| Repairing Trailer Bunks | | Print | |
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A cradle for your baby, trailer bunks need periodic service. Originally published August 2008 issue By Brett Becker You probably don't give trailer bunks much thought, right? But if you think about it, you'll find that trailer bunks are in contact with your boat more often than you are. And that means they're important enough to warrant your attention and periodic maintenance. 
For the most part, the carpeting will need to be replaced every couple of years. Worst case, the bunks will need to be replaced. Neither procedure is difficult or expensive, but it most likely will chew up a whole Saturday. And, of course, you'll need to find a place to put the boat. "That's the biggest thing we hear from customers is, 'What the heck do I do with the boat?'" said Dan Behrend, production manager for MYCO Trailers in Bradenton, Fla., which manufacturers trailers that average between 30 and 60 feet long. Obviously, you'd like your bunks and carpeting to last as long as possible, so there are steps you can take to extend the service life. One key factor in the life span of bunk carpeting is the weight of the boat. The heavier the boat, the harder it is on bunk carpeting. Hull characteristics, such as the sharpness of deadrise or steps and strakes also can affect the useful life of bunk carpeting. Say you have a Baja with a radiused keel and deadrise entry, it's going to be easier on bunk carpeting than, say, a Hustler, which has sharper hull features. "The other thing that affects them strongly is whether the carpeting is wet," Behrend said. "Water is a lubricant. When you bring the boat in, the hull is wet so you've got a little bit of water carried on there. But let's say you're launching the boat. You back the trailer far enough in the water that the stern starts to float, and then you fire it up and power it off in reverse. However long an area of bunk, the forward keel drags on the carpeting, it's just going to burn it." Because bunk carpeting is dry more often than it is wet, that can be a problem. PAM Cooking Spray and silicone are often used as a lubricant for trailer bunks—be sure to leave the bow eye attached while backing down a ramp—but they aren't necessarily good for the environment. "We have heard from customers who use those lubricants, and they do work," Behrend said. "I don't want to go on the record suggesting that we use something like that, and you back the trailer into the water and then you get all the nice little blue rings in the water from it." Alternative lubricants include dish soap—long used by wakeboarders and water skiers to slip into vice-tight bindings—and plain old water. Biodegradable boat wash soap, which is available at any marine store, is another possibility. It's a more environmentally responsible alternative and its lubricant quality lasts longer than water. Eventually, however, all bunk carpeting will need to be replaced. Typically, you don't have to remove the bunks to replace the carpeting. Use a flat-blade screwdriver and standard pliers to remove the old staples. Once you've got the carpeting off, you can inspect the wood underneath. If nothing is broken or loose, you can replace just the carpeting. But what do you use? "We use a 20-ounce, cut-pile carpeting that's designed for exterior use," Behrend said, adding that you should rent a pneumatic stapler and use galvanized staples for the job. "To be perfectly honest, I'm not certain it's designed specifically for boat trailer use or not." Behrend recommends sticking with a cut-pile, outdoor-style carpeting. MYCO also offers 26-ounce, loop-pile carpeting on more heavy-duty applications. The heavier carpeting and loop design is more durable, but it's more abrasive to the gelcoat. "You're better off eating up the carpeting than the bottom of the boat, and needing to repaint or do gelcoat work," he added. "The polyolefin cut pile is very soft. It feels very soft to your hand, whereas the 26-ounce loop pile, which is specified on commercial trailers, well, it feels rough to your hand." Most often, bunks that need to be replaced have broken. In some cases, the lag screws have backed out, and they can't be screwed back in unless the holes are wallowed out. But how do trailer bunks break? "To me, the single most important factor is how many knots are in (the lumber)," Behrend said. "Every once in a while we'll see a trailer come back and it's got the bunks just broken. The wood's actually broken. You think, 'How in the world can this happen?' And usually, there are a concentration of knots in that area." That should give you an idea of how to select the wood you use to replace the bunks. But what about plastic bunks? Or marine-grade lumber? Or pressure-treated wood? You can use those alternatives, Behrend said, but typically the benefits don't exceed the costs. "Actually, pressure-treated lumber is a poorer quality than is otherwise commercially available for dimension lumber," Behrend said. "We recommend whatever Lowe's or Home Depot has, like southern yellow pine, Douglas fir or spruce, but go pick it out yourself and look for the lumber with the minimum number of knots for maximum strength. "A lot of people worry that because it comes in contact with water they have to have pressure-treated (wood). You really don't," he said. "Taking the time to go yourself and pick out the wood is worth the time." Bunks attach to a trailer in one of two ways: They're either lag-screwed or through-bolted with carriage bolts. Obviously, through-bolting is the way to go, and even if your existing bunks are lag-screwed, you can retrofit them with carriage bolts. "What we do is use quarter-inch fasteners and the hole is drilled somewhat undersize, maybe 1/32" undersize, and you drive the carriage bolt in with a hammer," Behrend said. "Then just when the head seats, give it a really good swat and that countersinks the bolt. It compresses the wood enough that it more or less countersinks the carriage bolt head." Rather than using a nylon lock nut, Behrend advises using a double-nut system. A nylon lock nut can cause the square shoulder of the carriage bolt to spin in the wood. Then it never gets tight enough. Use a flat washer and a plain nut. Once the first nut is tight, use a box wrench to hold it as you screw on the second nut. Stainless hardware is the way to go. It might seem like a lot of trouble, but when you think about how much time your boat spends cradled on trailer bunks, it begins to make sense. After all, you want what's best for your baby. —Brett Becker is a freelance writer for Powerboat magazine. Contact Information If you like what you're reading, get more by subscribing to Powerboat magazine here. |
