Thu, 06 Nov 2014 08:41:26 -0600, Richard
wrote:

On 11/6/2014 7:28 AM, Ed Huntress wrote:
John, this has been bugging the heck out of me -- I really hate it
when I don't have a precise answer, so I did some checking to see that
the story is on polyester gelcooat resin.

Quality commercial gelcoats are made from an entirely different resin
than laminating resin. Gelcoats are based on ISO/NPG
(Isophthalic/Neopentyl Glychol) resins, which are much stronger,
clearer, and more scratch-resistant than ordinary laminating resin,
which is orthophthalic resin. In the course of checking this out I
read that high-quality boatbuilders are switching to ISO/NPG resin for
laminating, too, but that wasn't true when I was involved with it, so
I don't know anything about that.

You no doubt know that common plastic laminating resins, particularly
epoxy, have no natural thixotropic properties. Spray or brush them on
a vertical surface, and they drool. Commerical polyester gelcoat
resins are loaded with thixotropic agents so you can lay on a fairly
thick, even coat that doesn't drool. If you cut all the way through
the gelcoat on a cheap boat, you may find that the gelcoat is very
uneven in thickness. Sometimes you can see this as ripples on the
outside surface, because shrinkage upon curing makes the
thick-and-thin stand out. But most builders conquered that problem
decades ago. In the US, they use commercial gelcoat resin from the
start.

FWIW, even ISO/NPG resin, compared to most other resin systems, is
weak and brittle. Without the glass fiber in it for reinforcement, a
good gelcoat resin is mechanically much weaker than the laminate
beneath it. But it does the job acceptably well. And, as you pointed
out, it's cheap. g


Excellent research, Ed.

After all this comes the actual mix.

The resin to catalyst ratio is a few drops of MEKP
(methylethelkeytoneperoxide) per pound of resin.
So how big is a drop?
Rule of thumb? Roughly 50 CCs per gallon?
So you can see that a little bit goes a LONG way.

What might be the results from variations in the mix?

Or how well mixed the mix is in the first place?

At what temperature is this all done?

Humidity?

Alignment of the stars and planets?

Lots of possible very small variations that have rather profound
effects in the end product.

It's certainly a lot more complex than we've discussed so far. At
Ranger, laminating resin was mixed, IIRC, 5 gallons at a time. There
was a schedule for desired gel times, and a time/temperature chart
that told you how much MEK would be required to meet those specs. They
used a little graduated cup to measure out the MEK and it was mixed
with a mechanical mixer.

As I mentioned, I started there as a furniture bonder. We mixed much
smaller quantities. We had a rule of thumb, but it was up to us to
make small adjustments. My partner, who spoke no English, liked to get
it over with fast. Some of his mixes actually bubbled and turned
brown. He was overjoyed. The people who bought our boats may not have
been. g

In terms of end properties, polyester resins actually are quite
flexible. You can get away with a pretty wide range of MEK
percentages. The biggest danger, when you're working with large
quantities and going slowly, is to use too little. The resin may never
harden if you do that.

If there's money involved and if that happens, sometimes they'll try
to rescue the job by brushing on some kind of accelerator. Maybe it's
MEK, but I don't think so. Sometimes it works, but it's really
problematic.

Way back when I was in the Air Force the sheetmetal guys used what was
likely polyester to make certain repairs on the B-52's (and probably
other airplanes but I was in a B-52 wing :-) and in those days it was
a three part mix, resin, hardener and an accelerator that they
referred to as "cobalt". As I remember it the resin/hardener ratio was
a constant and the cobalt was used for a longer or shorter hardening
time.

This wasn't my area of expertise but I've seen the Tin-benders mix
stuff that set the paper mixing cup on fire.

Rather impressive I thought :-)

--
Cheers,

John B.

On Fri, 07 Nov 2014 08:48:37 +0700, John B. Slocomb
wrote:

On Thu, 06 Nov 2014 10:01:09 -0500, Ed Huntress
wrote:

On Thu, 06 Nov 2014 08:41:26 -0600, Richard
wrote:

On 11/6/2014 7:28 AM, Ed Huntress wrote:
John, this has been bugging the heck out of me -- I really hate it
when I don't have a precise answer, so I did some checking to see that
the story is on polyester gelcooat resin.

Quality commercial gelcoats are made from an entirely different resin
than laminating resin. Gelcoats are based on ISO/NPG
(Isophthalic/Neopentyl Glychol) resins, which are much stronger,
clearer, and more scratch-resistant than ordinary laminating resin,
which is orthophthalic resin. In the course of checking this out I
read that high-quality boatbuilders are switching to ISO/NPG resin for
laminating, too, but that wasn't true when I was involved with it, so
I don't know anything about that.

You no doubt know that common plastic laminating resins, particularly
epoxy, have no natural thixotropic properties. Spray or brush them on
a vertical surface, and they drool. Commerical polyester gelcoat
resins are loaded with thixotropic agents so you can lay on a fairly
thick, even coat that doesn't drool. If you cut all the way through
the gelcoat on a cheap boat, you may find that the gelcoat is very
uneven in thickness. Sometimes you can see this as ripples on the
outside surface, because shrinkage upon curing makes the
thick-and-thin stand out. But most builders conquered that problem
decades ago. In the US, they use commercial gelcoat resin from the
start.

FWIW, even ISO/NPG resin, compared to most other resin systems, is
weak and brittle. Without the glass fiber in it for reinforcement, a
good gelcoat resin is mechanically much weaker than the laminate
beneath it. But it does the job acceptably well. And, as you pointed
out, it's cheap. g


Excellent research, Ed.

After all this comes the actual mix.

The resin to catalyst ratio is a few drops of MEKP
(methylethelkeytoneperoxide) per pound of resin.
So how big is a drop?
Rule of thumb? Roughly 50 CCs per gallon?
So you can see that a little bit goes a LONG way.

What might be the results from variations in the mix?

Or how well mixed the mix is in the first place?

At what temperature is this all done?

Humidity?

Alignment of the stars and planets?

Lots of possible very small variations that have rather profound
effects in the end product.

It's certainly a lot more complex than we've discussed so far. At
Ranger, laminating resin was mixed, IIRC, 5 gallons at a time. There
was a schedule for desired gel times, and a time/temperature chart
that told you how much MEK would be required to meet those specs. They
used a little graduated cup to measure out the MEK and it was mixed
with a mechanical mixer.

As I mentioned, I started there as a furniture bonder. We mixed much
smaller quantities. We had a rule of thumb, but it was up to us to
make small adjustments. My partner, who spoke no English, liked to get
it over with fast. Some of his mixes actually bubbled and turned
brown. He was overjoyed. The people who bought our boats may not have
been. g

In terms of end properties, polyester resins actually are quite
flexible. You can get away with a pretty wide range of MEK
percentages. The biggest danger, when you're working with large
quantities and going slowly, is to use too little. The resin may never
harden if you do that.

If there's money involved and if that happens, sometimes they'll try
to rescue the job by brushing on some kind of accelerator. Maybe it's
MEK, but I don't think so. Sometimes it works, but it's really
problematic.

Way back when I was in the Air Force the sheetmetal guys used what was
likely polyester to make certain repairs on the B-52's (and probably
other airplanes but I was in a B-52 wing :-) and in those days it was
a three part mix, resin, hardener and an accelerator that they
referred to as "cobalt". As I remember it the resin/hardener ratio was
a constant and the cobalt was used for a longer or shorter hardening
time.

This wasn't my area of expertise but I've seen the Tin-benders mix
stuff that set the paper mixing cup on fire.

Rather impressive I thought :-)

Yeah, a hot mix can be pretty exciting. Someone who's used to mixing a
half-pint or less at a time, who mixes a gollon or two at the same
ratio they used for quick cures in small batches, is in for a real
surprise. g

You can't make hot mixes of polyesterin big quantities without risking
a fire and a complete loss of the batch. And a really hot mix can
start a fire even in much smaller quantities. If you have a paper cup
full and it catches on fire, that's 'way too hot to produce good
mechanical properties in the cured resin.

About the cobalt: Yes, and that's already pre-mixed in resins made for
laminating boats. I've seen contradictory words used in the
terminology, so I don't know which is really the catalyst, and which
is the accelerator. But the cobalt compound percentage is fixed in
ordinary resins. Military applications probably are much different.

I'm surprised they used polyester, though. Its adhesive properties are
pretty lousy, and a very small fraction of the adhesion of epoxy. And
if it's military, it sure isn't because they're trying to save money.
It may be the speed of cure that was required. Epoxies that cure at
room temperature, in the time range of typical polyesters, are not
strong epoxy resins, even if they set to an initial gel just as
quickly.

--
Ed Huntress

On Thu, 06 Nov 2014 21:14:39 -0500, Ed Huntress
wrote:

On Fri, 07 Nov 2014 08:48:37 +0700, John B. Slocomb
wrote:

On Thu, 06 Nov 2014 10:01:09 -0500, Ed Huntress
wrote:

On Thu, 06 Nov 2014 08:41:26 -0600, Richard
wrote:

On 11/6/2014 7:28 AM, Ed Huntress wrote:
John, this has been bugging the heck out of me -- I really hate it
when I don't have a precise answer, so I did some checking to see that
the story is on polyester gelcooat resin.

Quality commercial gelcoats are made from an entirely different resin
than laminating resin. Gelcoats are based on ISO/NPG
(Isophthalic/Neopentyl Glychol) resins, which are much stronger,
clearer, and more scratch-resistant than ordinary laminating resin,
which is orthophthalic resin. In the course of checking this out I
read that high-quality boatbuilders are switching to ISO/NPG resin for
laminating, too, but that wasn't true when I was involved with it, so
I don't know anything about that.

You no doubt know that common plastic laminating resins, particularly
epoxy, have no natural thixotropic properties. Spray or brush them on
a vertical surface, and they drool. Commerical polyester gelcoat
resins are loaded with thixotropic agents so you can lay on a fairly
thick, even coat that doesn't drool. If you cut all the way through
the gelcoat on a cheap boat, you may find that the gelcoat is very
uneven in thickness. Sometimes you can see this as ripples on the
outside surface, because shrinkage upon curing makes the
thick-and-thin stand out. But most builders conquered that problem
decades ago. In the US, they use commercial gelcoat resin from the
start.

FWIW, even ISO/NPG resin, compared to most other resin systems, is
weak and brittle. Without the glass fiber in it for reinforcement, a
good gelcoat resin is mechanically much weaker than the laminate
beneath it. But it does the job acceptably well. And, as you pointed
out, it's cheap. g


Excellent research, Ed.

After all this comes the actual mix.

The resin to catalyst ratio is a few drops of MEKP
(methylethelkeytoneperoxide) per pound of resin.
So how big is a drop?
Rule of thumb? Roughly 50 CCs per gallon?
So you can see that a little bit goes a LONG way.

What might be the results from variations in the mix?

Or how well mixed the mix is in the first place?

At what temperature is this all done?

Humidity?

Alignment of the stars and planets?

Lots of possible very small variations that have rather profound
effects in the end product.

It's certainly a lot more complex than we've discussed so far. At
Ranger, laminating resin was mixed, IIRC, 5 gallons at a time. There
was a schedule for desired gel times, and a time/temperature chart
that told you how much MEK would be required to meet those specs. They
used a little graduated cup to measure out the MEK and it was mixed
with a mechanical mixer.

As I mentioned, I started there as a furniture bonder. We mixed much
smaller quantities. We had a rule of thumb, but it was up to us to
make small adjustments. My partner, who spoke no English, liked to get
it over with fast. Some of his mixes actually bubbled and turned
brown. He was overjoyed. The people who bought our boats may not have
been. g

In terms of end properties, polyester resins actually are quite
flexible. You can get away with a pretty wide range of MEK
percentages. The biggest danger, when you're working with large
quantities and going slowly, is to use too little. The resin may never
harden if you do that.

If there's money involved and if that happens, sometimes they'll try
to rescue the job by brushing on some kind of accelerator. Maybe it's
MEK, but I don't think so. Sometimes it works, but it's really
problematic.

Way back when I was in the Air Force the sheetmetal guys used what was
likely polyester to make certain repairs on the B-52's (and probably
other airplanes but I was in a B-52 wing :-) and in those days it was
a three part mix, resin, hardener and an accelerator that they
referred to as "cobalt". As I remember it the resin/hardener ratio was
a constant and the cobalt was used for a longer or shorter hardening
time.

This wasn't my area of expertise but I've seen the Tin-benders mix
stuff that set the paper mixing cup on fire.

Rather impressive I thought :-)

Yeah, a hot mix can be pretty exciting. Someone who's used to mixing a
half-pint or less at a time, who mixes a gollon or two at the same
ratio they used for quick cures in small batches, is in for a real
surprise. g

You can't make hot mixes of polyesterin big quantities without risking
a fire and a complete loss of the batch. And a really hot mix can
start a fire even in much smaller quantities. If you have a paper cup
full and it catches on fire, that's 'way too hot to produce good
mechanical properties in the cured resin.

About the cobalt: Yes, and that's already pre-mixed in resins made for
laminating boats. I've seen contradictory words used in the
terminology, so I don't know which is really the catalyst, and which
is the accelerator. But the cobalt compound percentage is fixed in
ordinary resins. Military applications probably are much different.

I'm surprised they used polyester, though. Its adhesive properties are
pretty lousy, and a very small fraction of the adhesion of epoxy. And
if it's military, it sure isn't because they're trying to save money.
It may be the speed of cure that was required. Epoxies that cure at
room temperature, in the time range of typical polyesters, are not
strong epoxy resins, even if they set to an initial gel just as
quickly.

This was years ago, probably in the late 1960's so I don't think that
the guys in the sheet metal shop were that familiar with the stuff and
to the best of my recollection they didn't use it very often. I
vaguely remember them talking about temporary fixes on the B-52's but
that is about all.

I don't think that speed of curing was a critical part of it as the
burning coffee cup was a demonstration my buddy did to sort of awe the
natives - the natives being me and a guy from the welding shop :-0
--
Cheers,

John B.

"John B. Slocomb" wrote in message
...
On Thu, 06 Nov 2014 10:01:09 -0500, Ed Huntress
wrote:

On Thu, 06 Nov 2014 08:41:26 -0600, Richard
wrote:

On 11/6/2014 7:28 AM, Ed Huntress wrote:
John, this has been bugging the heck out of me -- I really hate
it
when I don't have a precise answer, so I did some checking to see
that
the story is on polyester gelcooat resin.

Quality commercial gelcoats are made from an entirely different
resin
than laminating resin. Gelcoats are based on ISO/NPG
(Isophthalic/Neopentyl Glychol) resins, which are much stronger,
clearer, and more scratch-resistant than ordinary laminating
resin,
which is orthophthalic resin. In the course of checking this out
I
read that high-quality boatbuilders are switching to ISO/NPG
resin for
laminating, too, but that wasn't true when I was involved with
it, so
I don't know anything about that.

You no doubt know that common plastic laminating resins,
particularly
epoxy, have no natural thixotropic properties. Spray or brush
them on
a vertical surface, and they drool. Commerical polyester gelcoat
resins are loaded with thixotropic agents so you can lay on a
fairly
thick, even coat that doesn't drool. If you cut all the way
through
the gelcoat on a cheap boat, you may find that the gelcoat is
very
uneven in thickness. Sometimes you can see this as ripples on the
outside surface, because shrinkage upon curing makes the
thick-and-thin stand out. But most builders conquered that
problem
decades ago. In the US, they use commercial gelcoat resin from
the
start.

FWIW, even ISO/NPG resin, compared to most other resin systems,
is
weak and brittle. Without the glass fiber in it for
reinforcement, a
good gelcoat resin is mechanically much weaker than the laminate
beneath it. But it does the job acceptably well. And, as you
pointed
out, it's cheap. g


Excellent research, Ed.

After all this comes the actual mix.

The resin to catalyst ratio is a few drops of MEKP
(methylethelkeytoneperoxide) per pound of resin.
So how big is a drop?
Rule of thumb? Roughly 50 CCs per gallon?
So you can see that a little bit goes a LONG way.

What might be the results from variations in the mix?

Or how well mixed the mix is in the first place?

At what temperature is this all done?

Humidity?

Alignment of the stars and planets?

Lots of possible very small variations that have rather profound
effects in the end product.

It's certainly a lot more complex than we've discussed so far. At
Ranger, laminating resin was mixed, IIRC, 5 gallons at a time. There
was a schedule for desired gel times, and a time/temperature chart
that told you how much MEK would be required to meet those specs.
They
used a little graduated cup to measure out the MEK and it was mixed
with a mechanical mixer.

As I mentioned, I started there as a furniture bonder. We mixed much
smaller quantities. We had a rule of thumb, but it was up to us to
make small adjustments. My partner, who spoke no English, liked to
get
it over with fast. Some of his mixes actually bubbled and turned
brown. He was overjoyed. The people who bought our boats may not
have
been. g

In terms of end properties, polyester resins actually are quite
flexible. You can get away with a pretty wide range of MEK
percentages. The biggest danger, when you're working with large
quantities and going slowly, is to use too little. The resin may
never
harden if you do that.

If there's money involved and if that happens, sometimes they'll try
to rescue the job by brushing on some kind of accelerator. Maybe
it's
MEK, but I don't think so. Sometimes it works, but it's really
problematic.

Way back when I was in the Air Force the sheetmetal guys used what
was
likely polyester to make certain repairs on the B-52's (and probably
other airplanes but I was in a B-52 wing :-) and in those days it
was
a three part mix, resin, hardener and an accelerator that they
referred to as "cobalt". As I remember it the resin/hardener ratio
was
a constant and the cobalt was used for a longer or shorter hardening
time.

This wasn't my area of expertise but I've seen the Tin-benders mix
stuff that set the paper mixing cup on fire.

Rather impressive I thought :-)

--
Cheers,

John B.

http://en.wikipedia.org/wiki/Cobalt(II)_naphthenate
http://en.wikipedia.org/wiki/Oil_drying_agent
-jsw

On 11/6/2014 7:48 PM, John B. Slocomb wrote:

This wasn't my area of expertise but I've seen the Tin-benders mix
stuff that set the paper mixing cup on fire.

Rather impressive I thought :-)


Golly. I've done that with plain old polyester mix.

Somebody "opened up" the hole in the MEKP bottle and the
drops were actually squirts.

Rather impressive, like you said.

On 11/6/2014 7:46 PM, Ed Huntress wrote:
On Fri, 07 Nov 2014 08:35:49 +0700, John B. Slocomb
wrote:

On Thu, 06 Nov 2014 08:28:51 -0500, Ed Huntress
wrote:

John, this has been bugging the heck out of me -- I really hate it
when I don't have a precise answer, so I did some checking to see that
the story is on polyester gelcooat resin.

Quality commercial gelcoats are made from an entirely different resin
than laminating resin. Gelcoats are based on ISO/NPG
(Isophthalic/Neopentyl Glychol) resins, which are much stronger,
clearer, and more scratch-resistant than ordinary laminating resin,
which is orthophthalic resin. In the course of checking this out I
read that high-quality boatbuilders are switching to ISO/NPG resin for
laminating, too, but that wasn't true when I was involved with it, so
I don't know anything about that.

You no doubt know that common plastic laminating resins, particularly
epoxy, have no natural thixotropic properties. Spray or brush them on
a vertical surface, and they drool. Commerical polyester gelcoat
resins are loaded with thixotropic agents so you can lay on a fairly
thick, even coat that doesn't drool. If you cut all the way through
the gelcoat on a cheap boat, you may find that the gelcoat is very
uneven in thickness. Sometimes you can see this as ripples on the
outside surface, because shrinkage upon curing makes the
thick-and-thin stand out. But most builders conquered that problem
decades ago. In the US, they use commercial gelcoat resin from the
start.

FWIW, even ISO/NPG resin, compared to most other resin systems, is
weak and brittle. Without the glass fiber in it for reinforcement, a
good gelcoat resin is mechanically much weaker than the laminate
beneath it. But it does the job acceptably well. And, as you pointed
out, it's cheap.g

Ed, I think I wrote something like "I saw local guys..." or "The way
that they do it here...". I can assure you that people here (however
unlettered) are mixing a color pigment with polyester resin and
slather it in the molds. Just about every "fiberglass shop" carries
the pigments, it is that common.

Oh, you did, and I don't doubt that they do it.


I think that the reason is that "proper" gel coat is very likely more
expensive and probably not as easily available in local shops so the
local guys don't use it as even with the recent doubling of the
minimum wage here materials are still the most expensive part of job
costs :-0

I don't doubt that, either. But if I recall, somewhere in that
discussion was the statement, or the implication, that gelcoat is
nothing but laminating resin with pigment in it.

Not at all.
But you COULD say that gelcoat is nothing but laminating resin with WAX
added...




I just wanted to clear up that point, in case anyone took that away
from what we were saying.

Mostly, I wanted to check my memory and clear it up for myself. I have
some vivid memories of that work, but it was a *long* time ago.

On Fri, 07 Nov 2014 10:59:49 -0600, Richard
wrote:

On 11/6/2014 7:46 PM, Ed Huntress wrote:
On Fri, 07 Nov 2014 08:35:49 +0700, John B. Slocomb
wrote:

On Thu, 06 Nov 2014 08:28:51 -0500, Ed Huntress
wrote:

John, this has been bugging the heck out of me -- I really hate it
when I don't have a precise answer, so I did some checking to see that
the story is on polyester gelcooat resin.

Quality commercial gelcoats are made from an entirely different resin
than laminating resin. Gelcoats are based on ISO/NPG
(Isophthalic/Neopentyl Glychol) resins, which are much stronger,
clearer, and more scratch-resistant than ordinary laminating resin,
which is orthophthalic resin. In the course of checking this out I
read that high-quality boatbuilders are switching to ISO/NPG resin for
laminating, too, but that wasn't true when I was involved with it, so
I don't know anything about that.

You no doubt know that common plastic laminating resins, particularly
epoxy, have no natural thixotropic properties. Spray or brush them on
a vertical surface, and they drool. Commerical polyester gelcoat
resins are loaded with thixotropic agents so you can lay on a fairly
thick, even coat that doesn't drool. If you cut all the way through
the gelcoat on a cheap boat, you may find that the gelcoat is very
uneven in thickness. Sometimes you can see this as ripples on the
outside surface, because shrinkage upon curing makes the
thick-and-thin stand out. But most builders conquered that problem
decades ago. In the US, they use commercial gelcoat resin from the
start.

FWIW, even ISO/NPG resin, compared to most other resin systems, is
weak and brittle. Without the glass fiber in it for reinforcement, a
good gelcoat resin is mechanically much weaker than the laminate
beneath it. But it does the job acceptably well. And, as you pointed
out, it's cheap.g

Ed, I think I wrote something like "I saw local guys..." or "The way
that they do it here...". I can assure you that people here (however
unlettered) are mixing a color pigment with polyester resin and
slather it in the molds. Just about every "fiberglass shop" carries
the pigments, it is that common.

Oh, you did, and I don't doubt that they do it.


I think that the reason is that "proper" gel coat is very likely more
expensive and probably not as easily available in local shops so the
local guys don't use it as even with the recent doubling of the
minimum wage here materials are still the most expensive part of job
costs :-0

I don't doubt that, either. But if I recall, somewhere in that
discussion was the statement, or the implication, that gelcoat is
nothing but laminating resin with pigment in it.

Not at all.
But you COULD say that gelcoat is nothing but laminating resin with WAX
added..

Don't get me started. g. Only the gelcoat that you spray on the
outside of a hull. The original gelcoat, which they spray on the
inside of a mold, has no wax.

Unless you make it out of laminating resin, then it *probably* has
wax. d8-)

It's preferred not to use wax when another layer of polyester is going
on top, and there's usually no wax in commercial gel coat made for
spraying in a mold. That's sometimes true with the laminating resin,
too, except for the last coat.

Or it was, decades ago. The wax doesn't make much difference if wet
resin it layed on top. The wax dissolves, and starts floating to the
top again. But you only need it on the final layer, because polyester
is air-inhibited.

Now I'm done. I have to get ready to go to FABTECH in Atlanta.

--
Ed Huntress




I just wanted to clear up that point, in case anyone took that away
from what we were saying.

Mostly, I wanted to check my memory and clear it up for myself. I have
some vivid memories of that work, but it was a *long* time ago.

Richard wrote in news:Ydqdncz1e6oLZ8HJnZ2dnUU7-
:
Not at all.
But you COULD say that gelcoat is nothing but laminating resin with WAX
added...

No. Commercial gelcoat does *NOT* contain wax as it would impair the bond
to the laminating resin in the layup being applied to the gelcoat in the
mold. Flocoat contains wax for a non-tacky surface cure. Some entry
level gelcoat repair kits contain wax, but if you are serious, you either
seal polythene sheet over the repair to exclude air or use wax in styrene
additive.

--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk
[at]=@, [dash]=- & [dot]=. *Warning* HTML & 32K emails -- NUL

On 11/7/2014 12:08 PM, Ian Malcolm wrote:
wrote in news:Ydqdncz1e6oLZ8HJnZ2dnUU7-
:
Not at all.
But you COULD say that gelcoat is nothing but laminating resin with WAX
added...

No. Commercial gelcoat does *NOT* contain wax as it would impair the bond
to the laminating resin in the layup being applied to the gelcoat in the
mold. Flocoat contains wax for a non-tacky surface cure. Some entry
level gelcoat repair kits contain wax, but if you are serious, you either
seal polythene sheet over the repair to exclude air or use wax in styrene
additive.


Ok, I guess I'll retract that.

The stuff I use does have wax so that it is self sealing, but I take the
point...

On Thu, 06 Nov 2014 08:41:26 -0600, Richard
wrote:

On 11/6/2014 7:28 AM, Ed Huntress wrote:
John, this has been bugging the heck out of me -- I really hate it
when I don't have a precise answer, so I did some checking to see that
the story is on polyester gelcooat resin.

Quality commercial gelcoats are made from an entirely different resin
than laminating resin. Gelcoats are based on ISO/NPG
(Isophthalic/Neopentyl Glychol) resins, which are much stronger,
clearer, and more scratch-resistant than ordinary laminating resin,
which is orthophthalic resin. In the course of checking this out I
read that high-quality boatbuilders are switching to ISO/NPG resin for
laminating, too, but that wasn't true when I was involved with it, so
I don't know anything about that.

You no doubt know that common plastic laminating resins, particularly
epoxy, have no natural thixotropic properties. Spray or brush them on
a vertical surface, and they drool. Commerical polyester gelcoat
resins are loaded with thixotropic agents so you can lay on a fairly
thick, even coat that doesn't drool. If you cut all the way through
the gelcoat on a cheap boat, you may find that the gelcoat is very
uneven in thickness. Sometimes you can see this as ripples on the
outside surface, because shrinkage upon curing makes the
thick-and-thin stand out. But most builders conquered that problem
decades ago. In the US, they use commercial gelcoat resin from the
start.

FWIW, even ISO/NPG resin, compared to most other resin systems, is
weak and brittle. Without the glass fiber in it for reinforcement, a
good gelcoat resin is mechanically much weaker than the laminate
beneath it. But it does the job acceptably well. And, as you pointed
out, it's cheap. g


Excellent research, Ed.

After all this comes the actual mix.

The resin to catalyst ratio is a few drops of MEKP
(methylethelkeytoneperoxide) per pound of resin.
So how big is a drop?
Rule of thumb? Roughly 50 CCs per gallon?
So you can see that a little bit goes a LONG way.

What might be the results from variations in the mix?

Or how well mixed the mix is in the first place?

At what temperature is this all done?

Humidity?

Alignment of the stars and planets?

Lots of possible very small variations that have rather profound
effects in the end product.

Indeed! Well stated.

With Luck and the sacrifice of ones first born child..one might get a
color match. As for its strength..it has none and it is rather
brittle as witnessed by the "spiderwebbing" on boat hulls in impact
zones and flex points


"At the core of liberalism is the spoiled child,
miserable, as all spoiled children are, unsatisfied,
demanding, ill-disciplined, despotic and useless.
Liberalism is a philosophy of sniveling brats."
PJ O'Rourke

On Fri, 7 Nov 2014 18:08:12 +0000 (UTC), Ian Malcolm
wrote:

Richard wrote in news:Ydqdncz1e6oLZ8HJnZ2dnUU7-
:
Not at all.
But you COULD say that gelcoat is nothing but laminating resin with WAX
added...

No. Commercial gelcoat does *NOT* contain wax as it would impair the bond
to the laminating resin in the layup being applied to the gelcoat in the
mold. Flocoat contains wax for a non-tacky surface cure. Some entry
level gelcoat repair kits contain wax, but if you are serious, you either
seal polythene sheet over the repair to exclude air or use wax in styrene
additive.

Ayup.


"At the core of liberalism is the spoiled child,
miserable, as all spoiled children are, unsatisfied,
demanding, ill-disciplined, despotic and useless.
Liberalism is a philosophy of sniveling brats."
PJ O'Rourke

On Sat, 08 Nov 2014 11:34:48 -0600, Richard
wrote:

On 11/7/2014 12:08 PM, Ian Malcolm wrote:
wrote in news:Ydqdncz1e6oLZ8HJnZ2dnUU7-
:
Not at all.
But you COULD say that gelcoat is nothing but laminating resin with WAX
added...

No. Commercial gelcoat does *NOT* contain wax as it would impair the bond
to the laminating resin in the layup being applied to the gelcoat in the
mold. Flocoat contains wax for a non-tacky surface cure. Some entry
level gelcoat repair kits contain wax, but if you are serious, you either
seal polythene sheet over the repair to exclude air or use wax in styrene
additive.


Ok, I guess I'll retract that.

The stuff I use does have wax so that it is self sealing, but I take the
point...

The stuff you have likely is made for applying *after* a part is
pulled from a mold, on the outside of the laminate.. You need the wax
for that, or the surface could stay tacky forever. As Ian says, there
are better ways to block the air from the gelcoat, but most external
application is repair work, and, at Ranger, we added wax (or our
repair specialist did) for making patches.

Gelcoat sprayed in a mold, where it's covered with layers of glass and
resin, doesn't need it -- and is much better off without it.

The gelcoat-to-laminate bond is the most critical one, and needs the
strongest bond. Since I have a few minutes g let me try to add to
this discussion.

Polyester resin is a very poor adhesive. If you lay one layer of cloth
or woven roving (which is very coarse cloth) on top of another, the
peel strength and shear strength are very poor. The same is true if
you lay any fiberglass, including random-oriented mat, on top of
already-sured resin or even gelled, but not cured resin. That's what
happens when you lay the first layer of mat (or veil -- see below) on
top of the gelcoat in a mold. It has to be firmly gelled before you do
that or you'll poke through the gelcoat. And the result of letting the
gelcoat partially gel before continuing the laminating is that you
need all the help you can get to stick it to the next layer of
laminate -- no wax, please.

Now, about the interlayer strength of the laminate. Again, adhesive
strength of polyester resin is very poor. Cloth-to-cloth layers often
can be peeled apart by hand. The highest quality laminates, as in
expensive racing dinghies, use a minimum of mat because mat layers are
weak. But those boats, like all other expertly done polyester
laminates, must use mat between layers of cloth. Or they use veil,
also called "scrim," which is a very thin, semi-transparent layer of
mat. You get the best strength-to-weight, and stiffness-to-weight,
using veil and fairly light layers of cloth. (you can look up E-glass
versus S-glass to get more detail on making the best polyester
laminates.)

When the resin, or the styrene monomer in the resin, dissolves the
binder that holds dry mat together, the fibers get loose and tend to
"cog" their way into the layers of cloth above and below as the layers
are brushed out, and poked with the brush, or rolled out with a disk
roller. This assumes that all layers are still wet.

That's where the interlayer strength comes from. Polyester is a lousy
adhesive but it has decent bulk strength, in a laminate, at least, and
it holds those cogged pieces of mat into an interlocked mass with the
cloth. (The cloth is inherently stronger because of the long-fiber
orientation, not really because the fibers are just longer.) That
overcomes the lack of peel strength and sheer strength in the resin.
Unfortunately, you can't achieve the high glass-to-resin ratios with
mat that you can with cloth, so the mat parts of a laminate are
inherently weaker and a lot less flexible. Any boat that uses more
than a minimum necessary amount of mat is less strong -- but cheaper
to build.

About wax: The best deal is to use resin without wax until you get to
the last layer, the one that will be cured while exposed to air. But
the wax dissolves in the resin, and, if you lay one layer of waxed
resin on rop of another, most of the wax will dissolve again and rise
to the top. How much, I don't know, but I know that many boats have
been made with waxed resin in each layer of laminate, and I've never
heard of it causing a delaminating problem by itself. Maybe it does;
perhaps Ian knows.

One final thing: None of this applies to epoxy laminates. Epoxy has
such strong adhesive properties that you can laminate one layer of
cloth on top of another. Epoxy laminates are a lot stronger to begin
with. Avoiding the use of mat makes them even stronger.

Watch out, though, that your glass cloth, or mat if you use any with
epoxy, are made for use with epoxy. The finish on glass cloth made for
polyester is actually weaker than a straight glass-to-epoxy bond.
Don't use it.

As for mat, the binder won't dissolve in epoxy. Try it, and you're
likely to get a real mess. (this is the voice of sad experience --
before I learned about this). But you shouldn't be using mat with
epoxy in the first place. Epoxy make a much stronger laminate without
it.

Phwew. g

--
Ed Huntress

On Sat, 08 Nov 2014 09:48:00 -0800, Gunner Asch
wrote:

On Thu, 06 Nov 2014 08:41:26 -0600, Richard
wrote:

On 11/6/2014 7:28 AM, Ed Huntress wrote:
John, this has been bugging the heck out of me -- I really hate it
when I don't have a precise answer, so I did some checking to see that
the story is on polyester gelcooat resin.

Quality commercial gelcoats are made from an entirely different resin
than laminating resin. Gelcoats are based on ISO/NPG
(Isophthalic/Neopentyl Glychol) resins, which are much stronger,
clearer, and more scratch-resistant than ordinary laminating resin,
which is orthophthalic resin. In the course of checking this out I
read that high-quality boatbuilders are switching to ISO/NPG resin for
laminating, too, but that wasn't true when I was involved with it, so
I don't know anything about that.

You no doubt know that common plastic laminating resins, particularly
epoxy, have no natural thixotropic properties. Spray or brush them on
a vertical surface, and they drool. Commerical polyester gelcoat
resins are loaded with thixotropic agents so you can lay on a fairly
thick, even coat that doesn't drool. If you cut all the way through
the gelcoat on a cheap boat, you may find that the gelcoat is very
uneven in thickness. Sometimes you can see this as ripples on the
outside surface, because shrinkage upon curing makes the
thick-and-thin stand out. But most builders conquered that problem
decades ago. In the US, they use commercial gelcoat resin from the
start.

FWIW, even ISO/NPG resin, compared to most other resin systems, is
weak and brittle. Without the glass fiber in it for reinforcement, a
good gelcoat resin is mechanically much weaker than the laminate
beneath it. But it does the job acceptably well. And, as you pointed
out, it's cheap. g


Excellent research, Ed.

After all this comes the actual mix.

The resin to catalyst ratio is a few drops of MEKP
(methylethelkeytoneperoxide) per pound of resin.
So how big is a drop?
Rule of thumb? Roughly 50 CCs per gallon?
So you can see that a little bit goes a LONG way.

What might be the results from variations in the mix?

Or how well mixed the mix is in the first place?

At what temperature is this all done?

Humidity?

Alignment of the stars and planets?

Lots of possible very small variations that have rather profound
effects in the end product.

Indeed! Well stated.

With Luck and the sacrifice of ones first born child..one might get a
color match. As for its strength..it has none and it is rather
brittle as witnessed by the "spiderwebbing" on boat hulls in impact
zones and flex points

Good points. Spider cracks are more of a problem in thin hulls, but
evern good polyester gelcoat on a thicker hull is not immune. Two-part
polyurethane generally is. Thus, some of the very best racing boats
are built with no gelcoat at all, and are sprayed with polyurethane
after they're pulled from the mold.

Color matching patches is a job for a very experienced pro, and even
then, God help you if your boat is a medium color, like red or medium
blue.

--
Ed Hutnress

On 11/8/2014 12:16 PM, Ed Huntress wrote:
On Sat, 08 Nov 2014 11:34:48 -0600,
wrote:

On 11/7/2014 12:08 PM, Ian Malcolm wrote:
wrote in news:Ydqdncz1e6oLZ8HJnZ2dnUU7-
:
Not at all.
But you COULD say that gelcoat is nothing but laminating resin with WAX
added...

No. Commercial gelcoat does *NOT* contain wax as it would impair the bond
to the laminating resin in the layup being applied to the gelcoat in the
mold. Flocoat contains wax for a non-tacky surface cure. Some entry
level gelcoat repair kits contain wax, but if you are serious, you either
seal polythene sheet over the repair to exclude air or use wax in styrene
additive.


Ok, I guess I'll retract that.

The stuff I use does have wax so that it is self sealing, but I take the
point...

The stuff you have likely is made for applying *after* a part is
pulled from a mold, on the outside of the laminate.. You need the wax
for that, or the surface could stay tacky forever. As Ian says, there
are better ways to block the air from the gelcoat, but most external
application is repair work, and, at Ranger, we added wax (or our
repair specialist did) for making patches.

Gelcoat sprayed in a mold, where it's covered with layers of glass and
resin, doesn't need it -- and is much better off without it.

The gelcoat-to-laminate bond is the most critical one, and needs the
strongest bond. Since I have a few minutesg let me try to add to
this discussion.

Polyester resin is a very poor adhesive. If you lay one layer of cloth
or woven roving (which is very coarse cloth) on top of another, the
peel strength and shear strength are very poor. The same is true if
you lay any fiberglass, including random-oriented mat, on top of
already-sured resin or even gelled, but not cured resin. That's what
happens when you lay the first layer of mat (or veil -- see below) on
top of the gelcoat in a mold. It has to be firmly gelled before you do
that or you'll poke through the gelcoat. And the result of letting the
gelcoat partially gel before continuing the laminating is that you
need all the help you can get to stick it to the next layer of
laminate -- no wax, please.

Now, about the interlayer strength of the laminate. Again, adhesive
strength of polyester resin is very poor. Cloth-to-cloth layers often
can be peeled apart by hand. The highest quality laminates, as in
expensive racing dinghies, use a minimum of mat because mat layers are
weak. But those boats, like all other expertly done polyester
laminates, must use mat between layers of cloth. Or they use veil,
also called "scrim," which is a very thin, semi-transparent layer of
mat. You get the best strength-to-weight, and stiffness-to-weight,
using veil and fairly light layers of cloth. (you can look up E-glass
versus S-glass to get more detail on making the best polyester
laminates.)

When the resin, or the styrene monomer in the resin, dissolves the
binder that holds dry mat together, the fibers get loose and tend to
"cog" their way into the layers of cloth above and below as the layers
are brushed out, and poked with the brush, or rolled out with a disk
roller. This assumes that all layers are still wet.

That's where the interlayer strength comes from. Polyester is a lousy
adhesive but it has decent bulk strength, in a laminate, at least, and
it holds those cogged pieces of mat into an interlocked mass with the
cloth. (The cloth is inherently stronger because of the long-fiber
orientation, not really because the fibers are just longer.) That
overcomes the lack of peel strength and sheer strength in the resin.
Unfortunately, you can't achieve the high glass-to-resin ratios with
mat that you can with cloth, so the mat parts of a laminate are
inherently weaker and a lot less flexible. Any boat that uses more
than a minimum necessary amount of mat is less strong -- but cheaper
to build.

About wax: The best deal is to use resin without wax until you get to
the last layer, the one that will be cured while exposed to air. But
the wax dissolves in the resin, and, if you lay one layer of waxed
resin on rop of another, most of the wax will dissolve again and rise
to the top. How much, I don't know, but I know that many boats have
been made with waxed resin in each layer of laminate, and I've never
heard of it causing a delaminating problem by itself. Maybe it does;
perhaps Ian knows.

One final thing: None of this applies to epoxy laminates. Epoxy has
such strong adhesive properties that you can laminate one layer of
cloth on top of another. Epoxy laminates are a lot stronger to begin
with. Avoiding the use of mat makes them even stronger.

Watch out, though, that your glass cloth, or mat if you use any with
epoxy, are made for use with epoxy. The finish on glass cloth made for
polyester is actually weaker than a straight glass-to-epoxy bond.
Don't use it.

As for mat, the binder won't dissolve in epoxy. Try it, and you're
likely to get a real mess. (this is the voice of sad experience --
before I learned about this). But you shouldn't be using mat with
epoxy in the first place. Epoxy make a much stronger laminate without
it.

Phwew.g


Preaching to the choir, Ed. I'm an epoxy guy.
I've used polyester in the (far) past, but gave it up as soon as I
found the light.

My first love was Dow 330, but it's not made any more.
It was fairly benign stuff as toxic chemicals go, but would crystallize
at cool temps. One only had to warm it up to be usable again, but that
was too much hassle for too many users.

These days it's mostly West 105, unless there is a physical requirement
that is beyond what that stuff can provide.

Strictly volan coated woven glass for me.

On Sat, 08 Nov 2014 15:45:53 -0600, Richard
wrote:

On 11/8/2014 12:16 PM, Ed Huntress wrote:
On Sat, 08 Nov 2014 11:34:48 -0600,
wrote:

On 11/7/2014 12:08 PM, Ian Malcolm wrote:
wrote in news:Ydqdncz1e6oLZ8HJnZ2dnUU7-
:
Not at all.
But you COULD say that gelcoat is nothing but laminating resin with WAX
added...

No. Commercial gelcoat does *NOT* contain wax as it would impair the bond
to the laminating resin in the layup being applied to the gelcoat in the
mold. Flocoat contains wax for a non-tacky surface cure. Some entry
level gelcoat repair kits contain wax, but if you are serious, you either
seal polythene sheet over the repair to exclude air or use wax in styrene
additive.


Ok, I guess I'll retract that.

The stuff I use does have wax so that it is self sealing, but I take the
point...

The stuff you have likely is made for applying *after* a part is
pulled from a mold, on the outside of the laminate.. You need the wax
for that, or the surface could stay tacky forever. As Ian says, there
are better ways to block the air from the gelcoat, but most external
application is repair work, and, at Ranger, we added wax (or our
repair specialist did) for making patches.

Gelcoat sprayed in a mold, where it's covered with layers of glass and
resin, doesn't need it -- and is much better off without it.

The gelcoat-to-laminate bond is the most critical one, and needs the
strongest bond. Since I have a few minutesg let me try to add to
this discussion.

Polyester resin is a very poor adhesive. If you lay one layer of cloth
or woven roving (which is very coarse cloth) on top of another, the
peel strength and shear strength are very poor. The same is true if
you lay any fiberglass, including random-oriented mat, on top of
already-sured resin or even gelled, but not cured resin. That's what
happens when you lay the first layer of mat (or veil -- see below) on
top of the gelcoat in a mold. It has to be firmly gelled before you do
that or you'll poke through the gelcoat. And the result of letting the
gelcoat partially gel before continuing the laminating is that you
need all the help you can get to stick it to the next layer of
laminate -- no wax, please.

Now, about the interlayer strength of the laminate. Again, adhesive
strength of polyester resin is very poor. Cloth-to-cloth layers often
can be peeled apart by hand. The highest quality laminates, as in
expensive racing dinghies, use a minimum of mat because mat layers are
weak. But those boats, like all other expertly done polyester
laminates, must use mat between layers of cloth. Or they use veil,
also called "scrim," which is a very thin, semi-transparent layer of
mat. You get the best strength-to-weight, and stiffness-to-weight,
using veil and fairly light layers of cloth. (you can look up E-glass
versus S-glass to get more detail on making the best polyester
laminates.)

When the resin, or the styrene monomer in the resin, dissolves the
binder that holds dry mat together, the fibers get loose and tend to
"cog" their way into the layers of cloth above and below as the layers
are brushed out, and poked with the brush, or rolled out with a disk
roller. This assumes that all layers are still wet.

That's where the interlayer strength comes from. Polyester is a lousy
adhesive but it has decent bulk strength, in a laminate, at least, and
it holds those cogged pieces of mat into an interlocked mass with the
cloth. (The cloth is inherently stronger because of the long-fiber
orientation, not really because the fibers are just longer.) That
overcomes the lack of peel strength and sheer strength in the resin.
Unfortunately, you can't achieve the high glass-to-resin ratios with
mat that you can with cloth, so the mat parts of a laminate are
inherently weaker and a lot less flexible. Any boat that uses more
than a minimum necessary amount of mat is less strong -- but cheaper
to build.

About wax: The best deal is to use resin without wax until you get to
the last layer, the one that will be cured while exposed to air. But
the wax dissolves in the resin, and, if you lay one layer of waxed
resin on rop of another, most of the wax will dissolve again and rise
to the top. How much, I don't know, but I know that many boats have
been made with waxed resin in each layer of laminate, and I've never
heard of it causing a delaminating problem by itself. Maybe it does;
perhaps Ian knows.

One final thing: None of this applies to epoxy laminates. Epoxy has
such strong adhesive properties that you can laminate one layer of
cloth on top of another. Epoxy laminates are a lot stronger to begin
with. Avoiding the use of mat makes them even stronger.

Watch out, though, that your glass cloth, or mat if you use any with
epoxy, are made for use with epoxy. The finish on glass cloth made for
polyester is actually weaker than a straight glass-to-epoxy bond.
Don't use it.

As for mat, the binder won't dissolve in epoxy. Try it, and you're
likely to get a real mess. (this is the voice of sad experience --
before I learned about this). But you shouldn't be using mat with
epoxy in the first place. Epoxy make a much stronger laminate without
it.

Phwew.g


Preaching to the choir, Ed. I'm an epoxy guy.
I've used polyester in the (far) past, but gave it up as soon as I
found the light.

My first love was Dow 330, but it's not made any more.
It was fairly benign stuff as toxic chemicals go, but would crystallize
at cool temps. One only had to warm it up to be usable again, but that
was too much hassle for too many users.

These days it's mostly West 105, unless there is a physical requirement
that is beyond what that stuff can provide.

Strictly volan coated woven glass for me.

I use both for small projects, depending on what is needed. I made
some giant clams out of polyester and mat, with a thin cloth coating,
for my wife's classroom presentation about the deep sea. I figured
they'd last long enough. g

I'm a fan of the WEST System, but I usually use System Three. It is,
or was, a lot less expensive. I've had good results with both.

BTW, speaking of the WEST System, I've sailed with the Gougeon
brothers, on Adazio, when all three were young.

http://www.westsystem.com/ss/old-lad...-70-mph-blast/

--
Ed Huntress

On 11/8/2014 3:57 PM, Ed Huntress wrote:
On Sat, 08 Nov 2014 15:45:53 -0600, Richard
wrote:

On 11/8/2014 12:16 PM, Ed Huntress wrote:
On Sat, 08 Nov 2014 11:34:48 -0600,
wrote:

On 11/7/2014 12:08 PM, Ian Malcolm wrote:
wrote in news:Ydqdncz1e6oLZ8HJnZ2dnUU7-
:
Not at all.
But you COULD say that gelcoat is nothing but laminating resin with WAX
added...

No. Commercial gelcoat does *NOT* contain wax as it would impair the bond
to the laminating resin in the layup being applied to the gelcoat in the
mold. Flocoat contains wax for a non-tacky surface cure. Some entry
level gelcoat repair kits contain wax, but if you are serious, you either
seal polythene sheet over the repair to exclude air or use wax in styrene
additive.


Ok, I guess I'll retract that.

The stuff I use does have wax so that it is self sealing, but I take the
point...

The stuff you have likely is made for applying *after* a part is
pulled from a mold, on the outside of the laminate.. You need the wax
for that, or the surface could stay tacky forever. As Ian says, there
are better ways to block the air from the gelcoat, but most external
application is repair work, and, at Ranger, we added wax (or our
repair specialist did) for making patches.

Gelcoat sprayed in a mold, where it's covered with layers of glass and
resin, doesn't need it -- and is much better off without it.

The gelcoat-to-laminate bond is the most critical one, and needs the
strongest bond. Since I have a few minutesg let me try to add to
this discussion.

Polyester resin is a very poor adhesive. If you lay one layer of cloth
or woven roving (which is very coarse cloth) on top of another, the
peel strength and shear strength are very poor. The same is true if
you lay any fiberglass, including random-oriented mat, on top of
already-sured resin or even gelled, but not cured resin. That's what
happens when you lay the first layer of mat (or veil -- see below) on
top of the gelcoat in a mold. It has to be firmly gelled before you do
that or you'll poke through the gelcoat. And the result of letting the
gelcoat partially gel before continuing the laminating is that you
need all the help you can get to stick it to the next layer of
laminate -- no wax, please.

Now, about the interlayer strength of the laminate. Again, adhesive
strength of polyester resin is very poor. Cloth-to-cloth layers often
can be peeled apart by hand. The highest quality laminates, as in
expensive racing dinghies, use a minimum of mat because mat layers are
weak. But those boats, like all other expertly done polyester
laminates, must use mat between layers of cloth. Or they use veil,
also called "scrim," which is a very thin, semi-transparent layer of
mat. You get the best strength-to-weight, and stiffness-to-weight,
using veil and fairly light layers of cloth. (you can look up E-glass
versus S-glass to get more detail on making the best polyester
laminates.)

When the resin, or the styrene monomer in the resin, dissolves the
binder that holds dry mat together, the fibers get loose and tend to
"cog" their way into the layers of cloth above and below as the layers
are brushed out, and poked with the brush, or rolled out with a disk
roller. This assumes that all layers are still wet.

That's where the interlayer strength comes from. Polyester is a lousy
adhesive but it has decent bulk strength, in a laminate, at least, and
it holds those cogged pieces of mat into an interlocked mass with the
cloth. (The cloth is inherently stronger because of the long-fiber
orientation, not really because the fibers are just longer.) That
overcomes the lack of peel strength and sheer strength in the resin.
Unfortunately, you can't achieve the high glass-to-resin ratios with
mat that you can with cloth, so the mat parts of a laminate are
inherently weaker and a lot less flexible. Any boat that uses more
than a minimum necessary amount of mat is less strong -- but cheaper
to build.

About wax: The best deal is to use resin without wax until you get to
the last layer, the one that will be cured while exposed to air. But
the wax dissolves in the resin, and, if you lay one layer of waxed
resin on rop of another, most of the wax will dissolve again and rise
to the top. How much, I don't know, but I know that many boats have
been made with waxed resin in each layer of laminate, and I've never
heard of it causing a delaminating problem by itself. Maybe it does;
perhaps Ian knows.

One final thing: None of this applies to epoxy laminates. Epoxy has
such strong adhesive properties that you can laminate one layer of
cloth on top of another. Epoxy laminates are a lot stronger to begin
with. Avoiding the use of mat makes them even stronger.

Watch out, though, that your glass cloth, or mat if you use any with
epoxy, are made for use with epoxy. The finish on glass cloth made for
polyester is actually weaker than a straight glass-to-epoxy bond.
Don't use it.

As for mat, the binder won't dissolve in epoxy. Try it, and you're
likely to get a real mess. (this is the voice of sad experience --
before I learned about this). But you shouldn't be using mat with
epoxy in the first place. Epoxy make a much stronger laminate without
it.

Phwew.g


Preaching to the choir, Ed. I'm an epoxy guy.
I've used polyester in the (far) past, but gave it up as soon as I
found the light.

My first love was Dow 330, but it's not made any more.
It was fairly benign stuff as toxic chemicals go, but would crystallize
at cool temps. One only had to warm it up to be usable again, but that
was too much hassle for too many users.

These days it's mostly West 105, unless there is a physical requirement
that is beyond what that stuff can provide.

Strictly volan coated woven glass for me.

I use both for small projects, depending on what is needed. I made
some giant clams out of polyester and mat, with a thin cloth coating,
for my wife's classroom presentation about the deep sea. I figured
they'd last long enough. g

I'm a fan of the WEST System, but I usually use System Three. It is,
or was, a lot less expensive. I've had good results with both.

BTW, speaking of the WEST System, I've sailed with the Gougeon
brothers, on Adazio, when all three were young.

http://www.westsystem.com/ss/old-lad...-70-mph-blast/

Nice read.

Martin

On Sat, 08 Nov 2014 13:16:28 -0500, Ed Huntress
wrote:

On Sat, 08 Nov 2014 11:34:48 -0600, Richard
wrote:

On 11/7/2014 12:08 PM, Ian Malcolm wrote:
wrote in news:Ydqdncz1e6oLZ8HJnZ2dnUU7-
:
Not at all.
But you COULD say that gelcoat is nothing but laminating resin with WAX
added...

No. Commercial gelcoat does *NOT* contain wax as it would impair the bond
to the laminating resin in the layup being applied to the gelcoat in the
mold. Flocoat contains wax for a non-tacky surface cure. Some entry
level gelcoat repair kits contain wax, but if you are serious, you either
seal polythene sheet over the repair to exclude air or use wax in styrene
additive.


Ok, I guess I'll retract that.

The stuff I use does have wax so that it is self sealing, but I take the
point...

The stuff you have likely is made for applying *after* a part is
pulled from a mold, on the outside of the laminate.. You need the wax
for that, or the surface could stay tacky forever. As Ian says, there
are better ways to block the air from the gelcoat, but most external
application is repair work, and, at Ranger, we added wax (or our
repair specialist did) for making patches.

Gelcoat sprayed in a mold, where it's covered with layers of glass and
resin, doesn't need it -- and is much better off without it.

The gelcoat-to-laminate bond is the most critical one, and needs the
strongest bond. Since I have a few minutes g let me try to add to
this discussion.

Polyester resin is a very poor adhesive. If you lay one layer of cloth
or woven roving (which is very coarse cloth) on top of another, the
peel strength and shear strength are very poor. The same is true if
you lay any fiberglass, including random-oriented mat, on top of
already-sured resin or even gelled, but not cured resin. That's what
happens when you lay the first layer of mat (or veil -- see below) on
top of the gelcoat in a mold. It has to be firmly gelled before you do
that or you'll poke through the gelcoat. And the result of letting the
gelcoat partially gel before continuing the laminating is that you
need all the help you can get to stick it to the next layer of
laminate -- no wax, please.

Now, about the interlayer strength of the laminate. Again, adhesive
strength of polyester resin is very poor. Cloth-to-cloth layers often
can be peeled apart by hand. The highest quality laminates, as in
expensive racing dinghies, use a minimum of mat because mat layers are
weak. But those boats, like all other expertly done polyester
laminates, must use mat between layers of cloth. Or they use veil,
also called "scrim," which is a very thin, semi-transparent layer of
mat. You get the best strength-to-weight, and stiffness-to-weight,
using veil and fairly light layers of cloth. (you can look up E-glass
versus S-glass to get more detail on making the best polyester
laminates.)

When the resin, or the styrene monomer in the resin, dissolves the
binder that holds dry mat together, the fibers get loose and tend to
"cog" their way into the layers of cloth above and below as the layers
are brushed out, and poked with the brush, or rolled out with a disk
roller. This assumes that all layers are still wet.

That's where the interlayer strength comes from. Polyester is a lousy
adhesive but it has decent bulk strength, in a laminate, at least, and
it holds those cogged pieces of mat into an interlocked mass with the
cloth. (The cloth is inherently stronger because of the long-fiber
orientation, not really because the fibers are just longer.) That
overcomes the lack of peel strength and sheer strength in the resin.
Unfortunately, you can't achieve the high glass-to-resin ratios with
mat that you can with cloth, so the mat parts of a laminate are
inherently weaker and a lot less flexible. Any boat that uses more
than a minimum necessary amount of mat is less strong -- but cheaper
to build.

About wax: The best deal is to use resin without wax until you get to
the last layer, the one that will be cured while exposed to air. But
the wax dissolves in the resin, and, if you lay one layer of waxed
resin on rop of another, most of the wax will dissolve again and rise
to the top. How much, I don't know, but I know that many boats have
been made with waxed resin in each layer of laminate, and I've never
heard of it causing a delaminating problem by itself. Maybe it does;
perhaps Ian knows.

One final thing: None of this applies to epoxy laminates. Epoxy has
such strong adhesive properties that you can laminate one layer of
cloth on top of another. Epoxy laminates are a lot stronger to begin
with. Avoiding the use of mat makes them even stronger.

Watch out, though, that your glass cloth, or mat if you use any with
epoxy, are made for use with epoxy. The finish on glass cloth made for
polyester is actually weaker than a straight glass-to-epoxy bond.
Don't use it.

As for mat, the binder won't dissolve in epoxy. Try it, and you're
likely to get a real mess. (this is the voice of sad experience --
before I learned about this). But you shouldn't be using mat with
epoxy in the first place. Epoxy make a much stronger laminate without
it.

Phwew. g

While you are accurate in saying that the binder used in common
chopped mat is dissolved by styrene based resins and not by epoxy
resins, common chopped mat can still be used with epoxy.

If you are careful and completely wet out chopped mat with epoxy you
can make a composite that is very satisfactory for most uses. The
difference between water absorbency between epoxy and cloth and epoxy
and chopped mat, for example, is about 0.4%.

The WEST Systems people have done tests of epoxy and common chopped
mate, see:
http://www.westsystem.com/ss/chopped-strand-mat-epoxy/
and while they don't suggest it as a first choice they do say that it
is usable.

I might mention that I've used a fair amount of chopped mat with epoxy
with no problems whatsoever. Not, I might add, because I thought it
was better but because I had a considerable amount of it on hand and
no woven cloth of the right weight :-)
--
Cheers,

John B.