RE: BVM F-4 CG
Motstud,
A 45 lb. model is probably over the limit to balance using "model airplane techniques". Why not use the full size method of "weight and balance" used on all full size aircraft? After all where would you "pick up" a full size Phantom??? The method uses a simple equation which gives the distance from an imaginary "datum plane" to the CG location. Here it is:
SUM OF THE CLOCKWISE MOMENTS=SUM OF THE COUNTERCLOCKWISE MOMENTS.
All you need to do is pick a location for your "datum plane" (it can be anywhere, i usually use the nose of the airplane). Take accurate measurments from the datum plane to the nose gear and to each main gear. Record the weight on each gear separately and then calculate three moments: 1) datum to nose gear X weight on nose gear (in in.lbs), 2) datum to left main x weight on left main, 3) datum to right main x weight on right main.
The left side of the equation then becomes: Total weight of the airplane X distance from the datum to the C.G.
The right side of the equation then is: the sum of all three counterclockwise moments (left main moment + right main moment + nose gear moment. In in. lbs..
Solving the equation for C.G. you have:
C.G. = the sum of the three moments (in.lbs.) divided by the total weight of the airplane. The units of lbs. cancels out in the division and you are left with a distance in inches which is the C.G.'s location from the datum plane. Much more accurate than trying to "balance an airplane on your fingers or using a makeshift balance stand which at the weight of a Phantom or F-100 could poke holes in the wings.