GAIsweetGAI From Norway, joined Jul 2006, 934 posts, RR: 7
Reply 1, posted (7 years 10 months 2 weeks 6 hours ago) and read 2600 times:
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 From , joined Dec 1969, posts, RR:
Reply 2, posted (7 years 10 months 2 weeks 6 hours ago) and read 2593 times:
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.
Scooter01 From Norway, joined Nov 2006, 1214 posts, RR: 8
Reply 4, posted (7 years 10 months 1 week 6 days 3 hours ago) and read 2379 times:
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
"We all have a girl and her name is nostalgia" - Hemingway
Vikkyvik From United States of America, joined Jul 2003, 10350 posts, RR: 26
Reply 5, posted (7 years 10 months 1 week 6 days 2 hours ago) and read 2360 times:
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.