[Public-List] Painting below water line

[Michael Connolly]

Dwayne, 

I agree with others especially if you expect to keep the boat for several more years to strip off all bottom paint at this time. 
If you wish to apply a barrier coat, then follow the mfg's application schedule to a 't'. I used Interlux Interprotect 2001  on a full keel 23 foot boat and used 4 or 5 gallons to get the mil thickness the Mfg required. They didn't necessarly specify the number of coats but the final mil thickness. There was a chart basically listing the average mil thickness of the product using different methods of application, spray, brush and roller. Then according to the product they specified the final mil thickness and you can then calculate the number of coats. Mine was 7 coats to achieve the required mil thickness. The little bit of extra which was left over from my calculations I used to place more coats on the heavy wear areas of the lower keel radius and the rudder surfaces.  I made the mistake of using a bit too thick a nap roller and ended up with an orange peel surface in the epoxy barrier coat. An orange peel surface is a slow surface for the bottom of a sailboat. 

I was hoping that the Micron CSC ablative would age down to a smoother surface. This did not happen, even over time. T he orange peel of the epoxy barrier coat telegraphed through the ablative. 



This was my first complete bottom job. In the future I will either use a very fine nap epoxy application roller or I will roll and tip the barrier coat and the bottom paint, or both. 



I question the use of Micron CSC in fresh water.  When I did my bottom in 2004 I researched paints and thought that the csc ablatives were for salt water applications. In fresh water I would use VC-17 for a nice smooth fast bottom. Especially, if you are in the upper great lakes where the water is mighty cold. VC-17 requires a new application at each spring splash in...........ablatives do not. 

Michael Connolly #133 

----- Original Message -----


From: "Dwayne Back" <sifuback at yahoo.com> 
To: "Alberg 30 Public List -- open to all" <public-list at lists.alberg30.org> 
Sent: Tuesday, April 30, 2013 10:03:49 AM 
Subject: [Public-List] Painting below water line 

I started to sand the bottom paint this year in preparation of a couple of new coats and noticed some areas that there was adhesion failure.  I began scraping and found that there was a general adhesion failure.  I have scraped about 1/2 the boat and find that ~10% scrapes all the way to the gel coat in various spots with the remainder being covered by what look like 1-2 coats of an unknown paint type that appears to adhere reasonably well. I purchased Micron CSC (fresh water boat), before I discovered adhesion failure, which is supposed to be compatible with a wide variety of paints.  My questions are whether it is best to just sand and paint as is, or would it be better to sand all the way down to the gel coat and start fresh?  Should I do anything extra to protect the exposed gel coat?   If I sanded all the way to the gel coat could I do more damage than good?  Thanks for the feedback. 

Dwayne 
#94 
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