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Boat Fenders: Our First Line Of Defense

Boat fenders come in a variety of shapes, designs, and materials – all intended to protect your hull. Here’s a primer on common types and how to deploy them

Up close view of damaged damaging gelcoat on the side of a white boat.

Choose the correct fender for the job and be sure to position it properly or you risk damaging your gelcoat against docks, as in this case. Photo: Frank Lanier

Most boaters don’t give much thought to their fenders until they’re needed for particular situations – then they can become the star players that save your boat in a storm or keep you from getting gouged at a boat raft-up. So let’s take a look at the different options for various fending-off jobs, what you may want to have aboard your boat, and how to select and get the most from those unsung protectors of gelcoat and boat-handling pride.

What they do and how they do it

A fender is simply an inflatable or padded cushion placed between your boat and some other object (e.g., dock, piling, another boat) to protect your topsides from potential dings and scratches that can happen while docking, rafting, or mooring. Most fenders (particularly inflatables) are constructed from soft vinyl, although a number of other materials like foam – or even woven hemp line found aboard some traditional craft – may be used as well.

A white and blue cylindrical fenders protecting a white boat next to a wooden dock.

Cylindrical fenders are the most common type you’ll see aboard recreational vessels. Photo: Frank Lanier

What’s your type?

Modern fenders come in a wide variety of styles and shapes designed for specific uses, such as that corner dock wheel that helps you maneuver into your slip when crosswinds or currents are present.

  • Cylindrical fenders (the most common type) have either a molded-in fairlead through the center or eyes at each end, allowing you to deploy them vertically or horizontally. Lines can be attached to the eyes using a bowline knot, while those using center ropes can be secured using a figure-eight stopper knot.
  • Round or spherical fenders are a popular choice for larger powerboats, as their increased diameter helps keep flared V-shaped bows away from docks or other structures.
  • Flat fenders are noninflatable foam pads or cushions. They’re typically found aboard smaller boats but can also come in handy aboard larger vessels for those odd cushioning jobs that crop up.
  • Transom-mounted fenders can be mounted on a transom or swim step, providing protection from unruly dinghies or when docking stern-to at a marina.
  • Rafting fenders and cushions are specifically designed for use when rafting boats together. Cushion-style rafting fenders are large and flat so they don’t roll or ride up, while cylindrical rafting fenders are longer than standard fenders for increased surface area and are designed to be hung horizontally via eyes or straps located at both ends (and often in their middle as well).
  • V-shaped fenders, used for docking next to a piling when traditional fenders won’t work, have a self-centering design to keep them properly positioned against a piling, regardless of boat movement. Longer cylinder fenders can be hung horizontally or on the diagonal (which provides a larger protective surface area). An alternative solution is a fender board. 
A large navy rafting fender cushion on a side of a vessel.

Rafting fenders and cushions are specifically designed for use when rafting boats together. Photo: Frank Lanier 

Two white sailboats next to each other on open waters and protected by a rafting cushions.

Photo: Frank Lanier

A vertically hung gray fender providing protection for a vessel next to a lock wall.

Vertically hung fenders are a good option for coming alongside a flat structure, such as this lock wall. Photo: Frank Lanier

Fender tips

1. Avoid positioning and tying off fenders while approaching a dock, when possible, as they can get snagged on pilings or docks, resulting in a loss of steering as the boat gets jerked askew. A better option is having one or two crew members man “roving fenders,” which can be quickly placed where needed.

2. Deploy fenders from the boat, not the dock. They’re easier to adjust from the boat, which allows them to follow and protect the hull throughout the tidal range. It also makes departing the dock easier, as the fenders can be removed and stowed once underway.

3. When coming alongside a protruding structure (such as a piling) deploy cylindrical fenders in a horizontal or diagonal (slanted) position, both to increase the area of protection and prevent the fender from “rolling” off the structure. When coming alongside a flat structure (such as a seawall), a vertically hung fender typically works best.

4. Check and monitor the tidal range and fender placement while docked, particularly when cruising in a new area, which may have more extreme tides.

5. In addition to the fenders on your dock side, hang a couple between you and your dock neighbor if you share a double slip. Either you or your neighbor may inadvertently drift onto each other when arriving or departing, especially in a cross breeze, so be ready for such a situation.

6. Keep fenders and extra line out of the water to prevent algae, barnacles, and other marine growth. Fenders must be kept clean and free of dirt and grime, or they will grind these contaminates into your hull’s finish. Fender covers can also help in this regard. They are typically constructed from polyester, fleece, or a poly-cotton blend fabric. Choose covers that are abrasion-, mildew-, and UV-resistant. Other features to look for include reinforced seams, adjustable straps, and ventilation panels. — F.L.

How To Make a Fender Board to Protect Your Boat

Undersized white and blue fenders providing little protection for a white vessel next to a dock.

Undersized fenders provide little protection. Bottom: If storage is an issue, look into inflatable fenders such as this one from AERÉ. Photo: Frank Lanier

A large white inflatable fender serving protection for a vessel next to a dock.

 A typical fender board. This one uses commercially available rubber end caps. Photo: Frank Lanier 

Sizing up fenders

When buying fenders, less is more and bigger is better. In other words, four properly sized fenders (the minimum number a midsized vessel should carry) are better than 10 undersized ones. Fender manufacturers often provide a selection guide, but if not, a commonly quoted “rule” recommends 1 inch of fender diameter per every 5 feet of boat length (2 inches for round fenders). That may seem like a lot, but I’ve never heard complaints about oversized fenders while trying to keep a boat off of a gnarly concrete dock during a stiff nor’easter.

If storage is an issue, look into inflatable fenders such as those offered by Easystow or AERÉ. Both companies offer large fenders that can be quickly inflated with a standard dinghy pump and deflated for easy storage when not needed.

Tie one on

Fender lines should be between 5/16 and 3/8 inches in diameter, a size that’s both easy to handle and strong enough to get the job done. Any marine-grade line will work, but avoid lines made of polypropylene, which is too slippery to be reliably tied on (and is prone to UV damage).

Secure fenders to railings or lifelines only if a lower spot (such as a cleat) is unavailable. To hang a centerline cylindrical fender horizontally, tie a half hitch or figure eight knot in the line on both sides of the fender to keep it in position.

Finally, while there are all sorts of hangers, straps, and other such doodads on the market to hang fenders, the simplest way to secure fender lines to a lifeline or rail remains a slippery clove hitch (a clove hitch finished with a slipped loop). It’s so simple to tie, reliable, can be quickly released, and costs nothing but the short time taken to learn it.

 A wooden fender board positioned on the side of a white vessel.

Photo: Frank Lanier

Fender boards

A fender board is a length of wood (typically around 4- to 6 feet long) used to protect your hull when moored alongside a pylon. It features commercially available rubber endcaps or uses attached fenders to protect the hull during use. When not in use, fender boards can be fairly easily stowed flat on deck.

A navy and white vessel next to a wooden dock with clear blue skies and green hills in the background.

Photo: Frank Lanier

Whip it!

While not fenders, mooring whips are another protection option for use at a vessel’s home dock (normally, they’re not allowed at commercial docks). These are typically a pair of long fiberglass whips (for bow and stern) mounted to the dock that keeps the boat a safe distance away while protecting it from chafe and impact damage from wakes, tide changes, waves, and wind. Mooring whips are a viable option for single-pier docks where the boat can’t be centered between two docks or an adjacent set of pilings. While effective, they’re typically not strong enough to keep your boat off a dock during major storm activity. Even while using mooring whips, have fenders in place as well.

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Author

Frank Lanier

Contributing Editor, BoatUS Magazine

Capt. Frank Lanier is a SAMS-accredited marine surveyor with over 40 years of experience in the marine and diving industries. He’s an author, public speaker, and multiple award-winning journalist whose articles on boat maintenance, repair, and seamanship appear regularly in numerous marine publications worldwide. Contact him via his YouTube channel “Everything Boats with Capt. Frank Lanier” or at captfklanier.com.