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General control line discussion => Open Forum => Topic started by: Bootlegger on March 17, 2009, 07:57:18 AM
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Guy's what way have you found that works best for checking the vertical c/g on your models, and what method are you using to change it ?
Thanks,
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The method that I use is the one shown to me by Jack Sheeks.
Balance the model on the bench for a correct Fore/Aft CG location per the plans.
Hang the model by the leadouts. The model should hang slightly nose down, Fore / Aft CG. Adjust leadout position to obtain the slight nose down condition.
The wings should hang vertically, Vertical CG. Adjust the height of the line guide as required.
I did this test on the Ringmaster Trainer and found that the outboard wing was going to fly high. Lowered the height of the leadout guide 1/4 inch and it helped, Lowered the line guide again 1/4 inch and got it almost perfect.
Jack showed this to me when I finished up a CL Scale F/A-18. It needed a line guide about 4 inches in front of the wing tip and 1 inch above the tip.
Clancy
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Gil,
Hang the model by its lead outs in a place where there is no motion in the air. If you have one of those Sears laser rigs use it to transmit a vertical line. Use the laser line to check the VCG. It should make a line perfectly wing tip to wing tip. Lacking the Laser thing you can use a plumb bob and eyeball it. You have to move the leadout vertically to get the correct VCG. One of the easy ways to adjust it without moving the lead out exit slot is to use heavier wheels. Those old Veco wheels did more for us that we thought.
Another Item;Also look at the model carefully and try to assess the drag of the model in reference to the centerline of the wing. Ideally there should be equal drag above and below the line. I think this is the logic with the midwing designs.
Cfeldman Stuart, fl.
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Thanks guy's I appreciate the help..... H^^
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Al Rabe, I think, hangs a plane by the leadouts and moves it close to a wall and if both wheels hit the wall at the same time the vert. c/g is good.