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Date: Wed, 18 Aug 1999 21:37:59 -0700
From: Walter Klatt <
Walter_Klatt@bc.sympatico.ca>
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To: " (Murphy Rebel Builders List)" <
murphy-rebel@dcsol.com>
Subject: Re: c of g
References: <
E11HFYd-0002Kg-00@mail4.toronto.istar.net>
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Yes, my Rebel is pretty bare bones, no carpets and minimal upholstery. Same
with my
panel and equipment. I went for utility and performance, not snazz, might do
that
later. I do have the lightweight Skytec starter, alternator and the Warp
Drive
prop. The firewall is back 3 inches and I have a conical mount O320. The
plane is
fully painted, even inside, and am just going through my final inspection
now. I
also have the old bungee landing gear.
You say that my c of g (8.9") is further forward than the factory
recommends. My
Flight Operations Manual tells me that the range is +7.7" to +19.7" Then a
further
bulletin #041096rb states that the recommended limits are forward: +10.85
and aft:
+18.10. It also says that it is OK for the empty weights to be outside these
limits, but not in a loaded condition. I notice that as you load the Rebel,
the c
of g moves back quickly and in my case, even with just pilot and minimum
fuel, it
moves past 13". Remember, that with the firewall back 3", the pilot and
passenger
are also back an additional 3".
Anyway, I'm just wondering how it flies and lands with the loaded c of g
around 13"
or 14". For test flying, I will be sure to move it back further if that is
the
recommendation.
My elevator is set at 30 degrees for the up position.
That motorcycle battery sounds interesting. Currently, I have a regular
Concord
battery that weighs a full 25 #. Can you give me more specifics on a
motorcycle
battery that will start an O320? Is there a make and model that is
recommended?
I plan to put the plane on floats after a year or so, and will have it fully
equipped with survival gear, etc., for flying out here in the BC
wilderness, so I
think I will have more stuff to put in the back of the tail to help the c of
g.
Thanks, and I appreciate the feedback and advice from everyone.
Bob Patterson wrote:
Gee, Walter, your c of g is definitely farther forward than the factory
now recommends ....
I must congratulate you - 908 LB. is <THE lightest> Rebel I've heard of
with an O-320 - should be a dazzling performer !! Did you move the
firewall
back 3" ?? Do you have much upholstery ?? Carpet back to the end of the
rear
floor would help, as does a "curtain" at the end of the baggage area .....
I'm not a big fan of moving the battery - longer cable, more weight,
line drop, and loss of sleeping space,- but it IS one way to move the
weight.
If you have a B & C lightweight starter, you don't need one of those
big,
expensive 'aircraft' batteries - the small 4" x 4" x 8" (approx.)
motorcycle
batteries will give you lots of spin ! (This might shave a few pounds up
front :-) ). The lightweight alternator will have no problem keeping it
charged. Possibly just moving the battery to the back of the firewall
would
do ...
You could also use a Scott 3200 tailwheel - several Rebels here have
them. That adds about 8 lbs., right out at the tail !! (And gives a softer
ride.)
When you paint your Rebel, it will gain about 35 lb. (or more), and
most of that weight will be on the tail, which will help. In fact,
ANYTHING
you add to the Rebel, like upholstery, strobe lights, etc. will move the
CG back ....
While there are Rebels flying with C of G's about like yours, it will
fly and handle better if it is farther back. When doing your test flights,
be sure to have over half tanks, and about 50 LB. to 80 lb of ballast,
tied
down, in the baggage area, and make sure you have AT LEAST 27 degrees of
UP
elevator (or even 30 !) (the book only says 25 - it's NOT enough !!)
Don't worry if this leaves only 20 or so of down elevator - that's lots.
This advice applies to ALL Rebels ....
....bobp
--------------------------orig.-----------------------------------------
At 07:44 PM 8/16/99 -0700, you wrote:
I am just now in the process of doing my weight and balance, and would be
interested in hearing about other Rebels' empty weights and empty c of g
positions. Also, would be interested in the empty weight of the tail
wheel
position and distance from the datum (front gear).
My Rebel, currently, is at 908 # empty with a c of g at 8.9". It has an
0320
with a Warp Drive prop, and my battery is in front. My tail wheel
position
weighs 42 # empty and is 193" from the datum. Will this work, or should I
be
moving my battery back?
Alister Yeoman wrote:
Hi,
My aircraft has been flight tested down to 11.86", no problem at all,
still
plenty of elevator control at slow speeds.
At the other end I went to 17.5" and hardly noticed the difference!
Cheers
Alister
-----Original Message-----
From: Brian Cross <
rebelair@idirect.com>
To: Murphy Rebel Builders List <
murphy-rebel@dcsol.com>
Date: Monday, August 16, 1999 6:08 AM
Subject: Re: c of g
any
case
pilot, no
never
and
Even
the
the
of
in
getting a
your c
engine
back
new
back.
firewall
about
tail.
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