This might have been pointed out earlier in the thread but I think the main advantage of epoxy resin adhesives over traditional glues is their gap filling properties. A perfectly formed joint using older conventional wood glues can be just as strong if not stronger than with one of the modern adhesives.  Most modern boats & glider wings using this form of laminated construction also use a glass fibre cloth covering to seal it from the elements. The glass fibre is bonded to the wood & becomes part of the whole structure making it extremely strong for its weight. I don't know when glass fibre cloth was first invented or how long it's been used for this purpose.

An extra consideration with boats or water planes is water saturation which will affect most forms of construction over a period of time to varying degrees. While epoxy resin is water resistant the wood isn't so unless the epoxy is bonded properly with the wood, deterioration will take place over a period of time. This would not have been considered so important during WWII as most aircraft only had a limited service life.

The question is a little unfair Woodlouse, considering the fact that production has only been happening for about 40 years on aircraft, and less on boats. (with the exception of some experimental craft).

I don't need converting, I've owned a traditional wooden vessel myself for twenty years, there's not a drop of epoxy in it. But I've also used epoxy extensively and I know it's strengths and weaknesses.

I really am only just realising that epoxy was around for quite a long time, and I was amazed at the spruce goose using the material. Until just recently, the oldest use I had heard of was in early FRP glider construction, around mid to late fifties, and I have seen those gliders still in regular service here in Australia.

As I said before, problems associated with epoxy construction are design and maintenance related, (though I should have included quality control in this list).

You will find the epoxy sailplane manuals state that ALL surfaces are to be painted WHITE and that a silicone free wax polish be applied at all times. Now, if someone paints the elevator blue or red, then he shouldn't be surprised when it starts to de-laminate. Silicones in polish penetrate the paint/gelcoat finish and actually permeate the laminate, this is dangerous, insidiously so, because if at some stage a repair is required, the repaired structure could have bond failure due to the introduced silicone.

If paint is allowed to wear thin, or colors are used, UV light breaks down the epoxy in no time, severely weaking the structure. These problems are known are they are merely a maintenance issue.

Quality control is important, and as an example I'll cite a well known problem in FRP boat manufacturing. I also have been wondering if this problem is what you may be mistakenly thinking of when you are bagging the use of epoxy.

FRP (Fibreglass Reinforced Plastic) boat construction predominately uses Polyester resins and not epoxies, Polyesters are cheaper and relatively easier for novices to use, (without critical mixing ratios).  Most FRP boats are built in production lines using un-skilled and semi-skilled labour, they get shown briefly how to do a glass layup and off they go building boats, often thinking of things back on the farm or whatever.............

A result of this practice is the phenomenon known as OSMOSIS in FRP boats, where the boat deteriorates at the glass laminate, rapidly and catastrophically. Without going into the exact bio-chemical process of osmosis in boats, suffice to say that inadequate care in the construction process allowed trapped air and unsaturated glass in the laminates, which allowed the osmosis to begin. As far as I'm aware this does not occur in epoxy constructed laminates, it is a product of polyester resins and improper layups. (Especially those boats built with or partially built with chopper gun layups). The chopper gun operator is semi-skilled, the guy rolling out the chopped glass laminate is usually unskilled and brain-dead from the fumes (wax in styrene added to the resin), or soon will be, and he really just wants to get away from the acetone so he can light a cigarette.

Now, I have seen such zombies clearly state that smoking around acetone is no big deal and to prove this fact, he promptly threw a lit cigarette into a bucket of pure acetone beside me, the cigarette fortunately extinguished itself, much to my bemusement at the time.

Now, consider the aircraft factory, where absolute precision manufacturing is being carried out with epoxy composites, I watched a friend of mine carefully and precisely make a laminate at the Jabiru factory in Bundaberg, the next day, the laminate was measured, weighed, and promptly discarded, again much to my amazement, as it was the most precise glass laminate I ever witnessed.    

Well, I guess epoxy in aircraft construction could be likened to aluminium in aircraft construction with the advent of WW2 fighter planes before alloy was 50 years old. Except perhaps that alloy has a known and relatively short fatigue life.