Antifoul how long does it last out of the water

[Gumpy]

I have just bought a boat that has been out of the water since last June. The antifoul looks in good condition apart from the patches where the surveyor did his tests I have no idea what make is on there. Now my question is can I just patch up the bits that have been scraped or will the old antifoul not be any good having been out of the water for so long.
As you can tell I have very little idea about AF as all my recent boats have been in freshwater and steel so have been covered in bitumen not AF

 

[charles_reed]

The instructions on the tin will tell you - it's usually 6-12 weeks, unless it's hard antifouling, in which case freshening it it with a light sand may do the job.

IMHO it will be a false economy to not put on two coats before she goes into the water.

 

[Twister_Ken]

It'll need to be repainted. Try to find out from the vendor what was used last time. If you can, one coat of that should reactivate what's already on there. If you can't, then two coats of whatever jollop takes your fancy would be the best bet.

 

[AIDY]

normally if the boat has been freshly anti-fouled... there is a maximum submersion period of 12 month's (well that's some international paints).

However i don't think it matter's if the boat has been in the water, as the other poster has said it's false economy not to paint the bottom if the boats out of the water.....

If your unsure of the previous anti-fouling.... use a barrier / primer coat over the top something like international primocon then slap a tin of anti-fouling over the top.....

the primocon will do for the patches as well as it's a sealer.

 

[PeterGibbs]

As anyone who's come into contact with the underside of a boat that's been antifuled will know, the paint goes quite soft in the water. The substrate that carries the active AF ingredients will not assume this soft ablative character after it's been hardened in the atmosphere, so the release of AF ingredient will not occur - they'll remain locked up.

Time to slap on some juicy new goop and write off the existing paint, but don't remove it - just patch with AF primer, as others have said. It'll then take the new paint without a murmur!

PWG

 

[Gumpy]

OK next question!
Do I sand it down first or just paint on top?

 

[Andrew_Palmer]

I just slap another coat on mine!

 

[Strathglass]

Unless you can find what antifouling is on it you will have to prime it and antifoul it.

The time before launching really depends on the exact antifouling that has been applied.

Fot example International Uno must be launched quite soon after application but there are other (more expensive) self eroding International antifoulings that can be left for 18 mounths before launching.

Iain

 

[AIDY]

don't whatever you do drysand it's toxic stuff !... some people just jetwash then paint.... if you want super smooth wizz over with some course wet 'n' dry. depends on the condition of previous A/F and how much time you have... Ideally it need a key to adhere.

 

[Twister_Ken]

As someone else has said, don't dry sand it. A/F is toxic (that's why it works - after a fashion) and you don't want to breath in A/F dust. Personally, unless it's like the surface of the moon, I wouldn't abrade it, just paint over the top. If it does need abrading to smooth it, use wet-and-dry wet, rubber gloves, and a disposable waterproof boiler suit - the Tyvek sort are good.

 

[gavin_lacey]

Given cost of lift outs it must be worth antifouling before launch. For surface prep. Giant plastic coarse 'brillo' pad used wet. You can get one that fits on a broom handle with a hosepipe attached. Fast effective and long reach. Sorry dont know manufacturers details. This preps the surface and gets rid of the crud, particularly around waterline, that pressure washers dont remove. The resulting coloured run off is probably classed as hazardous, discolouring a harbour can get you into a lot of trouble so be as sparing with the water as possible if this could be a problem.

 

[Gumpy]

Looks like a job for my unemployed step son!
Last one he did for me was blacking the bottom of our 60ft barge a 24ft yacht is going to be a walk in the park compared to that.
Thanks for the Plastic brillo tip

J

 

[Malish]

well, for an alternative view:
I antifoul once every three years but come out every winter for about 3 months. At the start of the season, normally a couple of weeks before launching I give the hull a good going over with a plastic brillo pad and water as per blue-elephant to refresh the surface and touch up the bits where the previous a/f coat (which is a different colour) shows through. I'm just starting year 3, at the last haul out there was very little growth, just a few v small barnacles near the prop. The approach of 2 coats every year, unless prior experience shows that it is required, is good profit for the antifoul companies and only speeds you towards the day when you pay the yard a few £100 to take it all off because it is flaking. (Tiger extra for me, no links to Blakes)

 

[Inselaffe]

I think it could be a very good idea to find out what is on there at the moment, before you try to put anything on top.

I say this because in my case the boat came with International VC antifoul on it which is incompatible with any other type of antifoul (probably due to the teflon in it).

My only options were to continue using the (expensive) same or strip it all off & start again. Since she is only small, I continued usin VC.

Maybe there are other compatability issues with other AFs?

Or you could even be unlucky & also have VC on there, onto which your new AF wouldn't stick.

Maybe worth a phone call to be sure before you start?