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Old Mar 26, 2007, 06:15 PM
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C.G. on the Dragonfly Strong


i went out last week and did some test glides. i started looking for that sweet spot. you guys who fly flat land t.d. know what it is. jack said his dragonfly was up to 72 oz. well i found the sweet spot on both my dragonflys. my c.g. is now set back 4 and 3/8 inches from the l.E. my tow hook is 1/8 of an inch in front of the c.g. and the weight is down to 67.5 oz. on the high start or the wench the dragonfly stands on its tail and goes straight up. it feels more alive now and points out thermals like an old hunting dog. hope this helps some of you guys flying the dragonfly strong. you will not belive the way this changes the way the bird flys.
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Old Mar 27, 2007, 10:43 AM
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Dragonfly CG


Mike;
thanks for the info.
so many times I see the manuf. suggested CG to be very conservative. A little "tweaking" and the plane takes on a whole new personality!

The reports we have say if flew good at the recommended, I can imagine what you are getting now....

Happy Landings!
Bob
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Old Oct 15, 2007, 11:19 AM
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I have mine set up at about 107 mm from the LE with a IB3800 NiMH 5 cell pack and no additional nose weight.

AJ
Old Oct 15, 2007, 09:18 PM
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Mine's at 112 mm from the leading edge. It's a bit twitchy, like I like it. Shows lift well, and stays in it.

Jack
Old Oct 16, 2007, 10:58 AM
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Cg


Looks like you both have it a little more aft than I have mine. Will try it with the CG further back, but will have to change out the IB3800 pack for a smaller one. Thanks
AJ
Old Oct 17, 2007, 03:51 AM
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Jack, are you still lowering the ailerons (instead of rising) for landing approach?
Congrats with your result!
Jurgen.
Old Oct 18, 2007, 02:50 PM
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Jurgen...

Yes, I still lower them. I am going to set up another program in my 9303 for this glider and fly with them raised slightly so I can fly it both ways in the same day. I'll report back.

Jack
Old Oct 18, 2007, 04:28 PM
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Quote:
Originally Posted by ajbhatta
Looks like you both have it a little more aft than I have mine. AJ
AJ, ever since I have know Jack he has always flown his C/G back in the danger zone. So be careful. You might work your way back a little at a time but I bet you stop before you get as far back as Jack.

Walt
Old Oct 18, 2007, 05:01 PM
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Thx Jack, curious for your findings, I gonna check the lowering out too my models (no DFS), weather/family/available stick time permitting.
What's your reason for far aft CG's? Performance? Signalling? Both? Where is the limit for you?
Jurgen.
Old Oct 18, 2007, 07:38 PM
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Reason for aft CG... Both... I find that models signal lift much better and cruise flatter at as near zeroed out (my term) as possible. My limit is where the model begins to tuck if I add more than half down trim. I have to be careful with reflex, and make sure I add a touch of up trim with it, so it won't speed up and tuck in that mode. It all varies - model to model - due to airfoils, moments, etc.

To set a model up, I balance it where it is recommended, or where I've calculated it to be. I then set the stab at 1 to 1.5 degrees positive pitch (depending on the airfoil). I remove weight until it gets squirriley, and add 1/4 oz. back. I double check everything to see if I can take more out. My "dive test" consists of adding 1/2 down trim and watching for tuck. If she moves out smartly without trying to scratch her tow hook with her tips, I'm there. If not, I double check everything again.

This doesn't work for everyone, but I've been doing this since I was a lowly Legionair builder back in the '70s. It hasn't failed me yet. My unballasted Dragonfly moved out nicely in the wind at TNT... with my reflex settings and aft CG, she ran very well with the slick-winged wonders.

Jack
Old Oct 19, 2007, 07:00 AM
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Thanks Jack, although the terms are open for interpretation (but this is inevitable the peculiar limit of forum communication and individual judgement). For example what is "squirrely", "move out smartly", "1/2 trim" if you don't have a clue of the total travel.
Anyway it gives us the philosophy you're following and the proof that it works. Not everyone is that open book
Jurgen.
Old Oct 24, 2007, 04:50 PM
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DS CG position


Thanks Walt. I will probably stay at close to present setting and see how it goes, but may move it a couple of mm back and check the response. Don't want any drastic changes. I have a beat up Amethyst 3.7 m that likes to fly on with the aft CG.
Cheers
AJ
Old Oct 24, 2007, 05:16 PM
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Flew the Dragonfly with both programs... drooped ailerons and reflexed. It flys slower with them drooped, but has only slightly better control reflexed. That could be due to the higher speed. I am just as accurate with them drooped a bit, and the landing is slower. I did notice that I use more rudder in the drooped mode. Probably more of a personal preference thing than anything else.

It's still for sale if anyone wants a good one.

Jack


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