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To: <murphy-rebel@dcsol.com> (Murphy Rebel)
From: Bob Patterson <bob.patterson@canrem.com>
Subject: Re: HELP - engine choices !!!
Message-Id: <E0yXzxe-0005jC-00@mail1.toronto.istar.net>
Date: Fri, 8 May 1998 23:06:06 -0400
I agree ! This is an excellent forum for these questions ! I missed
the original exchange (away at Sun 'n Fun & flying back to Brampton... :-) )
Here are my 2 cents, Rick. I hope it helps !!! ...
thatWe have been preparing an alloy V8 engine to date, but we now suspect
Probably WAAAAY too heavy !! I don't know of ANY successful V8 OR V6it will be too heavy and eat into our usefull payload unecessarily.
installations in Rebels (although I understand there is one in an RV-6 that
is working well, so far.
My wife & I each have a Rebel. Hers has a Rotax 912, and mine has a1) What engine / engine and reduction drive did you use ?
Lycoming O-235-C2C. I know of about a dozen Rebels with Subaru Legacy
engines,
most using the Ross (out of Texas) re-drive, although some have belt drives.
The Legacy is <slightly> heavier than an O-320, but gives power from 130 hp
to about 185 hp, depending on the convertor & computer. Fuel consumption is
<almost> half of the Lycoming O-320. Max level speed was about 135 mph at
5,400 rpm - prop not finally adjusted. Climb was over 1,000 fpm, 2 people,
full tanks.
[Please don't flame me !! These are only my <personal> observations, having
test flown a 165 hp. Legacy-powered Rebel... A lot of this engine choice
stuff is <very> subjective !]
80 hp for the 912, and 115 hp for the O-235-C2C.2) What horse power is it rated at ?
Rotax : GSC ground adjustable 72" Lyc. McCaully metal 72/443) What is your propeller diameter and pitch ?
912: 5,400 in summer, 5,200 in winter cruise is 97 mph. Stall under4) What R.P.M. do you cruise at...and what airspeed does that give ?
30.
O-235: 2,450. Cruise about 95 mph on wheels, 90 on Murphy 1500
amphibs.
(this is a fine pitch prop !)
If you have a choice, get the Lyc. O-235-L2C or -N2C - they are 116/118
hp.
on paper, but in reality give at least 10 extra horses, and at least an
extra 10 mph in cruise speed !!! (Enough extra power to pull you with
<2> notches of negative flapperon...)
R.P.M. ?5) What is your maximum airspeed attainable (in level flight) at what
912: about 120 mph at 5,800 O-235-C2: about 120 mph at 2,750 rpm
912: 716 lb. O-235-C2: 835 on wheels6) What is your empty weight (the planes',..not you personally) ?
(Mine: a LOT !!! - but I am trying to diet... )
devices ?7) Have you bothered to fit wheel pants and / or other streamlining
Standard wheel pants are just mudguards - no significant advantage.
The
tight, deep narrow pants that go over the 6" tires DO give about 3 - 5 mph.
I prefer the fat 8" tires - softer landings (and cheaper to replace!) for
grass fields.
The VERY BEST STEAMLINING THING YOU CAN DO IS ...
FAIR the main gear legs ALL THE WAY TO THE BELLY (no gap at the top!!),
and the gear tubes (upper & lower) & bungees. We have found 1/32" Lexan to
be ideal for this, as well as strut fairings. It is easier to work than
Aluminum, and you can see through it to drill into the channels that you
must add to support it. (DO <NOT> DRILL INTO THE GEAR TUBES !!! CRITICAL !!)
Fairings on gear legs should extend at least 2-3" ahead of the leg,
AND at LEAST 3-4" behind the back leg, to have proper taper. We put an
extra brake at the back, so the rivet heads are INSIDE. Whole leg fairing
was one piece, about 4' square, folded into a triangle.
Fairing the gear legs properly, and the strut fairings, will give you
AT LEAST <10 MPH> more cruise !!! (Our ACTUAL experience - on several
Rebels !) I know some think bare legs look macho, but boy, does it
cost you speed !!!
912: NO ! It is just cheap, fun flying, on wheels. Carries 2,Do you feel that you NEED more horse power from the engine ?
and camping gear, with no problems.
O-235-C2: Climb at full load is better than 912 (on almost twice
the fuel!). On amphib floats - YES! I would STRONGLY
recommend the O-320 for <dazzling> performance !!!
(about 12 seconds off the water, with 2 aboard !!)
Both engines get off the ground in 200 ft. or less, and land in about
the same, so performance is not a problem !! (FWIW - the higher powered
Rebels are HEAVIER (about 950 lb for an O-320), and take LONGER to take
off ! They DO climb and cruise faster, though ...)
All that said, I think almost everyone would like <lots> more power,
BUT - you have to balance the added cost to buy, run, and maintain those
extra horses, considering that the Rebel will never be a 300 mph aircraft.
For most general flying, the O-235 or 912 are the popular choices, while the
O-320 is the way to go for Amphib floats. The Subaru conversions appeal to
experimenters, and the thrifty, (although the savings in fuel & parts costs
you a LOT of experimenting & tinkering time - count on an extra year of
building/flying to sort out cooling, etc. ...)
Always happy to hear from Rebel builders anywhere - these are ALL
very important questions. Keep them coming !!
That is why we have our Rebel Builders Group here in Ontario, and
also the reason for this forum - to exchange info, tips, and tricks !!
Down off the soap box, and back to the airport ....
Good Luck !! ....bobp
-----------------------------------orig.---------------------------------
At 12:36 PM 4/18/98 +0000, you wrote:
thatRick, Group
Contrary to Ricks suggestion, why not post the replies to the list?
I am sure most of us who are not flying would be intertested in a good
discussion on the tech details of the engine / prop (pitch / dia / fixed
or variable/CS etc.) installation as well as the merits and benefits of
things like wheel pants (like, is it worth it, how much speed gain?).
This info will be a big help in making those decisions as time passes.
My .02!
Thanks
Dave Ricker
Richard Harper wrote:Dear Fellow Rebel builders;
G'day from "Down Under"....(Australia).
My wife and I are building kit #541 down here in sunny OZ (Sydney to be
exact).
We are looking at completion within the year (fingers crossed)....and we
need some guidance as to what engine to fit to our Rebel.
We have been preparing an alloy V8 engine to date, but we now suspect
Rebelsit will be too heavy and eat into our usefull payload unecessarily.
We would REALLY like to hear fron builders who have COMPLETED their
R.P.M. ?and are flying them / have flown them.
If you could possibly answer a few questions and e-mail your answers back
to us, we would be very grateful.
1) What engine / engine and reduction drive did you use ?
2) What horse power is it rated at ?
3) What is your propeller diameter and pitch ?
4) What R.P.M. do you cruise at...and what airspeed does that give ?
5) What is your maximum airspeed attainable (in level flight) at what
devices ?6) What is your empty weight (the planes',..not you personally) ?
7) Have you bothered to fit wheel pants and / or other streamlining
"net"..
### If you know of any Rebel owners who are flying but are NOT on the
send...could you also possibly ask them to answer theses questions for us and
isolatedtheir answers in your return e-mail to us please ?!
Sorry to bother you all with theses questions.....but we are rather
agentfrom the mainstream of avaition down here,..and we would love to find
out first hand what we need in the engine department from other Rebel
builders.
To date there are only two Rebels flying in OZ...one is the Australian
Rotaxwho has fitted an 0-235 ..115 HP Lycoming , and the other has fitted a
don't912, 80 HP. Both of these builders live about 800 miles from us...(we
friendget to see them often ,as you might well guess).
We PROMISE that this will not become a regular/repeat pain like our
Mr Dan Morehouse !!!
Thanks for your help !
Bye for now.....................................Rick & Wendy Harper
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