Osmosis Gelshield

[mudskipper]

Hello,
after having osmosis all over the downside of my jolly I have grinded all the bubbles and washed them out afterwards. Later I filled them with "Watertite"Filler. Next I took of (most) of the Antifouling with a grinder.

My question: Can I go over the remaining old layers of Gelshield 200 with the "Gelshield" epoxy, or do I have to remove ALL of the Gelshield 200 first (which is a whole lot of extra work!)?

I would be very grateful if anyone with experience could answer this question, thank a lot!

Mudskipper

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[Talbot]

I would really recommend that you discuss this with International for their recommendation.

If the original gelshield was applied correctly then it should have helped to delay onset of osmosis. Without knowing more about your boat and when the gelshield was originally applied, I would suspect that either the original prep work for the first gelshield coat was inadequate, or the layers have had some inpact damage and have cracked - either way I would suspect that there might be rather more work here than you suggest. - Did you get a moisture content reading before sealing the hull up again

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[oldsaltoz]

G'day Mudskipper and welcome to the forums with your first posting.

Sounds like you have some real work ahead of you though.

To provide you with the best advice 'we' need a little more information; can you tell us:-

How long the old coat of Gelshield was on the boat and was it in-tact over the blisters prior to grinding. if the Gelshield was in good condition the moisture may be trapped in the hull, no amount of grinding and filling will stop more blisters developing, the hull 'must be dry' prior to treatment.

When you ground out the blisters, did you see any signs of brown staining and was it ground to the point that all the stains were removed, also inspect for fibres that are pail in colour due to a lack of resin, all to be removed.

How soon after grinding and washing did you fill the ground areas, as any moisture in the hull will be trapped and will cause more problems.

What did you fill the holes with, type of filler and type of resin, and did you replace any fibreglass matting. This has to be an epoxy resin and a closed cell filler to ensure the water stays out.

I'm sure you will get some more comments from others, but if you can fill in questions above it will get you better advice on how to tackle the problem.

I hope this helps and avagoodweekend......



<hr width=100% size=1> Old Salt Oz /forums/images/icons/cool.gif Growing old is unavoidable. However, growing up is still optional.

 

[mudskipper]

Hello Old Salt Oz!

Thanks for your quick reply to my question. Gladly I will give you some more information about the problem, I´ll try to make it not too long:

I purchased the boat (a 30 year old "Kielzugvogel", which is a german jolly boat with a length of 5.8 meters) 4 years ago. At this time no blisters were to be seen. The former owner told me, that the coating of the watersurface was fairly new. Indeed, the boat was in a good visual condition. From April to October the boat lies in a lake. It was last autumn, when I first saw the blisters. (Without counting I would guess about 300 from needlehead size to the diameter of an Euro)

For me there are two possible reasons for the blisters:

1.) In summer of 92 I had a havary in the baltic sea, not dangerous but a whole lot of water poured in the polysterene filled chambers underneath the deck. Unfortunately I could not get all of the water out of these chambers (there was only one inspection hole) and so the polysterene soaked and stayed wet. Maybe this is the cause of diffusion of water through the hull from inside?!?
To solve this problem, I installed some more holes, and took out all the wet polysterene, so the hull can dry out from the inside too.

2.) Second mistake I propably made: Cleaning the hull in autumn 2 years ago with a high pressure water cleaner. This might have cracked the coating enough for water to diffuse!?!

Because of the fact that the boat is quite old, and the former owner told me that osmosis has never occured before, I am quite shure it is no problem of remaining resin in the hull.

Anyhow,
the blisters have been grounded out, until no stain or loose fibres were to be seen; I did this very accurately. After that I brushed the surface, and especially the ground areas with water and detergent, and let it dry for about a week or two in warm and sunny weather. Then I filled the areas with the "Watertite" epoxyfiller from International. At last I grinded the whole waterside to take away the spare filler and remove the antifouling. By doing this,the very little blister were also opened. Washed the hull again.

The situation right now is: 95% of the antifouling is completely taken away, only remaining "traces" are to be seen.
90% of the Gelshield 200 wich was underneath is still covering the glass fibre of the hull.
10% of the fibre is not covered.

My plan was to coat the uncovered fibre (or even the hole grinded waterside) with the Gelshield epoxy resin, and cover this with with several layers of Gelshield 200 to be followed by antifouling.
And here is my main question: Do I have to grind away everything down to the glass fibre (a whole lot of extra work!!!)?
or can I go on putting new layers of Gelshield and Gelshield 200 on the remaining coating?

Thank you for your help in advance, with best wishes,

mudskipper

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[oldsaltoz]

G'day again Mudskipper,

Leaving the exposed ground out areas for only a couple of weeks, even in warm dry conditions may not be enough to dry the hull; drying out is a very slow process as the exposed area is very small (water is inside the strands of glass).

To save a lot of work later and the cost of re coating, I would fist have a moisture reading taken of the hull, this will tell you if you have to re grind the repaired areas to release the remaining moisture, or, have confidence that you have the problem under control and can spend up on finishing the job.

As for re-coating the existing Gelshield, the answer would be yes, but make sure all antifoul has been removed the surface has been sanded with a 100 to 125 grit. Then wash it down with soap and fresh water, let it dry for an hour or so then just prior to coating, clean it with Acetone starting at the top and work down, use white rags only and lots of them, the contaminants will be picked up by the rags, if not changed you will only spread the contaminants.

Keep an eye on humidity, should be 74% or less and don't apply after about 2-30 PM as the temperature will start to drop and condensation may be a problem if the Gellshield has not fully cured.

I hope this helps.

Avagoodweekend......

<hr width=100% size=1> Old Salt Oz /forums/images/icons/cool.gif Growing old is unavoidable. However, growing up is still optional.