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post #4 of Old 05-25-2006
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This is partially cribbed from draft that I had written for another purpose but....

"Properly engineered "vacuum bagged, oven cured epoxy hull" and "vacuum bagged, infused vinylester composite" describes the resin being used and the method of controlling proper resin ratios to ensure an optimum resin to laminate ratio and in the case of oven curing, the best way to insure a proper cure in Epoxy.

Vinylester and epoxy are the best resins currently available for yacht construction. Both have excellent fatigue resistance resistance to moisture penetration. Both are immune to blistering. Depending on formulation each have substantially higher strength capabilities than conventional resins. When coupled with carefully sellected laminates (directional fiberglass, kevlar or carbon fiber) these resins can produce the highest impact resistance and flexural strength per pound of any boat building material out there. Vinylester is slightly more expensive than conventional polyester resin and Epoxy is significantly more expensive than vinylester. Vinylester is widely used in crash helmets and armoring vehicles and the vinylester developed for that purpose is actually pretty inexpensive and offers tremendous advantages in terms of resistance to damage and post deformation strength retention over other resins.

Vacuum bagging is a process in which the laminate is laid up and wet out typically as a whole, and then a temporary 'peel coat' absortive layer placed over the laminate. Then an airtight membrane is placed over that and placed under a vaccum. The vacuum compresses the resin and reinforcing fabric creating a dense evenly wet out layout. The peel coat, absorbs excess resin. By adjusting the vacuum pressure the ratio of resin to laminate can be adjusted resulting in a maximum strength at a minimum weight for any given panel design. These are the best ways of producing a composite hull currently in mankind's arsenal.

Oven curing is somewhat unique to epoxy. Left to its own devices, epoxy cures over a very long period of time and can cure un-evenly. Oven post curing is a way of precisely curing epoxy to achieve a higher ultimate strength and to achieve it sooner. It too adds cost but it is an improvement on standard epoxy construction.

The current data suggest that when coupled with moderately high density, crosslinked, closed cell foam cores, and proper laminates, these techniques will produce the highest strength and impact resistance per pound hulls and will produce the most durable constuction technique that we have available. Of course like anything that is high tech, this comes at a price in terms of higher material costs, the need for proper engineering and the need for more care during construction."

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