Peeling antifoul

[Sailfree]

Boat was prepared by Bob the Builder when it was new so hull not degreased or cleaned down properly.

Bob the Builder also fitted the bowthruster that leaked.

At that time I was still trying to work with the distributor to get boat corrected and agreed to them doing the second years antifoul FOC while they fixed the bowthruster leak. Gave up when I visited near the end of operation to see 2nd year antifoul going on a not very good pressure washed surface.

I did 3rd year antifoul while a quality firm tried to rectify the badly fitted, leaking bowthruster. Fortunately I had with-held money.

Each year since then I have had bits of antifoul peel off when antifouling due to poor base adhesion Over the last 8yrs probably taken 75% of the worst areas back to gel coat. This year I was lent a Metabo 150mm DA sander which was excellent. I will get one for next year.

Would like to pick others brains for best P80 sanding discs to use on Micron Extra Antifoul without clogging too quickly. Appreciate the need for face masks etc and don't want to go to any blasting scheme.

Advice on best sanding discs with 6 holes for hard antifoul appreciated.

 

[pvb]

Would like to pick others brains for best P80 sanding discs to use on Micron Extra Antifoul without clogging too quickly. Appreciate the need for face masks etc and don't want to go to any blasting scheme.

Advice on best sanding discs with 6 holes for hard antifoul appreciated.

Micron Extra is a soft eroding antifoul and is easily removed with an abrasive pad and a running hosepipe.

 

[Sailfree]

Micron Extra is a soft eroding antifoul and is easily removed with an abrasive pad and a running hosepipe.

I thought it was termed a hard antifoul. I always prepare the surface for the next application using a wet green scouring cloth but you cannot feather an edge between max thickness (where it has good adhesion) and bare gel coat where it has peeled off with a scouring cloth - you need a sander IMHO.

 

[William_H]

I can't imagine any form of sand paper not clogging fairly quickly with a/f paint. You might try one of the wire mesh type sanding medium. I feel the high speed of an angle grinder with sand paper and rubber backing disc might fling the paint off but will still be a big problem. (and the sand paper could quickly cut into the gel coat.)
So it might be a case of back to scrapers or paint remover. Sorry not much help. I think all you can do is try everything. I tend to end up using wet and dry sand paper on a block and then blast the sand paper with a sqirt from the hose to dislodge the build up of paint. But it is a tiny boat and I just trry to reduce the a/f build up.
good luck olewill

 

[john_morris_uk]

I am concerned at your mentioning 'bare gelcoat'. Whenever I've tried to get away without antifouling primer I have suffered exactly the same symptoms you describe. I used to think that the primer was a 'nice to have'. Nowadays I realise that its not just a way of the paint manufacturers getting some more of your money, it really does make a difference.

I suspect you won't get a really satisfactory job until the old a/f is all taken off and a primer applied.

(Soda blasting is the best way I've found to get the old a/f removed; it'll cost you a few hundred £ though...)

 

[Rigger Mortice]

Would like to pick others brains for best P80 sanding discs to use on Micron Extra Antifoul without clogging too quickly. Appreciate the need for face masks etc and don't want to go to any blasting scheme.

Advice on best sanding discs with 6 holes for hard antifoul appreciated.

If you must sand, you need to wet sand. I wouldn't want to do that using an electric tool. Possibly an air driven unit?
I think you are probably wasting your time trying to dry sand.

 

[Sailfree]

thanks John but as I mentioned over the last 8 years have "cured" most poor adhesion areas by rubbing down and antifoul.

When I scrape off loose antifoul the substrate appears to be shinny gelcoat as if I had just polished it! Rubbing down, feathering the edge seems to work as its not the same areas peeling now and as I said i think I have done 75% of the boat now.

Its just borrowing these 2 Metabo DA sanders really made it easy and we feathered the edges better than ever before. It made it more like working on an industrial project rather than DIY!

In the absence of any better sanding disc recommendation I will go for Automobile ones seen Mirki Gold on internet.

FYI I have 2 125mm DA sanders but these Metebo that an adjacent boat lend us seemed 3 times as good. I don't think it was the watts or the 150mm disc size but more the variable amount of orbital offset you can adjust (IIRC 2.8mm to 6.4mm).

Every year this one aspect reinforces my opinion that if I ever bought a new boat I would never buy it from a UK distributor but get it straight from the factory and instruct every commissioning aspect in the UK myself. The distributors penny pinching commissioning (deleted many factory ordered items to get Bob the Builder to fit them) has ruined the buying a new boat from a UK distributor experience, working in construction I thought I was experienced in dealing with cowboys but the UK boat industry is a lesson in itself!

 

[pvb]

I thought it was termed a hard antifoul.

No, it's quite a soft, eroding antifoul. International describe it as "polishing" and say that it "washes away with use", which is why it isn't suitable for high-speed craft.

 

[Robin]

I used to use a wire mesh type sanding cloth on a ceiling plasterers universal jointed holder, bought from a decorator supply store, they don't clog and you work up a slurry with Micron that works even better, We could do our 41ft Jeanneau back then in a couple of hours, one sanding, one using the hose. However when we had a duff batch of OPtima that had to be removed totally in limited time ashore we had the bottom blasted to take it all back to the gel coat, then primed it and recoated using Micron. Here in the USA we had the bottom sanded clean to gel coat (they dry sanded with a vacuum on the sander), we then had 5 coats of epoxy added and then Micron. Nice job achieved but not for me in Florida heat in summer as it was, even though they worked between 6am and 10 am daily only.

 

[grumpygit]

For sanding antifoul with a DA you can get hook and loop grit mesh discs from car bodyshop suppliers, very little clogging and quick. I find them brilliant