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Old Feb 01, 2013, 09:04 PM
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United States, MO, Manchester
Joined Nov 2010
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Wing tip shape

I am trying to fill the void of being absent from soaring for the last 15 years - hopefully someone can fill in this blank:

I see that most of the new design moldies use a wing tip shape that the tip sweeps back behind the trailing edge a short amount.

Does anyone know the concept/theory behind this? Some have carried to what I consider a aesthetic extreme. Is it a proven glide path enhancement or one copying another?

Thanks

Paul
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Old Feb 01, 2013, 10:32 PM
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jrs_123's Avatar
irvine, ca
Joined Apr 2002
253 Posts
its a method to reduce induced drag. along with winglets and leading edge sweep (schuemann planforms)

http://www.nature.com/nature/journal.../325435a0.html

http://www.spieltek.com/SunbirdSoari...ormArticle.pdf

http://ntrs.nasa.gov/archive/nasa/ca...1996034550.pdf

http://oddjob.utias.utoronto.ca/~dwz...nduceddrag.pdf
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Last edited by jrs_123; Feb 01, 2013 at 11:55 PM.
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Old Feb 02, 2013, 11:58 AM
Father of Fr3aK, DLG Pilot
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USA, OH, Worthington
Joined May 2002
6,733 Posts
It's hard to tell what's really happening out at the tips with modeling software. The tips that are swept back are doing so in an effort to reduce the vortices at the tip that create alot of non-laminar flow both at the tip and inboard of the tip. The thought is that reducing the vortex allows the wing to perform optimally closer to the tip, increasing the effective span.

With all of that being said... I still prefer a more symmetric elliptical tip for effective lift distribution, ease of transportation, asthetics, structural integrity, and durability.
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Old Feb 02, 2013, 12:45 PM
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Tennessee
Joined Sep 2003
2,336 Posts
Someone once said that the most important thing about wing tip is the distance between them. Raked tip at least increases the distance betweek them. I have used raked tips on all my sailplanes except two meter models for the last 30 years. I don't know if they reduce drag but the main reason I use them is that they are so light as well as being quick and easy to make for built up wings. This is the tip I am using on my current RES sailplanes. The edge is sanded as thin as possible.
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Old Feb 02, 2013, 04:39 PM
The Lone Blue Plaid Flyer
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Seattle
Joined Jan 2003
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Hi Paul,
I put them on my Riser 100, just because they look cool. I basicly copied the AVA wing tip on my Mini.

Bob in Seattle
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Old Feb 03, 2013, 11:54 AM
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United States, MO, Manchester
Joined Nov 2010
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Crescent Shape

I understand the swept, winglet and hoerner tips -- what I don't get is the crescent shaped trailing edge in the last inch or two of span.

Paul
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Old Feb 03, 2013, 05:10 PM
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USA, IL, Naperville
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It's a fashion statement.
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