starter/battery cg

[VIP620]

my current cg is 12.8 and if i stay at that cg and add a starter (9.2 lb) and battery (pc 680, 15 lb), to maintain original cg, the battery would be placed 22.5 inches. correct or wrong?

[6643]

Not enough information. How much does the plane weigh? Do you currently have a starter and battery you are removing? How much do they weigh, and what is the arm for each? Will the arm for the new items be the same?

[VIP620]

non electric from factory, c85, so starter should be around 24" from datum. trying to figure where the battery will go, to find battery cable length and maintain original cg

[6643]

The starter is forward (-25). The light weight starter is probably a few inches farther forward)) so the battery should be aft to balance. Original battery box is +56. Using these arms and your weights your CG will shift slightly aft to about 13.1". Putting the battery at +25 will put you about 12.6" but you'd be sitting on it... 13.1 is well within the acceptable range.

[VIP620]

thanks, i'm thinking under the seat. i have the spring seats instead of the cushion type, so there is plenty of room with battery laying or mounted on it's side