Gary
I tried for several years to equal the Cat 1 records with very light weight built up gliders. I never broke 40 seconds until I built my first Slow Poker. The Poker airfoil is very thin and has a lot of undercamber. My gliders with similar airfoils on fixed wings were a lot like trying to launch a parachute. With flatter airfoils altitude was not a problem but the sink rate was too much.
A couple of years ago I had my best contest day with gliders by breaking 80 seconds in Cat 1 in all 3 classes. The Slow Poker did it in HLG and UCLG and a similar shrunken version did it in Standard class.
Regardless of how hard the flap function is to analyze, they definitely do work.
----- Original Message -----
From: dgbj_at_aol.com
To: Indoor_Construction_at_yahoogroups.com
Sent: Sunday, February 11, 2007 6:37 PM
Subject: Re: [Indoor_Construction] IHLG Flappers
I've been wondering how those flaps worked ever since I first saw them. The
theory is that under the increased flight loads of a fast launch, the flaps
bend up, reducing the camber, the lift and the tendency to loop. But how
much force really exists on the wing? With typical loadings, there is around
0.1-0.2 gram per square inch load, most concentrated in the forward half, less
on the flap. How much force is required to move the flap? How much
difference in lift does that flap change make? The lift is also not directly
proportional to the square of the velocity. The excess lift will make the plane
loop, yes, but in looping the circular airflow reduces both the attack angle and
the decalage, both reducing lift and countering the tendency to loop.
Somewhere the glider finds a balance, and it isn't at the same attack angle as in
steady glide. What would that excess lift pull against? There is only 9
grams of airplane and it only pulls back when it is accelerated. In a steep
climb, most of the weight force is directed back toward the tail, not
perpendicular to the wing chord. The balancing around the CG that establishes attack
angle in steady glide is not at work here.
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Received on Sun Feb 11 2007 - 16:24:36 CET
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