"steve.t" wrote

Jim:

I've noticed and have flown C-15x with the exagerated wing tip (folded
down) and I've not really noticed any improvement at low speed (which
is what I think it is for, better handling at low speed for approach).

The fact that all small planes do not have that type of wingtip, is a
testamony to what little benefit they must provide. If they were
noticeable, by simple observation, everyone would be using them. I have no
doubt that they have a measureable gain in slow speed performance, when
measured in a wind tunnel, but enough for you to notice on the
plane?....Gimmic?... They do look cool. g


What I am interested in is increased lift, and better performance (in
terms of fuel usage) which is what the winglets do for the B-747
(something like 30% improvement in fuel economy! if memory serves me
correctly).

30% seems a little, or a lot high, from my memory.

Longer wingspan, high aspect ratio wings are almost always more efficient.
Look at sailplanes. That is the primary way winglets improve efficiency.
Also, remember my comment about them being better at higher speeds than
where we operate piston singles, or even piston twins.

So if we could obtain the equivalent above 6000' MSL without wrecking
the approach speed performance, I was wondering if it would be worth
it. Particularly when looking at US$3/gal for 100LL.

Unlikely. See above.

But if a single mod could take advantage of the vortice energy to
recover 30% at cruise, that might make it worth doing. Particularly if
it added to climb rates (which I also see with all the STCs I currently
have).

Climb rates are at slower speeds, so even less gain than cruise.

I am far from an expert on all things aerodynamic; I just read all I can.
My take on winglets for small planes is like the argument I made on the
drooped tips, earlier. If they were significant for use in small planes,
everyone would be using them. Are all of the major manufactures of light
planes using them? Nope. Wrong tree. (you're barking up) ;-)
--
Jim in NC