Building a Better Boat Fender

My main problem with boat fenders is that they appear to violate the cardinal rule of cruising: any object you bring on the boat should serve at least two purposes (the way your crewmate’s favorite yellow shirt makes a great Q flag). A fender, however, does only one job-cushion the blow between the hull and something hard-and then it swallows up valuable lazarette or anchor locker space when it’s not required.

Recently facing a shortage of fenders, I came upon a temporary substitute—heavy-duty dry bags. Filled with air, these simple roll-top bags work just like inflatable fenders. The main difference is that inflatable PVC fenders like the ones we’ve tested have urethane plastic bladders inside the outer shell (usually PVC), enabling them to hold air longer and be better protected against puncture.

Someone industrious sailor could insert an inflatable urethane liner into a more rugged, welded PVC dry bag, and achieve the same result. The outer bag could be easily fitted with web eyes for securing drop lines. When the dry-bag/fenders aren’t being used dockside, they can keep your off-season clothes dry in the forepeak, safeguard your wardrobe on the Colorado River, carry clean laundry in the dinghy, . . . and so on.

Durability is a question. I’m not sure how long a conventional dry bag will hold up when used as a fender. If they are constructed with a material similar to that used to make the inflatable fenders featured in our recent test, they should last several years if only used occasionally. I wouldn’t be surprised if a non-marine fabricator already sells a thick bag suited for this new purpose. During a recent trip in Idaho, I was impressed by the heavy gauge material used in the dry-bags for whitewater rafters. The ones I saw were made by Jacks Plastic Welding, a custom dry-bag maker located in New Mexico.

So here’s a challenge: Is there perhaps another fender design that could help it serve two distinct purposes? Or are there more uses for a conventional fender than first meet the eye? (I’ve thought of several since first writing this—buoying an anchor for later recovery, keeping chain catenary off a sensitive bottom, rolling a heavy dinghy ashore, etc.).

And for those who’d rather just stick with the tried-and-true, here’s a DIY approach to more conventional fenders.

DIY Fender Board

Fender boards are almost a necessity when docking against pilings because without them, no matter how you position and secure your boat and fenders, movement of tide and boat will displace the position of the fenders relative to the piles. The result is dinged topsides. Recently a number of high-density solid foam fenders that work like fender boards have appeared on the market, but I’m not keen to shred foam over the ocean already filled with plastic.

Fender boards, designed to ride outboard of two fenders, provide more durability and protect a much larger section of topsides much more effectively.

The simplest form of fender board is adequate for most needs. All that is needed is a 3- to 4-foot length of 2 x 4, 2x 6, or 2×8. As a guide, I’d start at a 2×4 for a 20-foot boat, 2×6 for a 30-foot boat, and 2×8 for a 40-foot boat.

On a larger boat, you may want to use a slightly longer board, perhaps up to 6 feet long. Anything longer than that, however, is likely to take two people to handle, and be a nuisance to store.

Just go the nearest lumber supplier and get normal dimension lumber, which may be any variety of softwood. Make sure that it doesn’t have any large knots in the middle of the board, which might make it cause it to break under heavy loading. A hardwood like ash will take more abuse, but the extra weight can make it a handful for one person to handle.

A hole slightly larger than the diameter of the suspension or drop lines (say 9/16-inch hole for a half-inch line), is drilled through the larger dimension at either end of the board, about 6 inches from either end.

Next, round the ends of the plank and chamfer all edges. Your lines should be long enough to suspend the plank down to the waterline from whatever stanchions or cleats you plan to use.

After threading the lines through the holes, tie a figure-eight, stopper knot at the bottom of each line, and you’re finished.

Because of the abuse fender boards are intended to take, painting or varnishing them is pretty much a waste of time. And, because you want a fender board to be as gentle as possible to your boat, complications like metal hanging straps or eye bolts are best avoided.

You can us your fender board with conventional round fenders, or you can purchase solid rubber cushions made specifically for attaching to 2×4 or 2×6 spars. Made by Taylor, they are available though most retail chandlers and online. In our experience they do not give the board quite as much standoff from the hull that a large round fender will, but because they are permanently attached to fender board, there is no risk that they will pop out of position, allowing the board to rest- and rub – against the topsides of your board.

The one embellishment you might wish to consider, if you have sufficient time and/or inclination, is a laminated fender board. This board is composed of three layers of 1x 3 fir, hickory, or ash. The layers are not laminated together, but slightly apart, separated by 1/8 strips of wood epoxied in at either end, creating a wooden fender that flexes like a leaf-spring. I saw one of these years ago, and, though I don’t imagine its much more effective than a length of solid 2 x 6, it certainly looked impressive and sowed a certain pride of ownership that a simpler board would lack.

If you find yourself in an exposed seawall, or are expecting a sloppy sea to toss your boat around in the slip, two reports can help ensure your boat emerges unscathed: Fenders and Lines for Seawalls and Spring Lines for Storm Preparedness. To prepare for the tidal surge, storm force winds, and waves that accompany severe weather fronts or tropical storms, our four-volume “Hurricane Preparedness Guide,” digs into details of mooring, anchoring, and docking that other hurricane preparedness guides ignore.