starter/battery cg

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620
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Joined: Tue May 01, 2018 7:00 am
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Occupation: fly the 120 over sunflower fields and shoot blackbirds at the same time from august thru october or until the crop is harvested

starter/battery cg

Post by 620 » Tue Mar 12, 2019 10:29 am

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?

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6643
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Re: starter/battery cg

Post by 6643 » Tue Mar 12, 2019 10:46 am

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?

User avatar
620
Posts: 18
Joined: Tue May 01, 2018 7:00 am
Location: 69nd
Name: ken tengesdal
Aircraft Type: 120
Occupation: fly the 120 over sunflower fields and shoot blackbirds at the same time from august thru october or until the crop is harvested

Re: starter/battery cg

Post by 620 » Tue Mar 12, 2019 1:14 pm

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

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6643
Posts: 791
Joined: Tue May 01, 2018 7:00 am
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Re: starter/battery cg

Post by 6643 » Tue Mar 12, 2019 2:29 pm

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.

User avatar
620
Posts: 18
Joined: Tue May 01, 2018 7:00 am
Location: 69nd
Name: ken tengesdal
Aircraft Type: 120
Occupation: fly the 120 over sunflower fields and shoot blackbirds at the same time from august thru october or until the crop is harvested

Re: starter/battery cg

Post by 620 » Tue Mar 12, 2019 3:16 pm

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

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