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wingtip aerodynamics

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wingtip aerodynamics

Old 12th Mar 2010, 21:54
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wingtip aerodynamics

Hi all

This is my first post on the forum and you will probably laugh at my question but it is annoying me now.

I am trying to work out the aerodynamic effect winglets have on an aircraft in the glide and turn but all I can find out is it reduces the induced drag with a slight increase in lift. Surely there is more to it than that.....

Can anyone help me please...how does the winglet make a differance on thrust, drag, lift and weight on the turn and glide....I cant see them make any differance on weight but maybe less thrust required due to a decrease in drag while gaining a slight increase in lift....

Any advice would be gratefully received..
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Old 12th Mar 2010, 22:49
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Yaw moment and stability...
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Old 13th Mar 2010, 14:05
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interested too

poking my nose in because I would be interested to know this to. From what little I learnt 25 years ago, seem to remember that one reason then cited was to avoid the end effect of the wing, ie circulation falling off the end of the wing, so it increased the efficiency of the wing by reducing a negative practical correction to (potential flow) theory. Presumably that could be equated to same lift at lower aoa and therefore same lift for less drag. Dihedral effect would also influence stability as mentioned above by giving a small added force at long radius arm, ie tip of wing.
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Old 13th Mar 2010, 15:06
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Just curious: Had the designers overlooked the winglets on the B777 . . . B787?
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Old 13th Mar 2010, 15:34
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Had the designers overlooked the winglets on …
A notice on the wall of the Hatfield aerodynamics department (Aahh de Havilland) read “a good wing does not require winglets”.
This was the home of the team who designed the original Airbus wing, and only after being pushed (marketing?) added ‘endplates’ to the A320 wing.
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Old 13th Mar 2010, 20:10
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Safetypee

That sign was later stolen and put on a wall in Bordeaux, France at AMD design headquarters. They succumbed to winglets, too.

GF
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Old 13th Mar 2010, 20:19
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Not a scientific response but I remember one of my aerodynamics profs at university saying that when Ohio State University was doing research into winglets, the discovered that the best angle for mounting them was...horizontal. By which he meant, they don't really do a whole lot that a well designed wingtip won't do.
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Old 13th Mar 2010, 20:46
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Dunno about the whys and wherefores, but a B757 with winglets burns around a tonne less fuel than an unmodified airframe on a return flight from the UK to Cyprus. Must be doing something good.
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Old 13th Mar 2010, 21:20
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Just a couple of inputs

"Horizontal" winglets = larger wingspan = doesn't fit

Winglets can increase weight due to higher aero loads and therefore additional structure
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Old 13th Mar 2010, 21:22
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This article Wingtip device - Wikipedia, the free encyclopedia may prove helpful.
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Old 13th Mar 2010, 22:49
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“a good wing does not require winglets”.

Probably true... I'm not an aerodynamiscist.. Supposedly the winglet will reduce induced drag..it also acts as a wing fence and generally improves performance and fuel efficiency...
There's usually more than one way to do a job and using a winglet as opposed to developing a more efficient wing is an option...
Interesting that one of the most aerodynamically efficient (and maybe THE most aerodynamically efficient aircraft outside of the military), the Piaggio Avanti, does not have winglets.... a result of something over 70 hours of wind-tunnel testing... the average military fast jet would typically get about 40+ hours of wind tunnel development.
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Old 14th Mar 2010, 17:22
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uh.. winglets basicly increase Aspect Ratio and Area with
the aerodynamic & structural pro's and con's that go with that.
Wing fences don't do that, they just reduce lateral flow of air
along the wing.

As mentioned, winglets also increase stability around the vertical
axis which means a bit more rudder might be required in e.g. a
decrab on landing. (which might reduce max xwind limit on some types)

M
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Old 20th Mar 2010, 22:17
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thanks for the replies.

What I am struggling to understand is if the aircraft is in a banked turn the upper wing will be travelling faster. This means that the winglet, which has an aerofoil shape, will be producing lift. With this lift and the cant angle will it cause the aircraft to turn more into the turn or will it try to draw it out the turn and back level?
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