On Mar 15, 4:12*pm, weersch wrote:
From the recent thread about winglets,http://groups.google.com/group/rec.a...wse_thread/thr...,
I read Mark Maughmer's article "THE DESIGN OF WINGLETS FOR HIGH-
PERFORMANCE SAILPLANES".
I was flabbergasted about how little these winglets actually bring in
performance improvement, considering the amount of discussion on this
topic.
I fly in the Sierras, mostly in conditions with more than 4 kts lift.
If I read Fig. 8 and Fig.11 correctly in Mark's quoted article, with
winglets I would gain at max 0.5% L/D at 75kts cruise and 0.5% XC
speed at 4kts lift (assuming that the D2 is close enough to the V2C).
0.5% that is 0.2 point L/D improvement for the V2C @ 75 kts !!!
With my 1000 hours and 1000 flights experience, I still make enough
piloting errors like wrong turn at thermal entry, picking wrong lift
line, etc., which cause losses of a magnitude higher then these 0.5%
gains.
Based on my safety requirements, I set my polar degradation to 20%.
I have many flying buddies that achieve better flights in ships with
less performance, based on the fact that they choose to fly with less
margin and higher risk ( and are better pilots than I am).

In the conclusion of his article, Mark refers to the fact that the
difference between competition winner and no.6 is 1.5% and that
therefore the winglet gains are significant. I guess if you belong to
the "must win" competition crowd, that argument is valid.
My conclusion: for the other 90% of sailplane pilots, winglets are
irrelevant.

Of course the winglets look cool and the coolness factor is always
very important.
But for me, the V2C (and myself) already have so much coolness that I
won't need new winglets (nor hair implants on my balding head, nor a
one inch extension on my willy if I have to believe all the emails I
get)

V2C 3U

my guess is that one time somewhere some guy with winglets beat a guy
without winglets.