RE: Twisted wing on 1st kit (Tower Hobbies Fun-51)
Alway, Always sheet your wings while pinned or weighted to your building board. Also be sure that your building board is straight. I've built wings that have a span as much as 11' and never had a problem so long as my wing had been pinned or weighted down. With careful checks of my building board they've came out straight as an arrow. But as stated earlier in this post you learned a very valuable lesson which hopefully will carry on to your next build. Most building instructions that come with the kits these days have good idea's or instruction on how to sheet your wings and keep them straight. The next gotcha that you might run into is seeing your wing warp again while ironing on your covering. Take your time and be careful when getting your covering material on and heating it to get it taught. If your not careful it'll warp in a New York minute. But in this case it is recoverable by simply heating the skin and twisting it back straight and hold it while letting it cool. A good technique that I like to use is to rubber band two arrow shafts to the wing running from the leading edge to the trailing edge(not span wise). I'll put one at the root of the wing and then another at the tip of the wing. Stand back about 3 feet back from the wing tip and see if they if they run parallel or evenly matched with each other. If not then you got a twist that needs to be sorted out. this works pretty slick with a flat bottom wing but you might have to manufacture some blocks if working with a semi-symmetrical airfoil. Reason I state the above is that I ran into this one time and nearly lost my airplane due to my ignorance. A check suggestion from an expert got me pointed in the right direction and since then have not had a problem.
Hope this helps....
Cheers,