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Proud Bird CG Question - 6/5/2006 12:32:20 PM   
tropejm


 

Posts: 11
Joined: 9/4/2002
From: Stamford, CT, USA
Status: offline 		Is anyone out there flying the Proud Bird? I need to know a good starting point for the CG.

Thanks.
       Post #: 1

RE: Proud Bird CG Question - 6/5/2006 7:38:47 PM   
daven



Posts: 6887
Joined: 12/7/2001
From: Andover, MN, USA
Status: online 		If you call Lyle, this is what He'll tell you.

Put the servo tray as far back in the saddle as possible. Put the Tank in the front, and the battery and receiver between the two and fly it.

Thats what I did with my Proud Bird, and it was a very good flying plane.

_____________________________

Dave Norman

klasskote.com
supertrc.com

(in reply to tropejm)
       Post #: 2

RE: Proud Bird CG Question - 6/5/2006 7:50:21 PM   
luv to race


 

Posts: 465
Joined: 12/10/2002
From: Liquored, FL,
Status: offline 		I didn't have the heart to say that... But Dave's right.

If you want a measurement use this.... No further back than 4" !!, however I did fly those things close to 4 1/4" and they were okay. BUT, if I was you.. I'd balance it at 3 1/2 to 3 3/34 and go from there.... that's a safe number. And be sure to measure from the front of the belly pan.

RB

(in reply to daven)
       Post #: 3

RE: Proud Bird CG Question - 6/14/2006 2:32:49 PM   
tropejm


 

Posts: 11
Joined: 9/4/2002
From: Stamford, CT, USA
Status: offline 		I flew two of my new Proud Birds yesterday. AWESOME!!! I'm surprised at how easy they are to fly. I started with the CG at 4" and left it there all day. The airplanes flew great. They were a little docile but landed very well. I may move the CG back as I get used to them but for now...4" it is. See you at the NATS!

< Message edited by tropejm -- 6/14/2006 2:33:32 PM >

(in reply to luv to race)
       Post #: 4

RE: Proud Bird CG Question - 10/28/2006 5:33:44 AM   
ehelibuff


 

Posts: 246
Joined: 10/28/2006
From: Saugus, CA, USA
Status: offline 		I'm building a Proud Bird as well. Like most airfoils, they balance 25-33% of the airfoil. Or commonly at the high point.

(in reply to tropejm)
       Post #: 5

RE: Proud Bird CG Question - 10/30/2006 2:19:13 PM   
kane


 

Posts: 255
Joined: 6/28/2002
From: Arlington Heights, IL, USA
Status: offline 		Be cautious of using this simple formula on tapered wings. 4" (at the root) is well more than 33%. The 25-33 should be measured at the MAC (mean aerodynamic chord) rather than at the root. Everyone tends to discuss the CG interms of the distance from the leading edge at the root just outside the fuselage.

On tapered wings the best way is to measure the cg (if you don't have the mfg's suggested range) is to measure half way out the left panel and draw a line from the leading edge to the trailing edge. And do the same for the right panel. Measure distance from the leading edge to the trailing edge and use this distance to calculate your 25-33%.

Dan

< Message edited by kane -- 10/30/2006 6:54:11 PM >

_____________________________

Dan Kane

(in reply to ehelibuff)
       Post #: 6

RE: Proud Bird CG Question - 10/30/2006 5:36:03 PM   
DHG


 

Posts: 896
Joined: 4/24/2002
From: Arvada, CO, USA
Status: offline
quote:

ORIGINAL: kane

The 25-33% should be measured at the MAC (mean aerodynamic chord) rather than at the root. Everyone tends to discuss the CG in terms of the distance from the leading edge at the root just outside the fuselage.

Once upon a time there was an airplane designed for Pattern (aerobatics) that had a swept-forward wing. I think it was called the Perigee. About half of the folks who built the Perigee measured the CG at the root, just as they would have with a Taurus or a Kwik-Fli or an Esquire (anybody under 45 years old, never mind about those names) and they'd put it at the usual 35%. Due to the forward sweep of the wing, this actually caused the CG to end up at about 50% of M.A.C. Oh, and the wing was tapered, too. Can you say "tip stall"? So the Perigee got a reputation as a hairy, scary, unflyable beast. Not true, the reputation was undeserved. It was just a matter of careless balancing.

An airplane with a swept-back wing that's mis-measured the same way will end up nose-heavy, but that isn't a disaster. It just makes the plane harder to turn tight and harder to slow down for landing. So they tend to survive long enough to get balanced correctly in the end.

Duane Gall
RCPRO

(in reply to kane)
       Post #: 7

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