VIC
344 posts
Hello,
I am just seeking some advice about prepping the surface of GRP boat for applying new antifoul. I've been googleing away and cannot find a good definite answer or technique for removing the old antifoul.
For example I have heard some people use electric scrapers while others use wet/dry sanding. I have also heard that their can be issues with using different antifoul products on top of each other.
I'm sorry for any vagueness in my query, I am new to this all.
Thanks!
NSW
7757 posts
It all depends on what you have at the moment. If the old antifouling is ablative then a hard hit with a pressure washer and a touch up with an undercoat of the bare patches with a product like Jotun 88, then antifoul. If the surface is hard antifoul and the surface is rough and or there is a build up then thinning this down is a good idea. I would not bother trying to remove it all and would wet sand. If I had to remove all the paint I would pay to have it blasted with dry ice.
Most antifouls will cover old antifouls. If you want to undercoat then Jotun 88 is good value and all antifouls go over it.
Hang about the local slips and ask questions.
WA
50 posts
I tried soda blasting but it didn't work. In the end I used a marine paint stripper, a big pressure sprayer and a hell of a lot of work. That was four a racing finish, I wouldn't bother with a normal boat. Id follow Ramonas advice
VIC
344 posts
That sounds like very sound advice. Thankyou very much.
I will give it a sand and then apply the jotun 88 undercoat.
*Most of the existing antfoul is smooth, but patches have come off. When I put the pressure hose on it the other day the color was coming out with the water.
Will I have issues using a dry sand? The club has a vac you can plug into your sander.
VIC
871 posts
If the antifoul is a few layers thick, and can be scraped of, do it.
Use a long handle 2 hand scraper, with replaceable flat blade (approx. $50), round the edges of the blade on the bench grinder first though.
Best results come from pulling down, and it's easier if you can work on an 'edge' of the antifoul.
If it's thick, it will come off as a continuous stream of chips.
It's a suck of a job, but you will only do it once, as every year after, a good high pressure hose, then you will have minimal build up, and avoid this problem.
Sanding antifoul is pretty inefficient, you need elbow grease on a scraper first. Dry sand with a 120 or 150, will remove any fine film left from scraping. Epoxy barrier coat, then antifoul and the job is done.
But beyond all, wear a DECENT facemask, with cartridge filters and cover up.
the joys of boat ownership.
NSW
2140 posts
Totally agree with the long handled scraper suggestion, but suggest that a hook scraper that you pull is more efficient than one that you push as it allows a more delicate touch by varying the pressure you can apply. You can buy ones that have replaceable blades so as a blade becomes dull, just replace it with new sharp one, remembering to reduce pressure for the first few strokes as it will cut more effectively.
VIC
344 posts
Where does one buy one of these long scraper implements?
NSW
2140 posts
Clever and enterprising people usually modify an ordinary short handled scraper by adding a suitably long enough handle to it. Try your local favourite hardware shop and as a last resort you can try the Green Shed Company (Bummings, and lots of luck with that.)
If you are going to go with the push type rather than the pull type try a tile shop.
