osmosis prevention

[DickB]

This sounds like garbage to me. When I bought my 3 yr old BAv the surveryor said, no problems, and with modern resins, you are unlikely to have for many years. So far so good - 5 years down the line I still have no problems... I would just forget about it and go and enjoy some sailing...

 

[tyce]

applying epoxy in uk is not a problem.
gelshield is fine down to 5 cel

 

[Wansworth]

Sorry,thought could get an opinion about Osmosis,whilst you are all talking about the subject!

 

[shaqra]

I have been reading International handbook on boat painting and its states for preperation before applying epoxy you should use 180 grit sandpaper!
A post from a reader says he uses 400 grade, a much finer paper. What grade is correct to use to rub the gelcoat prior to using epoxy?, and should you sandpaper between coats?.
Thanks

 

[Lakesailor]

Erm. Last time I looked International made paint and systems.
I'd go with them.
Unless the forumite who suggested 400grade was me in which case it is the latest and best advice.

 

[shaqra]

Hi Phil
No, it was not you, it was Vitalman, a number of posts above. Tks for your reply.

 

[ex-Gladys]

...He was talking about an oil rig epoxy tar product, not an International product....

 

[Stemar]

[ QUOTE ]
If a 3o year old boat does not have Osmosis will it ever?

[/ QUOTE ]IMHO, the answer is a definite maybe (not!)

As I understand it, osmosis/blistering, or whatever requires two factors. The first, easily measured, is moisture in the GRP. The other is faulty layup that leaves voids where fluid can gather and weakness that allows the pressure of this fluid to separate layers of layup or gelcoat from layup. If either of these is missing, you won't get problems.

Since neither gelcoat nor polyester resin GRP is completely waterproof (nor is epoxy, in spite of what the sellers of blister treatments may tell you, tho it is better), it really all depends on the second factor. The likelyhood of problems increases with time as more and more moisture penetrates, but the longer you go on without proplems, the less likely that you have the kind of faults in the layup that will cause blisters. Somewhere the two lines of probability cross...

Jissel's 36 this year and last time I looked had no problems, but I'm not uncrossing my fingers yet!

One final thought: boats of that age are usually built like the provebial brick privy, so, even if you do get a few blisters, they're pretty irrelevant, really.