[Public-List] Painting below water line

[richard.hazlegrove at wellsfargo.com]

Dwane,
As John suggested one (or more) coats of two-part barrier coat is recommended over the gel coat prior to applying the bottom paint.  It is also recommended that the bottom paint be applied while the last barrier coat is still "hot";  tacked up but still a little soft.  

I am in the middle of a similar project now due to adhesion failure after about twelve years of annual ablative painting.  The paint held up well until about two years ago when small patches began to fail down to the prior barrier coat. I decided to take it back down to the barrier coat and start over.  I was quoted $30.00/foot to soda blast the hull which seemed a reasonable alternative to hand sanding 12 years of paint from the bottom.  The contractor told me that he hauled away over 300 pounds of old paint from the tented work area. I plan to apply three additional coats of two part barrier coat followed by a "signal coat" of black hard paint and a final coat of red ablative. 

The boat had not been out of the water for more than a week at a time for 14 years.  I was amazed to see that there were no blisters or any water seepage out of the hull or rudder. A nice reminder of how well Whitby laid up these hulls.   

Richard Hazlegrove
Quest 433
Mobjack Bay, VA. 


-----Original Message-----
From: John Boor [mailto:mahseer at kos.net] 
Sent: Tuesday, April 30, 2013 2:47 PM
To: Dwayne Back; Alberg 30 Public List -- open to all
Subject: Re: [Public-List] Painting below water line

Dwayne.

Having gone this far continue to scrape down to gel coat.  This way you will get the best adhesion.  As an extra consider a barrier coat before the Micron CSC.

John Boor

> 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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