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Old 03-07-2013, 04:13 AM   #1
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Haul Out

Hi all,

Have just hauled out after 12 months, suprisingly not much growth on the bottom, except for some barnacles on the prop shaft strut(see pic) and in the bow thruster tunnel.
I have 3 areas zinc anodes, two small ones on the rudder(which were nearly gone) one on the end of the prop(30% gone) and one on the transom abt 3" dia and 2" thick this was virtually as new.
The guy who hauled the boat showed concern that the annode on the transom had not been eaten and said this was probally the cause for the barnicles on the stut and i should check the bond between the strut and the transom anode.
Also he said there was to much anode on the rudder and that is why i was loosing paint(see Pic), so he only put one back on, and put some more paint on the rudder
So I located two cables going from the strut to the transon anode(It was included in quite a sum of wires all going to the transom anode.
I also looked at the wiring diagram with the boat and relised that the rudder,engine and some components and engine exhaust are all bonded to this transom anode.
Any clues on this would be helpful
Regards Scott
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Old 03-07-2013, 06:13 AM   #2
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.................. The guy who hauled the boat showed concern that the annode on the transom had not been eaten and said this was probally the cause for the barnicles .............
Anodes have nothing to do with barnacle growth. If he told you that, I would discount anything else he had to say.
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Old 03-07-2013, 06:25 AM   #3
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Thanks for the reply Ron,
So in your opinion what has caused a concentrate of barnacles on the strut
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Old 03-07-2013, 06:59 AM   #4
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Maybe the concentrated force of the water rushing that close to the prop, had washed away more of the antifouling component of the paint, then the slow moving hull thru the water.

This theory would be better to explain paint washed off the rudder, but its the only one I got.

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Old 03-07-2013, 07:16 AM   #5
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How about the zinc on the bowthruster. Sidepower thrusters at least use a small zinc on the hub of the prop.

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Old 03-07-2013, 04:07 PM   #6
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Thanks for the responses;
I have a max power bow thruster, single prop, did not notice any deterioration of the zinc but did not realy look for it - I can see where it is in the owners manual, but will this have any bearing on barnacles growing on the bow truster prop suport?
Should I be concerned with the transom anode not deteriorating? Will this anode come into play if the ones on the rudder and prop(closer to the metal components) get fully eaten?
With the strut I was thinking propspeed? but I do not know about justifing the extra cost?Are these barnacles causing damage? The barnacles seemed to scape off easily and there was no visual corrosion of any metal parts.
Thanks Scott
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Old 03-07-2013, 04:13 PM   #7
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Again, anodes have nothing to do with barnacles.

Are the barnacles causing damage? They cause friction with the water and slow your boat down causing it to use more fuel than it otherwise would.

If an anode is not being consumed and the other anodes are, the one not being consumed is not protecting the boat, usually because it's not bolted tight to the metal it's attached to or because a bonding wire is loose or broken.

You cannot use copper based antifoulant bottom paint on underwater metal, it will cause corrosion. You need a special antifoulant paint that's designed for underwater metal.
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Old 03-07-2013, 04:24 PM   #8
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Barnacles attach and grow where there is insufficient or no anti-fouling coating. On our boat we use ablative bottom paint and the prop "blast" against each rudder wears the paint away faster on them than the boat's motion through the water wears away the paint on the bottom. So the trailing edges of the rudders is where barnacles first show up.

This is totally unrelated to the boat's bonding system with its zinc anodes, as Ron pointed out.
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Old 03-07-2013, 05:59 PM   #9
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Was ablative soft antifoul used for the hull applied to the running gear? That could explain it. Unless you go to Propspeed, use hard a/f on the gear, after primer such as Primocon, as a barrier and something the a/f will adhere to.
Bobbin Head, (the ex Halvorsen boat hire base) at the head of Cowan Creek (larger body of water than it sounds) has limited water movement, was your level of fouling normal for the area?
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Old 03-08-2013, 10:28 AM   #10
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Have a new antifouling paint with no cooper
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Old 03-12-2013, 04:45 PM   #11
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I started a reply a few days ago but internet has been poor so didn't retry.

Zincs or no zincs, as pointed out, does not affect barnacle growth. They adhered to the strut because either the bottom paint wore off from the water flow, was insufficent, or failed from poor mixing or preparation during application.

Your transom zinc, if not being used, is not connected. That could be from broken wires, dirty or loose connections including where the zinc itself is mounted. Those connections include the crimp barrel interior of any crimp connections for terminals. The voltages and currents involved in a zinc protection system are small and can be blocked by anything less than absolutely clean and secure connections and crimps.

I have taken to grinding/sanding/wire s.s. brushing lightly the mounting pad areas of my zincs and the item they are mounted to. I've found that sometimes the surface oxidizes enough to ruin conductivity.

Replace the zincs on the rudder. They are gone and reducing the zinc will leave the rudder open to problems even sooner. I realize from your mention of the schematic that there should be a connection between the transom zinc and the rudder but that has failed so in the meantime go with the full zincs as even from what you showed the zincing was inadequate. Then monitor when you get the transom zincing system connections up to snuff. Maybe in the future you can reduce rudder zincs but not until you KNOW the rest of the system is working.

Yes it is possible to overzinc and one of the signs is paint loss. HOWEVER< I don't see that here. Usually the paint loss from overzincing is a halo, although not a perfect circle, of missing paint around the zinc or fitting . That doesn't appear to be the case here. It looks like patches of it flaked off from poor preparation. Also general paint loss is usually water flow erosion particularily where prop wash can hit . Simply put another coat or two of the bottom paint on so that there is allowance for paint loss after preparation.

Bottom paints can fail to work for various reasons. Prep is the key. Not fancy but thorough. Also the paint itself , at least for the metallic based paints, have a heavy load of metal. That metal, copper usually, will quickly settle out of even the most thoroughly mixed paint. Remixing needs to be done fairly often as the paint supply is used or the copper will settle to the bottom of the can and not be present evenly in the painted layer.


You will need to trace every wire and connection in that bonding system to ensure all is well.. That may include replacing some wire and reterminating those wires that show any signs of corrosion.
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Old 03-12-2013, 06:46 PM   #12
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Quote:
You cannot use copper based antifoulant bottom paint on underwater metal, it will cause corrosion. You need a special antifoulant paint that's designed for underwater metal.
Ron that is absolutely not true. What is true is that it won't last long and or do very much to keep barnacles off. But if your having your bottom painted and have extra paint leftover (assuming the did some extra on the waterline and prepped the metal right) why not? Good bottom paint is expensive.

Now, over zincing can cause some burn off of the paint on the rudders, the guy made a pretty good guess there. One thing that is true is that the zincs and the barnacles are two different issues. And that there is likely a bonding issue on that transom zinc.

I have played with the idea of using PropSpeed or one of the cheaper equivalents, but have found a good diver coming once a month costs about the same and has the advantage of someone checking zincs, paint condition and other anomalies on a regular basis. My boat looks great on haul outs now that I wised up on that.
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Old 03-12-2013, 07:09 PM   #13
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Ron that is absolutely not true. What is true is that it won't last long and or do very much to keep barnacles off. But if your having your bottom painted and have extra paint leftover (assuming the did some extra on the waterline and prepped the metal right) why not? Good bottom paint is expensive. .
If by "prepped the metal right" you mean an unbroken coat of an epoxy primer, yes, you could use copper based bottom paint. Otherwise, it will cause corrosion of the metal. When bottom painting with metalic paint, you are supposed to leave a one inch gap between such metal and the paint.
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Old 03-12-2013, 07:37 PM   #14
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I have played with the idea of using PropSpeed or one of the cheaper equivalents, but have found a good diver coming once a month costs about the same and has the advantage of someone checking zincs, paint condition and other anomalies on a regular basis.
Ditto! I've been doing that for 17 years and my boat looks "pretty good!"
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Old 03-12-2013, 09:37 PM   #15
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George...agree...

Copper and aluminum as in outboars/outdrives are a problem....thus the 1" separation line.

Copper paint on stainless is not good (but have seen it done plenty)...but not because of the copper...stainless needs O2 to remain stainless...

Copper on bronze (plenty of copper in bronze) isn't harmful at all as there's lots slopped on many commercial boats all over the place without epoxy primers.

Plus I hardly ever see someone prime a bronze throughhull mushroom/scoop with a 2 part epoxy primer ..... copper paint goes on with no ill effects.
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Old 03-12-2013, 10:04 PM   #16
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All our through hulls as well as the rudders and V-struts on our boat are bronze. We use bottom paint with a high copper content. It is applied directly to the bronze with no issues.
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Old 03-13-2013, 08:19 AM   #17
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Even good shafts can be painted, which a couple yards have done as part of a bottom job, with no ill effects noted once the stuff wore off, but it's pretty much useless on running gear and does very little in my experiences in high growth areas to keep th creatures off.. some but not a lot. I tell them not to bother with the shafts and props anymore.



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Old 03-13-2013, 10:53 AM   #18
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New trawler owner here. Can I get so feedback on a yearly haul out time. Just had it done in fall for survey and bottom was painted. I guess spring would make more sense if the bottom needs painting
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Old 03-13-2013, 11:23 AM   #19
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Greetings,
Once one has some idea of how long your anit-fouling coating lasts and/or growth builds, one can then decide on a haul schedule particularly if the boat stays in the water year round. SOME anti foul needs to be "splashed" within a certain time of application so if hauling for the winter, it makes sense to paint in the spring. I think this is the case with some ablative coatings. If there's no "splash within time" then I expect it's up to you.
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Old 03-13-2013, 06:52 PM   #20
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...........SOME anti foul needs to be "splashed" within a certain time of application so if hauling for the winter, it makes sense to paint in the spring. I think this is the case with some ablative coatings. If there's no "splash within time" then I expect it's up to you.
My boat is painted with a hard, not ablative paint (Petit Trinidad SR 77)but it has this restriction, no more than three days out of the water.

Whatever it is, it's in the manufacturer's instructions for the paint.
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