I recently used SeeG to find out what would happen to my CG if I took
off with the tail dolly still attached, and I thought I would share my
results.

I fly a Ventus C, and I wanted to know if I would still be within
normal operating limits and would have enough elevator authority to
keep from ballooning/stalling on take-off (or possibly on release from
tow). The tail dolly weighs about 9.5 lbs according to the bathroom
scale, and my tape measure showed the moment arm from the leading edge
to the estimated center of mass of the installed dolly to be about 145
inches.

SeeG ( http://www.glideplan.com/ ) shows my normal, dry center of
gravity to be 57% aft. I duplicated my glider in the program, then
added a moment arm called Tail Dolly. I input 9.5 lbs for the mass
and 145 inches for the arm and found that my CG shifted aft to 88% of
limits. This is a little over 30% change in CG position. OK in my
case, but it might be alarming for those that fly with the CG a little
farther aft. I ran the numbers with the airplane full of water and it
went from 58% aft to 81% aft, a little less of an impact as one might
expect from the overall increase in mass.

I would be curious to hear if others have done this and what the
numbers came out to.

Matt Jr.