Welds on Your Boat Require Special Care

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The irregular shape of welds makes them difficult to inspect using ultrasound technology. Visual inspections can also be deceiving-especially with new welds. The prettiest bead can have internal voids and poor fusion. After a while, that pretty bead will begin to bloom with corrosion and cracks.

Critical welding, be it oil tanks, high pressure steam, or commercial shipping, all have minimum inspections standards, but the recreational marine repair industry does not. A full-blown X-ray inspection is overkill for minor hole repairs, but the welder needs to follow some basic steps to achieve the best results. The task is complicated if the alloy is unknown.

For new fabrication, the welder should prepare a test sample, joining two 2- to 4-inch strips of the metal to be used together, welded in the orientation in which the welder will be working (if it is overhead, they must be welded overhead).

When finished, chip the slag away and inspect closely for cracks. Cut the sample into strips about 1-inch wide, crossing the weld at 90 degrees. Clamp the test strips in a vise and bend them backward against the weld. A properly welded 90-degree angle should double over without cracking the weld.

Welds can also be checked for cracks and voids using a penetrating die. After welding, chip away all slag, grind smooth, and inspect as directed using a penetrating dye.

For welded tanks, diesel fuel has an uncanny way of finding pinholes. You can paint the inside of the weld with diesel fuel, wait 24 hours, and inspect for any evidence of seepage.

For more on non-destructive testing, see “DIY Materials Testing” from this issue.

Practical Sailor has been independently testing and reporting on sailboats and sailing gear for more than 45 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.

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