dean van winkle wrote:

Ref John Slade's comments on the Lyc at 310 lbs and the 13B at 260 lbs installed weight.  To keep the same aircraft CG, the 13B would have to move forward, not aft.  The goal is to have the same installed total moment (weight x distance to engine CG (arm)) with the 13B as with the Lyc.

Use the firewall as your fixed datum point rather than the aircraft CG which is a floating point.  For purposes of comparison assume the same prop weight and location, same cowl, and same engine mount weights.  Also assume that the Lyc with all accessories weighs 310 lbs with the engine CG 24 inches (arm)  forward of the firewall for a total moment of 7440 inch lbs. To give the same moment, the CG of the 13B with all accessories and redrive would fall 7440/260 = 28.61 inches (arm) forward of the firewall.  To be more precise, the weights and arms of the water and oil radiators with fluids should be summed into the 7440 inch lb moment which would result in the engine moving back slightly closer to the firewall.

Dean
RV-9A
89 13B NA

See the last message Dean. Pusher not tractor.

Paul Lamar
 
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