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Winglets or not? - 3/1/2008 8:08:04 PM   
Mike-G


 

Posts: 6
Joined: 2/6/2008
From: Terndrup, DENMARK
Status: offline 		I have been wondering a lot about increasing the performance of an airplane by making changes on the wings of the airplane. In a couple of days I am going to build a new glider, and my question for you is; what would be best to install on the glider. I have two possibilities either install winlets (which should be able to convert some of the otherwise wasted energy in the wing tip vortex to an apparent thrust) or I could just increase the area of the wing by a couple of centimeters. Which of these two possibilities have the greatest influence on the performance of the glider, and what would you recommend? I don’t have any ideas if the winglets will give any effects on a model airplane!

Regards:
Mike G
       Post #: 1

RE: Winglets or not? - 3/1/2008 8:20:27 PM   
HighPlains


 

Posts: 2639
Joined: 3/2/2003
From: Over da rainbow, KS, USA
Status: offline 		If you are not span limited, go with extra wingspan.

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RE: Winglets or not? - 3/1/2008 11:48:18 PM   
highhorse


 

Posts: 589
Joined: 11/16/2006
From: Memphis, TN, USA
Status: offline 		Seems to me that if winglets were worth the extra weight/drag/hassle then we'd see more of 'em in the full scale world??? They are kinda rare, aren't they? But a couple of extra cm seems like a darn-near freebie?

Heck, I don't know...just sort of wondering out loud.

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RE: Winglets or not? - 3/1/2008 11:57:18 PM   
vertical grimmace


 

Posts: 1142
Joined: 3/13/2004
From: ft collins , CO, USA
Status: offline 		It seems like you see quite a few on full scale aircraft. At least the new ones. Why not do both?

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RE: Winglets or not? - 3/2/2008 4:42:56 AM   
highhorse


 

Posts: 589
Joined: 11/16/2006
From: Memphis, TN, USA
Status: offline
quote:

ORIGINAL: vertical grimmace

It seems like you see quite a few on full scale aircraft. At least the new ones. Why not do both?

We obviously work at different airports !

You made me curios tho, so I looked it up. Various studies for boeing and Mcdonnel Douglas showed a cruise efficieny improvement of 2-5 % depending on the aircraft model for tips thoroughly tested and refined in a wind tunnel. The new 787 uses a raked tip rather than winglet in 3 of 4 787 variantls because the rake was more efficient.......

< Message edited by highhorse -- 3/2/2008 5:06:03 AM >

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RELAX already, it's a freakin' hobby !! :-)

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RE: Winglets or not? - 3/2/2008 7:17:16 AM   
iron eagel



Posts: 1211
Joined: 7/15/2004
From: Middleboro, MA, USA
Status: offline
quote:

ORIGINAL: Mike-G

I have been wondering a lot about increasing the performance of an airplane by making changes on the wings of the airplane. In a couple of days I am going to build a new glider, and my question for you is; what would be best to install on the glider. I have two possibilities either install winlets (which should be able to convert some of the otherwise wasted energy in the wing tip vortex to an apparent thrust) or I could just increase the area of the wing by a couple of centimeters. Which of these two possibilities have the greatest influence on the performance of the glider, and what would you recommend? I don’t have any ideas if the winglets will give any effects on a model airplane!

Regards:
Mike G


I think that is an important consideration with a sailplane, I would think that anything you can do to improve the efficiency of the wing can only help. The airlines are looking to save fuel, a glider need to save energy reducing your drag should be a major consideration which the winglets might do to some degree.

< Message edited by iron eagel -- 3/2/2008 7:21:38 AM >

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RE: Winglets or not? - 3/2/2008 10:48:37 AM   
Mr Cox



Posts: 342
Joined: 7/20/2007
From: Gothenburg, SWEDEN
Status: online 		I've had winglets on small gliders (in their original design) and I've assumed that there were other gains rather than just efficiency (if they're too large they can add more drag). They seem to add stability and reduce the risk of tip stalls etc. If you're scratch building why not make detachable with tips and do some research of your own, after all, the fun lies in trying different things.

(in reply to iron eagel)
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RE: Winglets or not? - 3/4/2008 9:27:36 PM   
gyrocptr


 

Posts: 36
Joined: 7/9/2006
From: Neenah, WI, USA
Status: offline 		For a glider, I'd vote for increasing the wingspan. Perhaps combine the extra wingspan with a bit of polyhedral at the wingtips to help hold tighter turns.

http://en.wikipedia.org/wiki/Wingtip_device
Raked wingtip
Raked wingtips are a feature on some Boeing airliners, where the tip of the wing has a higher degree of sweep than the rest of the wing. The stated purpose of this additional feature is to improve fuel economy, climb performance and to shorten takeoff field length. It does this in much the same way that winglets do, by increasing the effective aspect ratio of the wing and interrupting harmful wingtip vortices. This decreases the amount of lift-induced drag experienced by the aircraft. In testing by Boeing and NASA, raked wingtips have been shown to reduce drag by as much as 5.5%, as opposed to improvements of 3.5% to 4.5% from conventional winglets.[5] An increase in wingspan is generally more effective than a winglet of the same length, but may present difficulties in ground handling.

< Message edited by gyrocptr -- 3/4/2008 9:30:21 PM >

(in reply to Mr Cox)
       Post #: 8

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