warped plyboard

I cut my doublers from 1/8 birch 3 ply plywood but they have warped or bowed. How do I get them straight before epoxying them to 1/8 balsa fuselage sides?

Oh, boy. To be honest, I would,if possible cut new ones. If not, then soak them in water and put some very heavy weight on them until they straighten. Then put a piece of hard balsa perpendicular to the former, in other words sideways. Dope them, reapply weights. This should help to seal them from more moisture and stop any more warps. I have done this a few times. Once it is epoxied in place, it should not warp and the balsa cross member can be removed with a knife and sandpaper. I now try to use the thinner 5 ply wood. It has less tendency to warp. I know Midwest has it, and Sig, so I assume do Lone Star and Superior, assuming you have access to these folks.
All too often the person asking is in Oz or GB or Canada and we don't always know this and spout off brand names that may not be familiar to them.

I am going to suggest something really silly, but I think it will probably work. Just lay it flat against a flat surface and weight it down and let it sit a while. This plywood likes to take a bow, when you give it a chance, but will also settle out on its own as well. If you store it flat, it will probably not warp on you. If you store it on end, there is a good possibility that it will. But, if you store it flat again, well...

When you glue it up, also glue it on a flat surface and weighted down. I am assuming that you are building a profile. If the engine bearers are made long and extend to the wing, they will keep the fuselage from bending anyway.

I, too, would suggest using 1/16 5-ply birch next time. It is a bit more expensive, but will be equally as strong, no heavier, and much harder which means it won't crush as easily.

Leonard:
Pete said he is going to use these on 1/8" balsa fuselage sides. Sounds like a built up not profile.

Pete:
Why are you using 1/8" ply for your doublers? 1/16" should be more than strong enough for anything up to a 60.

>Leonard:
>Pete said he is going to use these on 1/8" balsa fuselage
>sides. Sounds like a built up not profile.
>
>Pete:
>Why are you using 1/8" ply for your doublers? 1/16" should
>be more than strong enough for anything up to a 60.

You are right. I missed that little part (just read the 1/8 inch plywood part and jumped to conclusions.

I will, then, carry this one step even further. 1/32 plywood is more than strong enough for anything including a 60. If you build an engine crutch, all you are using the plywood for is to get a secure mount for the engine bearers. But there will be little weight or strength difference between using 1/8 inch Lite Ply and 1/16 Birch. I would still favor the Birch, but the Lite Ply isn't really going to hurt you (other than making the fuselage a little wider.

Now, if it is a built up fuselage, you may even get by with gluing it down flat with weights while waiting for the epoxy to dry. I would still try to get as much out as possible before hand.