Boat climbing gear

Jack Pare


As you plan for the next boating season, you may want to consider outfitting your vessel with some boat climbing gear.

Loop sling

Among the simplest climbing gear, the versatile loop sling began as a continuous loop of rope tied to itself with a specialized sling knot. Today the modern ultra-high molecular weight polyethylene slings made of Spectra and Dyneema are enormously strong and are joined into a continuous loop by highly engineered bar stitching. Buy them pre-made; don’t try to homebrew these.

Adequate 1-, 2- and 3-foot (circumference) slings can be had for under $10. The width in millimeters is an indicator of breaking strength; so, 9-mm Dyneema slings typically test at 4,500 to 5,000 pounds.

When tied using a Prusik knot, these slings will grip an anchor line like an angry lobster. Yet, the knot can be easily pushed along the line to make an adjustment. Pull on the middle loop of the knot, and the lobster grip returns.

Prusik knot

This slip-then-grip knot was originally developed to permit vertically ascending a climbing rope caterpillar-like by using two slings: one sling for the upper body and another sling for one or both legs. The knot is tied by looping the sling around the larger line within itself three times around.

Stainless steel locking carabiners

On a boat, it’s better to only use locking carabiners. Utility grade 304 stainless steel locking carabiners work better in a marine environment than their aircraft aluminum climbing counterparts. The screw-gate stainless ones have no carbon steel in them. Stainless is also less expensive. The aluminum locking carabiner is salt water-resistant enough, but often the spring that closes the gate is steel and can rust, making automatic closure a problem. If you already own aluminum climbing carabiners, it’s OK to use them, but you shouldn’t go buying new ones for marine use. Apply silicone or other rust resisters to each gate spring and hinge of an aluminum carabiner several times during boating season—and pay attention to the gate getting stuck.

Utility-grade carabiners can be found at hardware and home building supply stores. Adequate stainless steel carabiners cost from $10 to $25. Aluminum locking carabiners for climbing are typically $20 to $30 each. Some are priced higher.

Read the specifications. You’ll find cheap knockoffs out there for both stainless and aluminum. Don’t buy it if it tests to less than a third of your boat’s displacement. The typical 304 stainless 7-mm rod diameter tests 5,600 pounds. This pairs well with 9-mm Dyneema slings and is adequate for most boat owners.

Prusiks and carabiners as snubber or bridle

Stainless steel carabiners can be used to join a single Dyneema loop sling around an anchor chain or an anchor line to connect a snubber (to take the shock out of jerking a chain rode) and to connect a mooring bridle (to help take the swing out of lying at anchor) as seen at left.

Prusik as line strop/stopper

A single Prusik knot tied around a fully loaded jib sheet or a taut anchor line can be joined via a carabiner to another line to take the strain off a winch to transfer the sheet/anchor line to a cleat (thus freeing up the winch).

Two Prusiks in a Bahamian mooring

One carabiner can join the Prusik knots on two anchor lines to lower the junction of a Bahamian moor safely below the boat. If these anchor lines are left attached at deck level and the tide shifts, these lines just love to find their way around bulb keels and centerboards on sailboats and around propellers and spade rudders on powerboats.

Stainless steel locking carabiners for crew overboard

Locking carabiners can be used to connect a long spinnaker halyard to a crew overboard sling or to a bosun’s chair. Avoid connecting the quick-release jaw of a spinnaker shackle to the load. Connect the closed eye to the load.

Rescue pulley

Combined with a locking carabiner and Dyneema sling, rescue pulleys can be used to provide a low-friction change of direction. The climbing equivalent to a marine snatch-block, they can be opened and closed around the middle of any line.

Typical uses are to redirect a long spinnaker halyard away from the small mast-mounted winch toward the more powerful sheet winches in the cockpit of a sailboat.

This arrangement can lift a person aloft in a bosun’s chair or be used to lift a crew overboard victim out of the water with a crew overboard sling. Using a Dyneema sling and carabiner, a powerboat owner can attach the rescue pulley to a strong handrail on the flying bridge, or to an upper strut of a T-top frame to help recover someone in the water.

Aluminum rescue pulleys cost $18 to $25. You want to have a breaking strength of 4,000 pounds or more to match the slings and carabiners. These pulleys are often sized in millimeters. If your boat uses ½-inch or 7/16-inch lines, be sure to get a 12-mm pulley. A 9-mm pulley is OK for ⅜-inch lines. These pulleys generally have bronze bushings with stainless axles, making them stand up well to salt water.

Jack Pare

Jack Pare is educational officer of America’s Boating Club Portsmouth.

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The Ensign magazine is an official channel of United States Power Squadrons, America’s Boating Club, a volunteer organization whose members teach boating skills and best practices to help improve the safety of our nation’s waterways. Learn more.

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