Optimum CG Range

jcarlyle wrote:
Fwd CG limit = 100 * (280 - 41) / 736 = 32% MAC
Aft CG limit = 100 * (400 - 41) / 736 = 49% MAC

John,
My experience and judgement tell me your figures are way too far aft.
I suspect the distance aft of the leading edge to the zero MAC is in
error. One sure way to check this is to mark the MAC on both wings
then assemble the wing without the fuselage on saw-horses. Then snap a
string from both zero MAC's and measure the distance from the string
to the leading edge at root rib.
Cheers,
JJ

JJ, I place great weight on your experience and judgement! I agree,
what I calculated is way far back. But I've looked over my figures
very carefully a number of times, and if there's an error I sure can't
find it.

As for the LE to zero MAC dimension causing the problem, we can get a
figure of merit by calculating the CG limits for the root chord:

Fwd CG limit = 100 * 280 / 900 = 31% root chord
Aft CG limit = 100 * 400 / 900 = 44% root chord

Of course it's different from the 32% to 49% MAC, or the 33% to 50%
for the arithmetic chord, but all three result are in the same ball
park. Measuring the actual wings as per your write-up is a good
suggestion, but due to available work area and the weather I won't be
able to try that for about 5 months at the earliest.

-John

On Dec 15, 10:49 am, JJ Sinclair wrote:
jcarlyle wrote:

Fwd CG limit = 100 * (280 - 41) / 736 = 32% MAC

Aft CG limit = 100 * (400 - 41) / 736 = 49% MAC

John,
My experience and judgement tell me your figures are way too far aft.
I suspect the distance aft of the leading edge to the zero MAC is in
error. One sure way to check this is to mark the MAC on both wings
then assemble the wing without the fuselage on saw-horses. Then snap a
string from both zero MAC's and measure the distance from the string
to the leading edge at root rib.
Cheers,
JJ