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Washout Tutorial Needed

Old 03-03-2003, 09:02 PM
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Big Sasquatch
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Default Washout Tutorial Needed

I have a basic understanding of what "washout" is but could use a good tutorial on how to build it into a wing. Something with pics would be awesome, all the previous threads that try to explain the construction method make my head spin.
I feel a little stupid because I can't figure out what they are saying......... Thanks
Old 03-03-2003, 09:52 PM
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MinnFlyer
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Default Washout Tutorial Needed

An easy way to do it is to make a spacer that runs the entire length of the wing. For a flat-bottom wing, it would start at Zero and end at whatever dimention of washout you want (Let's say 1/4").

So if your wing panel is 26" long, cut a scrap piece of 1/4" balsa 26" long. then make it taper down to nothing. Get your ribs in place on the spars, then place your tapered piece so that the thin end is at the root and the thick end is at the tip. Place it just under the rear ends of the ribs so that it is lifting the tip ribs more than the root ribs. Now glue the ribs to the spars, add shear webs, and LE an TE sheeting. The washout should be now a permanent part of the wing.
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Old 03-03-2003, 10:19 PM
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Default Washout Tutorial Needed

Viola, I think I've got it!

MinnFlyer you are a gentleman and a scholar. Thanks for the simple explanation. Is there such a thing as too much washout? How would I determine the correct amount for a particular model?

Also, what if the wing isn't a flat bottom? Is the process any different?
Old 03-03-2003, 10:51 PM
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Default Reflex vs Washout

Seanreit,

I Don,t know what kind of flying wing you have but the added up trim probably resulted from inadaquate reflex. Reflex is similar to washout (an upturned trailing edge) but for an entirely differant purpose. Unlike Washout reflex occurs the entire length of the wing. The purpose is to acheive pitch stability just as a stabilizer does on the back of a conventional airplane. Reflex can be designed into the airfoil or simply rigged into the elevons by adjusting the neutral point so that they are both up ten to twenty degrees. With out reflex a flying wing would just do a forward tumble.

Also a straight chord flying wing needs to balence somewhere around 15% of the chord unlike conventional airplanes that do well at 25 to 30%.

I once had a lot of fun by using a sixty size trainer the strip ailerons were enabled to function as elevons and adjusted with twentys degrees reflex (it was not an ideal airfoil) the ship was rebalanced at 15% and the main gear moved forward to match. The original elevator was removed and the original stab was remounted with a servo release to fall off in flight. Well you can just imagine the routine we had worked up and everybody loved it even when they were fooled.
Old 03-04-2003, 03:05 AM
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linclogs
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Default Washout Tutorial Needed

Excellent response, MinnFlyer!

I've expounded on your drawing to show what washout "looks like" when you view a wing with it built in.

Folks have also asked me what it is and what it looks like or how you can tell if a model has it. It doesn't matter what type or shape the wing is. The principle is the same whether it's a flat bottom or symmetrical wing; whether the tips are squared off, round or elliptical (like a Spitfire).
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Old 03-04-2003, 04:07 AM
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Dsegal
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Default Washout Tutorial Needed

> Is there such a thing as too much washout? <

Yes. I have seen a review of a trainer kit which recommended reducing the specified washout for better performance. BTW, when inverted washout will become wash-in. I have read about washout for over a decade and no one in my club pays the least attention to the subject- they just go fly their planes and have fun.

Dave Segal
Old 03-04-2003, 07:20 AM
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linclogs
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Default Washout Tutorial Needed

" BTW, when inverted washout will become wash-in."

Very true, Dave. But - you don't LAND while upside down! (At least, we hope not!) That's where washout really helps - on a model that lands hot and tends to want to tip stall and drop a wing when slowed down. Washout allows you to slow down without falling out of the sky.
Old 03-04-2003, 05:28 PM
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Default Washout Tutorial Needed

Originally posted by Kurt Tank
Also, what if the wing isn't a flat bottom? Is the process any different?
The process would be basically the same. Of course, the entire spacer may have to be lifted to meet the rear of the ribs.
Old 03-04-2003, 06:42 PM
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Default Washout Tutorial Needed

If you have a computer radio, you may be able to program washout in, to use, just flip the airbreak switch and you are ready to land. This does require a servo on each aileron. Sporty

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