Elastic Launched Gliders B

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bjt4888
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Re: Elastic Launched Gliders B

Post by bjt4888 » April 6th, 2019, 1:49 pm

AM,

By flap deflection, I am referring to the curvature of the flaps. See a sample of typical flap curvature for one of my gliders in the picture on reply 21 in this thread:

http://www.hippocketaeronautics.com/hpa ... ic=16492.0

I will look for a picture of what I am referring to as a shim.

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Re: Elastic Launched Gliders B

Post by bjt4888 » April 6th, 2019, 2:06 pm

AM,

See the pictures in reply 35 at the bottom of this thread. The fifth picture on this reply is of the shimmed wing mount on my high ceiling Littl Sweep. I think that the idea is the same as you are describing for your 3/64” tapered shim for your FF airplane. 1.5 degrees is a fair amount of wing incidence for a flapper glider as the curvature of the flaps provides some incidence also, even during the climb (again, depending upon the stiffness of the flaps).

http://www.hippocketaeronautics.com/hpa ... c=20281.25

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Re: Elastic Launched Gliders B

Post by AirplaneMan » April 6th, 2019, 2:20 pm

Yes that is how I am using the shim on my glider. By flap deflection I meant the amount that the flap is deflected from the normal wing. So when I said 3/8 inches of flap deflection I meant that the end of the flap is 3/8 inches lower than the flap-wing joint. But why exactly is 3/8 inches of flap deflection bad? How does it affect the glider's flight performance?

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Re: Elastic Launched Gliders B

Post by bjt4888 » April 6th, 2019, 2:47 pm

AM,

More flap deflection is not inherently a bad thing. The advice I am giving you is to setup your glider following conventional, successful past practices. Doing this will possibly help diagnose your transition issues.

My experience with readjusting flap deflection, or curvature, is that this just requires gently bending the flap to a different, lesser in this case, curvature. I’m not understanding why readjusting flaps involves “taking them off” or “ripping” them.

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Re: Elastic Launched Gliders B

Post by AirplaneMan » April 6th, 2019, 3:03 pm

Oh yeah I forgot about that. I'll lessen the flap deflection and then test the glider again on Monday when I have access to the gym at school.

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Re: Elastic Launched Gliders B

Post by bjt4888 » April 6th, 2019, 3:08 pm

AM,

Good luck. Be sure to note all the steps I suggested in the earlier post.

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Re: Elastic Launched Gliders B

Post by Pythagorean » April 9th, 2019, 12:13 pm

Hello all,

I am new to the forums, but not new to ELG.

So I am going to be flying at the OSU State tournament, where the air will be on. I have found modest success in our high school gym with the air on flying my FF glider at a low pitch (altitude) angle, somewhere between 20 and 25 degrees with a pullback of 55cm. My good flight times where 14.3-15.2 seconds. However, I will be flying against some of the best glider teams and would like some tips on what to do. Please note the air is flowing downward from circular vents and the flyable ceiling height is around 28 feet.

Also, another one of my FF gliders has a major roll issue. At low launch velocity (pullback of 30-40 cm) it banks left where it launches up moderately while rolling and turning around like the rudder/wing are creating to much roll to the left. However, at a higher launch velocity (45-50cm), the glider flies normally but then straightens out mid-flight. I pulled off my wing and its CG is slightly right of the pylon. I wonder if the CG of the wing is counteracting the rudder as the glider loses momentum. Any tips would be great, as I would like to change the CG to dead center over the pylon without reducing wing surface area and with minimal room for error (eg. minimal sanding or room for over/underestimating). I have re-glued my rudder at a less severe angle and will see how that affects flight when I get a chance. Upon further testing, I appeared to reach a "0" where the roll created by the rudder counteracted the CG difference of the wing. However, at the end of my flights, the glider would randomly swoop upwards into a stall, and then nosedive. This is a similar flight pattern to when I launch a glider without much roll, eg. no transition. Is it possible that my glider is "running out" of roll or cannot sustain itself in a circular flight pattern? Please note that this was observed at 35cm of draw length.

Thanks

P.S. I am using 1/16" rubber on a flat piece of 2"x4" softwood.
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Re: Elastic Launched Gliders B

Post by builderguy135 » April 19th, 2019, 3:48 pm

If my glider is flying kind of fast while hand gliding, is it right to increase flap deflection to try to increase lift with its speed?
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Re: Elastic Launched Gliders B

Post by bjt4888 » April 19th, 2019, 6:12 pm

Builder,

Flap deflection for the typical gym ceiling heights at SO competitions would typically be between 1/8” and 1/4”, depending upon flap size and stiffness. We usually use moderate size relatively soft flaps and start with 3/16” flap deflection for this year.

Best to test small differences in flap deflection by flying full flights and seeing what gives the longest flights.

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Re: Elastic Launched Gliders B

Post by builderguy135 » April 25th, 2019, 10:03 pm

What are some things i could do with a flapped foam glider in order to shoot it higher? (40 ft at nationals)
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