Tips for Using Boat Fenders

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using boat fenders with coversFenders (not “bumpers”) are inflatable or padded cushions that keep boats from bumping up against docks, moorings and other watercraft. They absorb shock to prevent damage to the hulls of boats that are docked, rafted or anchored.

Types of Watercraft Fenders

Fenders come in several shapes and sizes.  Here are some of the most commonly used:

Cylindrical fenders: The most common type of boat fender. Fenders with an “eye” on one end or both that can hang vertically with a rope secured by a bowline through one eye, or horizontally with a rope threaded through both eyes, held in place by a half-hitch or “figure eight” stopper knot.

Center rope cylindrical fenders are threaded with a rope that runs through a hole in the fender's centerline, and can be hung both vertically and horizontally.

Round fenders: Made of soft vinyl, round fenders are common on large powerboats with concave (flared) bows, where there is a significant distance from the dock.  They are often seen on commercial vessels like fishing boats, and can be used in raft-ups and as mooring buoys.

Flat fenders: Generally used by smaller boats, flat fenders are non inflatable, foam buffers that provide protection when secured to a boat's gunwales (pronounced “gunnels”) or life lines.

A “Type 4 PFD”: Square in shape, these fenders double as seat cushions and make a good alternative when other fenders aren't available.

The Size of Fender Matters

When setting up fenders, it's more important to have the right size fenders than to have a whole battalion of too-small ones. Typically, inflatable fenders should be about an inch thick in diameter for every five feet of boat length.

While smaller boats may only use a couple of fenders, boats in the 40-foot plus range should have at least four. Larger boats will use six or more fenders. Most recreational fenders can be inflated with a standard needle pump,  and should feel like a football when you squeeze them.

Docking and Rafting with Fenders

slip hitch with boat fenderDon’t secure fenders before beginning docking or rafting. Fenders will get caught on pilings, or the other boats when rafting, causing the person steering to lose control of the boat. Always ask crew to hold the fender line and move the fenders where necessary,  then secure the fenders once you’ve finished docking or rafting. Use a clove hitch or a “slip hitch”.

Once  you’ve docked or rafted, fenders should be hung near the widest beam point, at the lowest attaching point. Secure them to lifelines only if a lower spot, like a cleat, is unavailable.Hang enough fenders so that the boats will not rub or hit hard pilings or bulkheads.

  • If your boat will be in the same place for a while, keep fenders and extra line out of the water to prevent algae and barnacles from growing on the bottom of the fender.
  • When docking next to a piling, hang fenders horizontally to keep them from rolling aside. Or, use two cylindrical fenders against the boat, with a fender board laid across them both.  
  • To hang a center rope cylindrical fender horizontally, tie a half hitch or figure eight on both sides to prevent it from sliding out of position.
  • When at a dock, check the tidal range. Nothing is worse than coming back to your boat with fenders now below the dock, and damage to lifeline stanchions or hull because the tide went out.

Rafting up or anchoring

It’s worth repeating: When maneuvering your boat, have crew hold the fender line in their hands, and move the fender as needed. Do not secure fenders until boats are stopped and tied up.  

Place fenders on both sides of your boat, especially in crowded anchorages. This will help protect your rafted boats in the event of rolling caused by waves, or a boat drifting on its anchor.

For sailboats rafting up together, look up at your spreaders to make sure they won’t hit each other if the boats roll. Use a spring line to move spreaders forward or behind one another.

Stow your fenders once you have left the dock or raft up. Nothing says “newbie” like fenders hanging over the side once you’re sailing or motoring in open water.