I'm new to the hobby and have picked a Sig LT-40 to build as my first kit. I'm having what I think is a bit of a problem. I've done alot of reading before deciding to start building and I know the importance of keeping it completely flat and level. I got a 24" x 80" hollow core door as my building surface and have a celing tile on top of it. It ran my large T-square over it and it is indeed flat. My problem is both my balsa rear spars and TE's are a bit warped. I've read somewhere about moistening them with Windex and weighting them down until they dry to try to flatten them out. Is this an acceptable fix? I've read alot about how Sig has high quality kits but I"m a bit disappointed thus far. (I got my kit from Tower Hobbies).

Thanks.

I haven't buildt the Sig 4*, but I have built other kits. If the spars are not unreasonably bent you should be ok.

I'm not sure about the wing build on the 4*, but most kits. You pin the top spar (top of the wing, but you don't glue yet) to the plans straightening and holding in place to match the plan. Set your ribs on this spar and then set the bottom spar on top of the ribs and glue. The spar that is pinned down hold the ribs straight.

If both spars are bent, I turn the the bends opposite each other. That way they pull against each other. Then, usually you will glue the trailing edge on, and then the leading edge or sub leading edge. This too will help hold the wing straight.

Flop the wing over, pin the glued spar to the plans, and then glue in the top spar (actually the top of the wing).

I hope this helps. If the spars are unusually bent, I would go to my LHS and get new ones. They are usually only
a couple bucks each at most.

I ran into a few bent pieces of stock with my LT-40 kit and my Sig Somethin' Extra kit. I think it's just the nature of the beast when you have long narrow pieces of lightweight stock that might occur. In any case, the stock was pinned in place for the build and glued to the structure straight and then it was good to go.

The TE pieces for the LT-40 are pretty beefy. As long as the curve is not too extreme and you manage to get it pinned in place solid before you build you should be okay.

You can wet the wood with a mixture of water and a little ammonia, jig it up so the piece is bent slightly in the reverse direction and let it dry. This should remove the warp.

What John said.