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Author Topic: Trimming for flight  (Read 619 times)
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johnok
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« on: September 09, 2017, 03:09:00 AM »

Hi everybody,

Please can someone tell me what I'm doing wrong? I have built several all sheet glider in the range 15" to 24" wingspan for catapult launching. All were carefully balanced to bring the CG. to the spec. - hand launched to test glide successfully but when I catapult launch they all go up then straight down. Don't quite no where to go so any suggestions will be gratefully received.

cheers John K.
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billdennis747
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« Reply #1 on: September 09, 2017, 04:05:31 AM »

I have no idea but if you google ´trimming catapult gliders´there are a number of articles. Like this one;
http://www.roguehangar.com/aerocraft/documents/information/Tips%20on%20Trimming%20and%20Flying%20a%20Catapult%20Glider.pdf
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johnok
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« Reply #2 on: September 09, 2017, 08:44:31 AM »

Thanks !
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Fido
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« Reply #3 on: September 09, 2017, 08:47:31 PM »

The easy answer is:

Trim launch pattern with rudder and angle of attack. Trim glide with movement of cg and stab tilt.

There are of course a million tweeks beside of these, but the very base of hlg/clg are as simple as this! Smiley
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modler
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« Reply #4 on: October 03, 2017, 03:05:25 PM »

John, I like to bend one side of the stab up and the other down. This induces a barrel roll on launch and aids in a good transition to glide. The first launch should be with flat surfaces to see which way the glider wants to turn naturally. Play with bending the stab and rudder a little at a time to adjust launch and glide.

Bill G.
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Hepcat
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« Reply #5 on: October 03, 2017, 06:26:56 PM »

JohnK,
There is a fair bit of clever,clever stuff that might be needed later but there is one thing  that almost everyone does when starting CLG.  We nearly all did it, then got over it and then forgot about it!  What it was is this.  We had a new glider, cafefully made and did not want to damage anything so we pulled the catapult gently back and not too far and gave a nice slow launch so as not to break anything and, as you say the model climbs vertically, turns over and dives into the ground.  Try pulling the catapult back as far as you can. The glider will zip away too fast to see and, with any luck you will spot it gliding down quite well.  The other thing it might do is a fast loop almost to your feet.  If it does the loop you must then try another powerful launch but with more right bank as you launch.   I think cat gliders are probably more often damaged with slow launches than anything else. Please try some launches with the catapult pulled as far as you can and then report back so we can talk over the little problems!
John(Hepcat)
   
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Stan
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« Reply #6 on: October 03, 2017, 06:45:12 PM »

Listen to Hepcat, he is giving great advice.
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USch
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« Reply #7 on: October 04, 2017, 11:50:04 AM »

just my 2 pence worth....

From what you write it seems you dont launch the model into his natural turn.
Any hand launch or CLG glider has to climb in a helix pattern, right or left dependent if you are right or left handed. To do that you will have to bank the model accordingly about 45° during launch. At the most you will get some high speed circles nearly parallel to the ground, but not the damn... straight up, straight down sindrome.

Urs
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