CG location on a lifting body
05-22-2003, 07:49 PM
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CG location on a lifting body
The easiest way is to make a small glider of the exact shape out of foam and when you get it flying OK transfer that CG to the larger one. It then incorporates all the strange variations that might be happening.
05-22-2003, 10:18 PM
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CG location on a lifting body
Thanks Ben,
I was going to build a small glider like you said but was looking for a place to start with the CG. Any ideas???
Thanks,
I was going to build a small glider like you said but was looking for a place to start with the CG. Any ideas???
Thanks,
05-22-2003, 10:53 PM
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CG location on a lifting body
Honestly I just make a guess based on what has worked before. It's a wierd analog lots of failures based Zen thing.
Look at
http://perso.wanadoo.fr/scherrer/mat...glish/mce.html
for a multi panel wing MAC locater. Just change the inputs to approximate your shape and you should be fairly close to the location of the MAC. Then go maybe 5 percent of the MAC forward and put the CG there as a start.
Look at
http://perso.wanadoo.fr/scherrer/mat...glish/mce.html
for a multi panel wing MAC locater. Just change the inputs to approximate your shape and you should be fairly close to the location of the MAC. Then go maybe 5 percent of the MAC forward and put the CG there as a start.
05-23-2003, 01:31 AM
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CG location on a lifting body
You want to have a center vertical keel that mirrors the side view and a "wing" that mirrors the top view.
Start with the balance so that theres about 1/3 of the area ahead of the balance.
For setting it you need to look at the stall and dive pullout charactaristics. It's easy to make anything glide with enough reflex but it'll only fly efficiently with minimum reflex and the CG as far back as practical that still lets the glide recover from dives without zooming up into more and more viscious stalls. So keep moving the balance back and reducing the reflex at the trailing edge until it doesn't fly stable in pitch. At that point you've hit the most rearwards setting.
Start with the balance so that theres about 1/3 of the area ahead of the balance.
For setting it you need to look at the stall and dive pullout charactaristics. It's easy to make anything glide with enough reflex but it'll only fly efficiently with minimum reflex and the CG as far back as practical that still lets the glide recover from dives without zooming up into more and more viscious stalls. So keep moving the balance back and reducing the reflex at the trailing edge until it doesn't fly stable in pitch. At that point you've hit the most rearwards setting.
