C of G

[Mike Davis]

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Tim
Thanks for the info on the Phosphoric Acid. I had wondered about this.

For what it's worth, I was recently astonished to find two Rebel owners who
were
not aware of their Allowable C of G limits. Service Notice 071095RB
indicates
+10.85" (20% MAC) to +18.1" (32% MAC). There is also a 2 page article on C
of G
calculations that Murphy sent out this Spring. Same limits but with a nice
explanation. Interestingly this one says it was sent out because not
everybody
got 071095RB so I was really surprised to find someone who hadn't received
either of these. Hopefully everyone else has these documents but thought I'd
mention it anyway.

Ken




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From: Bob Patterson <bob.patterson@canrem.com>
Subject: Re: c of g
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Date: Sat, 14 Aug 1999 20:45:17 -0400


It probably won't be necessary to go even farther back, Ken. Geert's
Rebel did not have the firewall moved, and I don't think Rick's was moved
either, although my memory is a little weak ! :-) The Warp Drive prop is
a good idea, and you can do some test weighings before deciding on the
final battery size & position....

Both of those Subaru-powered Rebels flew great ! I'm really sorry I
didn't get a chance to try Dave Bangle's - maybe I'll just have to go out
to "visit the factory" later in the year, or early spring ! ;-)

C of G range sounds like a good topic for the next Rebel Builders
meeting - could everybody bring along their numbers for Sunday, Sept. 19th
???

I guess we'll be out there anyway, next July, on Rebel Ramble 2000 -
the factory wants to have a Murphy aircraft 'return to the factory' fly-in
then, too .... Come on, everybody - let's get 'em flying so you can all
come along !! (or borrow a spam-can, if you can't fly a Rebel or Renegade
or Super ...) :-)

.....bobp

---------------------------------orig.--------------------------------------
--
At 01:14 PM 8/14/99 -0400, you wrote:

First off, welcome aboard Sam and Ryan! This group is great for getting a

quick

answer or opinion. I know I appreciate it.

It's crunch time for positioning my engine. Brian do you recall how your c

of g

worked out? I know we both have cut back the firewall and my Ej22 engine

weight

is very close to the 0-320. Last I saw, you had the battery in the back and

a

Warp Drive prop.

Would anybody move their engine an inch if they had to custom build a new

engine

mount? If so please advise whether you have also cut the firewall back.

Only numbers I have are 10.23" , 989#, for Alister with 0-320 and firewall

and

seats moved aft 3".

An inch of engine movement (at 300# wet) seems to adjust the c of g about

three

times as much as moving the battery between the firewall and the tail.

thanks very much
Ken

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[Mike Davis]

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From: Bob Patterson <bob.patterson@canrem.com>
Subject: Re: c of g
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Date: Wed, 18 Aug 1999 19:55:52 -0400


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

Hi Ken

My numbers are very similar to Alister's, however, my empty C of G is
11.58". The aircraft flies very well at this C of G #. Of course, any
load added to the aircraft moves the C of G back. The most forward case
for C of G which I submitted on my report for inspection is for 1 pilot,

no

pax, 1/4 fuel, no baggage and that puts the C of G at 12.2". I have

never

flown it at those numbers, ( I am a 1/2 to 3/4 fuel type of guy).

Typical numbers with 2 guys & 3/4 fuel puts the C of G at about 16.8"

and

it flies very nicely. I usually don't need to use the trim at all.

Even

when out of trim the stick force is very moderate. No need to adjust

the

trim for cruise to final - the stick effort reduction is not worth the
bother. ( I always trim for final on the 172 to get a better feel on the
way done but not necessary at all in my limited l8 hours of experience

of

C-FRBL).

Will call you soon.

Best Regards

Brian #328R

PS Welcome to the group Gaetan! You should come down to our meeting in
September. Bob P. will let you know the time.

B


At 01:14 PM 14/08/99 -0400, you wrote:

a

quick

your c

of g

engine

weight

and a

new

engine

firewall

and

about

three *----------------------------------------------------*
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From: Brian Cross <rebelair@idirect.com>
Subject: Re: c of g
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Hi Walter

I talked to Robin Dyck a few months ago and asked him the same question.
He suggested that the
empty C of G should be in the 12" range. I don't know whether 8.9" is a
problem but certainly when you test fly it, it probably would be a good
idea to ensure the C of G is in the 14 to 16" range until you are familiar
with how it flies.

Regards

Brian #328R




At 07:44 PM 16/08/99 -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

Hi Ken

My numbers are very similar to Alister's, however, my empty C of G is
11.58". The aircraft flies very well at this C of G #. Of course, any
load added to the aircraft moves the C of G back. The most forward case
for C of G which I submitted on my report for inspection is for 1

pilot, no

pax, 1/4 fuel, no baggage and that puts the C of G at 12.2". I have

never

flown it at those numbers, ( I am a 1/2 to 3/4 fuel type of guy).

Typical numbers with 2 guys & 3/4 fuel puts the C of G at about 16.8"

and

it flies very nicely. I usually don't need to use the trim at all.

Even

when out of trim the stick force is very moderate. No need to adjust

the

trim for cruise to final - the stick effort reduction is not worth the
bother. ( I always trim for final on the 172 to get a better feel on the
way done but not necessary at all in my limited l8 hours of experience

of

C-FRBL).

Will call you soon.

Best Regards

Brian #328R

PS Welcome to the group Gaetan! You should come down to our meeting in
September. Bob P. will let you know the time.

B


At 01:14 PM 14/08/99 -0400, you wrote:

a

quick

your c

of g

engine

weight

and a

new

engine

firewall

and

about

three *----------------------------------------------------*
The Murphy Rebel Builders List is for the discussion
between builders and owners of Murphy Rebel aircraft.
Archives located at:
http://www.dcsol.com/murphy-rebel/lists/default.htm
*----------------------------------------------------*

*----------------------------------------------------*
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between builders and owners of Murphy Rebel aircraft.
Archives located at:
http://www.dcsol.com/murphy-rebel/lists/default.htm
*----------------------------------------------------*

*----------------------------------------------------*
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between builders and owners of Murphy Rebel aircraft.
Archives located at:
http://www.dcsol.com/murphy-rebel/lists/default.htm
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From: Brian Cross <rebelair@idirect.com>
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Hi Walter

I agree 100% with Bob. I have got about 32 degrees up elevator and 20
degrees down but the C of G is in the 16" range. At this loading, I have
never required full back elevator for landing. Only a very small movement
puts it quickly into the flare with more back pressure once the 3 wheels
are on the ground. I only use full up elevator for doing my runup.

Regards

Brian #328R


At 07:55 PM 18/08/99 -0400, you 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

case

pilot, no

never

and

Even

the

the

of

in

getting a

your c

engine

back

and a

new

back.

firewall

about

*----------------------------------------------------*
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between builders and owners of Murphy Rebel aircraft.
Archives located at:
http://www.dcsol.com/murphy-rebel/lists/default.htm
*----------------------------------------------------*

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between builders and owners of Murphy Rebel aircraft.
Archives located at:
http://www.dcsol.com/murphy-rebel/lists/default.htm
*----------------------------------------------------*

*----------------------------------------------------*
The Murphy Rebel Builders List is for the discussion
between builders and owners of Murphy Rebel aircraft.
Archives located at:
http://www.dcsol.com/murphy-rebel/lists/default.htm
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[Mike Davis]

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From: "Alister Yeoman" <yeoman@voyager.co.nz>
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Subject: Re: c of g
Date: Thu, 19 Aug 1999 15:08:55 +1200
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Hi Brian,
Could you confirn that your C of G is 16" empty.

That seems a long way back before you even begin to load it.

Cheers

Alister



-----Original Message-----
From: Brian Cross <rebelair@idirect.com>
To: Murphy Rebel Builders List <murphy-rebel@dcsol.com>
Date: Thursday, August 19, 1999 2:36 PM
Subject: Re: c of g

Hi Walter

I agree 100% with Bob. I have got about 32 degrees up elevator and 20
degrees down but the C of G is in the 16" range. At this loading, I have
never required full back elevator for landing. Only a very small movement
puts it quickly into the flare with more back pressure once the 3 wheels
are on the ground. I only use full up elevator for doing my runup.

Regards

Brian #328R


At 07:55 PM 18/08/99 -0400, you 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:

still

any

case

pilot, no

never

and

Even

the

the

of

in

getting a

your c

engine

back

new

back.

firewall

about

tail.

*----------------------------------------------------*
The Murphy Rebel Builders List is for the discussion
between builders and owners of Murphy Rebel aircraft.
Archives located at:
http://www.dcsol.com/murphy-rebel/lists/default.htm
*----------------------------------------------------*

*----------------------------------------------------*
The Murphy Rebel Builders List is for the discussion
between builders and owners of Murphy Rebel aircraft.
Archives located at:
http://www.dcsol.com/murphy-rebel/lists/default.htm
*----------------------------------------------------*

*----------------------------------------------------*
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between builders and owners of Murphy Rebel aircraft.
Archives located at:
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*----------------------------------------------------*

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Date: Wed, 18 Aug 1999 21:37:59 -0700
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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

and a

new

back.

firewall

about

tail.

*----------------------------------------------------*
The Murphy Rebel Builders List is for the discussion
between builders and owners of Murphy Rebel aircraft.
Archives located at:
http://www.dcsol.com/murphy-rebel/lists/default.htm
*----------------------------------------------------*

*----------------------------------------------------*
The Murphy Rebel Builders List is for the discussion
between builders and owners of Murphy Rebel aircraft.
Archives located at:
http://www.dcsol.com/murphy-rebel/lists/default.htm
*----------------------------------------------------*

*----------------------------------------------------*
The Murphy Rebel Builders List is for the discussion
between builders and owners of Murphy Rebel aircraft.
Archives located at:
http://www.dcsol.com/murphy-rebel/lists/default.htm
*----------------------------------------------------*

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<37B8CC8B.C9A6F2CE@bc.sympatico.ca>
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Hmmm, didn't realize 8.9" was possible!
I presume that is 42# on the tailwheel in the three point position, not in
the
level flight c of g measuring position?

Not as cheap as a motorcycle battery, but Start Stick had lead-acid thin
metal
film batteries at OSK. 4 lbs, 250 cranking amps, 4 amp-hrs, less than
US$100. if
memory serves. Have also heard of lighter ones with more cranking amps but
optimised strictly for starting that can be mounted right at the starter.
Start
stick also had a larger one about 11#, 1000 amp, about $130. Can look up the
details if anyone wants. I believe they have a webpage as does Bolder
Technologies.

Ken

Walter Klatt wrote:

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?

Can you give me more specifics on a motorcycle battery that will start >an

O320? Is there a

make and model that is recommended?




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Date: Thu, 19 Aug 1999 09:19:22 -0400
To: <murphy-rebel@dcsol.com> (Murphy Rebel Builders List)
From: Brian Cross <rebelair@idirect.com>
Subject: Re: c of g
In-Reply-To: <37BB8A26.11981767@bc.sympatico.ca>
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Hi Walter

You are right about the empty vs. flying C of G. Empty C of G does not
matter as you long as you load it properly every time for flight. The
original forward C of G was 7.7", then moved a few years later to 10.85"
and then last November, MAM faxed me a new forward C of G limit of 12". I
think they were changing this based on experience of customer built flying
Rebels. The rear C of G was also moved forward I believe on the last fax
on the subject. 13-14" should be fine based on what Alister says.
However, you should probably check with MAM to hear their latest thoughts.

Regards

Brian #328R


At 09:37 PM 18/08/99 -0700, you wrote:

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:

still

any

case

pilot, no

never

16.8" and

Even

adjust the

the

the

experience of

meeting in

getting a

your c

engine

back

a new

back.

firewall

about

tail.

*----------------------------------------------------*
The Murphy Rebel Builders List is for the discussion
between builders and owners of Murphy Rebel aircraft.
Archives located at:
http://www.dcsol.com/murphy-rebel/lists/default.htm
*----------------------------------------------------*

*----------------------------------------------------*
The Murphy Rebel Builders List is for the discussion
between builders and owners of Murphy Rebel aircraft.
Archives located at:
http://www.dcsol.com/murphy-rebel/lists/default.htm
*----------------------------------------------------*

*----------------------------------------------------*
The Murphy Rebel Builders List is for the discussion
between builders and owners of Murphy Rebel aircraft.
Archives located at:
http://www.dcsol.com/murphy-rebel/lists/default.htm
*----------------------------------------------------*

[Mike Davis]

Received: from bc.sympatico.ca (a3a23400.sympatico.bconnected.net
[209.53.56.157])
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Date: Thu, 19 Aug 1999 06:53:18 -0700
From: Walter Klatt <Walter_Klatt@bc.sympatico.ca>
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Subject: Re: c of g
References: <002101bee79c$d14929e0$ad1915cb@dialup.voyager.co.nz>

<37B8CC8B.C9A6F2CE@bc.sympatico.ca> <37BBFD7F.7C5E5753@albedo.net>
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No, the 42# is in the level position, not with the tail wheel on the ground.

Thanks for the tip on the battery. I will check it out.

klehman@albedo.net wrote:

Hmmm, didn't realize 8.9" was possible!
I presume that is 42# on the tailwheel in the three point position, not in

the

level flight c of g measuring position?

Not as cheap as a motorcycle battery, but Start Stick had lead-acid thin

metal

film batteries at OSK. 4 lbs, 250 cranking amps, 4 amp-hrs, less than

US$100. if

memory serves. Have also heard of lighter ones with more cranking amps but
optimised strictly for starting that can be mounted right at the starter.

Start

stick also had a larger one about 11#, 1000 amp, about $130. Can look up

the

details if anyone wants. I believe they have a webpage as does Bolder
Technologies.

Ken

Walter Klatt wrote:

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?

Can you give me more specifics on a motorcycle battery that will start

an O320? Is there

a make and model that is recommended?

*----------------------------------------------------*
The Murphy Rebel Builders List is for the discussion
between builders and owners of Murphy Rebel aircraft.
Archives located at:
http://www.dcsol.com/murphy-rebel/lists/default.htm
*----------------------------------------------------*

.





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Date: Thu, 19 Aug 1999 06:55:47 -0700
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Subject: Re: c of g
References: <E11HFYd-0002Kg-00@mail4.toronto.istar.net>

<3.0.6.32.19990819091922.007ba100@idirect.com>
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12" for the new forward limit? That is quite a change. Yes, I do plan to
contact
MAM, but wanted to know first what others were doing? Thanks for the info.

Brian Cross wrote:

Hi Walter

You are right about the empty vs. flying C of G. Empty C of G does not
matter as you long as you load it properly every time for flight. The
original forward C of G was 7.7", then moved a few years later to 10.85"
and then last November, MAM faxed me a new forward C of G limit of 12". I
think they were changing this based on experience of customer built flying
Rebels. The rear C of G was also moved forward I believe on the last fax
on the subject. 13-14" should be fine based on what Alister says.
However, you should probably check with MAM to hear their latest thoughts.

Regards

Brian #328R

At 09:37 PM 18/08/99 -0700, you wrote:

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:

be

g

wheel

an

0320

position

should

I be

all,

still

is

any

case

pilot, no

have

never

16.8" and

Even

adjust the

the

on

the

experience of

meeting in

getting a

how

your c

engine

back

build

a new

back.

firewall

g

about

tail.

*----------------------------------------------------*
The Murphy Rebel Builders List is for the discussion
between builders and owners of Murphy Rebel aircraft.
Archives located at:
http://www.dcsol.com/murphy-rebel/lists/default.htm
*----------------------------------------------------*

*----------------------------------------------------*
The Murphy Rebel Builders List is for the discussion
between builders and owners of Murphy Rebel aircraft.
Archives located at:
http://www.dcsol.com/murphy-rebel/lists/default.htm
*----------------------------------------------------*

*----------------------------------------------------*
The Murphy Rebel Builders List is for the discussion
between builders and owners of Murphy Rebel aircraft.
Archives located at:
http://www.dcsol.com/murphy-rebel/lists/default.htm
*----------------------------------------------------*

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Date: Thu, 19 Aug 1999 20:16:14 -0700
From: Walter Klatt <Walter_Klatt@bc.sympatico.ca>
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This was my initial weight and balance. I am still doing a few things to the
airplane, and will do a final one, hopefully later next week. I borrowed a
set of
scales from another builder. They are from Aircraft Spruce, and are really
pretty
nifty. For the front wheels, they have a frame that allows you to halve the
weight
to get accurate readings. Anyway, they are to be calibrated to a known
weight before
each use, and for the initial time, I just calibrated them to my weight, and
should
be each within about five pounds. So in total, I shouldn't be out more than
about 15
pounds. For my final weighing, I am going to stop in at local medical clinic
to get
my exact weight on their scale with shoes and clothing on, and immediately
then
after calibrate the aircraft scales to my weight. I think that should do it.

I already have my ELT as far back as I can put it, right in the last section
where
the fin is.

Thanks for the info on the motorcycle battery. I still find it hard to
believe that
it can start an O320, but will check it out.

Thanks again for your feedback. You guys and this builders mail list are
definitely
a great help.

Bob Patterson wrote:

WOW !!! I'm even MORE impressed - your Rebel is fully painted, and still
weighs only 908 lb !!!!! That REALLY IS the lightest Rebel with an O-320 !

No offence, but have you had your scales & calculations checked by
another builder or an RAA inspector/helper ?? Just a thought, that maybe
things aren't quite as bad as they seem .....

The motorcyle battery being used on Rebels now is:

Canadian Tire part # 2710140 model # 12N14-3A ($43.99)

How's that for exact detail ??!!! ;-)

Just another thought - perhaps you could move your ELT 'waaaay back
into the tail - my O-235 Rebel has it back at the very end of the floor.

I have flown Rebels with the forward C of G - it's still a GREAT

handling

airplane - just a little harder to flare, and possibly, to trim for level
flight !! You will be fine if you add a little ballast as suggested, for
test flying, and experiment from there....

Adding the floats will likely move your CG back another inch or so ...

....bobp

----------------------------orig.-----------------------------------------

-

At 09:37 PM 8/18/99 -0700, you wrote:

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:

be

g

wheel

an 0320

position

should I be

all,

still

is

any

case

pilot, no

have

never

16.8" and

Even

adjust the

the

on the

experience of

meeting in

getting a

how

your c

engine

back

build

a new

back.

firewall

g

about

tail.

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