The Murphy Builders Site

Typical FULL loading usage on mine going up to the lake (44 gallons fuel,
me, flight bag, clothes, couple of 5 gallon cans in back to top for coming
back home, tools, misc construction material, etc), on 1800 amphibs, puts
the operating C of G @ ~17" for a nice effortless/trimless cruise. Light
Warp drive prop, lightweight starter and O-320 Lyco on original firewall
positon. I did put my battery down the tailcone to be sure prior to the
float install...but I shouldn't have bothered as it would have been just
fine left on the firewall and when flying light a gallon of water in each
back float compartment would have fixed the nose heavy issue for me.

I also know it will recover from a spin...first I ever did with it in 10
years.....had to cork screw down thru a "hole" in August!


----- Original Message -----
From: "Walter Klatt" <Walter.Klatt@shaw.ca>
To: <rebel-builders@dcsol.com>
Sent: Monday, January 29, 2007 10:55 PM
Subject: RE: [rebel-builders] Rebel - Should you move your firewall back 3

When on amphibs, and even with the firewall cut back, hard to get much
more
than 13 c of g at 1730. But if you were to load it to 2000 (not saying
that
anyone does), that would also allow for some baggage, getting the c of g
back to past 16, which is still well within the c of g. Again, that is
with
my 10.7 c of g empty amphib 0320 Rebel.

Best to use an excel spreadsheet to play around with different weights.

I like the idea of saving 80 pounds of wing lift by moving the c of g
back,
and also reducing/reversing the tail stress at the same time. Of course,
that doesn't mean that the extra weight is free. Gross weight is still
gross
weight.

Walter

-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of
eric.r@dcsol.com
Sent: Monday, January 29, 2007 7:24 PM
To: rebel-builders@dcsol.com
Subject: Re: [rebel-builders] Rebel - Should you move your firewall back
3

O.K.If the airplane is always operated on amphibs and nearly always takes
off
at gross weight, then is the three inch cut a plus? (considering a clone
O-320
of light weight and light weight prop ...much lighter than the stock
lycs)
will the On 1/29/2007 3:17 PM, walter.klatt@shaw.ca wrote to rebel-
builders:

-> Yes, that was a good letter. That explained a few things, too, with
how
my Rebel behaves when really loaded up. There have been times when I have
had mine quite heavy with fuel, passenger, and baggage (and of course the
amphibs), where I was concerned about how it would fly after I took off
with
all that weight. To my surprise always, I found it handled nicely in the
air,
cruise was pretty close to the same, and even my climb was better than I
expected. I guess that is due to the c of g being more aft when loaded.
My
empty c of g is 10.7 IIRC, with the 0320 cut back firewall but Odyssey
battery up front.
->
-> Regarding engine choice, I do realize the Lycoming 0320 weighs about
140
pounds more than the 912, but that is really the only downside. Biggest
upside of course is the extra power with the 0320. On the cost side, that
little 912S new, when you include all the necessary accessories, is
pretty
close to the new cost of a clone 0320, and a used 0320 would be a lot
cheaper.
->
-> And despite popular opinion, fuel costs would be pretty well a wash.
But
with a 150 hp 0320 using reg mogas (like I do) likely cheaper than a 912S
that has to use premium. The reason I say this with some certainty, I own
and fly another plane with the 912 that also has a fuel monitor, like I
have in
my Rebel. What I found with testing and monitoring, and determining the
hp
utilized at different throttle settings, both engines end up using the
same SFC
ie. lb/hp/hr, which is .45. When leaned aggressively at lower power
settings,
that old Lycosaurous is surprisingly fuel efficient.
->
-> When at the lake in the summer taking people up for rides, I sometimes
cruise at only 5.0 US gph, and still do 80 mph (full reflex), by leaning
aggressively. I would bet that the 912 would also use 5 gph to do the
same
speed with that same weight.
->
-> And don't get me wrong, the 912 is a nice machine, but I also now have
a
lot more respect for these old Lyc engines than I used to. Plus you have
to
admit, they sound better, too.
->
-> Walter
->
-> ----- Original Message -----
-> From: Bob Patterson <beep@sympatico.ca>
-> Date: Monday, January 29, 2007 2:28 pm
-> Subject: Re: [rebel-builders] Rebel - Should you move your firewall
back
3"? A letter from Darryl Murphy.
->
-> >
-> > Thanks Darryl !
-> >
-> > And thanks, Mike ! This well-reasoned and thoughtful, detailed
-> > analysis of the physics involved will now be in the archives for all
-> > to refer to when making those big choices. I hope everyone will
-> > read it through and think about all the aspects at that point.
-> >
-> > One of the great things about the Rebel is that you can just
-> > go ahead and build it - you don't have to decide on an engine
-> > until you get right up to the front end ! At that point, you do
-> > have to decide on the kind of flying you are going to do - and
-> > pick the engine you think will best suit your needs.
-> >
-> > For me, the standard Rebel, with a 912-S, will do everything
-> > I need in the flying department. I hope that will be my next Rebel.
-> > I currently fly an O-320 Rebel with the firewall not cut back,
-> > and the empty C of G is 8.1" - very far forward. It stalls
-> > significantlyfaster than I would like when solo.... and would
-> > likely cruise faster
-> > with a further aft C of G. Fortunately, I usually travel with a LOT
-> > of baggage, giving a more rearward C of G, which makes the flying
-> > quality pleasant for my needs. As Darryl says, even if you
-> > don't
-> > make the best choices, the Rebel is still a LOT nicer to fly than
-> > production airplanes ! :-)
-> >
-> > The choice becomes especially difficult for those who want
-> > an O-320 now, but also want to go to a Rotax 912 later, if they
-> > have medical problems. My thoughts are: everything takes longer
-> > than you figure, gas prices are rising, you can't register at more
-> > than 1,320 lb. anyway - if you want to go LSA, and health seldom
-> > improves with age, soooooo, when you get up to installing the
-> > firewall, just bite the bullet & go with the 912 !! You will have
-> > a ball flying your Rebel, and save on gas too !!! :-)
-> > OR - cut it back, put in that honking big engine & have fun for
-> > a year or 2, and plan to sell it when things get tough .... :-)
-> >
-> > (Anna often reminds me - "There are always 2 choices !") :-)
-> >
-> > --
-> > ......bobp
-> > http://www.prosumers.ca
-> > http://bpatterson.qhealthbeauty.com
-> > http://apatterson2.qhealthzone.com
-> >
-> > -------------------------------orig.-------------------------
-> > On Monday 29 January 2007 20:04, Mike Davis wrote:
-> > > I just received the following letter from Darryl regarding his
-> > views on
-> > moving the firewall back 3". He asked that I share it with all
-> > the builders
-> > on the list. I have also posted this letter as a PDF file in the
-> > file
-> > library.
-> > >
-> > > https://mail.dcsol.com/file/area206/let ... arryll.pdf
-> > >
-> > > Mike
-> > >
-> >
-> >
-> >
-> >
-> > -----------------------------------------------------------------
-> > 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
-> > -----------------------------------------------------------------
-> >
-> >
-> >
-> >





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