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Old Jul 06, 2005, 08:43 AM
J Morgan is offline
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Help with CG on Mig-21 "Fishbed"?


Sorry this isn't EDF but looking for help on this delta planform and wasn't any experience in pushers for it. Trying to figure CG and was wondering what was a safe % of MAC ( MAC has already been determined)to start with this delta type wing?
BTW, it is 32" ws, Typhoon 15/10 on 3s-3100 and AUW is about 30 oz.
Should be pretty fast.

J
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Latest blog entry: AC-130E Vietnam era gunship
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Old Jul 06, 2005, 08:50 AM
philip noel is offline
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Scale Aircraft Designer
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could you send me the wing plan including the c/l of the aircraft

to mailto@philipnoel.co.uk

and i will sort it out for you

phil
Old Jul 06, 2005, 09:30 AM
J Morgan is offline
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Phil,
You've got mail!

J
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Latest blog entry: AC-130E Vietnam era gunship
Old Jul 06, 2005, 02:04 PM
Speed is Life is offline
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Quote:
Originally Posted by J Morgan
Sorry this isn't EDF but looking for help on this delta planform and wasn't any experience in pushers for it. Trying to figure CG and was wondering what was a safe % of MAC ( MAC has already been determined)to start with this delta type wing?
BTW, it is 32" ws, Typhoon 15/10 on 3s-3100 and AUW is about 30 oz.
Should be pretty fast.

J
These guys, www.goldenwestmodels.net, make a large DF/Turbine Mig-21. Maybe a call to them would give you a starting point for a safe CG.
Old Jul 06, 2005, 05:24 PM
jetset44 is offline
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J,
Although I haven't run any calculations, I think it's a safe bet that this bird will fly well with the CG at 20% MAC. That's where my F-15 Park Jet flew best, and while it doesn't have a true delta wing it's not that far off from it either. That may not be the overall best-handling CG for the Mig-21, but it should be close enough that the airplane will handle well for the first flight. You can then experiment to find the best CG location on subsequent flights.

In addition, I highly advocate flying this model as a chuck glider to verify the CG location and control throws. That's one of the beauties of these foam park jets--just remove the motor and power batteries, put in a small 110 mAh rx pack, and they make great RC chuck gliders! Nearly all of my park jets flew as gliders before they made powered flights. Heck, I could fly my F-18 over 100 ft as a glider, including big looping turns to bring the model back to me! That's the most fun way to test the CG. I just taped on quarters as necessary to experiment with the CG.

Steve
Old Jul 06, 2005, 08:55 PM
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Thanks for all the help here. I think it is worked out now. CG should be @ 42% of root chord from LE. I appreciate all the help and will now slink back to the "pusher" forum.

J
RCG Plus Member
Latest blog entry: AC-130E Vietnam era gunship


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