How far back can I move my CG?  
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All Forums >> RC Airplanes >> 3D Flying! >> How far back can I move my CG?
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How far back can I move my CG? - 9/9/2008 5:24:03 AM   
Ken4


 

Posts: 52
Joined: 7/8/2007
From: , SINGAPORE
Status: offline 		The instruction manual for the Flition Votec351 says 102cm to 122cm from the leading edge. I've already gone beyond that, about 124cm. Is it safe to go any further? Im learning to do more 3D stuff like harriers, hovers, etc. I've already added like 80g to the tail. My plane can hover now for about 10secs before it drops out of a hover. But I want to be able to do the 1min hover thing. Hehe. The plane still seems to fly ok. When the plane flies inverted, I still have to add a little bit of down elevator to keep the nose up. On landing though, the plane feels kinda weird, when i cut throttle down to half, I have to give some down elevator to make the plane glide down. If I give too little throttle, the plane might stall. What Im trying to say is that the plane is harder to land now. Advice appreciated. Thanks.
       Post #: 1

RE: How far back can I move my CG? - 9/9/2008 5:34:38 AM   
DMcQuinn



Posts: 1588
Joined: 1/9/2002
From: Chesterfield, MO, USA
Status: offline 		Your experience is exactly what you get as you move the cg back. Landings do get a little trickier. The tail wants to fall as the airspeed bleeds off. I'd leave the CG alone and just concentrate on your hovering skills. A rearward CG helps in the hover but really you just have to learn to do it with the sticks. If you move the CG back another cm, the flying and landing part will get more difficult and the hover will not improve all that much.

(in reply to Ken4)
       Post #: 2

RE: How far back can I move my CG? - 9/9/2008 5:35:01 AM   
freeair


 

Posts: 392
Joined: 5/10/2008
From: queensland, AUSTRALIA
Status: offline 		manufactures of many ARF models do not give correct COG measurements as i have found with my Katana where it was recommended to have the COG at 90mm where the correct cog was 140mm. you better off testing and measuring yourself until your happy with the flights. also a good long hover does need a good powerfull engine and the correct prop.

(in reply to Ken4)
       Post #: 3

RE: How far back can I move my CG? - 9/9/2008 5:35:14 AM   
JohnW



Posts: 1770
Joined: 3/22/2002
From: Lincoln, NE, USA
Status: offline 		If you are climbing when you throttle back, i.e. the need for down elevator on landing approach, you are too tail heavy in my opinion. If you want to keep moving it back, do so in very small steps until the plane gives you a warning that you are too far back, but I think you already got a warning with the need for down elevator on landing approach so I wouldn't go any further back, and would probably put it back into spec, i.e. the 102-122 range. Besides, the key to a 1min hover is not being tail heavy, but control.

(in reply to Ken4)
       Post #: 4

RE: How far back can I move my CG? - 9/9/2008 5:52:24 AM   
Ken4


 

Posts: 52
Joined: 7/8/2007
From: , SINGAPORE
Status: offline 		Wow. Thanks for so many quick replies. And at 5.35am in the morning! Kewl! I think I will leave my CG as it is.

(in reply to JohnW)
       Post #: 5

RE: How far back can I move my CG? - 9/9/2008 6:12:25 AM   
tIANci



Posts: 8556
Joined: 1/15/2004
From: Kuala Lumpur, MALAYSIA
Status: online 		For me I check CG by going inverted ... if its diving then you are nose heavy and if its climbing then its tail heavy. Try to get her settled at no input when you are inverted, that is a good start. Afther than take her back a bit at a time. I got friends who love tail heavy planes whereas I like them just slightly nose heavy. Adjust it to suit what you prefer once you can master a certain manuever ...

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(in reply to Ken4)
       Post #: 6

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