Blackbird
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Is It Possible To Develop A Flap...

Fri Feb 16, 2007 4:24 am

Is it possible to develop a flap that features a flip out winglet to increase overall lift and reduce flap vortices?

Andrea K
 
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RE: Is It Possible To Develop A Flap...

Fri Feb 16, 2007 5:20 am

There are 2 things I can think of that would prevent flap winglets from happening:
1. the extra weight of the device
2. how do you store the winglet? Using solid materials it would be impossible to store the winglet: the flap is too thin for the winglet to be stored inside, and/or it couldn't be folded easily; and it is impossible to make it sit on top of the flap when stored, as both are airfoils and have a convex shape.

That being said, I don't think I'm very knowledgeable about aerodynamics etc.
"There is an art, or rather a knack to flying. The knack lies in learning how to throw yourself at the ground and miss."
 
N231YE
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RE: Is It Possible To Develop A Flap...

Fri Feb 16, 2007 5:30 am

My best guess is that there really is no need for "flap-lets." The flaps are stored in cruise, which is where the winglet becomes advantageous. Despite the fact that they would make less drag and more lift, since only a small portion of flight is done in "dirty configuration," I would see it as extra weight.
 
oly720man
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RE: Is It Possible To Develop A Flap...

Fri Feb 16, 2007 9:08 am

Because of the high flap deflection angle, the tip vortices developed could well help the flow stay attached. By disrupting this flow it's possible that flap lift would be lost.
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Scooter01
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RE: Is It Possible To Develop A Flap...

Sat Feb 17, 2007 8:10 am

The Soviet team of Nikitin-Sevchenko designed a version of the Polikarpov I-15 biplane in 1939 which was called IS-1. It featured a lower wing (with inward retractable gear) that folded up along the sides of the fuselage and a hinged outer part that buried itself in the underside of the top wing.
The pilot could reconfigure this when he needed the low speed and maneuverability of a biplane, or the speed of a monoplane. Flight trials proved the design usable, but operational problems and maintenance in the war-time made further developments impossible.

Source: "Fighters Volume three" by William Green. Published by Macdonald&Co 1961

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vikkyvik
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RE: Is It Possible To Develop A Flap...

Sat Feb 17, 2007 9:12 am

Quoting Oly720man (Reply 3):
Because of the high flap deflection angle, the tip vortices developed could well help the flow stay attached. By disrupting this flow it's possible that flap lift would be lost.

Consider, also, that at higher flap deflections (say, flaps 25, 30, and 40 on a 737), in addition to adding lift, you're also already increasing the drag quite significantly. I'm not totally sure that a small drag reduction due to "flap-lets" would really be useful in those regimes of flight.

You'd also need some sort of aerodynamic housing that would contain the mechanism that deploys and stores the flap-let, which would add weight, and some profile drag.

Also, as was stated by N231YE, winglets are at their best over longer-range cruises.

~Vik
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