...."sprung landing gear." That's why I specified axle centers rather than
simply raising the tail. I didn't consider sprung gear and your information
is good on that account.

As to following the manufacturer's recommendations, I'm all for that. My
question should have been "why do they specify such a complicated method for
gliders with unsprung gear" though I didn't mention the suspension part.
BTW, my LAK-17a specifies an angle of 100:2.9.


"Andy" wrote in message
...
On Jan 11, 4:29 pm, "Dan Marotta" wrote:
Why don't the manufactures publish the height to raise the tail as a
difference between the axle center lines above ground? Then you don't need
to cut or calculate.

Oh, gee... That'd be too simple.

One possible reason is that the height is not a constant for any
glider that has a compressible pneumatic tyre or a sprung landing
gear. Both have deflection that depends on the glider mass. That
same deflection would need to be applied to the tail height. It may
not be neglible at max gross wt.

Speaking of sprung landing gear - in some cases the deflection changes
not only the height but also the distance between the tyre/ground
contact point and the datum. That applies to modern Schleicher single
seaters and probably other gliders. The best plan is to do the weight
and ballance as defined by the manufacturer.

I also calculated my own pilot arm as I considered the generalities in
the manual to be unacceptable. That can be done with a reasonably
accurate bathroom scale under the tail as the calculation is
independent of weight on the main gear.

Andy (GY)