prop balancing

[doc g]

So, long story,short. I had my boat hauled local prop shop said yeah no problem to straighten the props, 4 weeks ago. Now tells me that he can not balance the wheels due to the diameter( which he knew in advance) . I am told they can fix the issues but will not be able to balance the wheels. I can have another shop do them at 3X the price and I will lose two weekends if I do. These are 6 bladed 46 inch diameter running thru a 3.45:1 ZF gear, max rpm is 2350. How important is balancing the props?? What do the experts say????? Thx in advance for your response.......Pat

 

[racclarkson@gmail.com]

Pretty damned important. I don’t think it takes an expert to understand out of balance vibration accelerates wear and tear. But, you might get lucky. I doubt you’ll get double lucky. You might just have vibration at a particular rpm. But again, it might be two different speeds and that ain’t gonna work. Don’t cost much more than another haul out to see. Given the cost of a ZF gear, prop work is cheap. Good luck.

 

[doc g]

Unless I’m doing the math wrong max rpm for this is 681 rpm . ....

 

[Pascal]

4 weeks then sorry we can't balance ?

Big huge red flag. Get the wheel out of there and take it to a good shop. Turn around on a prop repair and high speed balancing is usually a few days not a few weeks.

 

[Boatsb]

Big six blade props probably should not have been taken to the shop that can't balance them but if they didn't let you know in advance shame on them.

Maybe another shop can step up and bail him out if he has a good relationship with them as some of the guys around here have done in the past.

Its not the cost of the work that would worry me. It's the damage that can be done if they're out of shape or balance.

I guess that's part of the cost of owning a big boat.

Who took them off and sent them out to the wrong place?

 

[motoryacht lover]

You didn’t mention what kind of balancing the shop can do. There is the old way (static??) and dynamic balancing. I always get mine dynamically balanced and can feel the difference. It seems that the prop shop maybe doesn’t have the dynamic balancer but you would think they would have the ability to “manually” balance them so that you would not harm the drivetrain by using them.

 

[Pascal]

Apparently even dynamic balancing can be done at various level of tolerance. These big wheels have a lot of mass spinning around and you need the best possible job.

I am awaiting the autopsy result on a 3.5 AQ22HS shaft which snapped for no obvious reasons a couple of weeks ago while running on the exuma bank. Came out of the blue, first got a small vibration while running 22kts/1800rpm. Not tooth rattling but enough to be noticed. I slowed down within 30 seconds and bang... shaft snapped and prop went swimming off. It was too choppy to search so we continued the trip on port engine and came back a week later looking for it. Found it after two days and raised it from the 24' bottom. A $14k Veem is worth a couple of days

Shaft manufacturer is looking at the isssue to find out what could have happened. We re hauling out today to install a new shaft and magnaflux the other one.. prop is being repaired (two dings where it hit the rudder) and high speed balanced.

Here are the pics... swipe sideways for the whole series

https://instagram.com/p/BjiA8x6DHfX/

 

[doc g]

Pascal,wow that looks like it was riding on the keyway and not fully seated/ lapped onto the taper . It will be interesting to find out what caused that failure. Unbelievable you found it !!!

 

[Reefgeorge]

Nice work on your persistence and finding that prop! Glad that it departed the boat without a major catastrophe. Keep us posted on what they determine to be the cause.

George

 

[jim rosenthal]

For 14K I'd be back there looking, too.

 

[Scarlett]

Best thing of all it was not your boat.

 

[Walter P]

Best thing of all it was not your boat.

True, not his boat but once again he proved the value of a good captain. I kind of suspect that most
"hired hands" wouldn't have been so diligent in searching. Good job Pascal... 14 attaboys for you...

Walt

 

[Pascal]

Prop shop owner didn't think it was caused by the key way, break is about 1/2 inch in fromt if the end of the keyway. Will get info tomorrow

 

[kelpy]

It appears that shaft was cracked for some period of time prior to finally twisting off.

 

[Pascal]

Yes. The shop sent close up pictures of the break to the manufacturer of the AQ22HS stock and they said there was a small crack which spread over time. They said it may have been aggravated by the underwater prop install but Can't be sure.

We pulled the other shaft this morning to get it magnafluxed. Prop is already repaired

If i ever need to get a prop replaced underwater, I will do a short haul whenever possible to pull and reinstall the prop...

 

[Westfield 11]

I am curious how they repaired your prop, there was a pretty good chunk taken out of it if I am seeing the pictures correctly. Do they weld in a piece of Nibral and remachine?

 

[Pascal]

Yes weld, machine and the balance. Supposed to be like new.