On Wed, 03 Mar 2004 12:46:45 -0800, Jay wrote:

And to answer the question about putting the turbo normalized Rotax
engine on an RV wing. Why not just build a longer (custom) engine mount
on the standard RV airframe and redo the fiberglass cowling. You'd end
up with a lighter plane and have the CG where you wanted it.
Also the longer nose (besides looking turbine cool) will save drag
because you're getting the prop a little further from the canopy and
wing roots. And yes the longer moment arm will increase the time
required for spin recovery, but it will also make it a more stable IFR
platform in pitch and yaw.


Putting a lighter engine further forward will probably increase the polar
moment of inertia slightly, which would tend to very slightly slow the
aircraft's response in pitch and yaw. But from a stability point of view,
the extra area forward will have roughly the equivalent effect to reducing
the area of the vertical and horizontal stabs. Thus it will reduce the
static longitudinal and directional stability, which would make it a less
stable IFR platform.

In pitch, the fix may be to move the CG aft limit a bit forward, or
maybe it will be OK as is. In yaw, flight tests would determine whether
it was necessary to add vertical stab area, possibly via a dorsal fin.

--
Kevin Horton RV-8 (finishing kit)
Ottawa, Canada
http://go.phpwebhosting.com/~khorton/rv8/
e-mail: khorton02(_at_)rogers(_dot_)com