Bending Plywood

[crazycyclist]

I'm working on my galley hatch and have the frame finished. Before I skin it I want to be sure my plywood is bent properly to avoid springback. I was talking with greekspeedoman today and heard his frustrations and have heard rumors of others. What's the best way to ensure your hatch doesn't spring back out of shape?

EDIT: I did find this article very helpful. http://www.woodweb.com/knowledge_base/R ... _Wood.html

What do you think of Bendable Plywood or Whacky Wood?

Still looking for ideas and tips.

[Steve_Cox]

Bendy plywood is too flexible to be of any use on a hatch exterior, but I'm sure there are exceptions to that statement.

Some people wet the plywood before bending, some use 1/8" plywood, I used 1/4" and just bent it, but after hearing all the spring back stories, I made my hatch spars with 3/4" more curve than the side profile. It worked for me, results may vary.

[kennyrayandersen]

If you use plywood ribs they should be pretty stable (as opposed to bent wood). If you couple that with bendable plywood or some 1/8 plywood, and epoxy or tight bond the plywood (inside and outside), I can imagine it should change shape too much. Also, if you keep it battened down (latched) it will keep a preload on it which will not allow it to bow back out straight. I forget who it was, but galley latches came up. He had a latch on both sides at the bottom (structurally this is the best place to put it to give maximum mechanical advantage when you are trying to make it conform to contour). I plan on getting around this by hotwiring the hatch out of rigid foam and then glassing it. There won’t be any preload in the door then to try and make it spring back.

One other thing, and I know it’s been mentioned before is to build the hatch first, then trim the tear to match. One advantage doing it that way is you could let it sit for a month or two and it would likely get to a position of quasi-equilibrium and then you wouldn’t have to worry so much about it opening further.

[TPMcGinty]

I used bending plywood on the exterior of my tear. I didn't have a problem.. I kept the spares fairly close together.

[Rock]

I'm kerfing the backside of the 1/4" plywood that I'm skinning the tear with.

Eric

[Mini Renegade]

I used bending plywood on the exterior of my tear. I didn't have a problem.. I kept the spares fairly close together.

Same here, 1/4" bendy ply, not the stuff with grooves in though, it has 3 layers with the centre one running length wise and the others across.

[crazycyclist]

Thanks for the feedback. I've purchased 1/8 oak and have found it very easy to work with.

[kennyrayandersen]

Thanks for the feedback. I've purchased 1/8 oak and have found it very easy to work with.

Did you have any trouble finding that in 5 foot wide?

[crazycyclist]

I'm just putting a seam in it.

built a steam tent and steamed a piece tonight. We'll see what it's like in the morning. I don't think I got it steamy enough.

[starleen2]

I'm just putting a seam in it.

built a steam tent and steamed a piece tonight. We'll see what it's like in the morning. I don't think I got it steamy enough.

A Sauna??

[2bits]

Baltic Birch is known to be pretty bendy, not enough for my inner radius though (or maybe not my patience) but it is really bendy. I almost got it to work, but decided not to pursue it and am going for the black aluminum since I already have it.