RivetBangers.com

Greetings,
Just found out about the new site from the EAA eHotline. I bought a used O-360 for the -7A I'm building and it came with a Sterba prop and a harmonic dampener. Anyone have any experience with the prop with or without the dampener. Ed Sterba checked out the prop and refinished it; also confirmed it's the proper diameter and pitch for my application. I'm inclined to use the dampener for the extra inertia plus a better CG location. Any thoughts and/or personal experience concerning this would be appreciated. Thanx.

Welcome N728E !! Im going to move this thread over to the new "Propeller" forum where I think it should get better visibility. You can be the first to post there. Congratulations

-- John

My RV-6 has a 160hp 0-320 with a Sterba Prop, with the harmonic balancer. The harmonic balancer was installed when I got the airplane. Judging from the idle characteristics, I don't think I would like it at all without it. They put em on there for a reason. I guess improving the CG location is a pretty good reason, but not shaking the airplane apart at idle was the one I was thinking of.
I get about 2300 RPM on take off. As the airplane gains speed, the engine picks up to about 2500 RPM at 100mph IAS. I live in a rainy climate. If I'm flying in rain, I have to throttle the engine down to around 2000 RPM to keep from beating the finish off the propeller. I have ordered a Catto Propeller that hopfully will remedy that situation. In fact, I'm expecting it any day now. For now, I'm planning to leave the harmonic balancer in place with the new propeller. Will see how it works out.

hngrflyr

Hey hngrflyr,

Thanx for the reply. The Sterba I got only had a few hundred hours on it but I wanted it blessed by the master so I sent it back to Ed and he refinished it to like new condition for next to nothing. I've already made arrangements to acquire a used Sensenich metal prop but I think I might like to try the Sterba anyway just 'cause. I'm in AZ so rain isn't a factor very often. I had also heard about the increased smoothness especially at idle with the dampener, so barring any first hand info I was planning on using it anyway. Thanx again.

--hawk

If I lived in AZ, I wouldn't change a thing. There are other places I would put the money.

hngrflyr

After a couple months with the Catto Propeller, I'm glad I changed. The Catto Prop is more efficient at converting the horsepower to thrust.

A little primer on vibration with our AC engines. These engines operate on fixed ignition timing. The majority of Lycomings operate at 25 deg. BTDC. Some at 23.
Both 23 and 25 is just plain too much timing at anything below 1200-1500 rpms. Add to that a wooden or composite lightweight prop, and it will shake. Metal props are heavier and will add inertia to the spinning crank, and will dampen some vibration. Still even the metal prop should idle above 1200.
Idling or anything below 1200 should be any where between 0 to 6 deg. Naturally, these engines spend little time idling or running below 1200-1500 rpms.
Solutions are higher idling speeds, or managed ignition timing, such as LASAR ot Lightspeed. Vibration dampeners are primarily used to damped vibration of a different nature. In the case of an engine idling, and with a lightweight prop, is a result of an engine trying to "backfire" if you will because ignition is taking place far ahead of the engine speed.

TT, thanks for that info.

hngrflyr wrote:After a couple months with the Catto Propeller, I'm glad I changed. The Catto Prop is more efficient at converting the horsepower to thrust.

hngrflyr, can you elaborate a bit more on this? The RV-4 I bought has a Sensenich cruise wood prop. It's a 68" with 82 pitch, and with 150hp motor, doesn't produce enough static rpm. My CFI suggested Catto prop. How is it in rain? Anything you don't like about it? I like that it's $1300, a good $700 cheaper than metal Sensenich from Vans. Of course with the metal prop I don't have to worry about rain or bolts coming loose. What are maintenance issues with Catto?