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Author Topic: Trimming for flight  (Read 1361 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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Ministick7
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« Reply #8 on: March 04, 2018, 11:46:36 AM »

Hello to all: Just getting back into freeflight a bit. Used to do some indoor. In looking for trimming tips for outdoor HLG. I read an article posted here. I guess most of these ideas will work with outdoor HLG, but I am looking for more, and perhaps even better tips.  I am very interested in advice from you flyers who have experience with outdoor. Our weather here in Philadelphia area is windy and snow just melting. Will have to wait a few days at least to fly the new ones I built: U S Kid from a Campbell's Custom Kit, Cleveland's Dart 12", modified Sweepette 9", and a Lawn Dartie 8". Thank you for all the great information here at Hip Pockets Aeronautics. I just became a member. Here is that article: http://www.roguehangar.com/aerocraft/documents/information/Tips%20on%20Trimming%20and%20Flying%20a%20Catapult%20Glider.pdf (by the way, I am the guy who wrote this article. A long time ago, it seems.)
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Ministick7
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« Reply #9 on: March 04, 2018, 11:48:31 AM »

Oops, I meant CLG, not HLG in above post.
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Rewinged
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« Reply #10 on: March 04, 2018, 08:31:22 PM »

See the following for starters:
http://www.hippocketaeronautics.com/hpa_forum/index.php?topic=14853.0

Note that the smaller gliders are harder to trim...a tiny, tiny change goes a long way, especially at launch because of the high speed!

--Bill
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OZPAF
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« Reply #11 on: March 05, 2018, 12:08:51 AM »

Rewinged's advice is good and should give a few pointers to different styles of trimming. I had a quick look at your article MS - and it seems similar to a method used by Curt Stevens, both employing low power almost horizontal launches to start with.
I have moved quickly into cat launching as soon as the glide seems reasonable and there are no indications of warped surfaces or bad misalignment.
As Yak 52 mentions in that link of RW's it is best to stick to a standard pull on the glider and then work from there. I also keep the bank and launch angle constant at around 60-70 deg and 50 or so bank angle. I then fine tune the climb and transition by adjusting the decalage and rudder in very small steps until the glider climbs and transitions within a 1/4 to 1/2 turn to the right and has a steep climb. If the transition takes more than 1/2 turn - I reduce the decalage,(providing the glide turn indicates sufficient rudder) if it is less than a 1/4 and/or lawn darts - I add decalage. Wash in on the inside wing is also used as part of the decalage adjustment.

Only after the climb/transition is ok will I worry too much about the glide and the turn circle radius. If the turn is open and the transition is more than around a 1/4 turn - I'll try a bit more rudder into the turn.

I'll then fine tune the glide by taking off/or adding small(pin heads)  of modelling clay to the nose, in some cases using wing tip weight if I'm happy with the rudder setting(in the climb) and it is still not turning enough on the glide

Finally these last adjustments may require a slight alteration to the launch angles to obtain a better height and transition.

This is the sequence which seems to work for me.

John
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cglynn
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« Reply #12 on: March 05, 2018, 01:55:15 PM »

Find Josh Finn's youtube channel.  He has an excellent video about trimming and flying CLG's.  I learned more in the 12 minutes of that video than I have in 3 years of flying.  The way Josh presents it, it just makes sense.

CG
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