Propeller mystery

Bouba

Bouba

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Two seasons ago while on the hard, I tested my propeller with a spanner, ding ding ding ding donk (it’s five bladed?). The blade was also pinkish compared to the others. Demineralization, leaching! Last season I repeated the test, ding ding ding ding donk!. This season I was determined to do something about it. I identified a propeller shop, near Cannes, that looked the business and had mentally designed a propeller puller.
So the boat is now on the hard. I retest, ding ding ding ding ding. No matter where or what I hit it with, it all dings lovely. I haven’t shined the prop yet (and I may not as I am doing it myself this year), so I don’t know yet about pinkness.
But what could have happened? I am at a loss to explain it. Fanciful theories pop into my head, like, is hub getting demineralized and it’s leaching back into the blade making it whole again? Madness I know.
So what do people think?
 
And on a lighter note I find it very hard to believe just one blade would be demineralized / zinced / whatever unless it stopped perfectly at the same point every time. Much easier to believe your memory and mind is playing tricks with you. But what do I know. Nuthin, thats what.
 
Do you know for certain it was the same blade going donk each time? ie did you mark it?

Could it be due to the rotational position of the blade as to whether it goes ding or donk (could the prop be binding slightly in one position that prevents the blade that went donk from ringing - long shot I know) ? and this time your prop stopped in a specific position which allows all blades to go ding, ie they are free to ring?
 
julians said:
Do you know for certain it was the same blade going donk each time? ie did you mark it?

Could it be due to the rotational position of the blade as to whether it goes ding or donk (could the prop be binding slightly in one position that prevents the blade that went donk from ringing - long shot I know) ? and this time your prop stopped in a specific position which allows all blades to go ding, ie they are free to ring?
Click to expand...

Good point! Maybe his shaft is bent and the P brackets are now worn out. That'll get his mind racing and heart beating. Bet he's rushing down to Maccie D right now for his fix.
 
julians said:
Do you know for certain it was the same blade going donk each time? ie did you mark it?

Could it be due to the rotational position of the blade as to whether it goes ding or donk (could the prop be binding slightly in one position that prevents the blade that went donk from ringing - long shot I know) ? and this time your prop stopped in a specific position which allows all blades to go ding, ie they are free to ring?
Click to expand...
I’ve been dinging the prop more times than a church service, and it’s all even
 
A few thoughts;
Dezincification is irreversible
Unless you're dinking and donking in a consistent way this already empirical test is worthless
polish the thing, photograph it and put it up here.
 
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penfold said:
A few thoughts;
Dezincification is irreversible
Unless you're dinking and donking in a consistent way this already empirical test is worthless
polish the thing, photograph it and put it up here.
Click to expand...
I’ve never actually polished a bronze prop before but I will see what my energy levels are after I finish the rest of the hull?
 
how did you clean the prop Bouba (this time and previous times)?
acid? jetwash?
was it a/f or not?

I'm a convert for a/f ALL metals below w/l (ok, except anodes-some ppl do that...) as I've noticed a reduction is exposed metal leads slower anode wear so that I can have a liftout every two years instead of one ?
diver cleans metals and whatever is needed in the other year.
Obvs a/f a prop (in a way that a/f stays on) means there's no path for electrolysis, which can only be a good thing.
 
vas said:
how did you clean the prop Bouba (this time and previous times)?
acid? jetwash?
was it a/f or not?

I'm a convert for a/f ALL metals below w/l (ok, except anodes-some ppl do that...) as I've noticed a reduction is exposed metal leads slower anode wear so that I can have a liftout every two years instead of one ?
diver cleans metals and whatever is needed in the other year.
Obvs a/f a prop (in a way that a/f stays on) means there's no path for electrolysis, which can only be a good thing.
Click to expand...
Hi Vas, every year the prop is jet washed, the prop has never been anti fouled. I don’t know what method was used to clean and polish the prop the previous years. But this year I am doing it myself. I have used acid and I have bought a abrasive disc for my angle grinder but haven’t yet used it. At the moment most of the barnacles are off and the prop is looking stained and dull.
Last season I put bigger zincs on (although the prop zinc is a fixed size). This season I have bought even bigger zincs and a shaft zinc as well (never had one before).
But the change in sound before was definite (if not scientific) and now it all sounds very tuneful.
Tomorrow, I will take photos
 
Ok, my first attempt at polishing




As you can see there is no pink. And I chimed them all again today and got beautiful notes.
Just out of interest, what do people use to get in all the nooks and crannies where the power tools don’t reach?
 
Bouba!!!

wft are you doing? planning to remove half the material out of the prop???
maybe the pics, but please soften your moves or you'll end up buying a new prop!
 
Relax it was a polishing disc on my angle grinder, it’s just contrasted against the unpolished parts. I have done a forensic fingertip test and there is no gouging or material removed
 
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