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).



I tried the first sheet.
Set the offset to 4 inches and got 8 something degrees angle!

That may have been a right answer for the problem you've set up.

But no way it would work on the airplane.



--

Richard

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