I have just pulled my boat out and discovered blisters localy ditributed just on the water line or above in places. They do not pop easily and in fact I have not managed to do it yet unlike common osmosis.
The boat was epoxied 2 years ago and the underwater surface is immaculate.
Has anybody suffered similar and what was your course of action.
Look forward to replies.
posted 16 October 2001 04:23 PM
I have a similar problem just above the water line – very small, very hard ‘blisters’. Apparently, during a respray if the old surface is not absolutly clean there can be a reaction over time between the new coating and the contamination and this is not to be confused with osmosis which occurs predominantly below the water line. If I ‘burst’ a large one, the old gelcoat is exposed, but is completely intact. I can see no other solution but to repaint the topsides.
posted 08 March 2002 02:02 PM
I have exactly the same blisters as you describe just around the waterline. I had them before the boat was resprayed and they have now appeared again – much to my annoyance!!
Have you had any success resolving the problem or is anybody else aware of a remedy?
posted 03 May 2002 07:49 PM
I received this e-mail from Mark Hickmott and have taken the liberty to post it on the website – Thanks Mark!
In respect of the blisters I confirm my boat has not been painted and accordingly still has the original Gelcoat on show.
I ground out the small blisters with a pointed grinding stone attached to a hand drill.
I then filled the holes with International Watertight but after having left the exposed gelcoat to breath for a couple of months. Interestingly the blisters did not reach the fibre glass. Once the filler dried I sanded down with 120 then 180 grade wet and dry flush with the gelcoat.
I then extended the boot top by approximately 4cm with 6 coats of International gelshield 200 over coating the filled remenents of the blisters. This will then be again over coated with anti-fouling.
We got very fed up with cleaning the weed off at the waterline and just above prior to every sail.
I trust this helps.
posted 14 May 2002 01:57 PM
These small ‘blisters’ are not the normal type of osmosis. In the typical case, small quantities of water seep through the gelcoat over time, then react with the resins in the fibreglass. The chemical reaction draws more water in by capillary action which eventually leeds to a bubble separating the gelcoat from the underlying fibreglass. However, in the case of many Sonatas, the reason is a releated chemical reaction at the surface of the gelcoat caused by VERY poor quality gel used by Hunter in those days. The result is pitting, which, in the case of my boat and many others, can extend all over the hull. If your boat does not have it, and is kept in the water, then you must epoxy it to keep the water away from the gelcoat. International Interprotect is what I used, but there are many others. They are easy to apply, just get the antifouling off, fill any existing holes and then paint on about five coats of epoxy, drying between each.