Message-ID: <19981231022719.10675.qmail@www06.netaddress.usa.net>
Date: Thu, 31 Dec 1998 02:27:19
From: Dan Schaefer <dfschaefer@usa.net>
To: lancair.list@olsusa.com
Subject: reflexing and flaperons
Mime-Version: 1.0

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Thanks, Scott, for the interesting comments about reflexing. I don't know
what airfoil Lancair used on the 320/360 models, though I believe
(rightly or wrongly, to be sure) that they all used *essentially*
the same wing with the same NLF series profile.

Just prior to buying my 235 kit, back in '85-'86, I researched the
airfoils that Lance used (the information was available, either in his
literature or in a magazine article) by contacting the folks at NASA - at
Langley, if I remember correctly (CRS due to age, they tell me) - as I
had heard a lot of wind tunnel data had been generated on this series
of foils, and they made their data available through a friend.

Two features stand out in the data (and I'm sorry, but I loaned the
package out many years ago and it never came back): When in the laminar
flow regime, the airfoil has better drag numbers, that is, lower, than
the turbulent flow shapes in common use today; second, and the one that
I thought was most impressive, if the laminar flow is tripped such
that it goes turbulent (due to rain or bug accumulation maybe), it
does not experience a large loss of lift - just higher drag (nice if you
run through a patch of rain on short final); and third, what you pay for
all this good stuff, quite a bit higher than "normal" (that is, compared
to commonly used airfoils) pitching moment. All wings want to turn nose
down when they are producing lift (well, all that I know about) and the
NLF series just want to do it with a lot more force.

One thing that impressed the importance of reflexing to relieve the
stresses set up in the wing by the high pitching moment was the factory
pilot who checked me out in my airplane (Mike DeHate) being VERY insistant
about going to full reflex at and above 160 MPH IAS. When the factory
guy speaks, I listen (particularly when it was his butt up there with me).

Later, 

Dan Schaefer