Preparation for antifoul and non slip paint

[Olivia Frances]

I’m ready to reapply anti foul to my boat, it was jet washed when it was lifted and appears quite clean, should I sand prior to reapplying? If so what grit pads should I use?
Also should I undercoat as I’ve no idea what was used previously?
I also want to repaint the nonslip on the deck, what grit should I use to prepare prior to repainting?
As usual , I am grateful for any help!

 

[MADRIGAL]

I’m ready to reapply anti foul to my boat, it was jet washed when it was lifted and appears quite clean, should I sand prior to reapplying? If so what grit pads should I use?
Also should I undercoat as I’ve no idea what was used previously?
I also want to repaint the nonslip on the deck, what grit should I use to prepare prior to repainting?
As usual , I am grateful for any help!

I am not an expert on anti foul, but for non-slip decks, I have used a red Scotchbrite pad prior to recoating a non-skid deck with International’s Interdeck non-slip paint. It is still in excellent condition two years later. I hope that helps.
By the way, there has been plenty of discussion about anti foul on the forum recently, so you may find the information you need by searching for previous posts. For what it’s worth, I don’t think the people in my club usually sand before applying anti foul to a hull in good condition. I’m sure others on the forum will reply with a more informed response!

 

[Stemar]

Most people on my club's scrubbing grid seem to jet wash the crud, let it dry and slap on the paint. It seems to work as well as any antifoul does these days. If you've got a build-up of flakey old antifoul, then I'd definitely want to get that off, but I'd scrape rather than sand.

In my book, sanding is for racers who must have every 1/100th of a knot, or to deal with a stubborn bit of barnacle shell.

 

[pvb]

I find that jetwashing often leaves a slight residue of slimy antifoul, so I always go over the hull with a Scotchbrite pad and a running hosepipe before re-antifouling. Usually no need to use any undercoat or primer, although if there are any patches of bare fibreglass they are best primed before antifouling. If you want the antifouling to work, you must apply enough of it - follow the maker's instructions.

 

[johnalison]

The areas covered by straps don’t get pressure washed at my yard. I use a Scotch pad on a pole and abrade it when wetted, and any other bits I feel like doing.

 

[V1701]

I would second interdeck, it's easy and durable and you don't need to go mad with prep - as long as your surface is clean, dry, free from grease and looose stuff you can go ahead. Get the paint up to room temperature if stored somewhere cold (bucket of hot water)...

 

[Spirit (of Glenans)]

Also should I undercoat as I’ve no idea what was used previously?
!

None of the previous posters have addressed this question; I would say yes, as has been advised in many previous threads and magazine articles on antifouling. The new AF might react badly with what's already on the hull. When the existing brand of AF is unknown, the standard practice is to either strip it right back to the substrate, or apply a barrier coat. There are examples of these in the links below, other products are also available:
Metaclor Teamac Antifouling Primer Barrier Coat Grey
Precision Antifouling Primer and Barrier Coat

 

[pvb]

None of the previous posters have addressed this question;

Ahem, post 4...

 

[Spirit (of Glenans)]

The OP says; "I've no idea what was used before" i.e. he's aware that some types of AF are incompatible with each other and will react together in an unfavourable manner. To prevent this, there are two options:
A. Use a type that is compatible with what was used before, or,
B. If that information is unavailable,
cover up with a barrier coat before applying your chosen AF.
I feel that he was asking for confirmation that, with no knowledge of what was already on his hull, the latter is his best course of action.