winglets
hello all,
just some more info,
1) winglets are angled so that they have a forward resultant (b737ng), opposed to wingfences(A320) that are not.
2) there are models (i don't recall which ones) that have both, upwards winglets and smaller downward winglets mounted just aft of the upwards ones, on the same wingtips.
3)winglets by their additional weight & momentarm, should give some bending relief at the wingroot, same as fuel in wingtanks & underslung pod engines do.
(b737, A320, A330,etc.)
4)fuel savings btw. 2 & 4%, depending on aircraft utilisation.
5) expressed in formulae: winglets artificially increase the AR( aspect ratio)
AR= b/cm = b2/S : b.b=b2 & cmxb= S
b= wingspan in m(meters) & cm = wingchord in m(meters), S= wingarea in square meters.
also cdi(induced drag coefficient)= cl square /pi. AR. e
cl= liftcoefficient, pi = 3.14, e= efficiency factor(real wing is not identical to a prandtl wing, which has an optimal elliptical winglift distribution à la spitfire). remember adolf galland,famous ace & chiefpilot of luftwaffe,(wwar 2), asked by goering(infamous nazi luftwaffe airmarshal), what he needed to beat the RAF(Royal Air Force):" herr goering, give me a spirfire!" goering went krimp & almost swallowed his marshalbaton.
AR being below the fraction line we can see that if AR increases, then cdi or induced drag decreases.