Could the assembled wisdom in here please relate the current thinking on osmosis regarding modern, supposedly well built yachts using all the best of everything? Now before everyone starts telling me how to repair it, let me say I don't have any, I'm just curious as to how it's addressed by the various builders these days.

One European manufacturer gives five years warranty against osmosis and even boasts of using vinyl ester resin in the gel coat. Now surely if you can use vinyl ester resin for the gel coat, surely you can build the entire boat with it as well and not increase the costs too much. In the quantities that I buy resin, there is a price difference, but that is retail quantities, not the 200 litre drums that factories buy by the pallet load.

The factory that uses vinyl ester resin for the gel coat is Delphia in Poland, I don't know what any of the other European brands such as Bavaria, Hanse, Baneteau or even Jeanneau use in their construction or what warranties they give for osmosis. My main reason for picking these brands is that they enjoy world wide popularity and therefore operate in wide and varied conditions and should provide a huge data base.

Now while osmosis is not a desirable thing to have in your hull, by the same token nor is it anywhre as serious a problem as is usually portrayed by the popular magazines and the armchair admirals.

As I said, I'm just wondering about it. ........... Harry

I doubt using a different variety of resin is going to do a better job of stopping osmosis, none of the resins are poreous by nature, and a gel coat done properly should be damn near completely waterproof, I think build quality is what's important, the water'll seep in at the joins/damage etc or anywhere there's a hole where the edge of the layers are exposed

Having said that using better resins will give better strength which will reduce the chance of damage, always a good thing.

The polyester resin available during the fuel crisis in 1973 was particularly poor in quality. Some builders were a little slow in understanding the requirements of a good layup. Some builders using polyester still turned out vessels that never have osmosis, its was not luck but good management.
I use nothing but epoxy these days, FGI 180 for everything. Its easier to use than polyester and because less is required with cloth than csm and polyester its actually cheaper to cover a fishing vessels deck for example, with the added advantage it sticks to wood and is actually waterproof.

We have now had a few relies to the thread and in nearly all cases people are saying what they are doing or what they are using as their preferred resin of choice. My original question was "What are the manufactures doing?"

I agree entirely with Cisco when he says the type of resin is not as important as is the methodology in applying it. The only time the resin is important is if the resin is "Hetron", a type that was developed for the US military and unfortunately had quite serious problems for quite a few builders, especially in the US and in Taiwan where there were builders doing business for US based companies. It wasn't the resin on its own that caused the problem but rather a combination of resin and poor glass choice as not enough research was done at the time.

As mentioned previously Delphia Yachts give five years osmosis warranty, Bavaria make no mention of osmosis and also give five years hull warranty. To my way of thinking If I had slapped down a bulk amount of loot for a new yacht then I would not expect to have any sort of osmosis problems for at least ten or even fifteen years.