Quote Originally Posted by CraigCantwell View Post
What happens with the numbers when you add the prop in?
Very small movement forward (of the aircraft empty CG-----about 0.2 inch, if I remember correctly.)

Have crunched numbers to the point that I'm blue in the face.....have decided to move the engine forward about 1.5 inches more than is now. That will give just enough clearance to mount a starter on back of Diehl case with a small clearance hole in firewall. (Will relocate the "standard" weight saving cut-out in the ply firewall to accommodate. And use a stainless bowl to provide firewall extension into the hole...).

Am currently building a jig to weld up a mount---located the mount points on the firewall in the extreme corners of the firewall to get the loads off the ply and transfer them more directly to the longerons. Have seen pics of several VP-1s, mostly from England, that have done the same.

Thinking very seriously about a simple "dummy-engine" to mount in the mounts and load it down to simulate g-loading the mount and firewall---not to destruction, but to a reasonable limit. How to do this and not destroy other structure will be my next 'research' project.

Oh--BTW----moving the engine forward 1.5 inches more---adding the prop and starter--and a 12 lb "cart" battery on the firewall moves the CG forward enough that with the lightest and heaviest pilot that we could expect (and that stays below the gross weight), from full fuel to empty, the CG stays in an acceptable range in all cases. Now, if the numbers work that well when we get it actually done and weigh it again, I will be tickled!