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Old 01-01-2007, 11:09 PM
  #3  
dbacque
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Default RE: wash-in in a PT-40 wing

Wash in is a bad thing. The tip of the wing will stall before the center of the wing, known as a tip stall. This means that when the plane stalls it will be prone to snapping.

But don't give up on the wing, it can probably be saved.

How much wash in is there and how much wash out should there be?

Once a the wing is covered with MonoKote, you can take a great deal of twist out of a wing just by stressing the MonoKote.

Cover the wing as usual. Then twist the wing the way you want it to go. The MonoKote will develop big wrinkles. Using your heat gun re-stretch the MonoKote while holding the wing twisted. Do both sides. Now check it. You'll be surprised how much you can change the twist in a wing this way! It will probably take numerous cycles to get it to where you want, just keep repeating the twisting and heating.

Even if you can't get quite as much wash out as the plans call for, if you get it at least back to neutral and preferably some wash out you should be fine.

If you can get your hands on an incidence meter, checking the twist is even easier.

Dave