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wash-in in a PT-40 wing

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wash-in in a PT-40 wing

Old 01-01-2007, 07:50 PM
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longboard
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Default wash-in in a PT-40 wing

I was building a Great Planes PT-40 MKII and mistakenly put the wash- out jigs on the wing backward.This was an older kit before the instruction manual was updtaed and the the placement of the jigs was not as clear.Anyway I built a new wing,and now have a perfectly good wing except for it having wash-in instead of wash-out.what would be the harm in using this wing on another project and what would wash indo as opposed to wash-out?
Old 01-01-2007, 08:09 PM
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BobH
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Default RE: wash-in in a PT-40 wing

Wash in will cause the wing to stall sooner rather than later. If you can live with that you'll be fine.
Old 01-01-2007, 11:09 PM
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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
Old 01-02-2007, 05:11 PM
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Default RE: wash-in in a PT-40 wing

Hi!
Many times this could be fixed by twisting the wing and warming it with an iron or heat gun!
Old 01-02-2007, 09:37 PM
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Default RE: wash-in in a PT-40 wing

I would have to go with Jakas idea. If you can at least get the wing straight (no wash in or out) you will have a better chance of success.
I have straightened a lot of wings this way. I think the PT wing is flexible enough that you can get it straight with a heat gun after you cover it.
Doug

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