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Old 28-10-2013, 00:52   #1
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Strange barnacle growth

Hello cruisers,

We have just started a pretty major haul out and overhaul, and I have run into something a bit odd below the waterline.

The boat came out of the water very clean, it was antifouled by the PO last October with two coats of altex af5 ablative, and they held up really well. However, the hinges on the rudder are really badly gunked up with barnacles and crud. When I first saw this I assumed they had not been antifouled, however while cleaning them up I noticed remnants of antifouling paint. I don't think it is a water flow issue, the delineation between the clean rudder and the gunked hinges is laser straight. I thought perhaps there should have been some kind of priming paint applied to the hinges first, but I can find no reference to it in the altex mds.

The hinges appear to be bronze, but I am not certain of this.

Is this growth something I should accept or is there a way of preventing this?

Thanks,

Matt
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Old 28-10-2013, 14:44   #2
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When you leave your boat, do you tie up your tiller or wheel to stop rudder movement?
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Old 28-10-2013, 14:59   #3
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Re: Strange barnacle growth

between the time of haul and anti fouling paint applications, was there any attempt at in water cleaning to remove the heavy growth that builds up monthly, or was it left to grow without hindrance

i have mine cleaned in water every month to 2 months as needed for growth.
yes it will grow on top of paint.
yes someone gets in water to scrape the hull with , in my boats case, a plastic scraper. that helps and every month or so, as needed, someone can do that.
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Old 28-10-2013, 16:53   #4
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Re: Strange barnacle growth

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Originally Posted by zeehag View Post
between the time of haul and anti fouling paint applications, was there any attempt at in water cleaning to remove the heavy growth that builds up monthly, or was it left to grow without hindrance

i have mine cleaned in water every month to 2 months as needed for growth.
yes it will grow on top of paint.
yes someone gets in water to scrape the hull with , in my boats case, a plastic scraper. that helps and every month or so, as needed, someone can do that.
Hi Zeehag,

We use an ablative paint, so the bottom stays clean all year without any kind of scraping or cleaning at all, PROVIDED I sail the boat regularly. (Which is hardly a chore )

So really, the boat came out spotless all over, except for those pesky hinges. It's as though the metal under the paint stopped the ablative doing its ablating thing.

I understand we may do things a little differently down-under when it comes to antifouling paints, though some of the serious racing guys at the club don't use antifouling paint and instead get their bottoms cleaned regularly. Not sure how regularly, but regularly.

Matt

P.S. You can see how clean the boat is from my Manera album under my profile, there's a picture of the boat out of the water (with my wife looking very proud) a month or so back when I was doing a quick bit of plumbing repair. Sadly the cradle masks the problem area, but you can see the rest of the boat, and it is pretty well spotless despite being in the water nearly a year at that time. It looked no different when we pulled it out on the weekend.
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Old 28-10-2013, 16:54   #5
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Re: Strange barnacle growth

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When you leave your boat, do you tie up your tiller or wheel to stop rudder movement?
Interesting question, but no, I don't. We are in a pen and the rudder never moves an inch.

I am curious, what is your thinking here...?

Matt

P.S. We have wheel steering, so there's a fair bit of drag to keep the rudder steady.
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Old 28-10-2013, 16:56   #6
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Re: Strange barnacle growth

ok so you actually use the paint correctly.
are the barnies tiny and clustered closely as in da kine after oil contamination?? i noticed after i saw diesel vs oil on surface there were tiny tightly clustered barnies on my waterline and leading edges

they also love tops of rudders and tight places.
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Old 28-10-2013, 17:04   #7
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On our Kiwi design 22ft mullet boat with a long keel we found having the rudder moving reduced the amount of growth on the rudder , dont ask me why . Read up about your antifouling, find out if it works on metals. Are you sure its got nothing to do with water flow?

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Old 28-10-2013, 17:05   #8
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Re: Strange barnacle growth

Matt, I have also had this experience. I think that the AF paint has (for whatever reason) blown off the metal surfaces to such an extent that barnies can get a foothold in the bare spots. Once that starts they seem to be able to propagate "sideways" to cover the area.

It has been suggested that the paint is blown due to electrolysis. Are the gudgeons, etc, electrically connected to a zinc anode in any way? I'm not sure how this works... have had some sorta contradictory explanations proposed... think the question is beyond my pay grade!

It may be that treating the bronze bits like a steel boat, with primers and epoxy barriers might help, but again the chemistry is a bit different, so I dunno. My general reaction has been to live with it, scraping when convenient and ignoring it the rest of the time!

Cheers,

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Old 28-10-2013, 19:46   #9
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Re: Strange barnacle growth

Wow, I've come back for a lunch break and all sorts of ideas, thank you.

In no particular order, Zeehag, they are pretty deep under the water, so probably not oil related, but you are right, they do love the top of the rudder and other little crannies, I always assumed it was because I was not careful enough getting the AF into those places, but as per d_design's point, there's not much water flow in those areas either, so the ablative can't do its thing.

Jim, I like your idea about the little buggers tracking sideways, but now I am alarmed about my anode protection, I'll double check those.

The MDS for the paint said absolutely nothing about how to prime for metal surfaces (aside from cautioning against use on Aluminium boats) so I will phone the distributor this arvo and see if I can get an answer from them.

Sounds like it might be one of those Aussie boat things. :^)

Matt
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Old 28-10-2013, 21:02   #10
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Re: Strange barnacle growth

It might be altex 5. I had my boat hauled a couple of weekends ago and I noticed that the manganese bronze stern bearing had a nice beard of growth and no a/f left underneath. It's not connected to a zinc (it's isolated from the shaft by the cutless bearing) but shows no signs of electrolytic erosion. I just assumed that the antifoul didn't stick too well to the alloy.
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Old 29-10-2013, 12:59   #11
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Re: Strange barnacle growth

Most metals need to be properly primed before applying anti fouling paint. What the OP describes sounds very much like what we call "burn back", where the paint has reacted to the metal and come off or been rendered ineffective.
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Old 29-10-2013, 14:42   #12
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Re: Strange barnacle growth

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Most metals need to be properly primed before applying anti fouling paint. What the OP describes sounds very much like what we call "burn back", where the paint has reacted to the metal and come off or been rendered ineffective.

Yes, I think you are right. Jim's description fits this also. I will interested to see what Altex have to say about the matter, but it seems increasing like I am just going to have to accept it.

As long as it is not doing any damage then I suppose only the fish see it, you can't see it from the dock.

Matt
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Old 29-10-2013, 14:44   #13
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Re: Strange barnacle growth

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Originally Posted by Reefmagnet View Post
It might be altex 5. I had my boat hauled a couple of weekends ago and I noticed that the manganese bronze stern bearing had a nice beard of growth and no a/f left underneath. It's not connected to a zinc (it's isolated from the shaft by the cutless bearing) but shows no signs of electrolytic erosion. I just assumed that the antifoul didn't stick too well to the alloy.
You too hey? Well if Altex gives me a solution I will post it here for the record.

Matt
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Old 29-10-2013, 14:59   #14
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I use Altex 5, its great stuff
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Old 29-10-2013, 15:18   #15
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Re: Strange barnacle growth

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I use Altex 5, its great stuff

Well, aside from the hinges the boat came out practically spotless, so I have to agree.

M
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