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Jan 24, 2014, 06:07 PM
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Huey N's Avatar
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Flattening warped plywood.

Hi all,

How do I flatten warped or twisted plywood?

I'm a proud new owner of a Top Flite SE5a kit but the plywood is slightly warped? Do I just mist water on the concave side and leave it to do its own thing?

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Jan 24, 2014, 10:55 PM
Registered User
I've had some limited success using an amonia and water solution (about 4 to 1 I think) then weighting the piece curved in the opposite direction of the warp. I can't give much more because it was trial and error for me. Been discussed in one or more old threads on this or another board. The thicker the piece, especially ply, will make it more difficult. If the piece(s) are too bad perhaps the kit manufactures will send new ones. Good luck!

Jan 24, 2014, 11:14 PM
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tacx's Avatar
I never had good luck with straightening warped ply. I would wet and press flat. then let sit for a few days. When taking off the weight the piece would be flat, but a day later it would revert back to the warp.
Jan 24, 2014, 11:36 PM
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portablevcb's Avatar
Heat. Iron it back in place. Only did it once but it worked. And it was 1/16". Took a while.

Have not tried it on thicker stuff. May not be able to apply enough heat.

Jan 24, 2014, 11:47 PM
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Huey N's Avatar
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The Top Flite stuff is 1/8 - 5 ply. I been looking on woodworking forums too and they just say apply heat and steam to the concaved side. I'll give go with everybody suggestions combined and we'll see what happens.

Seems like I might be better off using the originals as templates.
Last edited by Huey N; Jan 25, 2014 at 10:09 AM.
Jan 25, 2014, 08:12 AM
Registered User
I've had a fair amount of success using slightly warped ply in building by using extra strong braces while framing up. The fuse frame work held it straight after the glue cured. Just my experience.
Jan 25, 2014, 10:12 AM
Life is a Hobby
Canada`s largest balsa wholesaler lives close to me. Had a conversation with him a number of years ago about warped plywood. He said the only sure fix is to duplicate the original manufacturing process and apply multi tons of pressure under steam heat - a process not available to the hobbiest.

The worst were the Goldberg kits back in the 1990s. Bought an Extra 300 whose 1/8 lite ply full length sides were twisted like pretzels. Tried everything - ammonia water, as much heat as I could apply, weights. Nothing worked.

Final solution was same as Edwin - jig the hell out of it, clamp everything, glue one former at a time, let the glue cure a good 48 hours before un-jigging.

I can appreciate this process would be more difficult with multi-layer aircraft grade ply.

Jan 25, 2014, 10:40 AM
Registered User
What I have found and it saves weight and trouble - Trace the part on a new flat straight piece and cut out - After 40 years of modeling, I still have never had a warped piece of plywood "get perfectly" straight -
Jan 25, 2014, 11:09 AM
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Huey N's Avatar
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thanks all for the feedback.

I think I'm just going to make new parts after all. Heck might as well scan, retrace them on illustrator, and have the parts laser cut. This model is on the que to be built. Just collecting reference, prepping and replacing wood parts.

Jan 26, 2014, 12:14 AM
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kenh3497's Avatar
I had a 12" X 12" X 1/4 piece of aircraft ply warp on me after I brought it home from the LHS. It was "flat as a board" in the store It will only be used for firewalls and landing gear plates so it is not a huge deal.

Jan 29, 2014, 01:22 PM
Registered User
I had good success using a steam iron and a dampend paper towel. It took several tries on some severely warped pieces, but in the end, I didn't have to re-make anything. Steam the part, and weight it down with a heavy book, or anything heavy and flat.
Jan 30, 2014, 07:45 AM
Registered User
I haven't tried flattening ply, but the following seems to me worth trying:

Wet the concave side, clamp down piece so the concave side is now convex, play a heat gun over the wet side. Let dry, but keep clamping the piece with the old concave side still convex for several days in a dry place.

Jim R.

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