Guys,
There is a MAJOR misunderstanding in this forum regarding the porosity and subsequent water seepage through gelcoat. Gelcoat is porous, and given "enough time" it will eventually allow H20 penetration into the laminate (fiberglass) or worse - the core. BUT, this absolutely DOES NOT happen in a matter of hours or days so as to be identified by simple observation. Also, the rate of water penetration through gelcoat varies immensely from boat to boat - even within the same specific models/year of boat. I have personally seen serious penetration occur in a brand new (1 year old) 29 footer after less than 6 months in the water. And, I have seen glass boats 30 years old with no penetration at all - and no barrier coat.
There are many well-known reasons for these huge variances. There are also some reasons that are poorly understood or probably not known at all. In a nutshell; construction times, resin quality and mixing, chemical contamination, ambient temps/humidity during construction, consumer use/abuse, local water quality and consumer climate make up the majority of the known variables.
If you find water accumulation INSIDE a Hobie (or fiberglass boat) after a relatively short period of time in the water (weeks to a few months or less), it is due to; (1) Structural leakage (damage) - cracks in hull bottoms or hull lip... (2) Design leakage - around drain plugs, thru-hulls, or water following the side-rail into the corner casts and down into the pylons. (3) condensation accumulation.
But, if your Hobie is not being moored/docked in water for long periods of time, I can assure you that water is NOT simply seeping through the porosity of the gelcoat and accumulating in your hull...FOR SURE. That is just NOT how fiberglass and gelcoat works. In fact, water penetration of fiberglass/gelcoat does NOT even exhibit itself as "water inside a hull" unless the hull has become so water-logged (core and glass laminate) that the hull itself cracks/splits and lets the water in. This is the end-stage of the problem, and (generally) takes many, many years of sitting in the water to occur. Even then, most boats will not be around long enough to come to this.
The fact is, the vast majority of boats with this affliction appear perfectly dry inside the hull. Yup, you read that correctly - perfectly dry inside. This is because the water penetrates INTO the laminate and core where it cannot be seen. Water that finds its way to the inside of a hull (where you can actually see it) is usually another matter.
To really detect/diagnose water penetration, one must use (for the most part) an expensive moisture meter (especially on larger boats)to detect the water inside the fiberglass. Marine surveyers can do this for you.
As for gelcoat, and why it is used, the answer is simple and certainly no trade secret. First, it is very cost effective in two main regards - materials and labour (especially when using molds for construction). Gelcoat has the supreme advantage of being easily applied to the inside of a polished mold prior to laying the fiberglass laminate. When the part is finally pulled from the mold... voila - a perfect finish and replica of the mold - boat after boat... no big prep (other than building the mold), no sanding, no sags and no runs. Gelcoat is also much more repairable than painted surfaces. But, gelcoat is porous, it oxidizes (unlike good paint), has poor UV resitance, requires regular polish/wax maintenance, and it has a nasty habit of spider-cracking.
As good as gelcoat is, it cannot provide the kind of truly superb finish that a high quality, two-part polyurthenane paint will provide - though painting is much more expensive and labour intensive. By-the-way, gelcoat is the same (polyester) resin that is used to laminate the fiberglass and build the entire boat. It is just tinted with pigment (color), and fillers are added to help with workabilty and finish quality. Gelcoat is not generally used to cover over epoxy laminates/resin - although it can be used in this way - especially if an epoxy repair has been made on a boat.
Fiberglass boats (like the Hobie) are contructed with polyester resin - not epoxy. And, epoxy IS waterproof - Barrier Coat is made of epoxy. Epoxy is FAR too expensive to build a whole boat from - at least, it is for us mere mortals.
Also guys, the only Hobie that MIGHT benefit from a Barrier Coat (which is basically epoxy) is one that is moored or otherwise left in the water all season long. Do not confuse bottom paint (antifouling) with Barrier Coat. They are two different things designed for completely different purposes. For one, bottom paint has nothing to do with waterproofing - only scum and algae prevention (ie. anti-foul). Barrier Coat is for waterproofing and the rough finish it provides, although waterproof, will hurt the speed and performance of a sailboat like the Hobie.
As for racers worried about the gelcoat absorbing water and weight prior to a race - this is a myth, as it does not occur (except on a microscopic level). Besides, even if it were true, a coat of simple wax would stop it completely.
I hope this helps clear things up a bit. A lot of words - I know. But when it comes to resins and fiberglass, there is a lot of myth and misinformation out there. It can cause great expense and hardship to newbies trying to get a handle on all this - I know, because I was one of them - bad information has lead me to some costly boo-boo`s. Hopefully by taking the time to write all this, someone else will have a better learning curve than I did. Who knows, maybe it will be the guy or gal who finds a way to stop Gelcoat from oxidizing! - no more waxing!. Now that would be something.
Dave
