RV-3a 0-235 Sterba Prop Selection / Correction

On my newly aquired RV-3(a) with an 0-235 (108 HP) with a Sterba 68"x66" wooden prop. I have a take off RPM of 2150 (static RPM unkown at this time) full power cruise is 2550 RPM. Red line on the engine is 2,800 RPM. Should I be looking at a new prop? It is pretty low performace on take off. 1,100 FPM max or is this good enough?

I like the new Sensinich ground adjustable, but the price of $2,550 is pretty steep. Sterba props are $600 shipped.

I have an e-mail into Ed Sterba for his input.

Larry,

When you say, "full power cruise is 2550 RPM," what DA is that and have you leaned it for best power?

Your climb numbers are hard to interpret as you didn't say what elevation that 1,100 FPM climb is occurring at.

To put this in perspective, my 135 HP RV-9, which is 990 lbs empty will climb at around 1,800 FPM with full fuel and my 225 lbs butt in it on a 90 degree day. The down side of this is at 8,000' DA, I hit the 2,600 RPM redline at while putting out around 64% power and a lot of throttle left.

I hope to replace the prop with another one from Catto once I do some more testing. Right now I'm just enjoying flying the thing.

BTW, my current Catto prop is a 68" dia x 64" pitch and costs a little more than double the $600 Sterba charges.

My bad.

I'm at 1,500 MSL, and I was at 3,500' AGL, about a 65F day, leaned for best power I was at full power cruise.

According to some calculations I might be at a good point right now. I could drop the pitch to 68" x 62", but the RPM would be 2750 and I would be sucking more fuel to go the same speed. I guess I can live with the slow climb out on takeoff, and live with the 4.8 GPH fuel burn I now enjoy.

Geico266 said:

My bad.

I'm at 1,500 MSL, and I was at 3,500' AGL, about a 65F day, leaned for best power I was at full power cruise.

According to some calculations I might be at a good point right now. I could drop the pitch to 68" x 62", but the RPM would be 2750 and I would be sucking more fuel to go the same speed. I guess I can live with the slow climb out on takeoff, and live with the 4.8 GPH fuel burn I now enjoy.

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I think you're overpitched. One of the great joys of RVs are the short take off and steller climb performance. Its also possible that by going with a less pitched prop and more rpm you will use less fuel for the same speed and have the ability to go faster if desired. A lot of factors at play here, prop effeciency is a big one. Just for comparision, I have a cruise prop and a race prop from the same manufaturer built at the same time. The race prop climbs much better goes a little faster and equals the cruise props fuel burn for any given speed. Since removing the cruise prop a couple of years ago it sits on my hanger floor collecting dust. My experience with Sterba props are that they are not as efficient as Catto or Performance Props.
tin man
RV3 X 2
2000+ hours

Tin Man

Hi Tin Man, what size prop (HP?) are you running on your RV3B?
Robert "DOG" Ruggles RV3A
Surprise Az.

tin man said:

My experience with Sterba props are that they are not as efficient as Catto or Performance Props.
tin man
RV3 X 2
2000+ hours

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If I were to use a Catto prop and put my Sterba on the wall would I go with the same pitch I think would work better? 68" x 62"?

Sterba would repitch my prop to 68" x 62" for $50. Not bad! I need to refinish it anyway, and then I'd know if this pitch would work with the 0-235 engine.

robert ruggles said:

Hi Tin Man, what size prop (HP?) are you running on your RV3B?
Robert "DOG" Ruggles RV3A
Surprise Az.

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Robert
Its a first generation Catto two blade 68x82. Engine is an honest 165-170hp. the prop will pull 2850 @ 3000' da. I cruise at 26-2650rpm.
Tom

Geico266 said:

If I were to use a Catto prop and put my Sterba on the wall would I go with the same pitch I think would work better? 68" x 62"?

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Larry,

The prop pitch varies between these prop makers. I would give Craig Catto a call and see what prop he recommends. One key thing to ask him is how many props has he made for your engine-prop combo. He had never made one for an O-290 powered RV-9 like mine and I have one heck of climb prop but it is not so good for cruising.

N941WR said:

Larry,

The prop pitch varies between these prop makers. I would give Craig Catto a call and see what prop he recommends. One key thing to ask him is how many props has he made for your engine-prop combo. He had never made one for an O-290 powered RV-9 like mine and I have one heck of climb prop but it is not so good for cruising.

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Good info.

Thanks!

Larry, since this a used acft. (I assume), are you sure the engine is capable of producing full rated power? If I were doing this, I'd verify that the engine was really capable of full power. If not, you could end up wasting time and money on a different prop. that doesn't really solve your problem. Just something to think about. If I'm off base, sorry.
Best of luck.

Joel

Good point Joel

I had a friend that built a Zenith 701 wit a new Jabiru, disappointed with performance he ordered a different prop, turned out to be bad spark plugs .
Robert Ruggles RV3A
Surprise Az.

Prop me up...

If it turns 2550 and doesn't miss, it's not spark plugs! If all your fairings are on and it only turns 2550, you are overpitched. Ed makes a good prop for low bucks but they don't match the Catto, Warnke, MT, or Gary Hertzler for pure performance. (I have tried all 4) I would let him re-pitch it but you will need a spare prop eventually so I would start looking at the Catto, Ellipse, or Gary Hertzler, all great props.

http://www.cattoprops.com/

Rob Ray
F16,RV4ormerly
HR2 currently