Tackling The Osmosis

Actually Sunday, 4th November

I'd expected the Osmosis to be much more obvious with lots of large blisters all over the hull but in practise it was a lot less obvious although certainly there and in need of removal. With a couple of days of good weather it's been possible to start the Osmosis treatment by peeling off the gel coat and the outer layer of glass-fibre. The surveyor has specified that this should be done for all areas beneath the waterline as the problem was widespread. The exposed surface of the hull then needed to be finely grit blasted, thoroughly cleaned and dried. Only then could new woven rovings (a replacement layer of glass-fibre) be laminated on the hull, then filled and faired using epoxy fillers. 

The "peeling" was done by a man in a 1950's style space suit with a big, heavy device connected to a vacuum cleaner on steroids. It's not a job for the faint hearted as the peeler is very heavy and only takes something like a 5cm cut at a time so there are many passes! It's clearly rather skilled too as the surface left is remarkably smooth. The peeler is rather like an electric plane with a rotary cutter but makes even more noise, it's deafening! It's not a job I'd relish but the guy doing it was remarkably cheerful, clearly knew his stuff and enjoyed doing a good job.

This process covers the bulk of the hull but there are significant areas around the through hull fittings and just below the waterline where it's not sensible to go that will have to be stripped by hand. This includes the rudder which is going to be removed so that the shaft can be taken out; just as well, can't see how this could be peeled very well in situ!
Once all this is complete the hull can be taken into the Osmosis repair shed to be dried out which is accelerated using the "Hotvac" process which still takes several weeks. With the hull dry new laminate and layers of epoxy can be put on in a controlled environment

I'd thought that it was an occasional thing that happened once in a while, not true! There are so many yachts needing treatment that it's done in the form of a production line with several yachts in process at the same time. Apparently about 30 hulls a year are treated here.