How to Gel coat a newly built boat?

[Zenehet]

I am building a 24 foot Plywood stitch boat? Is it better to epoxy encapsulate the wood and then gelcoat? Or are there special gelcoats that I can apply to fresh plywood that will encapsulate as well as be the white coat I am looking for? Lastly I have read that gel coats are difficult to apply to epoxied wood is that true?

Thanks for any advice you might give.
Most of the searching I have come up with on gelcoats only addresses repairs and not fresh construction. Thanks

[PAR]

Epoxy use can offer much to a build, including cost, especially in small craft. Encapsulation and sheathing with epoxy can possibly double the material costs. Yes, real encapsulation can add many years to a boats live, with proper maintenance. Yes, 'glass sheathing, particularly if Dynel or Xynole cloth is used, can offer a lot of abrasion resistance to a hull, which is important in small, likely beached boats. As with all things, on the flip side are higher material costs, more difficulty with the build and working with not especially attractive fabrics, chemicals and solvents. You may want to consider pricing the build with just the bottom sheathed and no encapsulation, just taped seams to see how much you'd save over a full blown encapsulation and sheathed craft.

With stitch and glue construction methods, you have to use epoxy, so you're assuming these costs as part of the build. This method does very well with encapsulation and sheathing and usually is the better for it, trailered or not. Maintenance is the key to keeping any boat, of any build method, over the long haul. Encapsulation, nor sheathing will reduce this need.

To directly answer your questions, gel coat is for molded 'glass construction and typically not used else where except on repairs to these type of boats. Your assembled hull will need to be painted to protect the epoxy from UV (sunlight), with the color of your choice. Gel coat isn't compatible with epoxy coatings. It just doesn't stick worth a darn and the epoxy is a much better moisture barrier then the gel coat anyway. Epoxy can be pigmented, but this is usually outside the abilities of the average shade tree boat builder, at least to get a respectably smooth finish. Paint is the normal way we get color on epoxied surfaces.

[Zenehet]

Thank you Par!

I was wondering if I was over thinking this and all I needed was paint.

The boat will be trailered. Are there specific paints that you would recommend that will hold up well to beaching and trailering while still giving that shinny white look I associate with gel coats?

Is it better to epoxy the wood and then paint or Paint the wood and encapsulate the whole thing?

(hum... I suppose if I encapsulate the paint with epoxy then nothing is protecting the epoxy from UV. Probably better the first way I mentioned)

Any recommendations on brands or types of paint then?

Thanks again.

[trawler builder]

you can buy epoxy paints "PETTIT" makes epoxy paints in many colours and also epoxy anti-foulants . if you use fir select plywood and then resin it with polyester resin a couple times ,you will then be able to glass your seams and gelcoat the whole bottom and the gelcoat will adheare well .
TB

[PAR]

You can get away from epoxying the outside of your boat, if you want, but this is the place where most of the harsh treatment will occur. To save some costs you can sheath the outside and just do the seams on the inside (this is typical). Any epoxy will need to be painted or other wise protected from sunlight. Coated areas inside lockers and under side decks, etc. can live without painting, as they will not receive direct UV exposure, though some reflected light will eventually get to it.

Most epoxy paints aren't really epoxy, but use parts of the epoxy molecule, so they can legally say it's "Epoxy". I use an epoxy "undercoater" and epoxy topside paint and do enjoy is durability and ease of application. It's not the hardest stuff available, but it is very good. Epoxy paints can't become a substitute for epoxy coatings and sheathings. It's just paint.

Don't use polyester resin on wood. It doesn't stick and ruins the mechanical penetration an epoxy bond on raw wood can enjoy. You can use certain types of polyester fillers to smooth out the ripples in the hull (particularly if the planking is Douglas fur), but you'll likely be coating again with epoxy to seal everything in, before painting.

Specific paints are what you feel comfortable with. The best stuff is the two part linear polyurethanes, but these are difficult to apply for the amateur builder. Next on the list are the single part polyurethanes, followed by the epoxies, then the alkyds (oils), with acrylics (house paint) the very last choice for marine work.

As a rule you want the epoxy down, before anything else, so you can get the penetration into the raw wood fibers, then fill, sand, prime and play with the surface as you like.

The best built boats, have each and every single piece that goes into the boat, trimmed, fitted, adjusted, drilled for fasteners, then epoxy coated, before it goes in the boat. This way every nook and cranny is coated, which prevents moisture from getting in and ruining your day. Slopping on epoxy after parts are installed means some areas will not have a coating of plastic on them and these areas will be where the moisture gets in and bites your butt down the road. That said, total encapsulation is costly, but stitch and glue designs rely heavily on this goo, so if you're going this construction route, then use the interstate rather then the surface streets, if you understand my meaning.

[tja]

What do the build instructions call for? Most stich and glue that i've looked at call for epoxy resin and glass inside and out. It's not a cheap way to go. You may want to consider a more conventional style of construction, plywood over frames which you could epoxy prime and then paint with epoxy or urethane paint.

[Zenehet]

Thank you all for your replies, Especially PAR.

I am using Okume ply that will be full epoxy encapsulated and then painted likely with Interlux or Pettit

Thanks again