CG ?????

The instructions for my electric sailplane say to balance 68mm from
LE. When I check CG using GP CG Machine, the plane shows to be VERY
nose heavy even with the battery shoved all the way back to the servos
for the tail feathers.
When I look at the figures:
68mm ~ 2.68" ~ 2 11/16 ".
wing chord 7 1/4" tapered LE to 5 7/8" at the end of the aileron.
If I take 25% of root chord, I get 1.81".
" " 30% " " " 2.18".
Seems to me that there might be a misprint on the CG. If the figure
was 58mm ~ 2.28" ~ 2 1/4", I'd be very close to balancing.
Comments........
David
Reply to
David AMA40795 / KC5UH
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Is it only the le that is tapered? Is the te tapered at all. If not than it looks like 2.25 would be 25% of average chord.
Reply to
Frank
Want a really good online calculator...
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Reply to
SKYLANE42
The TE is straight. The LE is straight taper as noted. The wing tip is somewhat parabolic from the aileron out to the end.
David
Reply to
David AMA40795 / KC5UH
Interestingly, your calculator gives me 2.18" at 30% IF I entered the sweep correctly. When I view the page, there is a vertical black strip with a blue grid in it that obscures the right side of the calc box. I cannot see the 'B' or 'S' dimension letters - I assume they are at the wingtip and covered up by the strip.
David
Reply to
David AMA40795 / KC5UH
Hmmmmmmmm. After fiddling with the calculator to figure out how to use it, I came up with 2.64" - pretty damn close to 2.68".
Rats, now I have to figure out how to get the battery weight farther back to get balance, since adding lead to balance electrics is a 'last resort' move.
David
Reply to
David AMA40795 / KC5UH
Oooooooppppssss. After getting the figure from Jean-Claude's calculator, I went back to Palos RC page and fiddled with it. I had not entered a sweep since the wing is NOT swept, but noticed that the sweep dimension had to be entered to get the tapered LE - DUH.
Anyway, I then got 2.64", just as I did from J-C's calculator.
David
Reply to
David AMA40795 / KC5UH

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