Change of W&B?

A rookie question:

I recently changed out batteries to an Odyssey PC680 which is @ 7 lbs lighter than the generic 12v that came with the RV. How do I update the W&B? Can I simply subtract 7lbs off the empty gross weight and multiply that by the arm to get the new moment?

Since I'm the third owner of the RV-4 I don't have the "builders plans" or Vans instructions on how to do/update a W&B.

Just trying to keep the records and W&B as accurate as possible.

Thanks,

Bob

With only a 7 lb change, you're probably just as good re-calculating the W/B as you described. That's what I did when I made the same battery change on my RV-6.

On the other hand, if you have access to a good set of scales, it might be interesting and worthwhile to spend a few hours re-weighing and running the W/B on the airplane. No telling what undocumented modifications the previous owners made or how accurate their measurements were...