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Mar 19, 2002, 11:08 PM
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megawatt's Avatar

Question on washout


When adding washout to a wing, should the "twist" start at the root of the wing panel and gradually increase out to the tip. Or should the "twist" start at some point on the outboard portion of the wing panel, thereby leaving a portion (inboard) of the panel flat? Or, does it matter ....Jeff
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Mar 20, 2002, 12:08 AM
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davidfee's Avatar
I think most model builders just use a gradual (linear) transition from root to tip, but I have seen some wings (jig-built and molded) which had a non-linear twist. That is, the wing was essentially flat most of the way out, and then the last ~1/4 of the wing got all of the twist. I've even seen one set of wings where the washout was only in the last 10% of the span. It's all a matter of how carefully you want to massage the lift distribution across the span.

Linear twist is easiest in most cases, and generally works just fine.

-David
Mar 20, 2002, 08:48 AM
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megawatt's Avatar
Thank you David. Wasn't sure on this one. I guess as long as you insure that the inboard section of the wing has a bit higher AOT than the tip, then it shouldn't matter if all of the washout is located at the tip, or starts inboard and gradually increases out to the tip. It should still reduce the chance of the tip stalling first.
...Jeff
Mar 21, 2002, 10:40 AM
Registered User
Megawatt,

go to your local general aviation airport and look at airplane wings from their trailing edges. You'll find on high-wing Cessnas (IIRC) that the washout is in the outer wing panels. I looked at the washout on a Piper twin, and it seemed to be linear from the engine nacelle out to the tip (IIRC). I suppose the amount of twist and its exact location is dependent on a lot of factors. Not being an engineer, I use the "TLAR" approach. It's worked for me on a couple of my models, not so good on a couple of others. And it can be a bear to adjust to get the results you want.
Mar 21, 2002, 12:12 PM
Registered User
You can make the leading edge out at the tip blunt
and sharper at the root and get the same effect as washout. You can also add stall strips at the root. Just another way.
Mar 21, 2002, 05:00 PM
It's just PLANE silly!
balsaman's Avatar

foam wings


It's easiest to make it linear. Especially on foam wings, but also on built up wings so thats how most models are designed. The KISS method is always a hit for me

Eric


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