Catto prop /Dynamic propeller balancing.

[PerryB]

I just balanced my new Catto and am very happy with the result. A brief backstory: About a year ago I had my Borer reconditioned and bumped up to 42" pitch. It was tracked and statically balanced as part of the procedure but was not as smooth as it was before the work, so I took the plane to a man in Jackson,CA. and had it dynamically balanced on the engine. The improvement was significant. I don't remember the starting number, but we got it down to .04 in/sec.. I noted a static improvement of about 30-35 RPM and no more buzz through my heels. The climb-out RPM also improved slightly, for a given airspeed (at full throttle of course).
About 2 weeks ago I got my new Catto and really like the prop. Its an 82-39. The pitch is perfect for what I want. Takeoff and climb is identical to the Borer and cruise is about 3 mph faster for a given RPM. It felt pretty smooth but not as good as the aforementioned Borer with its balance job. Today I borrowed a Dyna-vibe ( the man from Jackson moved away but I found another fool to trust me with his equip.) to see how far out it was. I was rather shocked to see .38 in/sec. I guess the Catto soaks up some of the vibration and spreads it over a greater part of the arc, because I think a metal prop at .38 in/sec would feel like a tuning fork. Anyway, I got it down to .07 in/sec and called it good. I think its now the smoothest 4 cylinder I've ever operated, and I got the same 30-35 RPM increase that I got with the last balance job. I guess the construction/composition of the Catto will dampen the vibration, but it can't hide it from the accelerometer.
At this point I'm completely sold on dynamic balancing, regardless of how smooth a prop feels.

P.S. When going from an 82" Borer to an 82" Catto deduct 3" from the pitch. The Catto has more blade area and probably a more efficient airfoil. My static RPM's are identical, the takeoff distance and rate of climb are as close to identical as I can determine (including WOT brake release time to 1000' agl) but if forced to declare a winner in this dept. it would probably be the Catto. On the top end the Catto runs out at 2730 RPM and 106 vs. 2700 and 103 for the Borer, and as mentioned above it runs about 3 mph faster for a given cruise RPM. -- Hope I haven't bored anybody to death, but I found it to be an interesting and educational experience.

 

[spinner2]

I've had two Catto props dynamically balanced. The first was down to .02 ips and the one on the Cub now is .06 ips. They're both smooth and I'm a believer that everything on the plane lasts longer when the prop is balanced. Well worth it.

 

[PerryB]

Good to hear from you Dan. I probably could have done better, but when looking at the big picture I found .07 to be acceptable. I hit it in 3 attempts. It was something of a cost /benefit decision. I figured I could spend all day chasing perfection or smile in the face of dumb luck. Its like persuing sub 1/2" groups with a rifle, but you probably wouldn't understand that reference.8)8)

 

[Gordon Misch]

So Perry, is the Cato now STC'd on the -12? Or did you do it as a wooden prop per the TCDS?

 

[PerryB]

Yes.................

 

[RaisedByWolves]

Yes.................

My kind of answer

 

[skywagon8a]

Item 1 on the PA-12 TCDS A-780 "....or any other fixed pitch wood propeller which is eligible for the engine power and speed and which meets the following limits:..."

 

[Nodak33]

I went with an 84/37 on a 160hp 0-320. first time flying it today and can’t quit figure out if it’s in my head or if the difference from the 82/43 borer, but the vibrations are different than what I am used too.

How did you add the cw to the prop when you had it balanced.

I’m in the okc area and short on decent cub mechanics. I’m thinking it would be less of a head ache to get my own tester. Lol
I too fly a -12


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[courierguy]

Got one last week, haven't flown yet due to weather. http://www.balancemasters.com/

 

[Nodak33]

I saw those, have you used one before?


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[courierguy]

I saw those, have you used one before?


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Not on a prop, but I use a similar product, with the same concept, on my big truck's wheels (54,000 lbs) and don't even need to conventionally balance them anymore, while it rides smoother then ever before, so I guess I'm a believer in them somewhat already, we'll see.