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.
While many potential failures are easy to spot, some flaws are hidden under paint or within the structure, or are so small that a routine visual inspection won't pick them up. Standing rigging, hulls, decks and hardware fittings are the most common places where hidden structural weaknesses can lead to big repair bills, or even loss of life.
A key principle, at least from my perspective as an engineer, is knowing your boat. In 30 years of boat ownership, Ive only used contractor services for major sail work, new canvas (only because Ive never taken the time to learn), and hauling out. As a result, I know my boat inside out; thats a good feeling, an important part of seamanship, a blessing when something goes bust on a cruise, and a big help when time is available but funds are thin.
Our testers estimated that the exposure test was the equivalent of five years of exposure aboard a boat. Although the test demonstrated that a DIY solution using sandwich bags can nearly match performance, it also demonstrated that the makers claims of five years of protection could, in practice, be accurate.
We wished they could be as maintenance free as the carbon canister on your car, but they lack the regeneration cycles programmed into your car. The makers say the silica gel resin should be replaced annually, but Practical Sailor testers have found that three years is about right for diesel and five years for E-10 gasoline.
The fastest way to attach light hardware to a cored deck is a self-tapping screw. It is also the fastest way to have hardware rip out of the deck and end up with a wet core and delaminated deck. But how to replace screws that have gotten loose or prevent a wet deck in your future? One method is to drill and over-sized hole, remove some core, fill the enlarged hole with epoxy, and then replace them with small through bolts (see Spreading the Load Practical Sailor, August 2016). But what if the backside is inaccessible? Can we create an improved repair by filling and reinstalling a self-tapping fastener, without major surgery? What sealing and filling material is best?
We recently tested shear strength of many caulks on many different materials and delivered a few tentative recommendations (See Marine Sealant Adhesion Tests, December 2016). Here is the two-year follow-up focusing on resistance to weathering, dirt, and mildew, as well as the ability to maintain a good bond above the waterline when flexed. This is one of nearly a dozen similar tests that weve done in recent years. Be sure to see the online version of this article for links to previous reports covering other key characteristics (underwater bonding, sealing teak decks, sealing hatch glazing, etc.).
Sunbrella does not shrink. That is the mantra, and for covers and dodger that are left in place, it seems to be the true. It stretches a little when wet, and so long as it is maintained under tension while it dries, it retains it shape. So says Sunbrella. While this seems true for tensioned cloth (our dodger still fits) and it hardly matters for a sail cover, our real world experience with removable Sunbrella window covers has been different, shrinking as much as 5 percent over a period of years. The problem, no doubt, is that these are worst case scenario, repeatedly removed while still wet with dew and allowed to dry. The end result was that the covers became difficult to install and some of the snaps were being ripped out by the excessive tension.