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Old 20-09-2010, 12:37   #1
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Anti-Fouling of the Shaft

I painted my shaft (the boat's) last year because I could tell it had been done that way in the past (first year with the boat). But I wonder if maybe the bottom anti-foul paint isn't good for the stainless shaft (I power wire brushed it before and there wasn't any pits or corrosion on it). Being a chemical treatment guy that treats systems with mixed metal I can think of the copper in the paint not being good for the shaft as far as pitting. At the same time I can believe it's not a big deal.

What's the thinking on putting bottom anti-foul paint on the prop shaft?
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Old 20-09-2010, 13:54   #2
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Doesn't stainless steel need oxygen to stop crevice corrosion which it gets from water?

Having said that we paint ours but use a thin coat of International Primocon first which mostly keeps the soft antifoul on. Tried another special primers paint this year, but it hasn't worked as well so back to Primocon next Spring.

BTW replaced the shaft at the 19 year point because the old stuffing box had worn the shaft in several places, however the rest of the shaft was fine without a mark.

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Old 20-09-2010, 16:03   #3
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The only shaft (and propeller) coating that I have come across that seems to work well is called "Propspeed" PROPSPEED

If it is applied correctly, you should get a couple of years of growth-free shaft and prop. The downside? Its extremely expensive.
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Old 20-09-2010, 16:11   #4
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Quote:
Originally Posted by Weyalan View Post
If it is applied correctly, you should get a couple of years of growth-free shaft and prop.
That's much longer than I've ever seen it last.
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Old 20-09-2010, 17:36   #5
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Pettit Zinc Coat Barnacle Barrier - basically spray on zinc. Spray on the prop and shaft. Good for about one summer season.
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Old 20-09-2010, 17:39   #6
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so are we saying NOT to use standard bottom anti fouling on the shaft?
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Old 20-09-2010, 18:43   #7
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Quote:
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so are we saying NOT to use standard bottom anti fouling on the shaft?
Yeah, that is what we are saying.

Quote:
Originally Posted by fstbttms View Post
That's much longer than I've ever seen it last.
It is not hard to apply it incorrectly, in which case it will not last long. We have ahd good performance from it for 2 years (although I note that the water here is relatively cold, so maybe we are less prone to growth). I have also seen it fall off in 4 or 5 months, through incorrect applciation.

Hereabouts, now, you can't buy it any more. Only licensed painters can buy and apply it. I am told this is because there were so many problems with people not applying it correctly, and it falling off.
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Old 20-09-2010, 21:29   #8
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Hereabouts, now, you can't buy it any more. Only licensed painters can buy and apply it. I am told this is because there were so many problems with people not applying it correctly, and it falling off.
I am not surprised. I had two customers this year, both with J/120s who used a similar product (Hawk Speed), had it applied by the yard, and I swear to God, it didn't stay on the running gear from the yard to their slips, maybe a mile's worth of motoring.
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Old 20-09-2010, 23:59   #9
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Hey Don, I had a good laugh about the start of your post that started as:-

" I painted my shaft (the boat's) last year ........ "

Sorry it just touched my weird sense of humour and obviously yours as well seeing that you put the disclaimer in the brackets..

But back to the subject!

I have painted a lot of shafts on large twin screw cruisers over the years and the best way to paint the shaft is not to paint it at all. Let me explain.

What I have always done is remove all old antifouling from the shaft and get back to the stainless then polish it up with wet and dry paper. Then what you do is spiral wrap the complete length of the prop shaft with the one inch wide sticky blue tape. The same type of tape that you use when you mask up your hull for the antifoul border line. Make sure that you keep the wraps at a high angle so that the overwraps are not more than 1/4 inch so that you get a lot of wraps on the length of the shaft.

You then apply the antifoul OVER the tape. Give it a couple of coats of antifould and your job is done. The next time that you haul out all you do is use a razor blade and cut through the tape lengthwise and "wallah" you have a clean shaft that just may need a minor rub over with the wet and dry. The result is no growth on the shaft itself and no build up of antifoul.

As I said I have successfully used this system on large powerboats with high revving diesels on large diameter shafts with great success so give it a try as it has some real benefits and is a timesaver as well.
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Old 27-09-2010, 14:03   #10
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200+ views and hardy any posts by viewers on whether they paint bottom anti-fouling paint on their shafts or not. Right or wrong lets have some input as there is only 2 choices.
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Old 27-09-2010, 15:13   #11
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Quote:
Originally Posted by Ozbullwinkle View Post
What I have always done is remove all old antifouling from the shaft and get back to the stainless then polish it up with wet and dry paper. Then what you do is spiral wrap the complete length of the prop shaft with the one inch wide sticky blue tape.
Now that idea I like

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Old 27-09-2010, 15:19   #12
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so are we saying NOT to use standard bottom anti fouling on the shaft?
My answer would be - No. because the paint does not stay on the shaft long enough to make it worth it. There is a never-ending quest to find an anti-foulant that will stay on a rapidly moving piece of metal such as the propeller shaft and the propeller. Nothing so far has surfaced that works and doesn't cost two arms and a leg.
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Old 27-09-2010, 16:08   #13
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G'Day Don,

I'm not sure what the emphasis of your original query is, so here goes the shotgun answer:

1. Putting standard copper based anti-fouling on your stainless steel prop shaft will not cause damage to the shaft.

2. It is difficult to get anti-fouling to stick to smooth s/s, so it is likely to come off fairly quickly. If one puts epoxy based hi-build primer on the shaft it MAY help with this problem. Since the shaft is fairly small in diameter, the surface speeds are not huge, and since it is in front of the prop the water flow is not terribly turbulant, so there is some hope. Use of a hard paint rather than an ablative one also helps.

As of this writing our bottom paint is nearly 5 months old, and we have travelled almost 2000 miles since application. The shaft is still painted and still un-fouled.

Propellors are a different case entirely. Their high tip speeds, induced turbulance and worse yet cavitation will rapidly remove paints. We're trying Prop Speed for the first time this year, and so far it has kept the prop clean, even in high-fouling areas. I had a look yesterday and it had some fine "fuzz" on it, but it wiped off with my bare hand. We had just spent 17 days in the Trinity inlet (Cairns) where the unpainted bottom of our rib had acquired a lot of barnies and some soft growth.

Hope this helps with your decision.

Cheers,

Jim and Ann s/v Insatiable II lying Michaelmas Cay, Qld, Oz
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