Prop sizing

[Mike Kimball]

I've got my engine decisions pretty much completed. The only things I have
yet to figure out are which carb and I would like to find a way to have
redundant ignition. My first look at ignition was to put a mag in the
distributor hole. I know I could use dual electronic with a second small
battery for backup but I like the idea of a mag that will run without
external power. I just can't figure out how to have two with a single set
of plug wires. I really don't want to deal with dual plugs.

I was thinking about giving the three bladed in-flight adjustable IVO-Prop
with the electronic constant speed prop governor a try. It's only 26.7
pounds and $2130. Supposed to be good up to 700 HP. Can anyone tell me how
to size and pitch the blades? Here are the ranges possible according to
their website.

30"- 90" or 45" to 105" pitch range
58"-76" diameter

I keep hearing that the biggest blade I can run and have good ground
clearance is what I want. That being the case, then I guess I would go with
the 76" diameter which I think should have plenty of ground clearance in a
level attitude rolling down the runway. What pitch range would I want?
Using a prop tip speed calculator I found on the web a 76" diameter prop
needs to turn 3000 rpm to develop the desired tip speed between .88 and .92
mach to produce maximum thrust. (Only works between about 30-70 deg. F). I
want to limit my max engine rpm to about 5000 rpm so that means I will want
a gear reduction ratio of about 1.7. Then again, I also keep hearing that a
big slow turning prop is what we want on a Super Rebel. Perhaps 76" just
isn't big enough?

Mike Kimball
SR #044




*-------------------------------------------------------------------------*
To unsubscribe from this list go to:
http://www.dcsol.com:81/public/code/html-subscribe.wcx
Archives located at http://rebel:builder@www.dcsol.com:81/default.htm
To contact the list admin, e-mail mike.davis@dcsol.com
*-------------------------------------------------------------------------*








-----------------------------------------------------------------
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
-----------------------------------------------------------------

[Tim Saxton]

Mike,

A few weeks ago I talked to a local builder who is using a Ivoprop Magnum
airboat propeller on his Bearhawk project. This is mated to a Landrover
engine that he has converted. Retired fellow, he's done a nice job building
completely from plans. He is also using the electronic constant speed
governor. The propellor is basically the Magnum without the taper, also
rated to 700 HP. He had the 84" propellor, which sounds about right for a
Super Rebel. The Hartzell props sold by Murphy are also 84" diameter. I
believe he said that according to Ivo the the airboat model being used on
aircraft - if anything an airboat is harder on props than typical aircraft
use. Price is only $1240 for the 3 blade. This is great value if it works,
but I would like to hear of several success stories before I would get
serious about this option (just my opinion). This particular fellow won't be
flying until late summer and I'll follow with interest. I did see a ground
test run and one downside might be the square tips - you can expect extra
prop noise at high RPM.

Tim
SR060

----- Original Message -----
From: "Mike Kimball" <mkimball@gci.net>
To: <murphy-rebel@dcsol.com>
Sent: Saturday, May 10, 2003 3:12 PM
Subject: Prop sizing

I've got my engine decisions pretty much completed. The only things I

have

yet to figure out are which carb and I would like to find a way to have
redundant ignition. My first look at ignition was to put a mag in the
distributor hole. I know I could use dual electronic with a second small
battery for backup but I like the idea of a mag that will run without
external power. I just can't figure out how to have two with a single set
of plug wires. I really don't want to deal with dual plugs.

I was thinking about giving the three bladed in-flight adjustable IVO-Prop
with the electronic constant speed prop governor a try. It's only 26.7
pounds and $2130. Supposed to be good up to 700 HP. Can anyone tell me

how

to size and pitch the blades? Here are the ranges possible according to
their website.

30"- 90" or 45" to 105" pitch range
58"-76" diameter

I keep hearing that the biggest blade I can run and have good ground
clearance is what I want. That being the case, then I guess I would go

with

the 76" diameter which I think should have plenty of ground clearance in a
level attitude rolling down the runway. What pitch range would I want?
Using a prop tip speed calculator I found on the web a 76" diameter prop
needs to turn 3000 rpm to develop the desired tip speed between .88 and

.92

mach to produce maximum thrust. (Only works between about 30-70 deg. F).

I

want to limit my max engine rpm to about 5000 rpm so that means I will

want

a gear reduction ratio of about 1.7. Then again, I also keep hearing that

a

big slow turning prop is what we want on a Super Rebel. Perhaps 76" just
isn't big enough?

Mike Kimball
SR #044

*-------------------------------------------------------------------------*

To unsubscribe from this list go to:
http://www.dcsol.com:81/public/code/html-subscribe.wcx
Archives located at http://rebel:builder@www.dcsol.com:81/default.htm
To contact the list admin, e-mail mike.davis@dcsol.com

*-------------------------------------------------------------------------*



*-------------------------------------------------------------------------*
To unsubscribe from this list go to:
http://www.dcsol.com:81/public/code/html-subscribe.wcx
Archives located at http://rebel:builder@www.dcsol.com:81/default.htm
To contact the list admin, e-mail mike.davis@dcsol.com
*-------------------------------------------------------------------------*








-----------------------------------------------------------------
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
-----------------------------------------------------------------

[Mike Kimball]

I had to search a little bit, but I finally found the 84" airboat prop on
the IVO website. Now I have to go back to the number crunching. I'm sure I
will want the larger blades.

Mike Kimball
SR #044

-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com]On Behalf Of Tim
Saxton
Sent: Saturday, May 10, 2003 9:00 PM
To: murphy-rebel@dcsol.com
Subject: Re: Prop sizing


Mike,

A few weeks ago I talked to a local builder who is using a Ivoprop Magnum
airboat propeller on his Bearhawk project. This is mated to a Landrover
engine that he has converted. Retired fellow, he's done a nice job building
completely from plans. He is also using the electronic constant speed
governor. The propellor is basically the Magnum without the taper, also
rated to 700 HP. He had the 84" propellor, which sounds about right for a
Super Rebel. The Hartzell props sold by Murphy are also 84" diameter. I
believe he said that according to Ivo the the airboat model being used on
aircraft - if anything an airboat is harder on props than typical aircraft
use. Price is only $1240 for the 3 blade. This is great value if it works,
but I would like to hear of several success stories before I would get
serious about this option (just my opinion). This particular fellow won't be
flying until late summer and I'll follow with interest. I did see a ground
test run and one downside might be the square tips - you can expect extra
prop noise at high RPM.

Tim
SR060

----- Original Message -----
From: "Mike Kimball" <mkimball@gci.net>
To: <murphy-rebel@dcsol.com>
Sent: Saturday, May 10, 2003 3:12 PM
Subject: Prop sizing

I've got my engine decisions pretty much completed. The only things I

have

yet to figure out are which carb and I would like to find a way to have
redundant ignition. My first look at ignition was to put a mag in the
distributor hole. I know I could use dual electronic with a second small
battery for backup but I like the idea of a mag that will run without
external power. I just can't figure out how to have two with a single set
of plug wires. I really don't want to deal with dual plugs.

I was thinking about giving the three bladed in-flight adjustable IVO-Prop
with the electronic constant speed prop governor a try. It's only 26.7
pounds and $2130. Supposed to be good up to 700 HP. Can anyone tell me

how

to size and pitch the blades? Here are the ranges possible according to
their website.

30"- 90" or 45" to 105" pitch range
58"-76" diameter

I keep hearing that the biggest blade I can run and have good ground
clearance is what I want. That being the case, then I guess I would go

with

the 76" diameter which I think should have plenty of ground clearance in a
level attitude rolling down the runway. What pitch range would I want?
Using a prop tip speed calculator I found on the web a 76" diameter prop
needs to turn 3000 rpm to develop the desired tip speed between .88 and

.92

mach to produce maximum thrust. (Only works between about 30-70 deg. F).

I

want to limit my max engine rpm to about 5000 rpm so that means I will

want

a gear reduction ratio of about 1.7. Then again, I also keep hearing that

a

big slow turning prop is what we want on a Super Rebel. Perhaps 76" just
isn't big enough?

Mike Kimball
SR #044

*-------------------------------------------------------------------------*

To unsubscribe from this list go to:
http://www.dcsol.com:81/public/code/html-subscribe.wcx
Archives located at http://rebel:builder@www.dcsol.com:81/default.htm
To contact the list admin, e-mail mike.davis@dcsol.com

*-------------------------------------------------------------------------*



*-------------------------------------------------------------------------*
To unsubscribe from this list go to:
http://www.dcsol.com:81/public/code/html-subscribe.wcx
Archives located at http://rebel:builder@www.dcsol.com:81/default.htm
To contact the list admin, e-mail mike.davis@dcsol.com
*-------------------------------------------------------------------------*





*-------------------------------------------------------------------------*
To unsubscribe from this list go to:
http://www.dcsol.com:81/public/code/html-subscribe.wcx
Archives located at http://rebel:builder@www.dcsol.com:81/default.htm
To contact the list admin, e-mail mike.davis@dcsol.com
*-------------------------------------------------------------------------*








-----------------------------------------------------------------
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
-----------------------------------------------------------------

[Mike Kimball]

After number crunching it looks like all I have to do to get good mach
speeds from 0 to 100 degrees F with an 84" prop is limit my max RPM to 2600
versus 2700. That puts me at .85 mach at 60 degrees F which is about
halfway between the .80 recommended in this forum and the .88-.92 range the
calculator recommends. A 1.7:1 gear reduction puts max engine RPM at 4420.
5200 for a 2:1 reduction. I wonder if there are any 1.8:1 units. That
would be just about right.

Mike Kimball
SR #044

-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com]On Behalf Of
Mike Kimball
Sent: Sunday, May 11, 2003 3:10 PM
To: murphy-rebel@dcsol.com
Subject: RE: Prop sizing


I had to search a little bit, but I finally found the 84" airboat prop on
the IVO website. Now I have to go back to the number crunching. I'm sure I
will want the larger blades.

Mike Kimball
SR #044

-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com]On Behalf Of Tim
Saxton
Sent: Saturday, May 10, 2003 9:00 PM
To: murphy-rebel@dcsol.com
Subject: Re: Prop sizing


Mike,

A few weeks ago I talked to a local builder who is using a Ivoprop Magnum
airboat propeller on his Bearhawk project. This is mated to a Landrover
engine that he has converted. Retired fellow, he's done a nice job building
completely from plans. He is also using the electronic constant speed
governor. The propellor is basically the Magnum without the taper, also
rated to 700 HP. He had the 84" propellor, which sounds about right for a
Super Rebel. The Hartzell props sold by Murphy are also 84" diameter. I
believe he said that according to Ivo the the airboat model being used on
aircraft - if anything an airboat is harder on props than typical aircraft
use. Price is only $1240 for the 3 blade. This is great value if it works,
but I would like to hear of several success stories before I would get
serious about this option (just my opinion). This particular fellow won't be
flying until late summer and I'll follow with interest. I did see a ground
test run and one downside might be the square tips - you can expect extra
prop noise at high RPM.

Tim
SR060

----- Original Message -----
From: "Mike Kimball" <mkimball@gci.net>
To: <murphy-rebel@dcsol.com>
Sent: Saturday, May 10, 2003 3:12 PM
Subject: Prop sizing

I've got my engine decisions pretty much completed. The only things I

have

yet to figure out are which carb and I would like to find a way to have
redundant ignition. My first look at ignition was to put a mag in the
distributor hole. I know I could use dual electronic with a second small
battery for backup but I like the idea of a mag that will run without
external power. I just can't figure out how to have two with a single set
of plug wires. I really don't want to deal with dual plugs.

I was thinking about giving the three bladed in-flight adjustable IVO-Prop
with the electronic constant speed prop governor a try. It's only 26.7
pounds and $2130. Supposed to be good up to 700 HP. Can anyone tell me

how

to size and pitch the blades? Here are the ranges possible according to
their website.

30"- 90" or 45" to 105" pitch range
58"-76" diameter

I keep hearing that the biggest blade I can run and have good ground
clearance is what I want. That being the case, then I guess I would go

with

the 76" diameter which I think should have plenty of ground clearance in a
level attitude rolling down the runway. What pitch range would I want?
Using a prop tip speed calculator I found on the web a 76" diameter prop
needs to turn 3000 rpm to develop the desired tip speed between .88 and

.92

mach to produce maximum thrust. (Only works between about 30-70 deg. F).

I

want to limit my max engine rpm to about 5000 rpm so that means I will

want

a gear reduction ratio of about 1.7. Then again, I also keep hearing that

a

big slow turning prop is what we want on a Super Rebel. Perhaps 76" just
isn't big enough?

Mike Kimball
SR #044

*-------------------------------------------------------------------------*

To unsubscribe from this list go to:
http://www.dcsol.com:81/public/code/html-subscribe.wcx
Archives located at http://rebel:builder@www.dcsol.com:81/default.htm
To contact the list admin, e-mail mike.davis@dcsol.com

*-------------------------------------------------------------------------*



*-------------------------------------------------------------------------*
To unsubscribe from this list go to:
http://www.dcsol.com:81/public/code/html-subscribe.wcx
Archives located at http://rebel:builder@www.dcsol.com:81/default.htm
To contact the list admin, e-mail mike.davis@dcsol.com
*-------------------------------------------------------------------------*





*-------------------------------------------------------------------------*
To unsubscribe from this list go to:
http://www.dcsol.com:81/public/code/html-subscribe.wcx
Archives located at http://rebel:builder@www.dcsol.com:81/default.htm
To contact the list admin, e-mail mike.davis@dcsol.com
*-------------------------------------------------------------------------*





*-------------------------------------------------------------------------*
To unsubscribe from this list go to:
http://www.dcsol.com:81/public/code/html-subscribe.wcx
Archives located at http://rebel:builder@www.dcsol.com:81/default.htm
To contact the list admin, e-mail mike.davis@dcsol.com
*-------------------------------------------------------------------------*








-----------------------------------------------------------------
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
-----------------------------------------------------------------

[klehman]

You are starting to drop hints that you actually know a fair bit about
this but I'd add a couple of thoughts for you Mike.

You know that drag is proportional to V squared. Same is true for prop
tips. Well actually it is even worse than that due compressibility etc
at high percentages of mach 1. Probably especially true with wide tips
which probably should be avoided as they accentuate the lift
discontinuity at the tip and tend to be used where diameter is limited.
Remember the marvelous elliptical Spitfire wing? If the prop is making
lots of noise, you can bet it is not operating very efficiently.

Small differences in psru ratio are not likely too important with a
variable pitch prop. I found it helped to also run some numbers for
cruising with engine rpm in the vicinity of the torque peak. That's
probably where you'll be most of the time. Some guys don't seen to
understand that it takes more torque to turn a prop faster and in most
cases an auto engine will have to turn faster than the torque peak to
make rated power. i.e. for performance it's probably safer to err on the
high side when choosing a psru ratio for a STOL airplane...

Same for prop diameter. Err on the high side for STOL performance. A
high volume/mass of air with a small acceleration is more efficient that
a small volume mass with a large acceleration. Much less energy wasted
in vortices and turbulence. Disk area goes up with the square of the
radius. Same reason helicopters need large diameters to make high thrust
per hp. Same reason high wing span high aspect ratio wings are more
efficient.

Ken

Mike Kimball wrote:

After number crunching it looks like all I have to do to get good mach
speeds from 0 to 100 degrees F with an 84" prop is limit my max RPM to 2600
versus 2700. That puts me at .85 mach at 60 degrees F which is about
halfway between the .80 recommended in this forum and the .88-.92 range the
calculator recommends. A 1.7:1 gear reduction puts max engine RPM at 4420.
5200 for a 2:1 reduction. I wonder if there are any 1.8:1 units. That
would be just about right.

Mike Kimball
SR #044

-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com]On Behalf Of
Mike Kimball
Sent: Sunday, May 11, 2003 3:10 PM
To: murphy-rebel@dcsol.com
Subject: RE: Prop sizing


I had to search a little bit, but I finally found the 84" airboat prop on
the IVO website. Now I have to go back to the number crunching. I'm sure I
will want the larger blades.

Mike Kimball
SR #044

*-------------------------------------------------------------------------*
To unsubscribe from this list go to:
http://www.dcsol.com:81/public/code/html-subscribe.wcx
Archives located at http://rebel:builder@www.dcsol.com:81/default.htm
To contact the list admin, e-mail mike.davis@dcsol.com
*-------------------------------------------------------------------------*








-----------------------------------------------------------------
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
-----------------------------------------------------------------

[Rick Harper]

G'day Mike ;

The old saying goes ... "Keep the prop as long as you can , as long
as you can" ... Diameter is a biggie !
(of course , blade width will alter the amount of HP the engine can get
the air to absorb ... more width means the engine can unload more of its
energy into the air at a lower RPM ...... and / or diameter)

As for pitch .... You want the range to be less than the accepted "climb
prop pitch" and higher than the accepted "cruise prop pitch" .... so
ball park figures would indicate the 30" to 90" would be more applicable
to your situation.

Hope this helps

Rick & Wendy Harper
541R
----- Original Message -----
From: Mike Kimball
To: murphy-rebel@dcsol.com
Sent: Sunday, May 11, 2003 8:12 AM
Subject: Prop sizing


I've got my engine decisions pretty much completed. The only things I
have
yet to figure out are which carb and I would like to find a way to
have
redundant ignition. My first look at ignition was to put a mag in the
distributor hole. I know I could use dual electronic with a second
small
battery for backup but I like the idea of a mag that will run without
external power. I just can't figure out how to have two with a single
set
of plug wires. I really don't want to deal with dual plugs.

I was thinking about giving the three bladed in-flight adjustable
IVO-Prop
with the electronic constant speed prop governor a try. It's only
26.7
pounds and $2130. Supposed to be good up to 700 HP. Can anyone tell
me how
to size and pitch the blades? Here are the ranges possible according
to
their website.

30"- 90" or 45" to 105" pitch range
58"-76" diameter

I keep hearing that the biggest blade I can run and have good ground
clearance is what I want. That being the case, then I guess I would
go with
the 76" diameter which I think should have plenty of ground clearance
in a
level attitude rolling down the runway. What pitch range would I
want?
Using a prop tip speed calculator I found on the web a 76" diameter
prop
needs to turn 3000 rpm to develop the desired tip speed between .88
and .92
mach to produce maximum thrust. (Only works between about 30-70 deg.
F). I
want to limit my max engine rpm to about 5000 rpm so that means I will
want
a gear reduction ratio of about 1.7. Then again, I also keep hearing
that a
big slow turning prop is what we want on a Super Rebel. Perhaps 76"
just
isn't big enough?

Mike Kimball
SR #044





*------------------------------------------------------------------------
-*
To unsubscribe from this list go to:
http://www.dcsol.com:81/public/code/html-subscribe.wcx
Archives located at http://rebel:builder@www.dcsol.com:81/default.htm
To contact the list admin, e-mail mike.davis@dcsol.com

*------------------------------------------------------------------------
-*






*-------------------------------------------------------------------------*
To unsubscribe from this list go to:
http://www.dcsol.com:81/public/code/html-subscribe.wcx
Archives located at http://rebel:builder@www.dcsol.com:81/default.htm
To contact the list admin, e-mail mike.davis@dcsol.com
*-------------------------------------------------------------------------*








-----------------------------------------------------------------
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
-----------------------------------------------------------------

[Reed, Britt/FSC Salt Lake]

Mike - I had this back in the archives - What do you think of the square tip
Ivo?

(from November 02)

I called and talked to the folks there at IVO about the Magnum (it's max
length is 76" - I was looking for a longer length for the SR3500) and they
suggested the Airboat Magnum - It does not have the tip taper and they make
it 84". They also ponted out that the square tip on the airboat prop allows
them to inlay the stainless steel - unlike the "tape" they use on the other
models (even though the website shows how to change the leading edge tape on
the Magnum Airboat) - He mentioned that the 84" square tip was perfectly
applicable to the aviation applications. He did not have a list of
"satisfied customers" using the higher horsepower stuff.

Britt - 194SR

-----Original Message-----
From: Mike Kimball [mailto:mkimball@gci.net]
Sent: Saturday, May 10, 2003 3:12 PM
To: murphy-rebel@dcsol.com
Subject: Prop sizing


I've got my engine decisions pretty much completed. The only things I have
yet to figure out are which carb and I would like to find a way to have
redundant ignition. My first look at ignition was to put a mag in the
distributor hole. I know I could use dual electronic with a second small
battery for backup but I like the idea of a mag that will run without
external power. I just can't figure out how to have two with a single set
of plug wires. I really don't want to deal with dual plugs.

I was thinking about giving the three bladed in-flight adjustable IVO-Prop
with the electronic constant speed prop governor a try. It's only 26.7
pounds and $2130. Supposed to be good up to 700 HP. Can anyone tell me how
to size and pitch the blades? Here are the ranges possible according to
their website.

30"- 90" or 45" to 105" pitch range
58"-76" diameter

I keep hearing that the biggest blade I can run and have good ground
clearance is what I want. That being the case, then I guess I would go with
the 76" diameter which I think should have plenty of ground clearance in a
level attitude rolling down the runway. What pitch range would I want?
Using a prop tip speed calculator I found on the web a 76" diameter prop
needs to turn 3000 rpm to develop the desired tip speed between .88 and .92
mach to produce maximum thrust. (Only works between about 30-70 deg. F). I
want to limit my max engine rpm to about 5000 rpm so that means I will want
a gear reduction ratio of about 1.7. Then again, I also keep hearing that a
big slow turning prop is what we want on a Super Rebel. Perhaps 76" just
isn't big enough?

Mike Kimball
SR #044




*-------------------------------------------------------------------------*
To unsubscribe from this list go to:
http://www.dcsol.com:81/public/code/html-subscribe.wcx
Archives located at http://rebel:builder@www.dcsol.com:81/default.htm
To contact the list admin, e-mail mike.davis@dcsol.com
*-------------------------------------------------------------------------*




*-------------------------------------------------------------------------*
To unsubscribe from this list go to:
http://www.dcsol.com:81/public/code/html-subscribe.wcx
Archives located at http://rebel:builder@www.dcsol.com:81/default.htm
To contact the list admin, e-mail mike.davis@dcsol.com
*-------------------------------------------------------------------------*








-----------------------------------------------------------------
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
-----------------------------------------------------------------

[Bob Patterson]

Hi Mike !

Good choice ! The longer blades should work better on
the Moose - it's a pretty 'fat' fuselage ... ;-)
..... and you can turn them slower.

Can't blame you on the carb - <I'd> choose a carb over
"aircraft" fuel injection anytime !! ;-^) ;-)

Always said - "If aircraft magneto ignition (and most of
the engine technology !) was 1938 Tractor Technology, then
"aircraft" fuel injection (Lyc., etc.) is somewhere about
1958 Chevy Technology !! " ;-^) :-)

.....bobp

-------------------------------orig.----------------------------
At 03:09 PM 5/11/03 -0800, you wrote:

I had to search a little bit, but I finally found the 84" airboat prop on
the IVO website. Now I have to go back to the number crunching. I'm sure I
will want the larger blades.

Mike Kimball
SR #044

-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com]On Behalf Of Tim
Saxton
Sent: Saturday, May 10, 2003 9:00 PM
To: murphy-rebel@dcsol.com
Subject: Re: Prop sizing


Mike,

A few weeks ago I talked to a local builder who is using a Ivoprop Magnum
airboat propeller on his Bearhawk project. This is mated to a Landrover
engine that he has converted. Retired fellow, he's done a nice job building
completely from plans. He is also using the electronic constant speed
governor. The propellor is basically the Magnum without the taper, also
rated to 700 HP. He had the 84" propellor, which sounds about right for a
Super Rebel. The Hartzell props sold by Murphy are also 84" diameter. I
believe he said that according to Ivo the the airboat model being used on
aircraft - if anything an airboat is harder on props than typical aircraft
use. Price is only $1240 for the 3 blade. This is great value if it works,
but I would like to hear of several success stories before I would get
serious about this option (just my opinion). This particular fellow won't be
flying until late summer and I'll follow with interest. I did see a ground
test run and one downside might be the square tips - you can expect extra
prop noise at high RPM.

Tim
SR060

----- Original Message -----
From: "Mike Kimball" <mkimball@gci.net>
To: <murphy-rebel@dcsol.com>
Sent: Saturday, May 10, 2003 3:12 PM
Subject: Prop sizing

I've got my engine decisions pretty much completed. The only things I

have

yet to figure out are which carb and I would like to find a way to have
redundant ignition. My first look at ignition was to put a mag in the
distributor hole. I know I could use dual electronic with a second small
battery for backup but I like the idea of a mag that will run without
external power. I just can't figure out how to have two with a single set
of plug wires. I really don't want to deal with dual plugs.

I was thinking about giving the three bladed in-flight adjustable IVO-Prop
with the electronic constant speed prop governor a try. It's only 26.7
pounds and $2130. Supposed to be good up to 700 HP. Can anyone tell me

how

to size and pitch the blades? Here are the ranges possible according to
their website.

30"- 90" or 45" to 105" pitch range
58"-76" diameter

I keep hearing that the biggest blade I can run and have good ground
clearance is what I want. That being the case, then I guess I would go

with

the 76" diameter which I think should have plenty of ground clearance in a
level attitude rolling down the runway. What pitch range would I want?
Using a prop tip speed calculator I found on the web a 76" diameter prop
needs to turn 3000 rpm to develop the desired tip speed between .88 and

.92

mach to produce maximum thrust. (Only works between about 30-70 deg. F).

I

want to limit my max engine rpm to about 5000 rpm so that means I will

want

a gear reduction ratio of about 1.7. Then again, I also keep hearing that

a

big slow turning prop is what we want on a Super Rebel. Perhaps 76" just
isn't big enough?

Mike Kimball
SR #044

*-------------------------------------------------------------------------*

To unsubscribe from this list go to:
http://www.dcsol.com:81/public/code/html-subscribe.wcx
Archives located at http://rebel:builder@www.dcsol.com:81/default.htm
To contact the list admin, e-mail mike.davis@dcsol.com

*-------------------------------------------------------------------------*



*-------------------------------------------------------------------------*
To unsubscribe from this list go to:
http://www.dcsol.com:81/public/code/html-subscribe.wcx
Archives located at http://rebel:builder@www.dcsol.com:81/default.htm
To contact the list admin, e-mail mike.davis@dcsol.com
*-------------------------------------------------------------------------*





*-------------------------------------------------------------------------*
To unsubscribe from this list go to:
http://www.dcsol.com:81/public/code/html-subscribe.wcx
Archives located at http://rebel:builder@www.dcsol.com:81/default.htm
To contact the list admin, e-mail mike.davis@dcsol.com
*-------------------------------------------------------------------------*

*-------------------------------------------------------------------------*
To unsubscribe from this list go to:
http://www.dcsol.com:81/public/code/html-subscribe.wcx
Archives located at http://rebel:builder@www.dcsol.com:81/default.htm
To contact the list admin, e-mail mike.davis@dcsol.com
*-------------------------------------------------------------------------*








-----------------------------------------------------------------
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
-----------------------------------------------------------------

[Legeorgen]

Hi Bobp,

Just curious, why a carb over aircraft fuel injection?

Bruce 357R



*-------------------------------------------------------------------------*
To unsubscribe from this list go to:
http://www.dcsol.com:81/public/code/html-subscribe.wcx
Archives located at http://rebel:builder@www.dcsol.com:81/default.htm
To contact the list admin, e-mail mike.davis@dcsol.com
*-------------------------------------------------------------------------*








-----------------------------------------------------------------
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
-----------------------------------------------------------------