Hi everyone,

Related the rusty boat deck described in my previous question "Cutting
bolt with minimal heat" I encountered a new problem.

Most of the steel of my 4 mm mild steel deck is fortunately still
there, but there is one place where a section of about 20x40 cm is
completely eaten away by rust. I´m planning to cut out this area as
far until the surrounding steel is again 3-4 mm and weld a new piece
of metal in there. Only complication is that the deck is slightly
curved. Not much, but enough to make a flat piece of steel plate look
ugly there.

What I would like to ask is what the normal procedure is to fit a new
4 mm mild steel piece in the hole following the curve of the
surrounding area. The curve is mainly in one direction and in the
middle approx 1 cm away from the "straight line". Perhaps there is
also some (much smaller) slight curvature in the other direction.

I thought about preforming the metal on a roller, but measurement is
not easy for that. I´d rather take some in-situ approach. Only the
material is too thick to deform with simple tools. Perhaps welding
some sort of long lever on the plate and use that to curve it while
tacking every spot that is on the right position? And cutting the
lever away afterwards? Or is it possible to use a propane burner to
heat the material and have it bend itself?

Related to this I´m also not sure if any problems might occur after
the piece is tack welded in the perfect position. Can it deform while
make the final welding all around? I´ve heard that in bad repair jobs
like this, the curving "flips" inward.

I´d be very happy with any comments on this.

Joost

Hi Joost,
While you will get good responses here, you may also try rec.boats.building.
For the job you are describing, you neednt be too accurate with the rolling.
For a job like this, what we would usually do is just put it through a
roller to 'break its back' as the technique is known. Once you have put
even the slightest roll in the plate, it will flex more easily. Once you
have rolled it, it doesnt matter too much if you went slightly under or
over; this is only 4mm plate. tack the 'straight' side on, then put one
tack on either curved side. Now use dogs and wedges to progressively pull
the pate and tack it in place an inch at a time. You may even find you can
just tack some pipe or whatever to one end of the plate and use that to
leverage the plate instead of dogging.

Shaun



"joost" wrote in message
...
Hi everyone,

Related the rusty boat deck described in my previous question "Cutting
bolt with minimal heat" I encountered a new problem.

Most of the steel of my 4 mm mild steel deck is fortunately still
there, but there is one place where a section of about 20x40 cm is
completely eaten away by rust. I´m planning to cut out this area as
far until the surrounding steel is again 3-4 mm and weld a new piece
of metal in there. Only complication is that the deck is slightly
curved. Not much, but enough to make a flat piece of steel plate look
ugly there.

What I would like to ask is what the normal procedure is to fit a new
4 mm mild steel piece in the hole following the curve of the
surrounding area. The curve is mainly in one direction and in the
middle approx 1 cm away from the "straight line". Perhaps there is
also some (much smaller) slight curvature in the other direction.

I thought about preforming the metal on a roller, but measurement is
not easy for that. I´d rather take some in-situ approach. Only the
material is too thick to deform with simple tools. Perhaps welding
some sort of long lever on the plate and use that to curve it while
tacking every spot that is on the right position? And cutting the
lever away afterwards? Or is it possible to use a propane burner to
heat the material and have it bend itself?

Related to this I´m also not sure if any problems might occur after
the piece is tack welded in the perfect position. Can it deform while
make the final welding all around? I´ve heard that in bad repair jobs
like this, the curving "flips" inward.

I´d be very happy with any comments on this.

Joost

"joost" wrote in message
...
Hi everyone,

Related the rusty boat deck described in my previous
question "Cutting
bolt with minimal heat" I encountered a new problem.

Most of the steel of my 4 mm mild steel deck is fortunately
still
there, but there is one place where a section of about 20x40
cm is
completely eaten away by rust. I´m planning to cut out this
area as
far until the surrounding steel is again 3-4 mm and weld a
new piece
of metal in there. Only complication is that the deck is
slightly
curved. Not much, but enough to make a flat piece of steel
plate look
ugly there.

What I would like to ask is what the normal procedure is to
fit a new
4 mm mild steel piece in the hole following the curve of the
surrounding area. The curve is mainly in one direction and
in the
middle approx 1 cm away from the "straight line". Perhaps
there is
also some (much smaller) slight curvature in the other
direction.

I thought about preforming the metal on a roller, but
measurement is
not easy for that. I´d rather take some in-situ approach.
Only the
material is too thick to deform with simple tools. Perhaps
welding
some sort of long lever on the plate and use that to curve
it while
tacking every spot that is on the right position? And
cutting the
lever away afterwards? Or is it possible to use a propane
burner to
heat the material and have it bend itself?

Related to this I´m also not sure if any problems might
occur after
the piece is tack welded in the perfect position. Can it
deform while
make the final welding all around? I´ve heard that in bad
repair jobs
like this, the curving "flips" inward.

I´d be very happy with any comments on this.

Joost

Hit it with a hammer. You can stretch a piece of 4mm into a
hemisphere with a hammer
and some patience. It's how woks and steel drums are made.
Doesn't really take a
lot, just tap-tap-tap where you want it to stretch.

"BillM" wrote: (clip) I thought about preforming the metal on a roller, but
measurement is not easy for that.(clip)
^^^^^^^^^^^^^^^^
If you have a set of rolls, and measurement is what's holding you back, this
is my suggestion: mold some plaster of Paris to the deck adjacent to the
hole, and take this into the shop. You know that you will need a bigger
piece than the hole, because rolls don't work on the ends.

On Dec 27, 1:37*pm, "Leo Lichtman"
wrote:
"BillM" *wrote: (clip) I thought about preforming the metal on a roller, but
measurement is not easy for that.(clip)

^^^^^^^^^^^^^^^^
If you have a set of rolls, and measurement is what's holding you back, this
is my suggestion: *mold some plaster of Paris to the deck adjacent to the
hole, and take this into the shop. *You know that you will need a bigger
piece than the hole, because rolls don't work on the ends.

I think the usual way to shape ship plates is to make a wooden
template from the hull or frames and fit the plate to the template.
Trace and cut the curve of the deck next to the opening on the edge of
a piece of plywood. You can block up the edges of the plate and apply
the weight of your car to the center with a jack to curve it, or just
drive over it.

I've had better results slightly overbending a curve by crude means,
then straightening it to fit with a hammer or by jumping on it.

Jim Wilkins

BillM wrote:
"joost" wrote in message
...
Hi everyone,

Related the rusty boat deck described in my previous
question "Cutting
bolt with minimal heat" I encountered a new problem.

Most of the steel of my 4 mm mild steel deck is fortunately
still
there, but there is one place where a section of about 20x40
cm is
completely eaten away by rust. I´m planning to cut out this
area as
far until the surrounding steel is again 3-4 mm and weld a
new piece
of metal in there. Only complication is that the deck is
slightly
curved. Not much, but enough to make a flat piece of steel
plate look
ugly there.

What I would like to ask is what the normal procedure is to
fit a new
4 mm mild steel piece in the hole following the curve of the
surrounding area. The curve is mainly in one direction and
in the
middle approx 1 cm away from the "straight line". Perhaps
there is
also some (much smaller) slight curvature in the other
direction.

I thought about preforming the metal on a roller, but
measurement is
not easy for that. I´d rather take some in-situ approach.
Only the
material is too thick to deform with simple tools. Perhaps
welding
some sort of long lever on the plate and use that to curve
it while
tacking every spot that is on the right position? And
cutting the
lever away afterwards? Or is it possible to use a propane
burner to
heat the material and have it bend itself?

Related to this I´m also not sure if any problems might
occur after
the piece is tack welded in the perfect position. Can it
deform while
make the final welding all around? I´ve heard that in bad
repair jobs
like this, the curving "flips" inward.

I´d be very happy with any comments on this.

Joost

Hit it with a hammer. You can stretch a piece of 4mm into a
hemisphere with a hammer
and some patience. It's how woks and steel drums are made.
Doesn't really take a
lot, just tap-tap-tap where you want it to stretch.



Yeah, lay it on the ground and work it with a three-pounder, pretty easy
to get just the curve you need.

John