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Author Topic: Trimming tiny gliders for ballistic launch  (Read 1407 times)
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Alexandre Cruz
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« on: July 03, 2009, 11:46:55 AM »

Tiny gliders are HLG or CLG under 8” wing span, usually built for outdoor flying. The is postal contest going on during 2009: http://tinygliders.blogspot.com/

I use this the technique to try to get the maximum altitude during launch:
•    Build your model using a straight, non airfoiled rudder
•    Trim the model to roll right using only ailerons or wing warping
•    Once you have a consistent but slow right roll during glide remove the rudder
•    Install a new rudder airfoil sanded for providing left turn, not symmetric
•    Adjust the rudder until the model glides on a wide left turn

You are ready to go. My models will do a half roll to the left when climbing and then roll quickly to level when speed comes down. Try the technique; if you like the result, build your next model with asymmetric wings by adding more area to the left side (if left pattern is desired).
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Rewinged
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« Reply #1 on: July 03, 2009, 02:12:10 PM »

This doesn't sound too different from typical trim, but it is a very different technique for getting there relative to what I have been doing.

I would love to see a video of one of your launches that could be played in slow motion.

Thanks,
Bill
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Tmat
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« Reply #2 on: July 03, 2009, 07:50:55 PM »

Alexandre,
That's an interesting way that you trim your tiny catapult gliders!
I'm not sure that I understand the reasoning behind trimming the plane first with the flat plate fin, then with the airfoiled fin. Why not just build in the adjustments with the cambered fin and trim it that way to begin with?
With my 8" gliders I set the trim up on the work bench and they fly almost perfectly right away with no need to change the fin. Seems like an extra step to me. Is there something that is gained with this trimming method that offers an advantage?

Tony
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Alexandre Cruz
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« Reply #3 on: July 03, 2009, 11:03:44 PM »

 I am probably not that skilled to build. Consitent trimming is the benefit for me.
 In general my models did a roll or more to the left. Going this way makes me trim the model by the wing lift difference only an then adding rudder to make it go in the different direction. My models became a lot better after doing this. Most of them will climb on slow left half roll and roll to level on top.
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« Reply #4 on: August 27, 2009, 10:26:02 PM »

I built a "Round Tipper" CLG (6") by Billy Stiltner last night and had it at the field today. I modified the design to make it a bit more suitable (read: ROBUST) for an 8 yr. old that I'm mentoring, using 3mm for the wing and adding 0.8mm doublers to the fuselage front going back to just behind the wing TE - weighs 2 grams with a coat of lacquer. After trimming it to fly from a hand launch, I put it up with a 1/8 inch catapult. Took a few tries before I got it to come off the top in a glide, but all I can say is that it haas a rather unusual transition.

I CANNOT describe what happens as the thing is going up - it all happens too fast - but it goes STRAIGHT up and then BUNTS into level flight (MOST of the time) Huh. It literally SNAPS FROM VERTICAL TO HORIZONTAL. Sometimes this snap puts the model nearly inverted from which recovery occurs at 10 ft above the ground Lips sealed. Really weird but truly spectacular!!

Haven't tried a "full pull" yet, it got dark too early, but am up to 60% and averaging 30 seconds. I am REALLY surprised at the performance of this tiny plane, and so were the RC'ers present.

Pete
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