1/5 scale de Havilland chipmunk CG point
03-05-2017, 06:18 AM
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1/5 scale de Havilland chipmunk CG point
I believe I have a Ohio RC 80" wingspan chipmunk & I'm in need of the cg point.
I have contacted Ohio RC but had no luck. Can anybody point me in the right direction?
I have contacted Ohio RC but had no luck. Can anybody point me in the right direction?
03-05-2017, 04:20 PM
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That is where I normally set the cg but this plane has a tapered wing, meaning it's wide at the fuse & gets narrow as it extends away from the fuse, and I read somewhere that the cg point would be different on this type of plane.
I started with a finger in front of the spar and it flew fine but was too nose heavy. I'm just looking for the correct spot so that I don't have to keep doing the guessing game.
I started with a finger in front of the spar and it flew fine but was too nose heavy. I'm just looking for the correct spot so that I don't have to keep doing the guessing game.
03-05-2017, 08:12 PM
#4
Requests such as this planman for original CG recommendations of some particular model where the original companies may or may not even exist anymore are among the most sought after information on any of these types of forums.
Now I am sure you already know that an airplane with a straight chord wing is of course the simplest of all and lets say you want to balance at 25% its just a matter of measuring back one quarter of the distance between the front and rear of the wing to find your target point. However as you noted what do you do when the wing is a single/double taper or even an elliptical wing?
There is a very simple method that has worked very well with me over the years that may not be 'engineering precise' but does indeed work well for our balance needs. Its sometimes called mid span averaging, very fast as well as simple.
lets say we want to find that 25% mac (mean aerodynamic chord) by the way that 'mean' indicates average as in averaging. All we need to do is measure the chord (leading edge to trailing edge) out halfway between the fuselage and the wingtip. Now take this measurement and divide by four and measure back this sum from the leading edge out there (half way between the fuselage and the wingtip. All thats needed now is to project this point straight inward to the fuselage sides and this is your 25% mac.
John
Now I am sure you already know that an airplane with a straight chord wing is of course the simplest of all and lets say you want to balance at 25% its just a matter of measuring back one quarter of the distance between the front and rear of the wing to find your target point. However as you noted what do you do when the wing is a single/double taper or even an elliptical wing?
There is a very simple method that has worked very well with me over the years that may not be 'engineering precise' but does indeed work well for our balance needs. Its sometimes called mid span averaging, very fast as well as simple.
lets say we want to find that 25% mac (mean aerodynamic chord) by the way that 'mean' indicates average as in averaging. All we need to do is measure the chord (leading edge to trailing edge) out halfway between the fuselage and the wingtip. Now take this measurement and divide by four and measure back this sum from the leading edge out there (half way between the fuselage and the wingtip. All thats needed now is to project this point straight inward to the fuselage sides and this is your 25% mac.
John
