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kstaack · 11-21-2004, 08:55 PM

Today´s Swapmeeting was succesful. I bought a low-wing airplane. Around 80 inch wingspan. Absolutly unknown type. But is has to fly with a 25 cc engine. How can I now find the C.G. ? It gives no plan. I guess, but I am not sure, it might be under the highest point of the wing(root) ?!

treecutter · 11-21-2004, 09:00 PM

Thats a good starting point, or roughly 25-30% of the chord should give you a rel close estimate.

R Plante · 11-22-2004, 09:57 PM

If it is a constant chord wing yes. If it is a tapered wingit will have to be figured out . Don't have the link handy will try to find it and post later.

Randy

AJCoholic · 11-22-2004, 10:05 PM

Geometrically, this is how you find the MAC:

-draw a line thorugh the center of the wing from the middle of the tip chord to the middle of the root chord.
-then take the root chord length and add it to the top of the tip chord, and the tip chord length and add it to the bottom of the root chord (get me so far?)
-draw a line from the extreme points in step #2 conecting them. Where that line crosses line in step #1 is the MAC, parallel to the root chord.

Now the CG should be anywhere from 22% to 35% back from the LE on the MAC. I susually start with 25% to 30% back.

Guest · 11-22-2004, 10:08 PM

C of G Calculator

http://ourworld.compuserve.com/homep...le/page17.html

or

http://www.palosrc.com/instructors/cg.htm

MAC Calculator

http://www.palosrc.com/instructors/mac.htm

AJCoholic · 11-22-2004, 10:10 PM

here is a drawing...

I sure hope I am remembering this right!

Guest · 11-22-2004, 11:46 PM

Quote:

Originally Posted by AJCoholic

here is a drawing...

I sure hope I am remembering this right!

Ya that looks about right....

If the model is an aerobatics model which from your description it sounds like with a standard 4 digit NACA airfoil (which most have) a CG of around 33-34% of MAC will be optimum. Much further back then that and you start loosing the ability to have good heading tracking and wind performance.

kstaack · 11-23-2004, 07:53 AM

Great, all this Infos. The wing is fullsymetric and on the wingtip 2 5/8'' thick. It has a slight V Form. The Airplane looks like the Tiger60 but is build heavier. So you need a G23-Engine for it. Inside I have found a stamp "Made in Italy" . But now - with all this Infos - I will find the C.G.

Gelcoat · 11-26-2004, 08:16 AM

The plane you have sounds like a Taurus. If such, it is a very nice plane to fly. Have fun

Jean B.

11-22-2004, 10:05 PM	#4
AJCoholic RCC Supreme Contributor I am: Andrew Coholic Join Date: Sep 2002 Location: Timmins, Northern Ontario Radio of choice: JR 12X, 28X Feedback: 47 / 100% Posts: 12,277 Total Props: 61	Geometrically, this is how you find the MAC: -draw a line thorugh the center of the wing from the middle of the tip chord to the middle of the root chord. -then take the root chord length and add it to the top of the tip chord, and the tip chord length and add it to the bottom of the root chord (get me so far?) -draw a line from the extreme points in step #2 conecting them. Where that line crosses line in step #1 is the MAC, parallel to the root chord. Now the CG should be anywhere from 22% to 35% back from the LE on the MAC. I susually start with 25% to 30% back. __________________ Andrew Coholic -MAAC #26287L 1/2A to giant scale, IMAC, SAM, R/C sport, turbine jets, Heli's... if its got a wing or two and an engine - I like it!
	.

11-22-2004, 10:10 PM	#6
AJCoholic RCC Supreme Contributor I am: Andrew Coholic Join Date: Sep 2002 Location: Timmins, Northern Ontario Radio of choice: JR 12X, 28X Feedback: 47 / 100% Posts: 12,277 Total Props: 61	here is a drawing... I sure hope I am remembering this right! Attached Thumbnails __________________ Andrew Coholic -MAAC #26287L 1/2A to giant scale, IMAC, SAM, R/C sport, turbine jets, Heli's... if its got a wing or two and an engine - I like it!
	.

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11-21-2004, 08:55 PM	#1
kstaack Guest Join Date: Oct 2003 Feedback: 0 / 0% Posts: 128 Total Props: 0	Find the right C.G. Remove this ad - become a site supporter! Today´s Swapmeeting was succesful. I bought a low-wing airplane. Around 80 inch wingspan. Absolutly unknown type. But is has to fly with a 25 cc engine. How can I now find the C.G. ? It gives no plan. I guess, but I am not sure, it might be under the highest point of the wing(root) ?!
	.

11-21-2004, 09:00 PM	#2
treecutter RCC Senior Contributor I am: Chris l Join Date: Apr 2003 Location: Regina, Sk Canada Feedback: 3 / 100% Posts: 553 Total Props: 0	Thats a good starting point, or roughly 25-30% of the chord should give you a rel close estimate.
	.

11-22-2004, 09:57 PM	#3
R Plante RCC Contributor I am: Randy P Join Date: Dec 2002 Location: Stettler Alberta Feedback: 7 / 100% Posts: 477 Total Props: 4	If it is a constant chord wing yes. If it is a tapered wingit will have to be figured out . Don't have the link handy will try to find it and post later. Randy
	.

11-22-2004, 10:08 PM	#5
Guest Guest Join Date: Sep 2002 Feedback: 0 / 0% Posts: 0 Total Props: 57	C of G Calculator http://ourworld.compuserve.com/homep...le/page17.html or http://www.palosrc.com/instructors/cg.htm MAC Calculator http://www.palosrc.com/instructors/mac.htm
	.

11-23-2004, 07:53 AM	#8
kstaack Guest Join Date: Oct 2003 Feedback: 0 / 0% Posts: 128 Total Props: 0	Great, all this Infos. The wing is fullsymetric and on the wingtip 2 5/8'' thick. It has a slight V Form. The Airplane looks like the Tiger60 but is build heavier. So you need a G23-Engine for it. Inside I have found a stamp "Made in Italy" . But now - with all this Infos - I will find the C.G.
	.

11-26-2004, 08:16 AM	#9
Gelcoat RCC Senior Contributor I am: Jean B Join Date: Nov 2004 Location: Montreal (Quebec) Radio of choice: Futaba...Spektrum...JR # of RCs: 40+ Feedback: 25 / 100% Posts: 713 Total Props: 0	The plane you have sounds like a Taurus. If such, it is a very nice plane to fly. Have fun Jean B.
	.

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