Plywood, Epoxy and Sanding

my question, big question

In a small plywood sailboat construction ... it is possible to minimize or almost eliminate the need for sanding (!?)

For example:

(A) deck (that will not be stepped on): without fiber and without resin: directly on the plywood 3 coats of epoxy primer (interprotect, international) + 2 base/undercoat + 2 coats of paint

(B) hull: fiber and epoxy resin, "peelply" ... + interprotect epoxy primer +

(B1) antifouling
(B2) + 2 base coat + 2 top coat

I ask:

the aesthetic result is terrible ?

If I don't want a yacht or automobile type finish, is a work boat finish possible ?

 

No. And Yes. My last 2 ply-epoxy boats have gone without the fill coat/sand/fill/sand process, in favour of more carefull layup of fillets and sheathing and use of baking paper/peelply as an aid to smooth the finish.
I will say a good "filler-primer" paint is worth having, easy to apply, fast drying and easy sanding.

Anyone who has spent days on a 3-man sanding board knocking down epoxy bog, will do their best to avoid excessive sanding ever again. I hate sanding and can live with a 10 pace workboat finish.

 

thanks a lot, skaraborgkraft

 

Hi CarlosK2, you could get lucky if you have a workspace with almost clean room qualities, but just looking at your deck coatings, that's 3+2+2 times for bugs to suicide on your coatings, and they are usually a bit lumpy, and also can cause trails and runs in their efforts to get unstuck. Also many coatings stick better with a light coarse sanding to give a surface for the next layer to key into, unless you are well organised to do fresh coats on tacky coats, from start to finish, and if all the chemistry is compatible when tacky, which is a big ask in time and effort.
Same goes for the bottom. Bugs and dust are the enemy of nice wet paint. Oh and clumsy visitors.

One of my plywood small boats was painted with epoxy resin bottom and sides, when upside down, then sanded to eliminate obvious runs and drips, and give a flat coarse keying surface, then given 3 layers of paint in 3 different brush stroke patterns when barely dry enough to not make a mess of it, diagonal / , diagonal \ , then abeam - vertical. It was a brushed work boat type finish, with glossy oil based enamel paint, and worked well enough. The next maintenance time will see it touched up with epoxy where chipped and wherever needed, and sanded only to flatten out the modifications, plugged holes, repairs, and previous brush stroke crests, before a 'final coat' (a couple of years after the original enamel coats) with brush strokes fore and aft, to give a less flow resistant finish. Not that it would make any noticeable performance difference. Almost no one has had anything negative to say about the paint job so far.
Broad soft brushes, paint trays, and rags to wipe off drips, then self control and patience, and stay away until at least skinned.

 

Thank you so much

 

For now I'm alive, which is enough after a big scare when they told me - you don't have a problem with your eyesight but with your brain.

I cannot build my 1 ton WindSurf board that i dreamed of and designed to enjoy the years i have left, my intention is if i recover financially to commission its construction and i don't want it to cost me a fortune in thousands of hours sanding, which is what i see in many projects

On the other hand, for example, this ending:

 

....met a very "lumpy" home-built Bruce Roberts 36 in Costa Rica in 83: "I didn't know you could build them in ferrocement too..." owner-builder: " she's fibreglass & I just got tired of filling & sanding."

 

Yes

But fibreglass is not comparable to plywood

 

All my life since i was 6-7 years old i have had second or third-hand sailboats, and i have the perhaps silly illusion of at the end of my days having my first new sailboat, truly functional and summary of a life with this obsession.

New sailboats cost a fortune. With exhaustive and relentless cost control, the cost of hardware can be controlled: i have boxes full of everything i want to install. I don't want them to spend hundreds of hours sanding a fxxxing 5.99 meter long boat.

 

Plywood boats were built decades before epoxy became common. They were painted with oil based paint and lasted many years.

 

That's what i think, Gonzo, the first sailboat i sailed on was built by my uncle with a small saw and plywood, i was a little child and then i started sailing on old wooden Optimist that leaked water everywhere.

 

Working carefully, unlike me when I started, saves days of sanding. Tooling green epoxy is easy and fast. One thing that works brilliantly on runs and the like is taking a sharp cabinet scraper to them while the epoxy is still green.
Russel Brown has an inexpensive eBook on working with epoxy that is very helpful and inspiring. Look for his Mastering Epoxy videos too.
Working clean saves so much sanding.

EPOXY BASICS ebook link.
Bing Videos link.

I have no affiliation, just a fan of his methods.

 

The simplest way to build a deck is epoxy primer in a couple coats and a single coat of kiwigrip. You need to key for the kiwi, so a layer of glass is better because when you key; you can sand thru (the primer paint). I don’t know, but perhaps you can paint kiwigrip on green epoxy no key.

Peelply is not super easy to use, just so you know. It is easy in a stack, but not as easy to lay say on a vertical hullside after hand laminating 6-10oz woven. You run into timing problems and if you ever try to peelply near gel time; you’ll understand what I mean, but it is like laying fabric in honey and a simple sticky hell. Not only that, but peelply in open laminations tend to have a few open spots. Of course, it depends on cure times and the size of the project, but I really avoided it for anything real big not on tbe vac table. You can’t see the laminate under it and so it is a real bad idea on say a hull bottom unless you have a really good way to secure the peelply. I’ve done it by laying plastic over the peelply and then using masking tapes to pull it all down. It can be done, but not close to gel time.

Vac or infusion would offer best results. You bag the job and then no worries about air if u make a good bag.

 

what I wanted to point out: if a rough finish will be ok for you in the long run (!!!), then leave it rough.
I filled all my interior tabbing (+/-45° glass tapes) & just finished the first round of sanding (a second & maybe a 3rd will be necessary...) - and despite the boat only being 22' I sometimes think I should have just left them as they were after removal of the peel-ply,-sanding: awkward, dusty & boring work...(one has to embrace the pain)
On the exterior of the hull though: no compromises! One wouldn't want to be ashamed of ones work, would one, by being asked if it was concrete...!

 

@peelply: I found it best to use pieces no bigger than say 1,5m² & rolled up for application.
Until now I have been using linen-woven peelply, which does not conform to any sort of compound curvature at all, but I just discovered a supplier that has pp twill/denim woven,. I will try that, maybe it conforms a little bit