Antifouling preparation.

[puddock]

Having had Rosally's bottom cleaned with a slurry blast, I wondered what your recommendations might be for treatment before anti-fouling.
The keel has already had 2 coats of zinc primer applied.
Should I be looking at using an epoxy primer on the hull?

[DaveS]

I understand that paprika and tabasco is highly recommended...

Assuming the hull is GRP, then all that is really neaded is a rub down with sandpaper to give a key, then one layer of antifouling primer, followed by one (or two if you're really fussy) coats of your preferred a/f poison.

For the keel, assuming it's iron, I'm less certain: I've always used epoxy tar over rust converter, then primer and a/f, but no doubt others will have other advice.

[puddock]

Thanks Dave.
I thought an epoxy primer may be prudent as I'd had the bottom slurry blasted, which left the gelcoat nicely abraded.

[Clyde_Wanderer]

Yes two coats, min, of epoxy primer, followed by a couple coats of af primer then af.
When applying epoxy primer apply second coat while first is at the last stages of been tacky to give better adhesion.
A little cold for doing it now, especially if outside.

[puddock]

The Zinc Primer is only on the keel (I didn''t like to leave it exposed after blasting).
The blasted section of the hull (below waterline) has not been primed.

[Clyde_Wanderer]

Sorry read your op wrong, but have now edited reply.

[puddock]

Thanks for the advice - appreciate it.

[DaveS]

Thanks Dave.
I thought an epoxy primer may be prudent as I'd had the bottom slurry blasted, which left the gelcoat nicely abraded.

I suppose it really depends what you want. Having got the hull all nice and clean there's an argument for going the whole hog and applying epoxy as an anti osmosis treatment, but that involves lots of coats, 7 IIRC. I thought of doing this the first year I had the current boat, and as it happened that year March was unusually mild which would have been ideal... But I didn't.

[Silkie]

I've never been that keen on the idea of epoxying a grp hull.

There's the argument that the epoxy barrier is equally permeable in both directions and any damage to the epoxy would allow water in and keep it there. Then, if your hull is not new (in my case nearly 37yo) and has shown no signs of osmosis yet, why would you bother?

There's lots of other stuff to spend money on.

[puddock]

I see where you're coming from Silkie.
I am also finding out there is lots of other stuff to spend money on

[DaveS]

I've never been that keen on the idea of epoxying a grp hull.

There's the argument that the epoxy barrier is equally permeable in both directions and any damage to the epoxy would allow water in and keep it there. Then, if your hull is not new (in my case nearly 37yo) and has shown no signs of osmosis yet, why would you bother?

There's lots of other stuff to spend money on.

And indeed that was where I finished up.

My original thinking was that since my hull consists of two fairly thin layers of GRP sandwiching the foam it might be worthwhile adding a protective layer. Some years later, when cutting a hole for my FLS, I discovered that at least the bottom part of the hull is solid GRP about 30mm thick which was greatly reassuring! I haven't established at what point the transition from solid to sandwich construction occurs (I might try some experiments with a joist finder) but if it is below the waterline then there might be an argument for applying a belt of epoxy to that part only, leaving the solid GRP alone.

OTOH I may just go sailing!

[Sam_steele]

If you are slurry blasting you won't need to key in with sandpaper the slurry blasting will do that. Do check with your yard first that they will allow slurry blasting mine didn't and I ended up at the last minute having to use chemical rather than slurry blasting. They said it would be easy ...ha ha not my idea of a joke, it wasn't. I was then wishing I had a mirror dinghy and not a 38 foot boat. If you put epoxy on make sure all anti fouling is removed. Also it is good to use 2 different colour of coats with the epoxy that way you can tell that you have covered the surface with both coats. Good luck!
Regards
Sam

[puddock]

Thanks for all you replies. Much appreciated.