Prop performance after shortening

[denbobp]

I bought an io360 a3b6d with McCauley prop. From a mooney 201. The prop as is right now 73 inches on one blade and two inches of curl on the other blade. The prop shop suggested for experimental purposes that he could shorten them both to 70 inches and would be safe.
He didn't know how it would effect the performance on an 8 A.
Does anybody have any data with a shorter prop or should I just put on whirlwind blades into the McCauley hub and sell the remaining good blade?
Looking forward to any responses

[Mel]

I always recommend against shortening a metal prop beyond the manufacturer's limit. There has most likely been no testing for harmonics and they can be deadly.

If it cannot be OK'd for certified aircraft, it probably won't be any safer on an experimental. I've seen too many modified metal props come apart.

[BillL]

You probably can not do better in efficiency than the RV200 blade. Might be something to investigate with performance in mind.

[RV6_flyer]

Originally Posted by Mel

I always recommend against shortening a metal prop beyond the manufacturer's limit. There has most likely been no testing for harmonics and they can be deadly.

If it cannot be OK'd for certified aircraft, it probably won't be any safer on an experimental. I've seen too many modified metal props come apart.

The T-18s were using shortened metals props and there were a lot of them come apart. As Mel says, do not go shorter than the prop manufacturer recommends. There is a safety reason why they do not recommend shorter than a certain length.

[rockwoodrv9]

The propeller does not know if it is on an experimental or certified. If it isn't good enough for a certified, do you really want to fly behind it? I am taking a guess, but the amount of force needed to bend the ends could be enough to damage the rest of the prop? There has to be a better place to save money.

[denbobp]

Anybody have a single blade to make my mooney c/s prop usable for my project?...

[PCHunt]

I bought an RV-6 with a McCauley C/S prop on it. Great performance, and very smooth.

Being a bit cautious, I looked up the hub and blade model numbers, and couldn't find a match. So I called McCauley, and talked with a very knowledgeable tech guy, who informed me that the hub/blade combination had never been tested for harmonics, and that the blades were specifically prohibited from operation on a "Non-counterweight" Lycoming engines.

I have removed that prop, and replaced it with a Whirlwind 200RV prop, which I am very happy with.

You might want to "Google" metal prop harmonics.

One more data point.

[denbobp]

What did you do with the prop maybe one of those blades might fit. I do have a counterweight engine.

[PCHunt]

Originally Posted by denbobp

What did you do with the prop maybe one of those blades might fit. I do have a counterweight engine.

Denbob, if you are asking me about my old McCauley prop that I removed, the blades are not airworthy.

The tech guy at McCauley said that because they had been operated for an unknown number of hours on the wrong kind of Lycoming engine, they might have been subjected to harmonic vibration fatigue, and that the factory considered them to be not airworthy. They even went to the trouble to write me a letter stating the above, probably to cover themselves for liability.

Prop blades have been intentionally damaged beyond repair to ensure that they won't end up flying again.

[denbobp]

Any one have one for purchase?@