Building a Better Boat Fender

Posted by at 06:08PM - Comments: (3)

Frank Lanier
Frank Lanier

The Easystow fender on one of our tester's boats held up for more than seven years before the interior liner needed replacement. The new fenders have liners that are three times thicker than the original we tested.

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, of course, 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. 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 Jack’s 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.).

Jack's Plastic Welding (
Jack's Plastic Welding (

A white-water drybag/cum boat fender. Add a bladder and it's ready for service.

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.

Fender boards, designed to ride outboard of two fenders, 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”, 2”x 6”, or 2”x8”. As a guide, I’d start a t 2”x4” for a 20-foot boat, 2”x6” for a 30-foot boat, and 2”x8” 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.

Made with two fenders and a short length of framing timber, a simple fenderboard is is adequate for most docking needs.

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 2x4 or 2x6 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.

A laminated fender board with 1/8-inch spacers at each end produces a leaf-spring effect.

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 1”x 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 it’s 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. 

Comments (3)

I would like to hear comments about replacing the boards with PVC. I saw one sailboat that had used it. It seems to me that PVC is lighter and might stay cleaner. What say you?

Kokomo Jim
48 Hatteras LRC

Posted by: Kokomo Jim | February 19, 2018 8:19 AM    Report this comment

There is already a fender manufacted specifically designed to be mounted on a flat faced dock or as I have done, mounted on a 5' long 2x8. It is inflated with air as most fenders are, I would prefer for them to be filled with a flexible foam rubber as Barberton fenders were in past years. My fender board and another one like it allow my 49' DeFever to lie close enough to the finger pier to easily step across the gap safely. For a storm situation I would also place much larger fenders between the board and hull. One other thing, it is fairly difficult to drill rope holes thru the edge,of a two by two, I drilled my holes thru the side as large as I wanted and tied the lines with a bowline, the board hangs just as streight as if they were drilled thru the edge.

Posted by: Captain Bill | August 2, 2016 9:53 PM    Report this comment

Good suggestions here, especially about the fender boards. It amuses me though, that not just Practical Sailor but other 'reliable sources' suggest tieing fenders and bumper boards to the life lines. Especially on a sailboat with so much potential for leaks, you'd think the fenders would be shown tied to the toe rail or the bottom of a stanchion. The tension placed on the lifelines isn't necessary and could very easily create a wiggle which would eventually cause a leak and no one would know where it's coming from. I suspect that's why most sail boats are not dry inside. I'm lucky-mine is! And I want to keep it that way! Thanks for listening!

Posted by: NavySubVetDave | July 27, 2016 5:13 PM    Report this comment

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