How to Set up Fenders on Your Boat or Yacht

Setting Up Fenders On Your Boat

Marine fenders, or bumpers as some folks call them, are a necessary precaution against damage while keeping your boat or yacht docked or rafting alongside other vessels.

Below I’ll share answers to some common concerns boaters often have about fenders and docking.


What Size Fenders Do You Need For Your Boat?

The general rule of thumb is that a cylindrical fender should have 1″ of diameter (2″ for round / spherical fenders) for every 4′ to 5′ of boat length. See the sizing chart below for more specific sizing and type guidelines.

Boat Length In Feet Cylindrical Fender Diameter Round Fender Diameter Flat Fender Size
Under 10′ 3″ NR Small
10’–15′ 3″–4″ 9″ Small
15’–20′ 5″–5.5″ 12″ Small
20’–25′ 6″–6.5″ 15″ Medium
25’–35′ 8″–8.5″ 18″ Medium
35’–50′ 10.5″–12″ 21″ Large
50’–60′ 12″ 27″ Large
60’–72′ 15″–24″ 27″ Large

This is not a firm recommendation because fender size also depends on location, boat weight and conditions. Boats in waters with heavy chop or a tidal surge will need more protection than a vessel docked in a calm lake. Use this info as a good basis, but play it by ear.

When rafting with other boats, use the largest-diameter fenders you have available as different boats tied together will rock differently and have varying freeboard and hull flare.


How Many Fenders Should You Use?

A rule of thumb for how many boat fenders to use is = one fender per 10’ of waterline, with a minimum of three fenders. So a 20′ boat would need 3 fenders and a 40′ would need 4. At least one fender must be placed at maximum beam.


Should You Hang Your Fenders Vertically or Horizontally?

Based on where / how your boat will be docked, and the type of surface it will come in contact with, you’ll make the decision on whether to tie up the fenders vertically or horizontally with your dock line.

When tied up to a pier, bulkhead or floating dock, vertical placement is the easiest, most practical and preferred method of setting up your fenders. 

When tying up to a dock or pier with exposed pilings, horizontal placement is the way to go. Center the fender on the piling and tie it horizontally. 

If the waters are rough where you are docked, the space between pilings is large, or you will be leaving the boat unattended for longer than an hour or so, consider using a fender board as an alternative to horizontal placement to better protect your boat while docked under these circumstances.


How to Set Up a Fender Board

setting up a fender board

A fender board over two fenders is the best way to prevent them from slipping between the pilings and allowing your topsides to rub against the dock. A pair of cylindrical fenders placed vertically behind a two-by-four is as basic as it gets. The fenders protect the hull and the two-by-four takes the beating from the pilings.


How and Where to Hang the Fenders

Stand on your boat to correctly position the fender, adjusting its height so that it correlates with the dock or whatever else you may be protecting your boat from. For floating docks, set the fender a few inches above the surface of the water in order to prevent the dock from pushing the fenders up and out of position, and to keep it from getting gunked up.

Make sure to always place at least one fender at the widest point of your hull.

Tie fenders to a solid anchor point on your boat, such as a station or a cleat, as they have a low profile and cannot exert much leverage on the deck or the fasteners securing them. Rail stanchions are also okay to use. You want to tie fenders as low as possible on the boat. This limits swing arc, ensuring that the fender will better maintain its intended position.


Knots to Secure Your Boat Fenders

knots to secure your boat with fenders

Make sure you’re using a strong boating knot such as a cleat hitch (figure-eight) or clove hitch so your fenders will stay put on the cleat or railing.

To Tie a Cleat Hitch Knot

Step 1: Make a wrap around the base of the cleat. Begin your wrap on the edge furthest away from where the line originates.

Step 2: Make a figure 8 on the cleat. If the line is going to be under a lot of pressure, and the cleat is big enough, repeat this two or three times.

Step 3: Add a hitch to the final turn to lock it. Do this by making a loop with the tail end underneath, hook it around the cleat, and pull taut. The tail end should be pointing away from the line’s origin.


To Tie a Clove Hitch Knot


Step 1: Wrap the end of the line around the post (or whatever you’re attaching it to).

Step 2: Cross the line over itself and wrap it around the post again.

Step 3: Loosen the last wrap slightly and slip the end under, then pull it taut. This is a way of “locking” the knot.

Step 4: Give it a few tugs to make sure it’s secure.


Megafend Boat and Yacht Fenders

We carry Megafend boat and yacht fenders. Light-in-weight, easily inflated, and easily stowed in minimal space, Megafend’s EDW Extreme Duty Welded inflatable fenders are made with designed-in performance that can only be achieved by Megafend’s state-of-the-art, all-welded seam and end cap construction. Extremely tough and durable. You can find Megafend Marine Fenders, here. Free US Shipping.

Any questions or comments regarding fenders, we’re here!

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3300 NW 112th Ave, #4
Doral, FL 33172
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