WTB Climb Prop

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rightforlineup
Posts: 20
Joined: Sun Feb 11, 2018 11:41 am
Location: St Louie

WTB Climb Prop

Post by rightforlineup »

Looking for a climb prop, 74 x 38 or similar for C-90 motor. Let me know what you've got!!
Bob
Bob Miller EAA64
operator/caretaker GN-1 C-90
Based 1IL4 Millstadt, IL
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taildrags
Posts: 445
Joined: Tue Mar 07, 2017 10:39 pm

Re: WTB Climb Prop

Post by taildrags »

Bob; is the engine together and running, to where you could test a prop on it? I have a Prince 68x42 that is probably more than my A75 can handle but might be OK for your C90 since it was flown on a Skyote with an O200. The Prince P-tip isn't really the best 'look' on a Piet, but if you're looking to test-run an engine, it might get you started. I also have the infamous "fish scales" that have been passed around from user to user in Air Camper circles for thrust testing on the ground.

Oscar Zuniga
Medford, OR
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rightforlineup
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Joined: Sun Feb 11, 2018 11:41 am
Location: St Louie

Re: WTB Climb Prop

Post by rightforlineup »

Thanks for the offer Oscar. I have a 72 x 42 Hegy loaner that I can start with. I'm looking to buy a potential "forever" prop that optimizes Piety for an up to 2 adult loading.
Bob Miller EAA64
operator/caretaker GN-1 C-90
Based 1IL4 Millstadt, IL
User avatar
rightforlineup
Posts: 20
Joined: Sun Feb 11, 2018 11:41 am
Location: St Louie

Re: WTB Climb Prop

Post by rightforlineup »

[Edit: still looking- targeting 76" x 36"] Anybody with datapoints/experience with C-90 please let me know, I'm looking to optimize for climb.

Bob
Last edited by rightforlineup on Mon May 04, 2020 3:48 pm, edited 1 time in total.
Bob Miller EAA64
operator/caretaker GN-1 C-90
Based 1IL4 Millstadt, IL
User avatar
taildrags
Posts: 445
Joined: Tue Mar 07, 2017 10:39 pm

Re: WTB Climb Prop

Post by taildrags »

Bob; I fly behind a Culver 72x36 on my A75 and can spin it at 2600 RPM in cruise to get most of the rated HP out of it. However, I like to ease it back to 2350-2400 most of the time since it just feels more comfortable there and the plane doesn't seem to fly any faster if I firewall it. On the ground, the plane pulled 280 lbs on the unofficial Piet "fish scales" at a static RPM of 2300 at wide-open throttle. My tach was calibrated against a "DynaVibe" digital instrument, so those numbers are pretty accurate. You can see the prop here- http://flysquirrel.net/piets/engine/a75ready002.jpg .

Oscar Zuniga
Medford, OR
Air Camper NX41CC, A75 power
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rightforlineup
Posts: 20
Joined: Sun Feb 11, 2018 11:41 am
Location: St Louie

Re: WTB Climb Prop

Post by rightforlineup »

Thanks Oscar, I'm imagining it will be interesting to get a datapoint static thrust to compare.
Bob Miller EAA64
operator/caretaker GN-1 C-90
Based 1IL4 Millstadt, IL
User avatar
taildrags
Posts: 445
Joined: Tue Mar 07, 2017 10:39 pm

Re: WTB Climb Prop

Post by taildrags »

Well, come on, Bob- see if you can break the record ;o) The scales only go up to 330 lbs and to my knowledge, nobody has buried the needle yet. I have 'em in my hangar and can send 'em out to whoever is next in line.
scales.jpg
-Oscar
tom kreiner
Posts: 66
Joined: Sat Feb 25, 2017 9:49 am

Re: WTB Climb Prop

Post by tom kreiner »

Bob,

Which cam does your C-90 have? The original cam was P/N 530788, and an engine equipped with it would have the best torque of any small Continental engine.

Prior to assuming you need a 74x36, pitched prop, you might contact Douwe Blumberg, whose Piet Has a C-90 which climbs like a homesick angel. And, his Piet is rather heavy...
His Piet also has the hi torque cam IIRC.

Too little prop for the torque your engine produces would allow rpms to exceed the best torque rpm. Ideally, prop and power available are matched so best climb occurs at the rpm having max torque. For the C-90 with the -788 cam, best torque is about 2500 rpm.

Some late C-90’s had the O-200 cam, but an engine with that cam might also be underloaded...

Just another perspective.
tom kreiner
Posts: 66
Joined: Sat Feb 25, 2017 9:49 am

Re: WTB Climb Prop

Post by tom kreiner »

Bob,

Which cam does your C-90 have? The original cam was P/N 530788, and an engine equipped with it would have the best torque of any small Continental engine.

Prior to assuming you need a 74x36, pitched prop, you might contact Douwe Blumberg, whose Piet Has a C-90 which climbs like a homesick angel. And, his Piet is rather heavy. His Piet also has the hi torque cam IIRC.

Too little prop for the torque your engine produces would allow rpms to exceed the best torque rpm. Ideally, prop and power available are matched so best climb occurs at the rpm having max torque. For the C-90 with the -788 cam, best torque is about 2500 rpm.

Some late C-90’s had the O-200 cam, but an engine with that cam might also be underloaded...

Just another perspective.
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