On Dec 12, 7:36*pm, jcarlyle wrote:
...is there some way for getting them into the same frame of reference?

I'd recommend that you come to terms with MAC. As they say in Make
Magazine, if you can't open it, you don't really own it.

This article describes a graphical method for determining the MAC of a
double-taper wing such as that of your LS8:

http://www.djaerotech.com/dj_askjd/d...s/canard1.html

There are also calculators available on the Web for determining the
MAC of a multi-tapered wing numerically.

Once you determine the length of the MAC, locating it with reference
to the aircraft longitudinal axis is a matter of simple surveying that
you can do with a yard stick and some strings and plumb bobs.
Basically, what you do is find the location on the wing where the
actual chord equals the MAC, and then find the longitudinal location
of that chunk of wing, and that's where your MAC is. From there, all
you need to do is measure from the aircraft datum to the leading edge
of the MAC.

This Article on HP-18 weight and balance shows MAC location
graphically in relationship to the datum and side-of-body chord, and
the associated CG calculations:

http://www.soaridaho.com/Schreder/Sc...976_HP-18.html

Note that in the article, Schreder incorrectly equates mean chord with
average chord. However, in this instance the difference is very small
and makes the CG envelope more conservative, so I consider it a
forgivable simplification. But it is worth considering that you might
execute the same calculation in order to approximate the MAC length. I
think that the LS6 and LS8 in 15m trim have about 113 ft^2 like the
HP-18, so the average chord should be the same.

Thanks, Bob K.
www.hpaircraft.com