Tony.. I have referenced my L-23S manual and the USAF Flight Test Center
"SPIN TEST" report on the L-23.

The reference datum is 93.6 in aft of the sailplane nose (paragraph 6.3)
This also correlates to the leading edge of Rib #1, Table in Para 6.6, arm
for reference for installing instruments defines "Arm from the reference
plane (rib #1 in ft.", this becomes the "zero" line). Front instrument panel
is -5.82ft and rear instrument panel is -1.81ft. Yes.. moment arms are
negative because you are in front of the reference datum.

-5.82 x12 = -69.84 inches (moment arm), -1.82 x12= 21.72 inches
There are rear instrument panel references from -1.79 to -1.87 (something
lost in translation or factory typing error?)

I have made measurements for the seat positions (remember to measure to the
belly button) and determined that the P1(front) is apx -49.9inches and
P2(Rear) is apx -5.8inches (these are personal measurements of the aircraft
and not the manufacturers numbers).

Doing the math from the reference datum to convert %MAC to "inches", I came
up with 23%MAC = 4.397inches aft of datum and 40%MAC is 12.78inches aft of
datum.

For the particular L-23S that this was computed for (empty wt 712# at 21.54
arm (67.4%MAC)
Min pilot weight no ballast was 100#, extreme aft CG limit. Max Solo pilot
wt 225#, extreme forward limit.

Use the W&B factory data to get your numbers.

send me your email, I'll send you a spreadsheet
http://members.cox.net/btiz2 for my address.

BT

"Tony Verhulst" wrote in message
...
I understand how to determine the CG from the charts in the manual. But, I
would like to do it the traditional way - you know, moment = arm *
weight....

The manual does not provide the arm numbers for the various positions, not
does it tell you the numeric CG range. A bit odd, I think, but there you
are.

I would appreciate any one having that data to kindly point me to it.

Thanks and regards,

Tony V.