The Murphy Builders Site

Hi Mike !

Don't think your C of G is too bad, and you ARE lighter than several
Meeses !! Here are Brent's numbers: Right wheel 955 lb, -1.4",
Left wheel 956 lb., -1.1", tail 79 lb. 242", C of G empty was 8.4"
and a total empty weight of 1,990 lb. - still lighter than some M-14's.
Put a bit over 100 lb. at the front of the baggage area, and half
tanks - seems to work OK, perhaps still a bit forward, but able
to get the tail down for nice 3 pointers. Initially felt it was
too far aft, just like you, but, with more flying, it's becoming
comfortable.

I suspect your impressions were worse because of low thrust - had the
same experience yesterday when the governor went to full fine & stayed
there ! Over 6,000 rpm, and barely able to climb !! I've learned
a whole lot about governors !!!! Seems they work best with aircraft
oils, of 100 or 80 weight ( automotive 50 or 40) - they work less
well with thinner automotive oils - like 10W30 ... ans a WHOLE LOT
less well with thin auto oils that are over 260 degrees !!! When
the oil got too hot, the governor stopped working, and everything
went full fine ! :-( How were your water & oil temps ??

You would find that it seems to take a lot of forward pressure
to raise the tail on takeoff, that's pretty normal ... and with
more thrust, you'll be impressed. Opening up that LS-6 of Brent's
with normal fine pitch was pushing me back into the seat, and
climb stabilized at 2,000 FPM, at 70 knots !!! And that was still
only turning about 4,500 rpm at WOT - need to set it finer still.
When it shot up to 6,000 rpm, the thrust fell of dramatically -
just barely enough to sustain level flight ...

There is a fairly large pitch change with flaps - not unreasonable,
but you really want to re-trim for the loads.

Sounds like you are on the right track - be good to find out what
pitch angle Hartzell suggests for a fixed prop on the O-540 - just
to get a ballpark range. Suspect that something like 50 inches
might be a good start ... just (SWAG) guessing.

You might find it hard to do good landings with the standard SR
gear - the longer Moose legs make a dramatic improvement in ease
of landing !

Keep flying & fine tuning - it's a blast once you get it all
figured out !!

--
......bobp
http://bpatterson.qhealthbeauty.com
http://apatterson2.qhealthzone.com
http://apatterson2.qbeautyzone.com
-------------------------------orig.-------------------------
On Saturday 07 October 2006 04:58 pm, Mike Kimball wrote:

Just out of curiosity and for comparison between Chevy V8, M14, and
Lycoming, can you folks with flying SRs or Meeses tell me where your empty
CG ended up? Mine was 7.87 inches aft of the datum, which is 1.63 forward
of the forward limit if you go with the limit numbers that were in my manual
(9.5 - 21.38 inches aft of the datum).

I've also been doing some weight and balance scenarios and something doesn't
seem right. With my wife and I (370 pounds) in the front seats, my daughter
(115 pounds) in the back seat, 140 pounds in the baggage area, and 60
gallons of fuel that puts the CG right about where it was for first flight
(19.5) which produced poor flight characteristics. I thought the Super
Rebel should be able to do better than that. And with my engine I figured
on being nose heavy. Seems like I need to add some weight forward of the
firewall! How can that be?

Mike
044SR

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Can the fine pitch stops not be set to a more coarse setting? I always
wondered why the fine pitch limits tend to be so aggressive. There was a
factory delivery of a brand new DHC Beaver to a Caribbean island once
that had a prop fail full fine. He ended up flying for a couple of hours
skimming the ocean in ground effect at well above redline rpm and landed
on the first beach he saw as I recall the story. It came from "a usually
reliable source". Supposedly they scrapped the engine and also the
airframe due to excessive vibration damage, loose rivets, etc...

FWIW, the soob manual calls for up to 50W oil when it is worked hard in
hot climates. When you look at the specs for 5W50 synthetic you can make
a case for using something like that in all auto conversions year around
unless perhaps you are only burning leaded avgas. But you can also make
a good case for avoiding avgas when possible. So the soob runs on
regular grade mogas and 5W50 synthetic. I would not be comfortable with
10W30 non synthetic. I do not put synthetic in my cars despite normally
keeping vehicles till they are scrapped! The viscosity difference at
260*F is fairly dramatic as is the life of the oil etc. I measure my oil
temp in the oil pan, which is the cool point, but I'm pretty sure my
internal engine oil temps are at the upper limits for conventional (non
synthetic) oil.

Ken

Bob Patterson wrote:

Hi Mike !

Don't think your C of G is too bad, and you ARE lighter than several
Meeses !! Here are Brent's numbers: Right wheel 955 lb, -1.4",
Left wheel 956 lb., -1.1", tail 79 lb. 242", C of G empty was 8.4"
and a total empty weight of 1,990 lb. - still lighter than some M-14's.
Put a bit over 100 lb. at the front of the baggage area, and half
tanks - seems to work OK, perhaps still a bit forward, but able
to get the tail down for nice 3 pointers. Initially felt it was
too far aft, just like you, but, with more flying, it's becoming
comfortable.

I suspect your impressions were worse because of low thrust - had the
same experience yesterday when the governor went to full fine & stayed
there ! Over 6,000 rpm, and barely able to climb !! I've learned
a whole lot about governors !!!! Seems they work best with aircraft
oils, of 100 or 80 weight ( automotive 50 or 40) - they work less
well with thinner automotive oils - like 10W30 ... ans a WHOLE LOT
less well with thin auto oils that are over 260 degrees !!! When
the oil got too hot, the governor stopped working, and everything
went full fine ! :-( How were your water & oil temps ??

You would find that it seems to take a lot of forward pressure
to raise the tail on takeoff, that's pretty normal ... and with
more thrust, you'll be impressed. Opening up that LS-6 of Brent's
with normal fine pitch was pushing me back into the seat, and
climb stabilized at 2,000 FPM, at 70 knots !!! And that was still
only turning about 4,500 rpm at WOT - need to set it finer still.
When it shot up to 6,000 rpm, the thrust fell of dramatically -
just barely enough to sustain level flight ...

There is a fairly large pitch change with flaps - not unreasonable,
but you really want to re-trim for the loads.

Sounds like you are on the right track - be good to find out what
pitch angle Hartzell suggests for a fixed prop on the O-540 - just
to get a ballpark range. Suspect that something like 50 inches
might be a good start ... just (SWAG) guessing.

You might find it hard to do good landings with the standard SR
gear - the longer Moose legs make a dramatic improvement in ease
of landing !

Keep flying & fine tuning - it's a blast once you get it all
figured out !!

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