mocruising
Well-Known Member
Is it necessary to abrade a new hull or is it enough to put some kind of bonding (Primer) coat prior to the first coat of antifoul.
How to antifoul a brand new GRP hull
- Thread starter mocruising
- Start date
davidwf
Well-Known Member
You must abrade first to get rid of the mould release agent and to provide a key for the antifoul / primer.
On my last two new boats the dealer has simply abraded then used a hard antifoul for the first coat followed by a soft antifoul. This has worked well and I've seen no evidence of the antifoul coming away from the hull. Logic would say to use a primer but it seems from my experience this is not necessary.
On my last two new boats the dealer has simply abraded then used a hard antifoul for the first coat followed by a soft antifoul. This has worked well and I've seen no evidence of the antifoul coming away from the hull. Logic would say to use a primer but it seems from my experience this is not necessary.
sailorman
Well-Known Member
i_sail
Well-Known Member
As the hull is new I would recommend using an epoxy primer, such as International Gelshield 200, which will effectively protect the hull against osmosis, acting as an extra seal to the GRP hull. Applying such a product to a boat that is already antifouled is a nightmare and involves loads of preparation, however with a new hull, this is your perfect opportunity....well worht doing
Alternatively consider copper coat - a big investment now however it is guaranteed foul free for 10 years, independant tests show more like 15 years in many cases.
Alternatively consider copper coat - a big investment now however it is guaranteed foul free for 10 years, independant tests show more like 15 years in many cases.
VicS
Well-Known Member
In addition to Sailorman's link to Blakes take a HERE look at International Yachtpaint's website Loads of advice on there. Primocon is the recommended International primer.
Whatever brand of antifouling you use look up the product data sheet and follow the instructions closely.
Good advice to apply an epoxy now but it is not a job to be undertaken lightly. Again follow the instructions on the product data sheet.
Whatever brand of antifouling you use look up the product data sheet and follow the instructions closely.
Good advice to apply an epoxy now but it is not a job to be undertaken lightly. Again follow the instructions on the product data sheet.
Cloven
Well-Known Member
Cannot emphasise the importance of the initial preparation. YES it will need a lot of abrasion to take all the shine off the Gel coat as well as cleaning afterwards etc.
I did this with a new hull a few years ago. 32ft boat took me two long days under the hull with a palm sander and many many sheets of 80grit sandpaper. After the first sanding, it just looked as if I had just scratched the surface!!
I then went the Gelshield route as recommended by the boat manufacturer - 6 coats, followed by a coat of hard antifouling and then two coats of eroding antifoul. If you do this, you must put on the coat of hard antifouling BEFORE the Gelshield has fully cured or you will not get a bond. The alternative is a coat of antifoul primer on the Gelshield although you will have to lightly abrade the cured Gelshield to get a key.
Boat now in its fifth season and so far all it has needed is a light sand and a top up of antifoul at the start of each season.
Hope this helps
I did this with a new hull a few years ago. 32ft boat took me two long days under the hull with a palm sander and many many sheets of 80grit sandpaper. After the first sanding, it just looked as if I had just scratched the surface!!
I then went the Gelshield route as recommended by the boat manufacturer - 6 coats, followed by a coat of hard antifouling and then two coats of eroding antifoul. If you do this, you must put on the coat of hard antifouling BEFORE the Gelshield has fully cured or you will not get a bond. The alternative is a coat of antifoul primer on the Gelshield although you will have to lightly abrade the cured Gelshield to get a key.
Boat now in its fifth season and so far all it has needed is a light sand and a top up of antifoul at the start of each season.
Hope this helps
wooslehunter
Well-Known Member
I'd go for copper coat. It's expensive. But, every time we lift the club members boats the one that's coated is clean & everyone elses isn't. Frank just puts his boat back in & everyone else has to antifoul again.
Over 10 years it probably gets pretty close to the same cost anyway if you antifoul yourself. If you pay a yard for it it'll pay for itself in less than 10 years & you're quids & effort in.
Over 10 years it probably gets pretty close to the same cost anyway if you antifoul yourself. If you pay a yard for it it'll pay for itself in less than 10 years & you're quids & effort in.
oldsaltoz
Well-Known Member
G'day Mark,
Do not sand the hull until you have cleaned off all the wax and other contaminants.
Sanding will only spread whatever is on the hull, it is very important that the key you create is very clean.
Avagoodweekend......
Do not sand the hull until you have cleaned off all the wax and other contaminants.
Sanding will only spread whatever is on the hull, it is very important that the key you create is very clean.
Avagoodweekend......
Pasarell
Well-Known Member
Totall agree with Oldsaltoz. Clean mould release agent off before abrading otherwise you force the wax into all the sanding grooves and make it far harder to remove.
No foolproof method to remove the wax other than detergent and elbow grease as some of them are very hard. Use a scotchbrite pad and stron detergent solution until the rinsing water spreads into a thin continuous film on the surface and doesn't bead up. When all the wax removed abrade with 100 - 120 grit paper. Make sure all the sanding dust is removed before coating with your choice of primer or antifoul.
No foolproof method to remove the wax other than detergent and elbow grease as some of them are very hard. Use a scotchbrite pad and stron detergent solution until the rinsing water spreads into a thin continuous film on the surface and doesn't bead up. When all the wax removed abrade with 100 - 120 grit paper. Make sure all the sanding dust is removed before coating with your choice of primer or antifoul.
