IHLG Flappers

From: rreyno2001 <rreyno_at_earthlink.net>
Date: Sun, 11 Feb 2007 00:30:56 -0000

I have been tinkering with my flappers under our 37-39' ceiling and
I'm certain I don't have them shaped correctly. If I build lightly
at 6-7 grams, I can't get them anywhere near the ceiling but I can
with 9-11gm versions. These are 21-24" gliders.

Isn't the theory that under launch conditions the flaps will flatten
out due to air pressure and drop down as the airspeed decreases? If
so this gives a pretty good undercambered airfoil and a resultant
slow minimum sinkrate glide, all things being in trim.

It is likely that flaps need to be very, very limber in the hinge
area and this likely requires balsa with very few hard grain lines
so that the material is pretty much homogeneous. In addition, I
think I work that area much too thick for the flap to actually
respond properly.

So here is my question: How do you make the flap as flexible as it
needs to be and is there a way to judge that? I notice on Kurt's
website that the airoil detailed there has a top curvature that is
continuous whereas the undercamber has been carved into the front
section and it transitions up to a very thin flap.

So if I build this airfoil such that the flap is very thin and
flexible will it help get a lighter glider to the roof?

Thanks, Randy
Received on Sat Feb 10 2007 - 16:37:57 CET