snipThere's nothing to worry about if it wasn't moved - most builders
today do not move it back, regardless of engine. This gives a much
wider range of engine choices .... If it was moved, you are stuck
with an O-320 or similar
Based only on my aircraft, I don't think I'd agree that a moved FW
dictates an 0-320.
300 lbs of engine x 3" = 900 inch lbs. And the seats go back 3" as well
so say another 500 inch lbs when solo.
However keeping a 20+ lb battery on the FW vs back in the tail has as
much or more effect on the W&B.
Even the PC680 battery will be 20+ lbs with mounting brackets and wiring.
The archives have a recurrent theme of more up elevator, ballast, light
prop, light accessories, etc.,etc. The only Rebel owners that I've
heard say they needed weight in the nose had a rotax 912 or similarly
light engine.
And of course one can always make a custom longer engine mount.
Ken
PS. Ignore the following or read it critically including the disclaimer ;)
These comments are with the Mackenzie leading edge cuff and the Fife
wingtips.
The subaru engine has a more rearward engine c of g than a Lyc. but
similar weight and my FW is moved back. I generally cruise with lower
power than an 0-320 would. The Mackenzie leading edge cuff extends the
leading edge forward (and I think the center of lift) and it effectively
reduces the angle of wing incidence by drooping the leading edge. My wee
batteries are under 20 lb but they are on the floor between the rudder
pedals. I have 20+ lbs of fuel pumps and 2 gallon header tank back
behind the float attach points (behind the baggage area).
Disclaimer - the leading edge cuff may be a major factor here so I'd
definately pay more attention to what MAM and other folks are saying
about this and I haven't done any spin testing although it takes a lot
of back pressure to stall my airplane and it doesn't seem inclined to
enter a spin unintentionally. More power than I have would mean a faster
cruise and probably less up elevator in cruise. I followed Wayne's post
and did not raise the nose of the stab as much as the manual said. Think
I set 0.8 degrees rather than the 1 degree in the manual. However if
doing it again I would not even raise the nose of the stab that much
because I still always have some up elevator. Even at gross weight the
tail generally will come up immediately on the takeoff and it certainly
is easier to land 3 point with an aft c of g. An aft c of g does
generally reduce pitch stability in cruise but my Rebel is amazingly
stable in cruise.
-----------------------------------------------------------------
List archives located at: https://mail.dcsol.com/login
username "rebel" password "builder"
Unsubscribe: rebel-builders-unsubscribe@dcsol.com
List administrator: mike.davis@dcsol.com
-----------------------------------------------------------------
