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Old Jul 03, 2005, 09:12 PM
Registered User
Kirkland, WA
Joined Jul 2004
337 Posts
what is tip washout

how does tip washout affect the flight of a plane?

i am building a Gentle Lady and it calls for a 1/4" tip washout.. and just for confirmation, to me this means that the tip of the wing is pointed 1/4" backwards... basically i assume that since i am building on the plans the washout will just happen and i dont need to measure. the diagram that shows the washout is confusing to me.

thanks once again
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Old Jul 03, 2005, 09:32 PM
Registered User
US and Costa Rica
Joined Dec 2004
1,212 Posts
I guess there are lots of people here that can explain it better than I do, but basically the wash out is if you put the wing tip pannel on a flat surface with the most inner rib of it flat over it the outermost rib's TE should it be 1/4" over the LE.
I'm not sure if that is clear, but basically the whole bottom of the inner rib touching the table and the outer most rib LE touching it also but the TE 1/4' separated from the same surface.
I think I'll stop here or I'll make it worse.
Fernando
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Old Jul 03, 2005, 09:45 PM
Think Thermals!!!!
SoCalGliderFlyr's Avatar
Costa Mesa, California
Joined Mar 2004
2,964 Posts
As above root of wing tip (poly break) flat on building board. Leading edge flat on building board to tip. Raise the trailing edge at the rear of the last rib 1/4" above the building board.

An open frame wing can be twisted by heating the covering while holding a twist in the wing tip then letting the covering cool off. A sheeted wing must have the twist built into it.

Doesn't take much wash out (wing tip twist) just make sure both wing tips have the same twist. Check the center section too as this needs to be flat poly break to poly break or the plane will have tendency to roll one way or the other (depending on the twist).
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Old Jul 03, 2005, 11:53 PM
DrCarter
Princeton, TX
Joined Jan 2005
638 Posts
What the washout does is to have the tip be the last part of the wing to stall. With proper washout, when the wing does stall the nose will drop until airspeed is regained. Without it one tip or the other will drop followed by the nose. Since the GL is flown very close to its stall speed the later can be dangerous and make the plane hard to control.

You can add washout when the plan is done. !/4 inch seemed a little high to me. I placed a couple cents stacked under the tip trailing edge, weighted the wing down and then went over the last 10 inches with a heat gun. A hair dryer will also work. If you are at the field and discover the washout is gone, your cars exhaust will also work to heat it up.
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Old Jul 04, 2005, 04:34 PM
Registered User
Kirkland, WA
Joined Jul 2004
337 Posts
okay i think my idea of washout was wayy off. guess i dont have to worry about it right now though since apparently i add the washout at the end of the build.

thanks for the explanation as to what it does.
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Old Jul 08, 2005, 02:35 PM
I'm a pilot... 100 yrs to late
Thermalin's Avatar
USA, FL, Palm Harbor
Joined Jan 2005
3,423 Posts
I build my washout in on open bays as it's more precise... If you will be using covering to iron it in as it sounds.. you will most likely need to twist the trailing edge tip a snudge beyong the 1/4" so that it comes to rest at /4" above the table when all is said and done. Either way.. measure the final washout on both sides... don't assume b/c you braced it 1/4" up before heating that it ended up there.. wood densities, etc on both sides will be different and require checking each time you go out.
Mike
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