A budget finish for a plywood, ultralight, knockabout, indoor-stored canoe

[Mike Goodger]

This boat would be a cheaply built canoe/pirogue for a small child/children. The finish would be easily-maintained paint on the outside, but it might be either paint or a clear varnish on the inside. I don't know yet.
First tick-box is Waterproofness. No point in building an ultralight if it absorbs water. Does this exclude all water-based finishes? - ( But it does not have to be water-based, I have been disappointed before.)
Second tick-box is Budget and available in small tins.. This children's canoe/pirogue will spend 99.9% of its life hanging on a dry indoor wall. I hate Yotting prices. Are there Budget brands, or would that be Aldi Centre Aisle?
Third tick-box is User-Friendly. Yes, I have the technology to make accurate mixes of 2-pack paints/glues etc, even down to mixes of about 2 grammes, but it gives more fun, and less waste, to use something simpler.
Fourth tick-box is Funky Colours, would you believe it? The fave colour of this particular child is pink. Yotty colours tend to be red, white, blue, etc, etc. I may have to build up a waterproof base and then put a Farrow-and-Ball domestic or a Frenchic outdoor chalk paint on top, just for colour.

I am asking for advice because I used to paint boats, but there has been a long gap and my knowledge is way, way out of date.
I have a contact in Australia who is in an amateur group that builds wooden boats, and they use Norglass 1-pack polyurethanes, I think.

Thanks,
Mike

 

[fallguy]

The least expensive coating that will perform for a boat is polyurethane with UV inhibitors. Or the bottom of someone’s used paints from a project.

here in Mn, we have chemical recycling and reuse places and you might get lucky and find something free

 

[Tops]

It has been recommended to me to use an epoxy to seal the wood followed by alkyd enamel for color and UV protection. No specific brand names for either and no additional barrier or tie coats.
The epoxy would need to be free of amine blush and sanded a bit for tooth. It is not a mirror finish by any means but pretty DIY friendly. My rudder was refinished this way after repairing some structural damage and I have been happy with it so far. The unit is off-white and I added some accent color with spray cans.

 

[Mike Goodger]

The least expensive coating that will perform for a boat is polyurethane with UV inhibitors. Or the bottom of someone’s used paints from a project.

here in Mn, we have chemical recycling and reuse places and you might get lucky and find something free

"Polyurethane with UV inhibitors" - yes, that sounds about right.
We used to have boat jumbles locally, great places to find surplus paints or paint in dented dented tins. There must be online places like that, I'll look. Thanks!
Mike

 

[Mike Goodger]

It has been recommended to me to use an epoxy to seal the wood followed by alkyd enamel for color and UV protection. No specific brand names for either and no additional barrier or tie coats.
The epoxy would need to be free of amine blush and sanded a bit for tooth. It is not a mirror finish by any means but pretty DIY friendly. My rudder was refinished this way after repairing some structural damage and I have been happy with it so far. The unit is off-white and I added some accent color with spray cans.

Thanks, that is helpful - yes, I have American MAS Low Viscosity Epoxy with a fast hardener and a slow hardener, I have used it for gluing and taping for many years. Often I use both hardeners in the mix to get intermediate speeds. Non-blush but I still prefer to arrange warm epoxy-friendly working conditions. I have used it somewhat as a coating on its own, but it was never a structure which would be out in the sunlight for long periods. Cost is the only problem.
I would have to look at Alkyd enamels, I am not aware of these, but I think that a suitable 1-pack Polyurethane might go well over epoxy as well. Or maybe on its own if it is cheaper than my epoxy.
Mike

 

[Tops]

For sure you will want to cover the epoxy with something, I tried the epoxy-only thing and it did not work.
Alkyd enamel is a fancy name for 1 part oil-based paint.

 

[gonzo]

For what you describe, oil paint will work fine. Epoxy won't hurt, but it adds expense and labor. I have built several cheap boats with exterior grade plywood and they have polyester resin and mat on the joints only. They stayed in the water no more than two days. After three years they were still fine. You are in the UK, so the equivalent would be machinery paint.

 

[Mike Goodger]

For sure you will want to cover the epoxy with something, I tried the epoxy-only thing and it did not work.
Alkyd enamel is a fancy name for 1 part oil-based paint.

Ah, oil paint, thanks. Yes, I grew up with that. The undercoat/primer seems to be water-based, often, these days, or ?
Mike

 

[Mike Goodger]

For sure you will want to cover the epoxy with something, I tried the epoxy-only thing and it did not work.
Alkyd enamel is a fancy name for 1 part oil-based paint.

I guess I'll compare oil paint with 1-pack Polyurethane paint re cost.
The Devil is in the Detail, as usual. Where I have epoxied joints and epoxied taping, the top coats can go straight on. Where I have bare wood, if I do not want to prime with epoxy, I shall have to decide on a primer/undercoat, as recommended by the paint manufacturer.
Mike

 

[Mike Goodger]

For what you describe, oil paint will work fine. Epoxy won't hurt, but it adds expense and labor. I have built several cheap boats with exterior grade plywood and they have polyester resin and mat on the joints only. They stayed in the water no more than two days. After three years they were still fine. You are in the UK, so the equivalent would be machinery paint.

Thanks, yes, I note that no-one is advising me to use water-based paint.
I guess I'll compare oil paint with 1-pack Polyurethane paint re cost.
The Devil is in the Detail, as usual. Where I have epoxied joints and epoxied taping, the top coats can go straight on. Where I have bare wood, if I do not want to prime with epoxy, I shall have to decide on a primer/undercoat, as recommended by the paint manufacturer.
Mike

 

[jehardiman]

Look for a porch/patio/deck paint. As gonzo says, as long as the boat is not left sitting in water for days, this is what those paints are formulated for.

 

[Mike Goodger]

Look for a porch/patio/deck paint. As gonzo says, as long as the boat is not left sitting in water for days, this is what those paints are formulated for.

Thanks - Are you talking about solvent-based paints or water-based paints?

 

[jehardiman]

Thanks - Are you talking about solvent-based paints or water-based paints?

Either/or, it is not like it is going to be sitting in water for a long time. Modern acrylics are fairly impermeable when fully cured.

 

[Mike Goodger]

Either/or, it is not like it is going to be sitting in water for a long time. Modern acrylics are fairly impermeable when fully cured.

I have now read that our DIY mega-chain B&Q sells mainly Valspar/ Sherwin Williams paints etc, including their own-brand GoodHome. So anything "Exterior" from there ought to do the job.
We don't usually see the description "porch/patio/deck paint" over here.
Mike

 

[jehardiman]

Time to paint, stain or oil your decking | Outdoor & Garden | B&Q https://www.diy.com/ideas-advice/how-to-paint-stain-or-oil-your-decking/CC_npcart_400188.art#:~:text=Start%20in%20the%20furthest%20corner,back%20from%20the%20painted%20deck.&text=Work%20along%20the%20length%20of,down%20to%20the%20other%20end.

and

Decking Paint | Deck Paint Colours | DIY at B&Q https://www.diy.com/painting-decorating/paint.cat?Navigation+type=Decking