Hello and paint advice

[allforham 1]

Hi all

 

New here, after some advice about paint for a cat I built last year. Had a paint failure between epoxy and a single pack epoxy primer. Likely from not allowing sufficient cure time or trusting Google and not sanding before application. Luckily i was tight and only glassed to the chine. The paint has stuck fine to the ply above so could have been worse..

 

Boat lives on trailer in a shed but spends a good chunk of summer in the water and had some growth even with cleaning so have decided to antifoul this time, sounds like ablative is my only option to hopefully not be completely useless after spending time out of the water. Have removed the old paint and now have it back to bare epoxy. Would any paint experts have a recommendation on a primer if any prior to antifoul? After a sand this time! Seen some people online claiming they're basically just epoxy anyway so not sure what I'm gaining, have learnt to be wary of what I read online now though!

I have been looking at either interprotect or altex epoxy primer then either hempels olympic or altex no 5. Also contemplating just painting the antifoul right up to the chine being maybe 300mm above the waterline, any reason this is a terrible idea? Any advice hugely appreciated!

 

Adam

[Bad Kitty 341]

Caveat, I’m certainly no paint expert!

We used interprotect on Bad Kitty 19 years ago, & on alterations since, it’s been great. So there’s a vote for Interprotect.

We found Akzo Nobel great to deal with, and had good technical info, I’d go that route again.

Antifoul above the waterline generally doesn’t do too well, discolours, can flake off etc. Someone with better technical knowledge will chime in hopefully.

Great to see people still building boats, especially when it’s a cat, not half a boat!

 

[allforham 1]

Thanks bad kitty, yeah sounds like that might be the issue with antifoul being out of water, although while on the trailer the whole lot will be above the waterline! Would save me buying more topcoat for that little bit up to the chine and trying to remember where the waterline was though so I'm not too sure. Its just a fishing boat so not particularly worried about looks, the paint all peeling off was a bit much though! Regret cheaping out with the single pack primer and being in a huge rush now..

[Frank 192]

+1 for Interprotect although any  2k marine epoxy primer is damn good stuff compared to a single pack product, try Protective Paints in Otara for something a bit more affordable or less "unaffordable"  its a good product ( I don't work there or know the owner  

https://protectivepaints.co.nz/product/01-99-epoxy-primer-undercoat/

I put the primer on and wait about 12 hrs then roll on the first coat of AF it will chemically bind tightly to the semi cured epoxy , then follow up with a second coat the next day and she's good to go. There's no harm in having 50 to 70 mm of antifoul above the true waterline, the UV does affect it some but it still seems to defeat the green greeblies, this is typical for boats on a swing mooring. If you are  fussy use a hard AF above the waterline such as Pettit Vivid, a 500 ml tin is $76 at Burnsco. 

 

PS 

You may have been defeated by epoxy blush so just in case ensure you do this before painting 

 

To remove epoxy blush, wash the cured surface with warm, soapy water and an abrasive pad, such as a Scotch-Brite pad, to scrub off the water-soluble blush. Rinse thoroughly with clean water, ensuring no soap residue remains, then let it dry completely.

 

 

[allforham 1]

Thanks Frank much appreciated, yes I think it may well have been epoxy blush that caused it, i may have been too focused on achieving a chemical bond and didn't allow sufficient curing time, along with possibly half arseing the soapy water clean. Will certainly give it a really good clean before I sand this time. 

 

Great might just antifoul right up to where I've left the old paint on at the chine then, save me guessing the waterline and when it's parked in the shed most of the time it will be out of the sun

Cheers!

[allforham 1]

One more thing any suggestions how many coats of interprotect I should be putting over epoxy? See wildly varying opinions from one to 5 coats and It looks like I might need about 4l per coat

[K4309 439]

51 minutes ago, allforham said:

One more thing any suggestions how many coats of interprotect I should be putting over epoxy? See wildly varying opinions from one to 5 coats and It looks like I might need about 4l per coat

In my time painting our boat (done it a couple of times now, owned the boat for 26 years) I've found that reading the technical specifications and requirements to be useful. I don't mean just reading the back of the tin standing in the boat yard before you whack it on. But sitting down at home and reading the technical requirements sheets when planning out the job. As in before you even buy the paint, to make sure you get the right paint in the right quantities, and know how you can get it onto the boat without falling off again.

Then, if you still aren't 100% sure exactly what to do, phone the tech support. Both International (Akzo Nobel) and Altex have local technical support guys.

I've spoken to both tech support outfits. They are super helpful and like to chat. As in, I've had 1hr 1/2 calls with these guys. You might not get them on the first call, but leave a message and they will get back to you. Super valuable info, and far more accurate than google, chatGPT or some guy on a forum that says he knows what he's doing but you never really know.

There are a lot of minor details that add up, that the tech support guys can tell you. Like the type of brush or roller, the need or importance for say a tac cloth, and how to get layers to adhere, such as cure time, the weather (temp, humidity during cure etc). How or why to sand between layers. There could be some minor details overlooked last time that caused the loss of adhesion. Its free to talk to the tech support guys and will save you doing the job again or wasting paint / product.

 

And as an aside, if you are wanting to leave the boat on the trailer a bit with AF, I'd go for a hard one. Not many AF's can handle being left dry for long periods. Again, this is a very good question for the tech guy. Saves guessing, applying costly AF and having it all buggered up in 6 months time.

[Frank 192]

If it spends more time out of the water than in and its a ply/glass hull then I wouldn't think anymore than one maybe two good coats of primer is necessary , its already encapsulated in epoxy resin. I agree that a hard AF would be better if its not permanently on a mooring, but yes consult the supplier tech support.

[allforham 1]

Thanks guys, will give akzo Nobel a call and see what they say. I would certainly prefer a hard antifoul as I imagine it would stand up to trailering a bit better. I had read that once it dried up it was next to useless though, but yes you're right I'll ask the people who actually make/sell the stuff! Much appreciated 

[Psyche 879]

If you use interprotect or similar you need to hot coat the first coat of antifoul otherwise it wont stick. That  means as soon as your thumb pressed into the interprotect does not pick up wet paint you need to get the antifoul rolled. I suggest a hard antifoul, not a soft ablative for a trailer boat, make sure you get one that can still work after extended periods on the trailer. The issue you had with adhesion is most likely because the epoxy was not washed and sanded. 

[allforham 1]

Thanks psyche

Yeah I think you're right, I did wash it but maybe not well enough, and i was trying to hot coat the primer but I probably should have just let the epoxy cure for a month and sanded it. And used a two pack! Was in a rush to have the boat ready for summer. Lesson learnt..