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Why Epoxy

In a boat that is not highly stressed, such as a Tasar, the amount of fibre that is available because it needs to cater to abrasion resistance and idiot factor is excessive, relative to the loads that are subjected to it, and there is no need to resort to “exotics”.

With any skiff that is likely to travel at speed and occasionally plunge into a wave head first, where it may either stop or plough right through, the loads that the rig subjects to the boat, and that the water subjects to the boat, are such that there are no excessive materials, and the laminate schedule reflects this.

The reason for using epoxy and woven cloth laminates is as follows:

Epoxy has a far greater elasticity than polyester. As extreme loads are subjected, the entire matrix is able to move and as a result the entire matrix takes the load rather than the fibre being loaded first.

Epoxy cross-links to a far greater extent than polyester or vinylester, so that it is load bearing in itself, and the resultant matrix is far tougher, with a longer life.

Epoxy is impervious to water, all the included solids react with all the other solids so there is no styrene to “burn off” and no catalyst to vaporise and therefore no holes left to fill with water.

There is no chop strand matt used so there is less wicking, all the fibres are load bearing and are oriented to take the appropriate loads and will continue to do it for a very long period of time.

The use of epoxy also allows very long cure periods which in turn allows more processing to be done in one application, reducing time and cost as well as allowing a better product to be produced.

In terms of laminate weight, an Eighteen, which carries far greater loads and now lasts for 4-5 years competitive life, has about 200g per sq meter structural laminate. The 49er, which carries about half the peak load of an Eighteen, has close to double that laminate, around 410g per sq meter. The 49er has substantial additional carbon mast bands and uses carbon and other exotics in the appropriate areas.

The boat is fully cored with impervious ridged PVC foam varying in thickness from 5-8mm and a full glass epoxy space frame to handle all those loads. It all adds up to a hull that will have a long competitive life.

There are a couple of points that need to be made here. Because there is no surface tissue or  oz CSM (chopped strand mat) in the laminate, what is called “print through” may be seen in the surface. This is the sign of a well-built boat because the gelcoat has been kept to a minimum and the gelcoat is shrinking around the glass fibres.

Normally it is very slight, and is in no way detrimental, and if it really concerns you then wait about 2-3 months for the gelcoat to fully cure and settle then give it a light sand and buff.

A dark brown liquid may come out of the bung when the boat is new and the reason for this is that glass fibre, carbon in particular, and all epoxy resins are hygroscopic, that is they like water. As the epoxy reaction goes through to completion that water is expelled and takes some free reactives with it. This is what is coming out and it will stop when the cure is complete.

A full epoxy cure will happen at 20oC in about 3-4 weeks, 7 days at 25oC and it can be much longer at lower temperatures. All s are “post cured”, that is they are initially cooked at a moderate temperature, cooled, then heated again for a longer period of time so as to achieve the best practical cure within the available time frame.