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Old 09-12-2017, 01:43 AM
  #10  
ron Sweeney
 
Join Date: Mar 2006
Location: West KirbyWirral, UNITED KINGDOM
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Originally Posted by john491
Ron,
I have been lurking in the shadows for years trying to answer the CG question. When I found the Motion RC manual I really only lucked out. I was at that Jets over DeLand in 72. I think that was the year I met Bob Parkinson and purchased a Regal Eagle off the tailgate of his station wagon.
I worked out a rough CG from the Motion planform, so here goes. This assumes the same cores, which from the picture posted at the beginning appears is the same.
Assuming leading and trailing edges added to the core the wing root chord will be 420 mm.
The CG is at 90 mm in front of the spar cut out slot. The gear is 40 mm behind the spar cut out slot.
That makes the CG about 110 mm from the leading edge at the fuse without the chines ( extend the leading edge straight to the fuse )
That makes the gear at about 235 mm from the leading edge ( same point ).
I feel this would be a good starting point.
On my kit, I acquired it already started, evidently by someone attempting to follow the prints, so I have a bit to undo to get to the starting point. The elevators were attached with no anhedral ( the amount of which I am still trying to find- I think it is supposed about 7 deg ). The vertical stab was made of a flat slab of balsa so will have to be redone as well. I have been tinkering with going EDF because of the twin pipes, but may spring for a Tam bifurcated pipe before I get to the decision point.
Good luck with your build.
John
Thanks John for all the info'. I will take it on board. I fly from a grass strip so weight is my enemy. Also the wren gold only gives 10 pound plus' I used a bifurcated pipe in the small yellow aircraft f18 but with such a small model the wing loading was getting a bit too high and no matter how well designed the pipe is there will be a certain amount of thrust loss. Re jets over Deland '92......what a coincidence. Ron.