I'm building another aquarium stand for a 90 gallon tank. The previous stand
was built with 2x4's using half lap joints and a plywood skin. I wanted to
build the new stand (open top) using face frame construction with 1x4 oak
for the rails and 1x3 oak for the stiles. I was originally considering using
pocket joinery to fasten it all together, but I've been reading about pocket
screws working loose in moist environments. Does this story hold water or is
it over blown?

Bill Stock wrote:
I'm building another aquarium stand for a 90 gallon tank. The previous stand
was built with 2x4's using half lap joints and a plywood skin. I wanted to
build the new stand (open top) using face frame construction with 1x4 oak
for the rails and 1x3 oak for the stiles. I was originally considering using
pocket joinery to fasten it all together, but I've been reading about pocket
screws working loose in moist environments. Does this story hold water or is
it over blown?

I think that you'd be fine as long as you use glue on the joints in
addition to the pocket hole screws. Make sure that you use a glue made
for damp applications, such as Gorrilla Glue or Titebond III.

Apart from the joinery, are 1x3's and 1x4's strong enough to hold the
weight of a 90 tank? This will depend largely on your construction
details.

Bill Stock wrote:
I'm building another aquarium stand for a 90 gallon tank. The previous stand
was built with 2x4's using half lap joints and a plywood skin. I wanted to
build the new stand (open top) using face frame construction with 1x4 oak
for the rails and 1x3 oak for the stiles. I was originally considering using
pocket joinery to fasten it all together, but I've been reading about pocket
screws working loose in moist environments. Does this story hold water or is
it over blown?

750 lbs just in water, I wouldn't trust that to a frame that is just
screwed together butt joints.

Pocket hole joinery is meant to "hold until the glue dries"
not actually create a joint. It is quite strong without glue
but only in non-loadbearing situations, which is rare.

It should have been called pocket hole clamping...

Do a little reading from the folks who made it
famous for the average woodworker...

http://kregtool.com/education_center...p?FAQ_CAT_ID=1


RayV wrote:

Bill Stock wrote:

I'm building another aquarium stand for a 90 gallon tank.

Mike wrote:

Apart from the joinery, are 1x3's and 1x4's strong enough to hold the
weight of a 90 tank? This will depend largely on your construction
details.

I built one for a 30 gallon tank using 3/4" plywood. No problems yet.

And oak is a lot stronger than plywood. Wood in compression is remarkably
strong. If this is the standard 90 gallon tank (48x18) I'd use two vertical
dividers and tie all together with a fixed horizontal shelf.

Don't forget to rest the tank on a piece of rigid insulation foam. Makes up
for any little irregularities in your construction.

For those still wondering about strength, visit your local pet store and look
inside some of the particle board stands they sell :-).

--
It's turtles, all the way down

"Larry Blanchard" wrote in message
...
Mike wrote:

Apart from the joinery, are 1x3's and 1x4's strong enough to hold the
weight of a 90 tank? This will depend largely on your construction
details.

I built one for a 30 gallon tank using 3/4" plywood. No problems yet.

And oak is a lot stronger than plywood. Wood in compression is remarkably
strong. If this is the standard 90 gallon tank (48x18) I'd use two
vertical
dividers and tie all together with a fixed horizontal shelf.

Yes I plan on 16" supports, so even 1x4 is probably overkill based on the
span calculator I checked.

Don't forget to rest the tank on a piece of rigid insulation foam. Makes
up
for any little irregularities in your construction.

Thanks Larry, but this one won't have a top, just an edge frame. The tank
has an overflow (bottom plumbing) so it will just be edge supported.

Below is a quote directly from the site you referenced.

How strong is a pocket hole joint compared to a mortise and tenon joint?
This is a question we get asked quite often. A independent lab completed
testing a few years back that showed that a pocket hole joint failed at 707
pounds when subjected to a shear load while a mortise and tenon joint failed
at 453 pounds (approximately 35% stronger). Pocket hole joints are
tremendously strong for a couple of reasons. 1. The use of a mechanical
fastener (screw) is significantly stronger than the material around it
(wood), and 2. The amount of direct clamping force placed on the joint by
driving the screw combined with today's glue technology makes for a
sensationally strong bond.





"Pat Barber" wrote in message
...
Pocket hole joinery is meant to "hold until the glue dries"
not actually create a joint. It is quite strong without glue
but only in non-loadbearing situations, which is rare.

It should have been called pocket hole clamping...

Do a little reading from the folks who made it
famous for the average woodworker...

http://kregtool.com/education_center...p?FAQ_CAT_ID=1


RayV wrote:

Bill Stock wrote:

I'm building another aquarium stand for a 90 gallon tank.

"CW" wrote in message
ink.net...
Below is a quote directly from the site you referenced.

How strong is a pocket hole joint compared to a mortise and tenon joint?
This is a question we get asked quite often. A independent lab completed
testing a few years back that showed that a pocket hole joint failed at
707
pounds when subjected to a shear load while a mortise and tenon joint
failed
at 453 pounds (approximately 35% stronger). Pocket hole joints are
tremendously strong for a couple of reasons. 1. The use of a mechanical
fastener (screw) is significantly stronger than the material around it
(wood), and 2. The amount of direct clamping force placed on the joint by
driving the screw combined with today's glue technology makes for a
sensationally strong bond.

Yes, but this would appear to be at a point in time and does not address the
strength of the joint over time. Although they do address the "weather"
issue in another point.

[quote]
I am afraid to use pocket holes because I am worried about wood expanding
and contracting with changes in the weather. What do you recommend?

There are a couple of easy ways to compensate for this type of wood
movement. Let's assume an example of attaching a rail or apron to a solid
tabletop. First, set your depth collar on the drill bit so you barely drill
through the edge of the rail or apron. This will create a larger pilot hole
for the screw shank and will create the effect of a "floating top".
Secondly, drive the screw into the top until tightened, then back off 1/4 of
a turn.

. A independent lab completed
testing a few years back that showed that a pocket hole joint failed at
707
pounds when subjected to a shear load while a mortise and tenon joint
failed
at 453 pounds (approximately 35% stronger).
Snipped

"Sheer load"

Of course this is dependant upon the OP's design, but I suspect that the
mode of failure that would be of greatest concern would be racking force
resulting in screw withdrawal.

-Steve

Bill Stock wrote:
I'm building another aquarium stand for a 90 gallon tank. The previous stand
was built with 2x4's using half lap joints and a plywood skin. I wanted to
build the new stand (open top) using face frame construction with 1x4 oak
for the rails and 1x3 oak for the stiles. I was originally considering using
pocket joinery to fasten it all together, but I've been reading about pocket
screws working loose in moist environments. Does this story hold water or is
it over blown?

My big tank stand was made with pocket screws and glue. The high end
stands at the big pet store are built similiarly.. in fact, they go so
far as to pockethole the plywood sides together on the carcass.

Anyhow, my stand has worked fine for approximately 5 years.

The scary thing I've seen is people using particle board/MDF for big
tank stands (even commerical ones)

C & S wrote:

"Sheer load"

Of course this is dependant upon the OP's design, but I suspect that the
mode of failure that would be of greatest concern would be racking force
resulting in screw withdrawal.

-Steve

Good point on racking, but I'm sure the OP will put a plywood back on
his stand.
That will hold the case square.

Bill Stock wrote:

Don't forget to rest the tank on a piece of rigid insulation foam.**Makes
up
for any little irregularities in your construction.

Thanks Larry, but this one won't have a top, just an edge frame. The tank
has an overflow (bottom plumbing) so it will just be edge supported.

That makes no difference. All tanks are supported solely by the edges,
regardless of whether or not the top of the stand is solid. The foam still
evens out any little irregularities in the stand that might put a heavier
load on the tank frame at a specific point and cause it to rack. You could
cut the center out of the foam for the plumbing.

I will admit that this is an issue on which there is a lot of argument. Some
say it's overkill. But I say it's cheap insurance.

--
It's turtles, all the way down