Old antifoul layers

[MM5AHO]

About to put annual coat of eroding antifouling on. There's layers of previous stuff on the fibreglass hull so that its now rather lumpy (0.5mm high?). The old stuff will scrape off relatively easily, but should I?
If I should why? It doesn't fall off on its own.(cruising, not racing)
If so best way? (sanding, scraping?)

 

[VicS]

I'd say scrape off what's lose leave wha'ts not (They'll be 30 layers on mine within a week or so!)

DO NOT sand dry. Hopeless doing it wet as well!

Far to lousy a job to comtemplate using paint stripper

Only way to remove it IMHO is slurry or sand blasting or better soda blasting. That costs and i am not thinking of forking out to have it done either!

 

[TheBoatman]

Vic
I've just had 3 of our club boats blasted ~ 2 at 22' amd 1 at 23'.

Total cost £650 to take it down to gelcoat.

Peter.

 

[charles_reed]

I put a power sander over it before putting on the 2 new coats, mainly to get a good key and rid of uncleaned areas.

Don't have much build-up with eroding antifouling - only taken it off once in 18 years, before 6 coats of epoxy Gelshield - and then used hot-air gun and scraper.

The key is how much you use the boat and a mean of 3200nm a year is probably the key.

Whichever way you do it it's uncomfortable, toxic and tedious and IMHO best avoided!

 

[mortehoe]

IMO, having tried in the past to a) use a power chisel/scraper; b)use wet chemicals plus a hand scraper ; c) get somebody in to do a wet slurry blast ..... the only way is #'c'

Why: ????

a) causes nasty dust that gets up your nose/in your throat lungs .... and it's not only carcogenic but toxic as well!


b) wet chemicals just don't work over 5 'self eroding' layers thick and the manual effort of ~30minutes hard scaping per sq m results in another application of the wet so-called 'upto 20 coats of antifoul removed' in the twinkling of an eye .... So apply another £££20 of 'genuine wet remover' ... wait another 12 hours .... REPEAT at least another 5 times and boost your local chandlery's profits /forums/images/graemlins/laugh.gif /forums/images/graemlins/laugh.gif /forums/images/graemlins/laugh.gif

c) Wet slurry blasting is (IMO) more user friendly on/to other nearby boats-on-the-hard than grit blasting.

My take is that you've no real need to take off antifouling buildup until it gets to at least 15 proven years of self-eroding applications unless you are either a wierdo; about to cross the pond or are a committed can(ned) racer.

 

[swampthing]

Ive been doing this today.Chemical stripper. Called Strippit from Reactive Resins.£19 2.5l. Found it real easy.

 

[Lakesailor]

I just did a Prelude 19 by hand with a chisel. Much smaller hull area of course, but the a/foul build-up was severe and starting to "ripple". Some areas fell off like wall paper, but most chipped away slowly. It took about 16 hours and was hard work.
I've stripped a power boat with multivarious layers of both hard and eroding a/foul which got the same treatment. I did try stripper on that, even using the apply-and-cover-with-polythene method. What a bloody mess. Goop all over the shop and, as someone else said, it only does about 2 layers at a time.
ie: If stripper works, it didn't need doing.

If slurry-blasting is an option it would be my choice for your size boat.

 

[pmyatt]

It was Geoff Pack, the former editor of Yachting Monthly who unfortunately died of lymphatic cancer, who reckoned that antifouling should not be removed from cruising boats until such time as it had formed a ledge big enough to use as a step when boarding from the dinghy.