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Curved wing tips: Pros, cons, discuss!

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Created by IndecentExposur Thursday, 12 Sep 2019
IndecentExposur
132 posts
Thursday , 12 Sep 2019 2:20AM
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There are a lot of designs on wings and stabs out there. What is the advantage/disadvantage to having the curved ends? What are the flight characteristics?

Although I'm sure we'll get tons of opinions (I'm open to these too), I'm curious to know a little more scientific evidence that these work/don't work. What's the intent?

Discuss!

LeeD
644 posts
Thursday , 12 Sep 2019 4:19AM
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Do all airplanes need canard tips?
Maybe there are different thoughts, all of which can work.

Paducah
469 posts
Thursday , 12 Sep 2019 11:44AM
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Downturned wingtips do a couple of things: keep kiters and SUPfoilers from impaling themselves; and help keep the tips underwater when turning. While it's easy to point at airplanes, especially passenger jets, and see all sorts of things, we shouldn't jump to conclusions. Some of the reasons they use wingtip devices include trying to squeeze performance out of wings that are restricted by gate size and that very long wings pose structural/weight challenges. The 777, for example, doesn't use any wingtip devices because, usually, the gates it flies from aren't as space restricted.

www.businessinsider.com/boeing-airplanes-winglets-nasa-2016-9
aviation.stackexchange.com/questions/8556/is-a-winglet-better-than-an-equal-span-extension

This is also why you are seeing quite wide racing wings like the AFS 1000 - a wing that has raked wingtips which can show an improvement over a straight wing.

One of my two main foils has curved wingtips and stabs, the other is dead flat. I don't notice any difference in directional stability - another reason mentioned.

But shaped ends do look cool!

stehsegler
WA, 2996 posts
Thursday , 12 Sep 2019 12:12PM
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apparently safes 10% in fuel...

Paducah
469 posts
Thursday , 12 Sep 2019 1:22PM
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stehsegler said..
apparently safes 10% in fuel...


Source? Most versions I read about it's about 3-5% - almost always on planes that can't extend their wingtips. Read the stackexchange link above.

en.wikipedia.org/wiki/Wingtip_device

Plus - almost all those are upswept tips unlike windfoils which are downswept. There are downswept aero wings but those usually are for STOL purposes

stehsegler
WA, 2996 posts
Thursday , 12 Sep 2019 2:53PM
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Select to expand quote
Paducah said..




Source? Most versions I read about it's about 3-5% - almost always on planes that can't extend their wingtips. Read the stackexchange link above.


No idea. Read it somewhere in a magazine...

Paducah
469 posts
Thursday , 12 Sep 2019 8:17PM
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stehsegler said..

Paducah said..




Source? Most versions I read about it's about 3-5% - almost always on planes that can't extend their wingtips. Read the stackexchange link above.



No idea. Read it somewhere in a magazine...



segler
140 posts
Friday , 12 Sep 2019 11:04PM
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It is probably not good to try to compare foil wingtips with airplane wingtips. Just look at the Reynolds numbers.

An airplane with 45" chord at the wingtip flying at 300 mph is running a Re orders of magnitude larger than a 3" foil wingtip chord running at 20 mph.

On all flying devices, the purpose of wingtips is to reduce drag by suppressing tip vortices. At any Re in any fluid.

RM, retired Boeing

Paducah
469 posts
Friday , 13 Sep 2019 12:40AM
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segler said..
It is probably not good to try to compare foil wingtips with airplane wingtips. Just look at the Reynolds numbers.

An airplane with 45" chord at the wingtip flying at 300 mph is running a Re orders of magnitude larger than a 3" foil wingtip chord running at 20 mph.

On all flying devices, the purpose of wingtips is to reduce drag by suppressing tip vortices. At any Re in any fluid.

RM, retired Boeing


So, does a higher Re mean tip vortices are more or less of an issue?

The new 777x will have folding wing tips - wingtips at the gate (for space reasons) and extended wingspan in flight. Interesting that they are choosing a more complex solution of a folding tip/longer wing rather than a winglet to increase performance
www.boeing.com/777x/reveal/video-777x-Folding-Wingtip/

WhiteofHeart
131 posts
Friday , 13 Sep 2019 2:25AM
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In windsurfing the wing tips dont have the same goal as those an airplane have. To begin with the tips are the wrong way round on most windfoils compared to airplanes... I've tested numerous wings with different shapes (and tips) and there is quite a feelable difference, mostly when powered up and banking the board, the flat wings tend to slip away/out from under you and are overall less locked. Curved tips are way easier to keep steadily banked over simply said, they have more "grip".

LeeD
644 posts
Friday , 13 Sep 2019 2:52AM
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That's what some AmericanAirlines pilots tell me. Straights, no diff, but in squirrelly crosswinds, the canards help stabilize noticeably.
Should I add wingtip canards to my 1st gen Naish WS-1?
Slip happens mostly on low powered jibes.

Paducah
469 posts
Saturday , 14 Sep 2019 12:22AM
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Not discounting others experiences but this is interesting

"???? Just tried for the first time the new speed wing 550cm2 from @phantominternational with the new 200cm2 Stab ?? 0 spin out, despite I was pushing as hard as possible, turning sharp and lifting up and going down quickly intentionally to find the limit. I think I have never been flying so stable and no-stress as such high speed ?? can't wait to try the 350cm2 now !
??I was on 9.0m with 15 knots and 91cm wide. Very probably better with much smaller sail and more wind. But interesting to see it was working really good in terms of balance and control.Need to buy a new gps watch as I lost mine ... rip ????@ Plage Des Minimes"

www.facebook.com/thomasgoyardwindsurfing/posts/2430676057022519?__tn__=-R








WhiteofHeart
131 posts
Saturday , 14 Sep 2019 12:26AM
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Select to expand quote
Paducah said..
Not discounting others experiences but this is interesting

"???? Just tried for the first time the new speed wing 550cm2 from @phantominternational with the new 200cm2 Stab ?? 0 spin out, despite I was pushing as hard as possible, turning sharp and lifting up and going down quickly intentionally to find the limit. I think I have never been flying so stable and no-stress as such high speed ?? can't wait to try the 350cm2 now !
??I was on 9.0m with 15 knots and 91cm wide. Very probably better with much smaller sail and more wind. But interesting to see it was working really good in terms of balance and control.Need to buy a new gps watch as I lost mine ... rip ????@ Plage Des Minimes"

www.facebook.com/thomasgoyardwindsurfing/posts/2430676057022519?__tn__=-R











Yes interesting indeed, but what does it have to do with the topic? Phantom has medium curved wings for the front wing, and a little more than medium curved wings for the stab. Tbh when I tried the Phantom (F) it felt very sensitive in roll stability (so side to side). I attributed that to the fact the winglets on the front and backwing are both aimed down.



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"Curved wing tips: Pros, cons, discuss!" started by IndecentExposur