The Murphy Builders Site

Hi again
I have to choose a prop fairly soon.I have an 0-320 160hp.It'll be on
wheels for a year or so then on amphibs.I'm hoping to get a prop that
willsuit for when its on the floats.What is the concensus on the
Prince props.Wayne sugested that I find a prop that will just redline
when the plane is on wheels.It should then hopefully suit well when on
floats.Anyone with experience with the prince prop that might share
what I should be asking for?Any other proven lightweight props?
thanks
Jason
817R



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Hi Jason
I have the 0-320 B2B de-rated to 150hp and had a 74/45" Prince which
was too fine for me. Cruise at 2400 was about 105-110 mph. It would
easily redline in level cruise but felt it would have been perfect
for floats. Lonnie sent me a second prop at 47" and is still a bit
too fine for wheels. The first prop was silky smooth but the second
was out of track about 3/16" which created a bit of a "buzz" on the
foot peddles. Have corrected most of the tracking error by shimming
the prop flange. Get about 800 fpm climb here at 2200' elevation at
gross weight of 1800 lbs at 25*C with the 47" prop. Steve W #637R
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Hi steve thanks for the reply,Iwas thinking 74/47(with my
vast
experience,not!)I just needed some idea of what I needed
before
calling them.Is Lonnie a tech guy at prince?
Thanks
Jason
On 15-Jan-09, at 12:05 PM, steve whitenect wrote:

Hi Jason
I have the 0-320 B2B de-rated to 150hp and had a 74/45" Prince

which

was too fine for me. Cruise at 2400 was about 105-110 mph. It

would

easily redline in level cruise but felt it would have been

perfect

for floats. Lonnie sent me a second prop at 47" and is still a

bit

too fine for wheels. The first prop was silky smooth but the

second

was out of track about 3/16" which created a bit of a "buzz"

on the

foot peddles. Have corrected most of the tracking error by

shimming

the prop flange. Get about 800 fpm climb here at 2200'

elevation at

gross weight of 1800 lbs at 25*C with the 47"

prop. Steve W #637R

_________________________________________________________________
Keep in touch and up to date with friends and family. Make

the

connection now.
http://www.microsoft.com/windows/windowslive/



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Hi again
I have to choose a prop fairly soon.I have an 0-320 160hp.It'll be on
wheels for a year or so then on amphibs.I'm hoping to get a prop that
willsuit for when its on the floats.What is the concensus on the
Prince props.Wayne sugested that I find a prop that will just redline
when the plane is on wheels.It should then hopefully suit well when on
floats.Anyone with experience with the prince prop that might share
what I should be asking for?Any other proven lightweight props?
thanks
Jason
817R

When selecting a prop for the Rebel amphib, it is better to have a
finer pitch prop. Locally here, I have compared performance with
several Rebels now with different props, and the biggest mistake
hindering performance has always been too much pitch. You might as
well install a smaller engine, if you don't want to use the power of
a 320. On initial take-off or static, you should be tuning at least
2500 rpm, and WOT straight and level at least 2700.

For example, I had a Sensenich 74 X 54 when I had the 320. I flew
with a couple of other guys that had 74 X 56 on otherwise identical
planes, and they had significantly less performance on take-off,
climb and top speed. They then changed their pitch to what I had,
and their performance improved dramatically.

What I found when comparing different props, is that 2 inches pitch
equates to 200+ fpm climb. Same holds true with my 360. I tried both
a 76 X 54 and a 76 X 56, and there is a big difference in
performance between these two props.

And a finer prop does not mean more fuel consumption at cruise
speed. I have a fuel monitor on mine, and found that gph (measured
to one decimal place) was the same when going the same airspeed,
even though your engine had to turn higher rpm.

Top speed was also dramatically improved if you could get it
spinning over 2700 rpm. My amphib 320 topped out at 2720 rpm and 125
mph with the 54 pitch. The guys with the 56 had trouble hitting 120.

Also, have been told by Bart at Aerosport not to worry about over
revving these engines a little, if that might be a concern. So if
you want to get the most performance out of your amphib, don't be
afraid of a finer pitch prop.

JMHO
Walter

----- Original Message -----
From: Rebecca Brownell <brownell@candlelight.ca>
Date: Thursday, January 15, 2009 9:46 am
Subject: Re: [rebel-builders] Prop selection
To: rebel-builders@dcsol.com

Hi steve thanks for the reply,Iwas thinking 74/47(with my
vast
experience,not!)I just needed some idea of what I needed
before
calling them.Is Lonnie a tech guy at prince?
Thanks
Jason
On 15-Jan-09, at 12:05 PM, steve whitenect wrote:

Hi Jason
I have the 0-320 B2B de-rated to 150hp and had a 74/45" Prince

which

was too fine for me. Cruise at 2400 was about 105-110 mph. It

would

easily redline in level cruise but felt it would have been

perfect

for floats. Lonnie sent me a second prop at 47" and is still a

bit

too fine for wheels. The first prop was silky smooth but the

second

was out of track about 3/16" which created a bit of a "buzz"

on the

foot peddles. Have corrected most of the tracking error by

shimming

the prop flange. Get about 800 fpm climb here at 2200'

elevation at

gross weight of 1800 lbs at 25*C with the 47"

prop. Steve W #637R

_________________________________________________________________
Keep in touch and up to date with friends and family. Make

the

connection now.
http://www.microsoft.com/windows/windowslive/



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When selecting a prop for the Rebel amphib, it is better to have a
finer pitch prop. Locally here, I have compared performance with
several Rebels now with different props, and the biggest mistake
hindering performance has always been too much pitch. You might as
well install a smaller engine, if you don't want to use the power of
a 320. On initial take-off or static, you should be tuning at least
2500 rpm, and WOT straight and level at least 2700.

For example, I had a Sensenich 74 X 54 when I had the 320. I flew
with a couple of other guys that had 74 X 56 on otherwise identical
planes, and they had significantly less performance on take-off,
climb and top speed. They then changed their pitch to what I had,
and their performance improved dramatically.

What I found when comparing different props, is that 2 inches pitch
equates to 200+ fpm climb. Same holds true with my 360. I tried both
a 76 X 54 and a 76 X 56, and there is a big difference in
performance between these two props.

And a finer prop does not mean more fuel consumption at cruise
speed. I have a fuel monitor on mine, and found that gph (measured
to one decimal place) was the same when going the same airspeed,
even though your engine had to turn higher rpm.

Top speed was also dramatically improved if you could get it
spinning over 2700 rpm. My amphib 320 topped out at 2720 rpm and 125
mph with the 54 pitch. The guys with the 56 had trouble hitting 120.

Also, have been told by Bart at Aerosport not to worry about over
revving these engines a little, if that might be a concern. So if
you want to get the most performance out of your amphib, don't be
afraid of a finer pitch prop.

JMHO
Walter

----- Original Message -----
From: Rebecca Brownell <brownell@candlelight.ca>
Date: Thursday, January 15, 2009 9:46 am
Subject: Re: [rebel-builders] Prop selection
To: rebel-builders@dcsol.com

Hi steve thanks for the reply,Iwas thinking 74/47(with my
vast
experience,not!)I just needed some idea of what I needed
before
calling them.Is Lonnie a tech guy at prince?
Thanks
Jason
On 15-Jan-09, at 12:05 PM, steve whitenect wrote:

Hi Jason
I have the 0-320 B2B de-rated to 150hp and had a 74/45" Prince

which

was too fine for me. Cruise at 2400 was about 105-110 mph. It

would

easily redline in level cruise but felt it would have been

perfect

for floats. Lonnie sent me a second prop at 47" and is still a

bit

too fine for wheels. The first prop was silky smooth but the

second

was out of track about 3/16" which created a bit of a "buzz"

on the

foot peddles. Have corrected most of the tracking error by

shimming

the prop flange. Get about 800 fpm climb here at 2200'

elevation at

gross weight of 1800 lbs at 25*C with the 47"

prop. Steve W #637R

_________________________________________________________________
Keep in touch and up to date with friends and family. Make

the

connection now.
http://www.microsoft.com/windows/windowslive/



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I have several questions concerning this discussion.

First could someone explain the reason for the big pitch
difference between that of a Prince prop (46) and a
Sensenich prop (54 or 56). There are differences in the cord
of each prop at various circumferences but the difference
should not be that great.

Second, why does Sensenich recommend a 74DM()S8-0-58 as a
standard prop and a 74DM()S8-0-56 as a climb prop for a
Murphy Rebel? This seems to be in disagreement to what Walter
is saying and has experienced.

Third, I would like to know the configuration of Walter's
and his two buddies' planes. Were they all on bungees, or coil
spring gear like that supplied by Wayne O'Shea, or did they
have spring gear? The reason is that drag enters into the
picture and can effect the performance of an aircraft
considerably. For example I calculate the drag of the
various gear configurations at 120 mph as: bungee gear at
99 lbs, O'Shea coil spring gear at 93 lbs, and the spring
gear at 27 lbs. So for a plane that has about 375 pounds of
total drag at 120 mph, this is a significant difference. These
calculations assume no fairings or wheel pants on any of the
configurations.

The speed difference between spring gear and the bungee or
coil spring gear then would be between 5% and 7.5% for
equally powered Rebels based solely on drag.

Lastly, does not the prop pitch have to vary with the speed of
the aircraft to maximize prop efficiency? According to my
calculations a 6% increase in speed would call for a 2" increase
in pitch.

I may be all wet but my calculations are based on 'NACA
Report 485' and 'The Cost of your Airplane's Parasite Drag'
by Harmen Koeffeman.

At 06:01 PM 20/01/2009 -0500, you wrote:

I have several questions concerning this discussion.

First could someone explain the reason for the big pitch
difference between that of a Prince prop (46) and a
Sensenich prop (54 or 56). There are differences in the cord
of each prop at various circumferences but the difference
should not be that great.

Second, why does Sensenich recommend a 74DM()S8-0-58 as a
standard prop and a 74DM()S8-0-56 as a climb prop for a
Murphy Rebel? This seems to be in disagreement to what Walter
is saying and has experienced.

Third, I would like to know the configuration of Walter's
and his two buddies' planes. Were they all on bungees, or coil
spring gear like that supplied by Wayne O'Shea, or did they
have spring gear? The reason is that drag enters into the
picture and can effect the performance of an aircraft
considerably. For example I calculate the drag of the
various gear configurations at 120 mph as: bungee gear at
99 lbs, O'Shea coil spring gear at 93 lbs, and the spring
gear at 27 lbs. So for a plane that has about 375 pounds of
total drag at 120 mph, this is a significant difference. These
calculations assume no fairings or wheel pants on any of the
configurations.

The speed difference between spring gear and the bungee or
coil spring gear then would be between 5% and 7.5% for
equally powered Rebels based solely on drag.

Lastly, does not the prop pitch have to vary with the speed of
the aircraft to maximize prop efficiency? According to my
calculations a 6% increase in speed would call for a 2" increase
in pitch.

I may be all wet but my calculations are based on 'NACA
Report 485' and 'The Cost of your Airplane's Parasite Drag'
by Harmen Koeffeman.

Different prop makers use different methods for calculating pitch so it's
very hard to compare props just using those numbers. Interesting drag
calculations I had no idea that the spring gear made that much difference
to total drag. Sounds like using streamlined tube for the gear legs would
make a noticable difference.
Drew



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I have several questions concerning this discussion.

First could someone explain the reason for the big pitch
difference between that of a Prince prop (46) and a
Sensenich prop (54 or 56). There are differences in the cord
of each prop at various circumferences but the difference
should not be that great.

Second, why does Sensenich recommend a 74DM()S8-0-58 as a
standard prop and a 74DM()S8-0-56 as a climb prop for a
Murphy Rebel? This seems to be in disagreement to what Walter
is saying and has experienced.

Third, I would like to know the configuration of Walter's
and his two buddies' planes. Were they all on bungees, or coil
spring gear like that supplied by Wayne O'Shea, or did they
have spring gear? The reason is that drag enters into the
picture and can effect the performance of an aircraft
considerably. For example I calculate the drag of the
various gear configurations at 120 mph as: bungee gear at
99 lbs, O'Shea coil spring gear at 93 lbs, and the spring
gear at 27 lbs. So for a plane that has about 375 pounds of
total drag at 120 mph, this is a significant difference. These
calculations assume no fairings or wheel pants on any of the
configurations.

The speed difference between spring gear and the bungee or
coil spring gear then would be between 5% and 7.5% for
equally powered Rebels based solely on drag.

Lastly, does not the prop pitch have to vary with the speed of
the aircraft to maximize prop efficiency? According to my
calculations a 6% increase in speed would call for a 2" increase
in pitch.

I may be all wet but my calculations are based on 'NACA
Report 485' and 'The Cost of your Airplane's Parasite Drag'
by Harmen Koeffeman.


-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On
Behalf Of
Rebecca Brownell
Sent: Monday, January 19, 2009 9:04 PM
To: rebel-builders@dcsol.com
Subject: Re: [rebel-builders] Prop selection

Thanks all for the responces.I spoke to "Lonnie" at prince and
he
suggested a 74/46.Hoping that will do for floats.
Thanks
Jason 817R
On 15-Jan-09, at 2:08 PM, WALTER KLATT wrote:

When selecting a prop for the Rebel amphib, it is better to

have a

finer pitch prop. Locally here, I have compared performance

with

several Rebels now with different props, and the biggest

mistake

hindering performance has always been too much pitch. You

might as

well install a smaller engine, if you don't want to use the

power of

a 320. On initial take-off or static, you should be tuning at

least

2500 rpm, and WOT straight and level at least 2700.

For example, I had a Sensenich 74 X 54 when I had the 320. I

flew

with a couple of other guys that had 74 X 56 on otherwise

identical

planes, and they had significantly less performance on take-

off,

climb and top speed. They then changed their pitch to what I

had,

and their performance improved dramatically.

What I found when comparing different props, is that 2 inches

pitch

equates to 200+ fpm climb. Same holds true with my 360. I

tried both

a 76 X 54 and a 76 X 56, and there is a big difference

in

performance between these two props.

And a finer prop does not mean more fuel consumption at

cruise

speed. I have a fuel monitor on mine, and found that gph

(measured

to one decimal place) was the same when going the same

airspeed,

even though your engine had to turn higher rpm.

Top speed was also dramatically improved if you could get

it

spinning over 2700 rpm. My amphib 320 topped out at 2720 rpm

and 125

mph with the 54 pitch. The guys with the 56 had trouble

hitting 120.

Also, have been told by Bart at Aerosport not to worry about

over

revving these engines a little, if that might be a concern. So

if

you want to get the most performance out of your amphib, don't

be

afraid of a finer pitch prop.

JMHO
Walter

----- Original Message -----
From: Rebecca Brownell <brownell@candlelight.ca>
Date: Thursday, January 15, 2009 9:46 am
Subject: Re: [rebel-builders] Prop selection
To: rebel-builders@dcsol.com

Hi steve thanks for the reply,Iwas thinking 74/47(with my
vast
experience,not!)I just needed some idea of what I needed
before
calling them.Is Lonnie a tech guy at prince?
Thanks
Jason
On 15-Jan-09, at 12:05 PM, steve whitenect wrote:
which would perfect bit second on the shimming elevation at prop. Steve W #637R the

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I like drag... helps me land shorter ! LOL !

----- Original Message -----
From: "Drew Dalgleish" <drewjan@cabletv.on.ca>
To: <rebel-builders@dcsol.com>
Sent: Tuesday, January 20, 2009 6:55 PM
Subject: RE: [rebel-builders] Prop selection

At 06:01 PM 20/01/2009 -0500, you wrote:

I have several questions concerning this discussion.

First could someone explain the reason for the big pitch
difference between that of a Prince prop (46) and a
Sensenich prop (54 or 56). There are differences in the cord
of each prop at various circumferences but the difference
should not be that great.

Second, why does Sensenich recommend a 74DM()S8-0-58 as a
standard prop and a 74DM()S8-0-56 as a climb prop for a
Murphy Rebel? This seems to be in disagreement to what Walter
is saying and has experienced.

Third, I would like to know the configuration of Walter's
and his two buddies' planes. Were they all on bungees, or coil
spring gear like that supplied by Wayne O'Shea, or did they
have spring gear? The reason is that drag enters into the
picture and can effect the performance of an aircraft
considerably. For example I calculate the drag of the
various gear configurations at 120 mph as: bungee gear at
99 lbs, O'Shea coil spring gear at 93 lbs, and the spring
gear at 27 lbs. So for a plane that has about 375 pounds of
total drag at 120 mph, this is a significant difference. These
calculations assume no fairings or wheel pants on any of the
configurations.

The speed difference between spring gear and the bungee or
coil spring gear then would be between 5% and 7.5% for
equally powered Rebels based solely on drag.

Lastly, does not the prop pitch have to vary with the speed of
the aircraft to maximize prop efficiency? According to my
calculations a 6% increase in speed would call for a 2" increase
in pitch.

I may be all wet but my calculations are based on 'NACA
Report 485' and 'The Cost of your Airplane's Parasite Drag'
by Harmen Koeffeman.

Different prop makers use different methods for calculating pitch so it's
very hard to compare props just using those numbers. Interesting drag
calculations I had no idea that the spring gear made that much difference
to total drag. Sounds like using streamlined tube for the gear legs would
make a noticable difference.
Drew



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