Epoxy vs Polly & Vinyl

[RichardM]

I am boat shopping and I'm fairly new to boating and I'm confused by the different types of resins and methods being employed. Everyone seems to agree vacuum bag wet-out and epoxy resin apears to be the superior method of hull construction. Lighter, stronger and overall most cost effective.
If it were simply a matter of economics, i.e. epoxy cost more than vinyl and vilyl more than polly I could understand why manufacturers choose different methods, but I am finding sport fish boats fabricated with epoxy construction competitively priced to their polly and vinyl counterparts.
Am I missing something? Why don't all builders use epoxy?

[glassman]

I deal with a lot of boat manufacturers and some have gone to epoxy but went back to vinyl and polly due to the cost and the lay up time also training that the big nut.

[Karsten]

There are mechanical differences between the resins. Generally you want a tough resin. A tough resin can be deformed allot before it breaks. In practical terms this means that your structure can flex more without develloping cracks in the resin / gelcoat. Epoxy is about twice as tough as vinyl and vinyl is about twice as tough as poly. Epoxy also sticks better to the fibre. Because of this you can use less structure in the boat. Less structure reduces material and labour costs because you have to put in less frames and/or stringers. Lots of builders just change the resin system without changing the structure. They probably find that the epoxy boat is too expansive. Also with epoxy you can use different production methods more reliable. The gel time is much longer and can be accurately adjusted. Because of the long gel time you can infuse a whole hull in one go in a few hours saving further costs.
The point is that epoxy can be cost effective if all of it's advantages are used and the boat is reengineered (we are not even talking about osmosis here). We engineered a RIB for a coast guard. The previous one was poly CSM and weight a ton and needed a huge engine to get going. It turned out that carbon prepreg was the cheapest method. I think only 4 stringers were left in the boat and all frames removed which saved about 70% of the labour costs. Because the much lighter boat needed a much smaller engine for the same performance running costs were also reduced. In the end it was cheaper than the low tech ultra cheap poly / CSM boat.