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The Cabot 36: Classic Blue Water Sailor

A site to celebrate this great Canadian passage maker.

Thursday, August 02, 2007

That Osmosis Problem

Thomas Groeneveld (JULY 27/07)

This is Tom Groeneveld on Morning Light II , hull 29, in Curacao. Just put the boat on the hard and discovered a few blisters, maybe a dozen. Had many more 2 years ago and even more 4 years ago.
Ground them out, let them dry and filled with epoxy and silica. Am amazed that the hull is in such good shape. Put a few holes in the rudder but hardly any fluid coming out.

All is well and I will keep on sailing the Cabot.

Scott Schloesser here, hull 32 ( Cimba C36-32 )

I haven't dealt with it yet but Cimba has about 100 blisters in the range from 1" about 80 to 2" about 20 probably from the time it spent down in the islands , plus the rudder core is wet , trying to schedule for a fall haul out.


Bob Ciupa (Hull #50) July 28/07

I did my bottom for osmosis, voids, and barrier coat the hard way during the winter and spring of 05-06. Fell free to have Jan get hold of me, I have loads of info I'd be happy to share.

P.S. If I ever get my hard dodger finished, I'll send you some pics of the boat and info regarding a name change.

Roy Mac Keen (July 29/07)

I would be surprised if 'osmosis' was not a problem with the Cabot, but up until the closing of the factory, we had no indication of the problem. As you are aware osmosis is the penetration through differential pressure of moisture through the gel coat. In the days of the Cabot, gel coat was resin thickened with calcium carbonate ( highly porous) with the addition of colour.

There really is only one way to defeat it: Peel, dry, and barrier coat .

Banff Luther, Sailbluemagic (Hull 33) email July 31/07

If you’re talking about blisters, well I’ve done that job as well. Strip the bottom of the gel coat, let it dry and put on barrier coat. I used a grinder to take off about a 1/16 of an inch off the bottom. At the same time I replaced ALL thru hull fittings. If you don’t replace them, you need to at least pull them out and re-seal them.

I highly recommend that you hire a professional to either sand blast off the gel coat or use a machine to do the work. Its back breaking work and took over two weeks.

If you have your fuel tank and water tank both in the floor, (fiberglass) then you have a bilge in the bottom of the keel that you can’t get to. I used a vacuum with a small tube to pull out over 5 gallons of water from the keel. This caused blisters from the inside to go to the outside. Once I got it dry, I sealed up the access with marine epoxy. Now the two bilges are separate and not connected as were before.


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