I found with my Slow Pokers etc that if flaps are too thin ( much thicker than you quote) that they flutter at launch or deflect so easily that the model won't recover trim from a slightly imperfect launch. Presumably you haven't had this problem.
Bob
----- Original Message -----
From: Bill Gowen
To: Indoor_Construction_at_yahoogroups.com
Sent: Sunday, February 11, 2007 1:16 AM
Subject: Re: [Indoor_Construction] IHLG Flappers
Randy
Last season I was flying a 100si version of the SlowPoker in both HLG and UCLG. It weighed about 8 grams. I could HL it about 27-28' and catapult it to maybe 40'. The limitation on the HL height is my arm strength. Cat 1 times for both classes were around 42 seconds and the best flights at Kent were around 53 seconds.
For flaps my big glider uses .020 A-grain wood that is actually a little thinner than that now. At the farthest point in that I can reach with my caliper the thickness is about.016". For SCLG for Cat 1 I've gone to .010 or .012 wood for the flaps. When you get into the .010 range I don't think it matters too much whether the wood is A grain or C grain. To me it's a lot easier to use thin wood than to try to sand down something thicker so that it will deflect properly. I would read Stan Buddenbohm's SlowPoker article a couple of times to understand his philosophy.
I think it's going to be difficult to get a 6 gram glider to almost 40' with a handlaunch but Buxton could probably do it. My feeling is that a larger glider would give you more launch energy and more altitude potential.
I don't have any experience at high altitudes - yet. I think for catapult that a slightly stronger version of a Cat 1 glider would do well. For HL I really don't have a clue what will work. I'm planning on building a new Cat 1 SCLG to take to Colorado Springs in hopes that the thin air will let me get an extra 10 feet of altitude.
----- Original Message -----
From: rreyno2001
To: Indoor_Construction_at_yahoogroups.com
Sent: Saturday, February 10, 2007 7:30 PM
Subject: [Indoor_Construction] IHLG Flappers
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
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Received on Mon Feb 12 2007 - 04:42:03 CET
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