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Ericthenorse

Steam bending plywood?

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Can you steam bend plywood??  I haven't actually started building a boat yet, but I have a "moaning chair" and a nice tool box to put my boatbuilding tools in...   I have an old Gerstner tool chest that I want to fix up, and the bottom piece is warped so that the front cover does not close... All of the joints on the box were loose, and I was able to disassemble it quite easily....   I don't want to just replace the pannel since this is where all of the manufacture markings are...  Will plywood even respond to being steamed???

Here is a shot of the box before I litterally pulled it apart...

Boats015.jpg

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Yes, you can steam bend plywood, but wrapping in towels and soaking with boiling water does the same thing on small pieces.

BUT, and this is a huge but-

Many of the really older pieces of furniture and things like your tool chest might not have glue in them that will take the hot water. MANY of the old pieces that have what LOOKS like plywood, don't really have plywood. Many of them have a thin solid core with a veneer laid on it, often with hot hide glue. Hide glue will dissolve in hot water. Makes it simple to restore a pice because it's easy to take apart. I'd bet that's what that chest is put together with.

So test carefully with a small part of the chest that isn't normally visible to be sure BEFORE you try steaming or whatever. Otherwise you might be very unhappy with what happens.

Another way to test is to use a wet rag on the residue in one of the joints. If hot water softens and washes the residue away, it's hide glue - DON"T steam the thing.

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Thanks... I am prety sure that Gerstner uses hide glue to assemble the box, that is why it came apart so easily... It has been stored for the past few years in a very moist place...  The pannel is actual ply, I can see all 7 layers.. Whatever glue they were using in about 1975 is what I have...  I wil give the soaking a try, if it doesn't work, I will just cut a new board... After all, it is just a tool box... And, I have two more similar bases, and three top boxes, so I will not be hurting for tool storage

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1975??? Hey I thought you meant an OLD toolbox!!! 1975 was just a short bit ago- I hadn't even begun building my tri then. ;D

Seriously, by that time they may have switched to a white or yellow glue- but the water test would still work- hot water won't dissolve white or yellow glues.

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Aw Greg- I left Iceland in 1963. I was there for a long long year :)

But, on one of the last flights I made from there, we flew over the boiling smoky area south of Iceland that is now the island of Surtsey- it was just beginning to erupt at that time- no land above water yet.

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1975, that's the year I dropped over 2 thousand Army troops in practice jumps at Fort Campbell KY. I was pilot of a C123 and got over 8 hundred hours that year. The drops were OK, but the assault landings in rough fields was no picnic.

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Torturing plywood into shape with steam has very limited results. The main drawback is the interior veneers don't get the steam, because the hot moisture can't move past the glue lines.

Heat is better and why towels soaked with boiling water works. The towels hold the heat and moisture against the surface longer and the plywood eventually develops a "set".

You can soak the plywood panel under water for 24 hours or longer, which will help a lot, especially if you use hot towels and cuss at it, just the right amount.

Plywood can only be bent to certain radiuses comfortably and reliably. I have a list of radiuses for different panel thicknesses and species, that I refer to when I need to ask a lot out of a piece of plywood.

The risk is over stressing the core veneers, internal defects, permitted voids, etc. The panel may take the tortured shape, but is right at or very near the catastrophic failure point. You'll not know it until the panel is stressed a little more, like underway in a breeze, then pop and a deformed location appears in the panel. I've bent plywood around molds and had everything looking good, just to come back in day or two to see a panel has buckled, fracturing along an unseen internal veneer seam or void. I've also had them just about explode, during the "talking it into place" stage. After a while you get a feel for how far you dare bend a panel.

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Thanks for all of the replies.... I am just trying to straighten a slightly warped panel, so severe radiuses are not a problem....   I will definitely use the cussing idea though... ;D   There is only about 1/8inch of bow over a 27inch piece of ply, but it is enough to keep the door from working...  

I am making a jig to put pressure where I need it, and I think I will try the wet towel thing first...

Sorry about the crappy picture, but it gives an idea of what I am working with..

bow005.jpg

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I have had some luck with what you are trying to do, by reversing the panel and placing a weight on it to slowly bend it back to a flat shape.  Sometimes a hot, steamy towel will help too, but a higher humidity works the best.  Could you build a fog chamber from plastic sheeting and a steamer?

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I am going to try wet towels and clamps first, and if that doesn't work, I might try a steam box....  If all else fails, I might just screw it down to another piece of ply, and edge band it in oak so I just have a REALLY sturdy base....

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