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Author Topic: Adjusting Incidence on a Tumblng Pigeon DT CLG  (Read 1326 times)
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Rewinged
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« Reply #25 on: August 29, 2018, 08:18:18 PM »

A little late, but in case more pictures help...  This is of a well-trimmed glider, and you can see that there is plenty of room left for adjustment. Since I don't like constructing DT systems, I build the wing and tails but buy the largely completed fuselage from Stan Buddenbohm.
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Sailaway
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« Reply #26 on: August 30, 2018, 10:35:17 AM »

Those pictures makes the concept real clear to me. Thanks for taking the trouble. I did order the glider from Stan to learn. I figure a 0.5 or degree  down TE should be about a  32nd on a 3.5 inch chord. So there is enough place to make the whole TE go down as needed. In the photo it appears your left side of the tail is way higher. Is that for the turn or avoid the thumb strike? Or a dihedral on tail? 

Again thanks to all of you. Dan, yes  I just joined the NFFS.
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danberry
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« Reply #27 on: August 30, 2018, 10:44:23 AM »

Good deal on joining NFFS.

Stab tilt induces glide turn. It will turn toward the high side of the stab.
The story on how this got figured out is a good one.
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flydean1
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« Reply #28 on: August 30, 2018, 12:11:32 PM »

The story on how this got figured out is a good one.

Well Dan, let us in on it. Huh Huh
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mike
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« Reply #29 on: August 30, 2018, 12:17:50 PM »

....Stab tilt induces glide turn. It will turn toward the high side of the stab. ....

Birds showed us this one.  Tilting your tail gives a sideways force to cause yaw.
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Rewinged
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« Reply #30 on: August 30, 2018, 01:14:25 PM »

Glad the pictures were useful!

Yes, the stab tilt is to help the glide turn.  A contest CLG is typically adjusted with a tiny bit of rudder for the climb, and stab tilt for the glide turn.  (L rudder for a flyer who holds the launch stick in their left hand and the glider in their right.  Just bend the rudder near the fuselage a tiny bit, not higher up on the fin.)

With a rearward CG, (and associated minimum decalage as is present in most free flight planes), the stabilizer will be lifting. With a tilted stabilizer, part of that lift force will be sideways, inducing a turn.

The dihedral in my stab is to help avoid the stab strikng my thunb or finger that were holding the glider.  I was told it wouldn't help, but It does seem to help me.
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« Reply #31 on: August 30, 2018, 08:42:19 PM »

i hurriedly put together a sort of pigeon DT glider to understand the concept. I get it now. Drove to the field to get get a few pulls. On my fourth pull, got a stab strike on me left hand. That was the end time to go home.
So what is your secret to estimate the dihedral on the tail? Can any flat stab be converted to Dihedral. Would i be wrong in saying left side dihedral more than the other to make it turn left after transition ? I think, I will need it too, unless there's a way to adjust( longer?) hold button and the  front hook design?

Just thinking out load, that would it not be great to have V-tail design in such case? Get rid of the rudder ( lighten the tail) and reduce the possibility of stab strike tremendously. However, never seen a CLG with a V-tail design yet.  Just thinking.
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Rossclements
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« Reply #32 on: September 24, 2018, 11:31:50 AM »

These guys only use v tails with great success: https://www.youtube.com/watch?v=FNuYjOAwV_E

They have how to's with dimensions and all on their main channel page too.
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danberry
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« Reply #33 on: September 25, 2018, 12:08:36 AM »

The story on how this got figured out is a good one.

Well Dan, let us in on it. Huh Huh


Frank Parmenter had built a new gas plane, finished it on a Friday night. He noticed that the stab was glued on with a tilt but didn't fool with straightening it. Flew the plane on Saturday. It flew with a beautiful glide turn. He was unable to live with the tilted stab and fixed it overnight. On Sunday he had lost the turn. The only change was the stab tilt. The engineer mind took over and here we are.
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