There seems to me to be something of a strange, blind enthusiasm for epoxy and CPES amongst the members of this Forum. I say strange because in other contexts, say relating to similar materials in fibreglass boats, there are howls of derision and derogatory comments like "snot buckets". Yet recently these catalytic resin compounds in a new guise have been hailed as the holy grail for wooden boat construction and maintenance.
I had thought we we had all been here before and seen the error of our ways. Some years ago, it was all the rage to slather the outside of elderly wooden hulls in resin and fibreglass mat. This step was many times undertaken as a last desperate measure to keep the old girl afloat for a few more seasons, or much worse, performed on a perfectly sound hull with reduced maintenance as the only object. I think almost everyone agrees now that this was an appalling thing to do, and far from prolonging life and reducing maintenance it has often pretty well finished off the boat it was intended to save.
So how come epoxy, CPES, and glass cloth are that much different? Aha, you say, but epoxy and CPES are far superior to polyester resin in this context. They bond to wood in a way that resin could not, and they are impermeable to water. And of course, you say, we are applying these techniques to new build, not bodging up an old clunker. Hmm. Here's why I don't agree:
I've probably told you before, we have this sweet little clinker 12 foot dinghy, only 5 years old. A while ago, I wanted to modify the rowlock points and fix an attachment point below the side-benches for a line to prevent the rowlocks jumping out of their sockets. To do this, I needed to drill a couple of holes into the stringer just below the side-bench. No problem, thought I, I'll just unscrew the side-bench, lift it out, drill the holes, and re-assemble. Duh... no screws. Looked underneath, and guess what? Yes, the side-benches, and ALL the thwarts, are epoxy glued in place. So that's why there are no knees. No possibility of ever dismantling, or repairing, the thwarts and side-benches on this boat without a chainsaw. Terrific.
Take this a step further with all-glued lapstrake ply construction or similar, and what do you have? An un-repairable boat, period. And don't try to tell me that it will never need repair - maybe not in your lifetime (you hope), but one day it will either be repair or Doc's marshmallow bonfire. One of the joys of wooden boats with traditional materials and construction is (should be) that such artefacts are infinitely repairable and re-buildable. If you glue the thing together with epoxy it simply defeats the object.
CPES doesn't sound much better to me. A lot of folks seem to be regarding it as some sort of maintenance panacea. Slosh it all over the dodgy bits, use it as a prep before painting, seal the planks and seams on new build. Well, if it penetrates and or sticks half as well as it's been hyped up to do, once again heaven help you if you need to dismantle that bulkhead or stringer some years down the line. You might undo the screws, but if the CPES has done its job it'll take a crowbar to move it.
The idea of encapsulating wood within any sort of layer of glass or epoxy or resin is fatally flawed. Why? Because the encapsulating layer is bound to be punctured eventually. When it is, water will penetrate and saturate the wood. Snag is, unlike paint which is always permeable and allows the wood to breath, the epoxy layer will trap and contain the water within the wood. You can then expect rot, delamination of the wood to epoxy interface, and resultant big trouble. The jury is out on this technique, because it is so new. Why is everyone so anxious to be a guinea-pig? Because they have been seduced by this nonsense of the low-maintenance wooden boat. If you wanted that, why not buy or build in fibre-glass?