Optimum CG Range

jcarlyle wrote:
There are summaries of Frank Irving’s 1981 OSTIV paper that say he
concluded the optimal CG for a standard class glider is 0.3 to 0.35 of
the Mean Aerodynamic Chord. DG’s web site has an entry that says the
2001 Akaflieg Braunschweig flight test results concluded best glider
results are obtained when the CG is 30-35% in front of the rear CG
limit.

I can calculate an optimal CG for my LS8-18 using the Akaflieg
Braunschweig results quite easily. However, I can't calculate an
optimal CG using Frank Irving’s results, because RS doesn't provide
the length or starting position of the MAC.

Are these two results in agreement? If not, is there some way for
getting them into the same frame of reference? (I'd prefer restating
Irving’s results in terms of CG rather than MAC, if possible.) Or have
these findings been superceded by something else in the last 8 years?

-John

CofG may be stated as a distance aft of a given reference station which
may be at (or in front of) the nose
OR
A percentage of MAC behind the wing LE
OR
A distance behind the Wing LE

The middle definition is probably the most fundamental, because there
is a known range of allowable CofG's in terms of %MAC which is similar
across a wide range of airframes

Brian W