What is the final verdict regarding encapsulation?

[serdarbas]

I'm currently building a cold molded slipper launch with plywood. I just finished fairing as of today and soon I'll start planking.

I have to decide right now if I should encapsulate or leave it as it is.

I know that a perfect encapsulation will create a perfect barrier against water and decrease the maintenance time BUT I know that I will miss some spots. A hard to reach frame corner here, a screw hole there, several missed epoxy layers in various places all around since the boat is huge (7.7 meter) etc.. And I fear that if the water gets in, an imperfect encapsulation would be way worse than no encapsulation since the moisture would be trapped. Imagine an encapsulated frame immersed in water for weeks with a needle size hole in it that will slowly absorb water in to the frame. Now there is absolutely no way for the water to evaporate back from this tiny hole so it will rot the wood inside?

My current options:

1- Man up and encapsulate everything.
2- Don't encapsulate
3- Encapsulate only parts under waterline
4- Encapsulate only outside of the hull (marine plywood)
5- Paint gun inside, encapsulate outside.

There are so many conflicting views regarding the encapsulation that I really don't know what to do!

 

[kapnD]

Your boat, Your call.
You obviously know the pros and cons, and long range internet guesses won’t be helpful.
Encapsulated or not, the issue will be keeping the interior dry.
Strategically placed and sealed large limber holes leading to a sump will make your job easier.

 

[skaraborgcraft]

The last 3 plywood boats i built 12/15/18 ft, where all epoxy coated inside and out with 3 coats of epoxy. Im more concerned about why your boat might be filled with water for weeks? For the record, I lived and cruised on a 25ft plywood yacht that was nearly 50 years old, that had no epoxy or polyester or glass covering of any kind. I used a good primer (aluminium based), and a matched undercoat and top coat, which were simple oil based. The interior bilge was done in red lead. I use epoxy today as the cost difference is not that great on decent paint, and is a harder coating.
Encapsulating parts on the bench before fitting is also common practice. No reason for any missed spots.

 

[serdarbas]

Im more concerned about why your boat might be filled with water for weeks?

Possible scratch / dent on the hull under the water line that may not be visible for a long time or rain water after a possible storm on the harbor that will seep through the covers.

 

[skaraborgcraft]

another alternative is epoxy outside, and oil saturation on the inside timbers. Be mindfull that any coating only sinks in to the first veneer on plywood and stops at the glue-line. I have used 20 litres of tung oil and turpentine mix to soak timbers on the inside of a dry 6m trad boat, and the same mix on plywood frames for skin-on-frame craft. It goes on quick, but is time consuming to saturate wood till adsorption stops. The difference is the oil is "in" the wood, and not just an exterior coating that can be split/chipped.

 

[Rumars]

It's not rocket science, in general:
Okoume, pine, fir, birch: encapsulate with 3 coats on both sides, paint over it.
Sapeli, mahogany, meranti: encapsulation is optional, varnish or paint are not.
Always saturate edges and penetrations with epoxy.

If concerned about dents or scratches, fiberglass the areas in question as heavily as you like.

Example, chined boat, okoume, lives in the water: fiberglass the outside or at least the chines, three coats of epoxy applied on the table before installation, paint.

 

[Blueknarr]

I have repaired thousands of rotten non-encapsulated boats.
And only one rotten encapsulated. It had many items secured with unsealed fasteners.
There's no doubt that encapsulation increases lifespan.
But raw wood can last long enough.