How long will antifouling last?

[MedMan]

Every year without fail I put another two coats of self-eroding antifouling. Despite its name, if doesn't all erode away during a season so twice now since I have owned my boat, I have removed the build-up back to the epoxy coating and started again. The last time I did that was in 2001 so I may well have to think about doing it again in a year or so.

When antifouling costs so much it grieves me to scrape off what has cost so much to put on and it grieves me even more to have to fork out more cash for more antifouling when there is such a decent thickness left on the hull. The rationale, of course, is that the remaining antifouling is 'spent'. It is no longer toxic and it is unable to do its job. But how do we know this is true? The manufacturers tell us so, of course, but then they would, wouldn't they?

Has anyone tried just refreshing the surface of last year's antifouling with wet and dry and re-launching? If so, how did you get on? What type and how old was the antifouling and how long had the boat been out of the water? How long was the boat back in the water after launching?

 

[andy_wilson]

Rumour does indeed have it that the active ingredients leech out leaving dud coating behind.

As A/F is so crap now I have choosen not to paint this year at all, there will be little or no fouling until June as the water is too cool, and I will dry out to scrub off and assess the situation again.

Part of the thought process is to remove the build-up. Previously I have reduced several years worth down to the epoxy (in places) by drying out and using nylon scourer to scrub with (about 300 x 125mm on a holder on a broom handle). I appreciate you can't dry out in the med, but you can do the waterline down to almost a metre from the dinghy, and could do more with a scrubber on a rope round the bottom. The rest, who knows, or hire a diver.

Your problem is probably a high rate of growth in the Med. Might be worth seeing how many scrubs by a diver you could get for the price of a haul, scrub and 2 coats, followed by labour, hardstanding and dilunet to remove the spent stuff.

 

[andy_wilson]

Oh, and...

.. I don't think sanding down will do anything to expose biocides. A/F has a very open matrix once applied t let the stuff out in a controlled manner - in theory.

 

[oldharry]

Re: Oh, and...

The theory is that while there is Af, it will work. In practice it gets weaker and weaker as the coat thins and the active ingredients leach out and detriorate. Drying out for the winter finishes it off.

My boat normally lives in a mud berth in winter, and floats every second week for around half a dozen tides. I find a single coat every six months seems to keep things going nicely. (Blakes Tiger), and keeps the little beasties well at bay.

 

[ex-Gladys]

Re: Oh, and...

Many a/f's say 2 coats from a fresh start then one per season afterwards...

 

[Malish]

Re: Oh, and...

I'm now into my third season without putting on any fresh antifoul. At the start of last season (March) I took a coarse plastic scouring pad to the hull (with some water) and scrubbed off the surface layer. At the end of the season the hull looked fine, a little surface slime but no other growth / attachments. I have repeated the process this season. The hull had a coat of Blakes Tiger applied followed by a coat of Seajet Shogun and I've yet to erode down to the Blakes (it was a different colour). Yacht is in a marina berth on the Medway.

 

[tcm]

Hi.

We're in the med as well. A year ago I painted over two existing coats of antifoul with two+ coats of Trilux mixed 1kilo-1litre with copper powder. This gives a slightly gritty surface but the oxides of copper means we have no barncles/crustiness at all, not one. I dive down to clean props etc every couple of months. I think this will last a few years and haven't hauled out this year.

 

[Otter]

Re: Oh, and...

As all the marinas in the Medway are lock controled, the water in them may be highly toxic anyway. I certainly grew no weed in Gillingham Marina!

 

[trouville]

Where did you buy your copper?what did it cost for the kilo?

That sounds very good.i always thought copper was only effective in fresh water lakes,which is what copper AF used to be sold for.And lakes(in europe)only allow copper AF.

All those in the med that have their own AF made up still use TBT a few fishermen also told me they add other things which put me off swiming for a while!

The copper sounds a good solution.

 

[Malish]

Re: Oh, and...

'Highly toxic' is a bit dramatic and inaccurate - there is a reasonable aquatic life in the marina (fish, bugs etc), there is an exchange of water via lock exits and free flow around high water + inputs of fresh water via surface drainage that may in turn impact on salinity.

 

[rwoofer]

Bit off topic, but since it is really important for Mobos to have very clean props, can I ask what you clean your props with?

I last did mine with the back of a washing up brush and a scouring pad - it did an OK job, but I'm sure I could do better. I was thinking about something like wet and dry.....

I also learnt how knackering it is to work underwater with scuba gear - the guys who do it for a living are obviously very fit.

 

[samwise]

For the past two seasons I have used Blakes two pack Ocean Performer which seems to erode right down so that all I need to do is use the scourer pad with water to prepare the surface, dry off and slap on another couple of coats. In the past on other boats I have used single pack products such as Tiger and even Cruiser Uno but I was aware that the stuff was building up and that I would eventually have to get scraping. There seems to be no build up problem with Performer. It is, however, expensive at £95.50 per 2.5 litres ( need two tins) but there are offers around and this year I got it for £79.95 a tin. In answer to your original question, I doubt that sanding down will do the trick to liven up the biocide.

 

[angelsson]

I am in the Med in Sardinia and about to haul out and clean the hull, then decide if I need to A/F again. A local chandler offered me a 'self polishing' A/F, and from his gestures indicated it was an excellent product. It was in a smaller size tin and when I told him the boat is 11m at waterline he suggested 6 tins to do the job, around about 180 euros in total.
Has anyone else in the Med come across this self polishing A/F, not sure what it means exactly, or used it.

 

[angelsson]

Sorry, but what is TBT?

 

[trouville]

Its tri butal tin and was banned for use on small boats but still used on commercial vessels.It works realy well providing you dont sit in port all year go out once a week for a good sail your bottom will be spotless untill its gone!

Self polishing is just that the surface keeps clean as you glide through the water!

Since TBT was banned everone is looking for the best solution.thats why i asked TCM what his copper cost?

I did think of copper plate but looking at boats with copper bottems and seeing them antifoul i dident do it

It will be that or lead against the worm if i spend summers in the med though(very expensive and crowded i sometimes think that boats come for the summer just to be "seen" that they can aford to be there?)

 

[tcm]

Spose it depends on the props - ours are a bit big bout 850mm dia, I use a 6-inch wide paint scraper for the rough stuff, and finish with a rust removal pad. I need need super-calm water and tanks good for 30-40 mins. It is certainly hard work and not an option in colder n european waters really. Lanyard for the scraper for when you lose grip of it...