Epoxy ???

J

jimiboy

Active Member
Joined
18 Jul 2002
Messages
47
www.
Having read some recent comments on anti-fouling a hull, I would like to know exactly what is meant by "epoxy treatment". Both why it should be done, i.e. is there some problem with the original gel coat, and how does one go about it should it be necessary. Is it an expensive yard job or is it just a case of cutting back to the original gel-coat and painting on a coat of resin?
Most importantly, how do you know if and when it is required?

jim
 
Gelcoat on layups before about 1985 - 92, dependent upon manufacturer, allowed moisture to penetrate to a small extent. The result can be osmosis, dependent upon the quality of the remaining layup, fibreglass used, etc. Gelcoat applied after these dates is far more resistant to moisture penetration but it can still let some through.

Epoxy is a lot more resistant to moisture penetration. Where osmosis is an evident problem, either with blisters or with high hull measured moisture content, it may be necessary to remove all the gelcoat and replace it with an epoxy layer. International's product for this is called Gelshield. Having this done by a yard will cost an arm and a leg, count on something like 5 - 10% of the worth of the boat, more for a small boat. In cases where there is less of a problem, or to delay the almost inevitable, it is possible to apply a solvent-based epoxy before antifouling on a new hull, or after stripping all existing coatings off. International's product is Gelshield 200. This is an easy DIY job, not very expensive. International recommend six coats.

There is another, even cheaper way, but I'm not sure of the current health and safety status of this one. VC-Tar was a coal tar epoxy product that may have had some HSE considerations. It seems to be still available so it may have been reformulated. It produces a thicker coat than Gelshield and seems to work well. A professional version of this stuff is still used used on oil tankers and offshore platforms, where it gives very good corrosion protection. I used it about 10 - 12 years ago, it was easy to apply and functioned as desired. From memory only three coats were needed.
 
VC Tar2 now sold is tar-free and claimed to be as effective as Gelshield.

Even better IMHO is Sigma Tar, a real tar/epoxy product. It's otherwise used for below waterline treatment of bridges, locks, and houseboats. Unlike VC Tar, that I had one an old boat, Sigma Tar does not get brittle and styas thus better on the flexing parts of hulls. It is also better value for money! Just awee bit more messy to apply than Gelshield as it comes in black only.
I applied 3 layers and it left a smooth surface than covered with VC17 teflon AF -> added 0.5kn to my average speed.

chris
 
Have you got it??..just sand off the antifoul in a few small(4inch square ) areas, if you find blisters in the gell coat (usually very apparent as high spots asyou sand) then you have got it! try pricking a blister and you will probably find a strong smelling liquid trapped behind.
West systems have a vidio showing how this can be tackled. It need not cost an arm and a leg if you are prepared to do some of the work.
I am going to get a 'profesional' to do the peeling and will clean and epoxy myself.
Be prepared for a long wait to allow the moisture in the hole to dry out.
 
G'day Jim.
Re: "why it should be done, i.e.. is there some problem with the original gel coat",

Almost nothing is 100% waterproof, and Gelcoat is far from it; after a time water will pass through and the resin is diluted/dissolved/contaminated, often wrongly referred to as osmosis, the cause is water in contact with fibreglass and resin, water will be drawn up a strand of fibreglass (some are hollow) and cause blister, the cure is to remove the contaminated areas and replace the fibreglass and resin as well as the protective cover.

Re: "How does one go about (repairing) it should it be necessary".

You can hire a specialist to do all the work; stripping the gelcoat, fairing and apply protective coat, primer or intercoat and top coat, followed by antifouling.
You can do some or all of this yourself but you do, you will not have any warranty to fall back on.

Re: Is it an expensive.

This will depend on what treatment you decide on, the type of epoxy resin/s to be used, also some specialists prefer to put some new layers of fibreglass on after fairing and prior to applying protective coating; the type of coatings selected to be applied after the hull is treated will also effect the total cost, as will the antifouling selected. it could cost around 500 pounds per foot of boat length at the waterline.

Re: "Most importantly, how do you know if and when it is required"?

The first visible signs are blisters, they may be as small as 5 mm or much larger, an early warning is to have a moisture test carried out, however be warned that this method can be misleading, as the results depend on the experience of the operator; not a test that I would ask the yard owner to do.

I hope this helps

Avagoodweekend Old Salt Oz....../forums/images/icons/cool.gif
 
Getting a warranty or a guarantee is not so easy nowadays. I understand that International/Blakes and so on will no longer guarantee the materials, so the yards are not prepared to take the risk on
 
G'day again Jim,

Have a look at <A target="_blank" HREF=http://www.yachtsurvey.com>http://www.yachtsurvey.com</A> it's full of information on the subject.

Old Salt Oz....../forums/images/icons/cool.gif
 
All of the previous posters have posted good and accurate information, so I won't belabor the point. One exception though......if you ever do "puncture" a blister on your hull, make sure that you are wearing eye protection and gloves as well as a long sleeved shirt or other covering over your arms and such. The liquid in the blisters which may shoot out under pressure is essentially "styrene" in its composition and and is not healthy for humans to come in contact with and can cause blindness. Caution is the codeword.

Reality is the cause of all stress!!
 
Our Kelt 850 sloop was built in 1985 and has been laid up ashore every winter since then.In September 2002 she was lifted out and surveyed.The hull moisture readings taken by the surveyor were 0.She was then moved to the yard workshop and has been under cover since then.In his report the surveyor says we should consider having her epoxied.It would appear from Vyv Cox's post that she may well be just inside the period from 1985 onwards when the standard of resin used was improved.From my limited knowledge it would appear that the hull is as dry as it is likely to ever be so it would seem to be a good time to epoxy her if it is worth doing.I would welcome opinions as to whether:
1. Epoxying would be worthwhile or whether it would be safe to assume that if she has not developed any obvious problems over the last 18 years it is not worth the effort?
2. Should we continue to lay her up ashore if she is not epoxied or - if she were epoxied - could she be laid up afloat ? (We intend taking her down to the Med later this year - either the long way round or through the canals so the lay up afloat option would be handy)
 
If she hasn't developed any problems in 18 years, I would think it's a re3asonable assumption she wont now. But of course if she does develope "osmosis", it will probably be cheaper and easier to do the epoxy in the meddy, due to the weather, drying her much quicker. IMHO
 
You must log in or register to reply here.

Share this page

Top