PS Advisor: Do Alcohol and Antifouling Mix?

Thinning VC-17 with rubbing alcohol gets thumbs up.

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Today I went to paint the bottom of my boat with Interlux’s VC-17m, which I have used since it first came on the market. I had always cut/thinned the paint a bit with acetone. Today, the West Marine store manager (who is an experienced boater) told me that Interlux changed the VC-17m formula and that you should thin it with simple rubbing alcohol. When I used the paint with the alcohol, I noticed that it did not dry as quickly

PS Advisor: Do Alcohol and Antifouling Mix?

Photos courtesy of Bob Ptak and Interlux Yacht Finishes

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as it had with acetone and seemed thicker than usual after mixing the copper powder. Is it correct that you can now use isopropyl (rubbing) alcohol to “thin” VC-17m antifouling?

 

Bob Ptak,
Synergy, 1994 Catalina C-320,
Muskegon, Mich.

We hadn’t heard that tip before either, so we asked Jim Seidel, assistant marketing manager at Interlux Yacht Finishes, about it. According to Seidel, the VC-17m formula was changed in 1999. The solvent formerly used was Tri-Chlor 111, which proved to be an ozone-depleting solvent. To maintain the drying speed and handling characteristics, Interlux went to an alcohol-based formula. The VC-17m thinner that the company now sells, called V-172, is a combination of isopropyl alcohol and n–propyl alcohol, in the same ratio as what is in the paint. The n–propyl alcohol cuts the resin better and is slightly faster than the isopropyl, Seidel said. Because the ratios in the V-172 match those of the alcohol in the VC-17m, Interlux recommends thinning the antifouling paint with the V-172 for the best results; however, isopropyl can be used.

 

Hull Blistering

PS Advisor: Do Alcohol and Antifouling Mix?

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I recently purchased an Airmar in-hull transducer. The installation instructions call for gluing the base of the unit to the inside of the hull, then filling it with propylene-glycol antifreeze. I have read that standing water in a bilge can lead to osmotic blistering. Wouldn’t the antifreeze, which is in permanent contact with the hull where the transducer is mounted, also pose a risk of blistering?

 

Peter Reiner,
Via e-mail

 

A hull’s vulnerability to blisters has a lot to do with the gelcoat, laminating resins, and process uses during construction, as well as what happens after the boat is launched. However, internal water tanks have been cited as a contributing factor. We’ve not heard any reports of propylene-glycol causing hull blistering, but if you are concerned about it, we suggest using mineral oil, a low-toxicity, non-conductive general-purpose coolant/lubricant. Airmar’s installation instructions for an in-hull P-79 depth transducer specify that mineral oil or propylene-glycol can be used.

(http://www.airmartechnology.com/) Note that this type of installation works only on non-cored hulls.

 

 

 

 

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Darrell Nicholson
Practical Sailor has been independently testing and reporting on sailboats and sailing gear for more than 50 years. Supported entirely by subscribers, Practical Sailor accepts no advertising. Its independent tests are carried out by experienced sailors and marine industry professionals dedicated to providing objective evaluation and reporting about boats, gear, and the skills required to cross oceans. Practical Sailor is edited by Darrell Nicholson, a long-time liveaboard sailor and trans-Pacific cruiser who has been director of Belvoir Media Group's marine division since 2005. He holds a U.S. Coast Guard 100-ton Master license, has logged tens of thousands of miles in three oceans, and has skippered everything from pilot boats to day charter cats. His weekly blog Inside Practical Sailor offers an inside look at current research and gear tests at Practical Sailor, while his award-winning column,"Rhumb Lines," tracks boating trends and reflects upon the sailing life. He sails a Sparkman & Stephens-designed Yankee 30 out of St. Petersburg, Florida. You can reach him by email at practicalsailor@belvoir.com.