Painting my hull, just checking I don't do something silly.

[MattA24]

Hello hello,

Now that the weather here in the UK is finally threatening some reprieve, I'm hoping to repaint the GRP hull of my boat. I've read pretty much everything this forum and the internet at large has to say on the topic, but I'd like to just check that I'm on the right track.

The boat is is 70's and low value. It has it's gelcoat on the topsides, but that's been 'touched up' with paint here and there by the PO.

On the topsides, I plan to abrade the surface with a sander, removing as little gel and as much touch-up paint as possible, fair out any marks with West if necessary, then paint with a couple of coats of the posher type of Dulux Weathershield.

Below the waterline is pretty smooth, so I plan to rough things up and get rid of anything loose, apply anti-foul primer to necessary patches, then antifoul just before putting in the water.

The iron keel is bubbling in places, so I plan to strip the paint, red oxide it, epoxy it, prime it, then antifoul it.

Does this seam reasonable?

The datasheet for the Trade Dulux Weathershield recommends no primer for clean good quality surfaces. Obviously that's for houses not boats. Does this forum recommended primer between gelcoat and Dulux on topsides?

Much obliged for your assistance,
Matt

 

[Rigger Mortice]

Not a good idea to put epoxy on top of red oxide. It will probably lift it.

 

[VicS]

Like RM I wonder if epoxy could be put on top of red oxide. Generally two pack coatings should not be applied to single pack coatings

Follow the recommendations of the coatings manufacturer diligently.

Do Dulux say the Weathersheild is suitable for grp? Surely its a masonry paint?

 

[MattA24]

RM and VicS, thank you both for the advice, and so quickly.

I remember reading a couple discussion threads somewhere (possibly here) which discussed this topic. On these threads it appeared that an "anti-rust" paint for chemical protection and a coat of epoxy resin as a barrier to moisture was considered good form.

I wish I could find those threads now.

May I ask what you would do in the situation? Epoxy first? Skip the red oxide? Skip the Epoxy?

My gut says red oxide is because it's the only thing I've found which stops my 2cv disintegrating like a dandelion clock.

Again, much obliged.
Matt

 

[elton]

I just paint Hammerite over rust on the keels, and paint over with antifoul. Cast iron Keels don't rust away to nothing like car body panels

 

[William_H]

I just paint Hammerite over rust on the keels, and paint over with antifoul. Cast iron Keels don't rust away to nothing like car body panels

No but new rust will bubble up to destroy anti fouling paint pretty quickly. OP doing it on the cheap might like to give just the red lead a go under a/f but I think a more permanent job will involve cleaning the steel keel right down then epoxy then a/f. I imagine the weathershield will be OK for topsides and certainly easily touched up if it gets scratched. 2 pack polyurethan is much more expensive but much tougher.
good luck olewill

 

[Lakesailor]

Hammerite is a pale imitation of it's previous tough paint. I'd use a zinc primer if you don't want to strip it entirely. It's presumably quite old already and a few more years won't see it falling to dust, like Elton says.

Some people have had good results with Weathershield. I would prefer to use a marine paint system using the proper primer/undercoat. It's not expensive if you use single-pack paints as you only need to buy enough to cover the boat.
The only problem I found is that the Blakes (Hempel) range became a bit "soft" and bruised easily in darker colours.

I found a litre tin would do an 18ft boat.

Primer/topcoat

Topcoat

Topcoat ( antifoul primer)

18ft yacht

 

[MattA24]

Thanks again everyone for your opinions.

I've been disappointed by hammerite enough before to not bother with that again.

I worry that if I encapsulate the keel in Epoxy without an anti-rust coating (eg Red Oxide) underneath, the inevitable drop of water that sneaks in through a scratch or a pinhole in the resin will have the chemically unprotected keel to play havoc with.

Lake Sailor, those finishes look smashing! I don't imagine myself getting anything like that this time around. May I clarify one thing? Are you advocating a zinc primer on the keel then straight to antifoul, with no epoxy resin encapsulation?

Thank you all again,
Matt

 

[Tranona]

Waste of time and money putting epoxy on a cast iron keel unless you can blast it completely. Old cast iron keels will almost certainly have pockets of impurities and rust in them which will continue to rust and just push the coating off. Just clean as best you can, prime and antifoul. Every year you will need to do bits of it again, but it is cosmetic rather than structural.

Also don't waste your efforts using Weathershield. The additional cost of using a good single pack such as Toplac is minimal and as Lakey's pictures show the potential superior finish with a bit of care is well worth it.

 

[Lakesailor]

As Tranona says, pointless using epoxy, it's like putting a vinyl glove on your hands after you've drain the oil from your engine. Your hand is already oily.
If you epoxy it you'll find you are stripping it all again in a couple of years time.
It's just surface rust, it's underneath the boat. Just freshen it up each time you antifoul.

 

[lw395]

I've had good results using an acid phosphate rust treatment, followed by epoxy, but I think getting the keel dry is important as cast iron is often porous.

Topsides paint, IMHO it is a case of whatever you can do a good job with.
I once failed miserably with a marine paint, maybe it was too cold but it ran horribly.
I did a job I was quite proud of using Dulux Trade gloss, the sort you get mixed to choice of colour.
I think it's about finding a paint that matches your technique and skill, as well as the temperature.
Find something to practice on!
I found putting on a very thin coat using a foam 'jenny brush' worked for me.

Lakey is obviously a bit good at painting.

 

[KellysEye]

>eg Red Oxide

It should be Zinc rich epoxy two coats. If you don't get rust back to bare metal then the rust will get worse.

 

[MattA24]

I'm entirely in favour of not using up lots of epoxy on the keel if that's the consensus.

I live right by a Dulux centre and the trade Weathershield under half the cost of Toplac and in any shade of the rainbow. On this forum and others I've seen plenty of people voice that Toplac trumps Dulux, and a similar number boast that Dulux pips Toplac, so I'm going to just go with the cheaper and more convenient choice.

Part of my car is painted with zinc oxide (black) and part of it with red oxide. The zinc oxide bits bloom with rust every year. The red oxide bits do not. This is why I lean towards the latter. My car isn't dipped in the sea though, so this might not be relevant experience.

Once again, many thanks everyone here for your thoughts.

 

[itchenseadog]

Topsides, use Toplac, dont touch Wrathershield with a barge pole. Dont paint outdoors in tne wind if you want a good finish - the english weather is too unpredictable. Thin the topcoat 5% to get 'flow' and apply with a 4" double ended foam roller and 'tip' out with a decent quality brush and, provided the damp doesnt get into it, you'll get a top quality finish

 

[Lakesailor]

You need good quality rollers as well. The cheap ones react with the paint solvent and flop around the roller centre.
You don't need a brush to tip with. You can use the exhausted roller to tip off with before recharging it.

Oh. I have found 5% solvent absolutely the limit for thinning. Too hot is bad as well, but no worry about that at the moment. Humidity is not good.

 

[macnorton]

For the keel you could clean it with a wire brush angle grinder attachment, give it a coat of rust eater (naval gel?) then coat it with black tar varnish like the nb's use.

 

[Rigger Mortice]

If you want a decent gloss on your topsides why use a masonry paint? When is the last time you saw a house with shiny walls?

 

[TQA]

For the keel you really need to grit blast it and paint immediately. A needle gun is the next best thing. Wire brush or grinding just remove the loose rust. I fact there is a theory that an angle grinder on cast iron seals rust in the pores.

I kept my old steel boat reasonably healthy using 2 coats of zinc rich epoxy primer followed by two more coats of whatever epoxy primer I had handy, the zinc rich stuff is OK. Then a topcoat.

Topsides If you are willing to put in the prep work then apply two to three coats of hi build primer a stunning finish can be achieved using 'roll and tip' to apply International Perfection 2 part polyurethane. But this does require some serious sanding as you go along. Whites are easiest.

I would always apply a primer over bare fibreglass. Even for Weathershield.

 

[MattA24]

I would always apply a primer over bare fibreglass. Even for Weathershield.

Can anyone recommend a primer to use with Weathershield on grp in a marine setting?

I'm open to the idea of epoxy primer for the keel. Does such a thing exist in one-pack form?

Thanks again everyone who has chipped in their thoughts. LakeSailor it is very rotten of you to keep posting pictures of those super finishes.

 

[Lakesailor]

Sorry. This was just the bottom planks. Is that better?

but this was a whole boat