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I doing the final weight and balance calculations, I have found that my dimensions from spinner to wing leading edge, (book 56.5", mine 55.5") and spinner to bottom of firewall (book 47.5" mine 46") differ quite a bit. What to do? I understand that the MAC is the key, but I wonder why the book numbers differ from mine so much. I built exactly to the plans.

BV

Hi Bill, for a start, don't worry about it. A large part of the difference between your numbers and the book values could be a different propeller. I used to have a prop fitted that had a much thinner hub than the usual Sensenich. OK, I can't think of a reason for the other missing 1/2". Just pick your reference point, tip of the spinner or whatever, and stick to it. Even the distance from your reference to the leading edge is going to vary at least 1/8" from one wing to the other because of the spar overlap.

Peter

your spinner being too low could indicate the need for shims under the bottom mounts. Check to see that the center line of the engine is correct to the airframe.

I think its the Prince prop. I'm told its hub is thinner than the Sensinich