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Posted for Gary Hall <gary.chris@comcast.net>:
Hi Gang,
Interesting discussion. I have always heard that slow speed aircraft (except
for certain sailplanes) do not derive any "real" benefits from winglets.
In this article (below) they state, "The energy expended in this phenomenon
is directly responsible for the induced drag, which can be extremely large for
certain aircraft wing configurations--particularly under high-lift, low-speed
flight conditions."
As I have heard Burt Rutan state they do not appreciably help the Long or
Veri Eze aircraft which have very large airfoil winglets. He has said that the
desired effects are only for speeds that really exceed the speed for his
designs. So I find that comments on both sides interesting.
http://oea.larc.nasa.gov/PAIS/Concept2Reality/winglets.html
In this brief article;
http://library.thinkquest.org/18033/whitcomb.html
They say, "The research showed that the winglets could increase an aircraft's
range by as much as 7 percent at cruise speeds." Which backs up what Rutan
said.
In this article, "The winglet flight test program brought together NASA, the
U.S. Air Force, and Boeing, which began the effort with configuration studies
and contractual work to design and manufacture the test articles which
measured 9 feet high and 6 feet across at the base.
Flight conditions in which test data was obtained included a cruise speed of
about 500 mph at altitudes of 30,000 to 35,000 feet;"
Again this seems to support what Burt has said.
In the next article (if you can get through the technical gibberish), they
state, "using a full-scale model of the outboard 5.6 feet of a 15-meter-class
high
performance sailplane wing. Marchman, Manor, and Faery13 found that symmetric
winglets were best for general aviation aircraft, but were less
effective on tapered wings."
http://www.star-tech-inc.com/papers/aiaa/aiaa.pdf
Here is an interesting discussion.
http://www.eng-tips.com/viewthread.cfm?qid=87793&page=1
Bottom line is that I can't see where the Lancair winglets (as they are
today) add any measurable beneficial help. I would like to see some actual
wind tunnel tests done on the Lancair wing and winglet combination to convince
me otherwise. They do look cool though.
Warm regards,
Gary
FXE (Fort Lauderdale Executive)
http://www.uslan.com/hinge-kit.html
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