Water does not pass through wood or epoxy but moisture does otherwise you could not season it!
Water molecules enter the intercellular spaces between the wood cells. Call it moisture or call it water; it is all the same, but the intercellular spaces only allow so much water. They still behave as a sponge when water rests on a board. A few days in a pond and a board will bend when saturated.
The rate of transportation varies with the material and an epoxy glass layer has very low but not zero moisture transportation rates. Epoxy mixed as a glue has a higher transportation than the glass coat (it is thinner), paint is significantly higher than epoxy and wood is relatively permiable. As a result a fully encapsulated hull even with no defects will slowly absorb moisture if left in the water.
epoxy in a single layer or three layers will behave differently; the only point here I agree with is a poorly encapsulated boat is really far worse than not at all because water gets into intercellular spaces, but leaves very slowly, multiple layers of epoxy applied correctly as primary bonds are esstmentially waterproof
If the permiability of the inside skin is the same as the external skin then the vapour pressure needed to move moisture out of the hull into the interior will need to be high so the equilibrium moisture level in the core will be high. If the vapour permiability of the inside is lower than the outside moisture can move out of the hull to the interior faster than it can move through the outer skin leading to low hull moisture levels (assuming the inside is kept reasonably dry, for example using a dehumidifier during winter storage or lighting the hot stove regularly) This is why traditional wooden boat hulls do not become saturated.
sorry, but you are making a grave error here...the reason traditional boats dry out is they are not encapsulated at all! They actually survive in a saturated or swollen state and this is how they seal up.
Do this experiment. Take two sponges of the same material. Set on in a glass container so only the top can dry and the other expose all six sides and see how quickly the intercellular water leaves each. The one in the glass will take a couple weeks to dry. The one exposed on all sides, far less.
Now, consider wood is not as open celled as a sponge and consider how bad it will dry near the exterior glass.
Establishing an effective moisture permiability gradient is a fundamental part of designing wooden building in the construction industry and there are many vapour barrier materials available with different translation rates to achieve this. I am simply applying the same principals (as do Spirit yachts I believe)
The second issue is the initial moisture content of the wood. Kiln dried wood should have a moisture content around 7 or 8% but as soon as you move it out of the kiln that will start to increase unless you can build in an environmentally controlled building. Given that I expect to take about a year to build the boat I don't think I would be able to garentee to keep the moisture content below the critical 12% threshold for rot to develop and hence would be sealing moisture in not out by encapsulating. The only way I can see to avaiod this is to buy kiln dried timber and immediately shape and encapsulate each individual piece. I don't t think that is practical and getting kiln dried cedar in my area is difficult and expensive. Air dried timber is available at the local mill and they will select and reserve 'boat Grade' pieces for me.
definitely more challenging; thanks for mentioning the commercial builder using this method
