On Mon, 17 Nov 2008 20:41:30 -0800, John Kimmel
wrote:

wrote:
On Sun, 16 Nov 2008 00:58:06 -0800, John Kimmel
wrote:


wrote:


Spreadsheet is not quite right.Prop center is BELOW the CG by about 13
inches.
One inch change in prop height according to your spreadsheat makes a
change of 2.14 degrees.
I cannot buy that. Particularly since it would go from 1.5 down to .64
up.

Here is REV A, with a couple math errors fixed:
http://www.spiretech.com/~guynoir/sl...thrustreva.xls



That looks a lot closer.

What is it based on?

"Vector Mechanics For Engineers: Statics and Dynamics", by Beer and Johnston, 5th edition, Chapter 4: "Equilibrium of Rigid Bodies",
page 126, equation 4.1. Equation 4.1 can be easily found on the internet, just type "statics" into Google and go to the first hit,
which should be Wikipedia.

All my spreadsheet does is keep the distance from the thrust line to the CG the same with different engine locations, so that the sum
of moments about the CG remains the same (as in: Zero. See equation 4.1).


Only problem I see is you still have it set up with the thrust above
the CG. The center line of the prop is significantly lower than the
CG. Do I just use negative numbers? Or should the spreadsheet still be
corrected?