Fiberglass encapsulation or not?

Just curious to see how people finished the insides of stitch and glue boats, im working on nancys china dc15 currently and wasn't sure what to do on the interior plywood.. I've read in a few spots that fiberglass encapsulation can trap moisture and lead to rotting, and if that's the case what does everyone do to protect the wood? Would gelcoat be an acceptable finish?

 

Have you sheathed the outside with glass and epoxy?
If so, then I would just apply a couple of coats of epoxy to the hull interior to seal it.
If you don't paint it, then you can easily see early on if any rot is happening anywhere.
But if it is well sealed with epoxy both inside and out, the chances of getting any moisture trapped or the wood rotting would be very slight.

 

A good exterior house paint would be my choice, if the boat is not going to be used hard daily or kept in the water.
Epoxy would provide the best protection against water intrusion, but will require a pigmented overcoat to protect the epoxy from the sun.
A light fiberglass cloth with epoxy provides an even more durable surface, but will require much more resin, and will add some weight, a lot more work, and, like the neat epoxy, will still require UV protection.

 

Yes the outside is sealed, and that's a good tip with the epoxy, the main thing I worry about is not being able to see the rot, trying to keep the boat as open as possible

 

The best thing to do is 6 oz woven glass and epoxy with a paint over top.

The omission of epoxy a/o glass is generally a mistake for most climates. Paint only, as kapn conditionals, is subject to wear and sun and water and the substrate in Florida will heat and cause plywood to check. In a northern climate; despite no hot sun; your hull will be attacked by water ingress and temp swings from minus 30F to 100F or even higher if dark color. Transom tops are always trouble if not glassed and painted. A late November rain and outside storage can result in water freezing in any paint flaws and forcing them larger,

You can also mix and match approaches. Footwells are always hard to keep painted and if paint is all that protects the plywood; you'd always be putting it at risk.

So, another option is to use glass n epoxy on foot areas and paint the less impacted sides.

 

How much of the boat can spray or rain land on?If there is no cover ever put over the boat and it lives outside year round,you would be justified in glassing it.If you keep the boat under a cover,its a lot of work for not much of a gain.Careful use of a wooden boat that has had the bilge properly painted with Danboline or similar should see the boat last a very long time.

 

Here is a link to Nancy's China - Nancy’s China 15 | Devlin Designing Boat Builders https://devlinboat.com/nancys-china-15/

NLF is not too sure what to do about the interior plywood - I think he means the wood inside the cabin and under the cockpit, so it should generally be fairly well protected in these areas?
But I would agree definitely that 'hard wear' areas should be glassed with epoxy, rather than just painted.

 

Just so you know NLF, many of the ply boats built and used in Florida with marine plywood are painted only. The general finding is that the paint jobs do not last as long, oftentimes face checking of the ply under even light paint occurs due to hot sun.

For a ply on frame boat, water ingress is your biggest enemy. In Minnesota, rain is the culprit. Water gets in betweeen frame and ply and rots stuff. Best way to beat it is epoxy. Epoxy bonds, epoxy fillets made with wood flour or fumed silica, epoxy and glass on soles.

 

Many years ago we had a Mirror sailing dinghy, built of marine plywood in the 60's, using glass tape and polyester resin on the seams.
Epoxy as we know it for boats had probably not even been thought about then.
The hull panels were only painted on the outside (and left bare on the inside), and the boat lasted for many years.
But that does not mean that I am advocating that we should still build this way - far from it!
Epoxy is marvellous stuff - make the most of it, but use it wisely, as it is also rather expensive.

 

I sometimes wonder if this section of the forum ought to be re-named "Epoxy is the answer,now whats your question".

 

We should have a symbol to separate the epoxiers from the polyesterians.

 

Absolutely!
Epoxionians and Polyesteronians ??
Or vice versa?
Or ??

 

Haha good to have so many heads on this, the boat will only be used for maybe 4 or 5 months of the year and stored in a building in between uses, epoxy in high wear areas is a good idea, it's my first boat so im just making sure she'll be protected

 

Epoxy interior then clear. No opaque paint.
Epoxy will keep the water out until there is a crack in the Epoxy shield. Then it will start to prevent water from leaving the substrate.
Clear coats will allow this to be seen before serious damage is done. Opaque paint will hide potential damage until it is too late.

 

Well, I never.

That's Epoxians to you, not Epoxionians.

We require less than the Polyesteronians to be sufficient.