Wednesday, September 12, 2012

Fender Boards

rev. 9-24-2012

Do you need em'? Yup, if there is a lot of tide, strong storms or wakes, yup.

Example. In Chincoteague, as much as we like the town dock, there are few "no wake" signs, no posted speed limit, and you get rocked now and then by small but speedy boats. There is also a good tide range. and a 3 knot tidal velocity. The picture was taken only a few hours into their first use and we've  already worn a noticable grove. There was always a small pile of saw dust resting on the board.

Example. We got hit beam-on by a powerful storm while in Rockhall, tied to a bulkhead. Fortunately, we had a spring line and good breast lines, and our fender board. I've had fenders pop out in these circumstances, and the pounding on the pilings is scary. All we felt this time was some gentle swaying, even as the hail blew horizontally.

Note the grove in the middle, only a few hours old on a calm day. Yes, it should be centered up on the rub rail; we moved it up later. It seems fenders are always placed when dead tired from a long run, in this case about 85 miles. Lucky we got it deployed at all.

Very simple to make from a scrap of 2x6 treated lumber. Any thinner and it will wear through rather quickly. Forget paint.
  • Pick a length. Too short, you can shift off the piling. Too long it will be weaker and harder to store. Don't underestimate the side force of a strong wind and chop; 500 pounds is common and 1,000 pounds is possible. Thus, I wanted an unsupported span (the part between the fenders) of only a few feet. Ours is ~ 4 1/2 feet overall and I'm happy with it.
  • Drill holes for the line that restrains the fenders horizontally. Our are 5/16-inch polyester line, though some suggest bungee cord. I trust line more. Counter bore the holes so that the stop knots are recessed (reduce wear and reduce snags).
  • Drill vertically through the board (3/8-inch to take a 5/16-inch line) to take the time that suspends the board (loop on one end, stop-knot on the other). This takes a long bit, which I was lucky to have.
Deploying the board is sort of a 2-person job and we don't use it at every marina, but if you suspect storms or wakes, it is very nice. Don't know why I waited so long.

I've seen 2 other variations worthy of note:
  • Fenders on both sides of the board. Sometimes, depending on the dock configuration, it can make sense. In this case, the dock had some horizontal boards that would catch the board as the tide changed, and vertical pilings, that would slide between fenders. A bad dock design.
  • Perminant fender boards. Some boaters will hang these on poorly designed docks, to make a smooth surface for their fenders. It can work.
  • Fenders on the wrong side, Yup, I've seen boats where the wood rubbed on the hull. Just not thinking.


  1. Nice post Drew. I have to use fender boards at my home dock, and they have come in very handy during our travels around the lower bay. After making a few sets, I gave up on drilling the hole. I just make a bowline and loop the line around the board. As long as your spring lines are set to keep the support lines off the piles you don't get any wear on them. Also, if you have the space to store them, I have had better luck keeping the fenders in place by making the boards longer. 6 feet is my standard now. I use 2x4's (pressure treated) to save on weight and haven't had any excessive wear problems as long as I replace them once a year, which is quick and easy to do if you skip the hole drilling part. We saw a boat at a marina in Fisherman's Bay that was using 4x4's for fender boards. Now that is protection.

  2. Good points.

    Ours are shorter because that's what stores well. Otherwise, longer is better.

    2x6 vs 2x4. I'm certain this is boat-dependent. I know, both from calculation and observation that my high-windage cat can generate well over 500 pounds of side force in a good storm; a 2x4 might be taxed, as would a very long board.

    Loops vs. Holes? I'm guilty of over engineering on nights when the alternative is TV. But I do laugh when I see varnished fender boards.

  3. Great post.

    Don't have any fender boards here - with our big tidal swings, all the docks here are floating. It's highly unlikely you'd ever tie up to a piling in Puget Sound.

    But your engineering analysis is spot on, as usual.


  4. We made a big fender board to protect our boat from Hurricane Isaac ... definitely helped ease our nerves (a little bit)!