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General control line discussion => Open Forum => Topic started by: Paul Allen on September 22, 2018, 03:18:07 AM
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I was at the field today and a guy asked me why I had the leadouts in the wing
he has models with leadouts on top of the wing,he really wanted to know? I had to admit
the only time I had a model with leadouts on top of the wing was a solid wing trainer.
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You want the leadouts to be lined up vertically with the center of gravity. Otherwise the mismatch between leadout position and CG will force a different amount of roll on the inside and outside maneuvers.
This is why a scale airplane whose wingtips aren't on the vertical CG location may bring them out above or below the wings (or in between, in the case of a biplane).
This airplane is designed with solid foam wings and the control system out in the air for ease of construction and maintenance. To make the leadouts come out right, I made it a low wing.
(https://stunthanger.com/smf/building-techniques/build-cartoon-scale-mooney-mite/?action=dlattach;attach=245114;image)
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Tim, thanks for the reply.
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Paul,
Mostly for appearance. Modern ships are designed with the vertical CG approximately lined up with the centerline of the wing cord. As Tim said the VCG effects the roll attitude of the ship. If the VCG winds up above or below you should trim the weight distribution to move it in line with the leadout tip guide exit point.
This can be done by adjusting the weight of the wheels, wheel pants, muffler (tilt up or down, full or tongue style) etc. You check this by hanging the model by the leadouts and seeing how it hangs. It is most apparent on low wing profiles (Sterling Yak, Mustang), for these models you can try to locate the leadout exit point as high as you can on the top side of the wing and use heavy wheels. The last little bit of roll can be trimmed out with a flap tweak.
Best, DennisT