Knot & Rope Safety

Intermittent Loads and Security:

Intermittent Load: Many knots can loosen with prolonged intermittent strain. For example, a bowline just "floated undone" when Grog was swimming around scrubbing the boat's waterline; a perfectly good scrubbing brush sank before he realized it was no longer attached.

Additional Half Hitches: Mooring lines also present intermittent strains and it is wise to use additional half hitches or seizings to provide greater security. A seizing is a wrap of small line holding the bitter end against another adjacent part of the knot. Although a seizing may be very secure, it is a nuisance because it cannot be easily "untied". By contrast, it is quick and convenient to add extra half hitches, and they are commonly found on the: Round Turn & Two Half Hitches, Rolling Hitch, Anchor (Fisherman's) Bend, the Clove Hitch and, of course, the Reef (Square) Knot.

Stopper Knot: Climbers are particularly wary of the bowline especially when carried around at the end of a coil of rope. One technique they recommend is to use a stopper knot to secure the bitter end round the adjacent part of the bowline's loop.

Under Load: Four knots are valuable specifically because they can be tied and untied under load: the Round Turn & Two Half Hitches; the Cleat Hitch; the Rolling Hitch; and the Munter Mule, combination. Learn these well. By contrast, the bowline is impossible to tie or untie under load.

Safety:

Rope, and sports associated with rope, can be dangerous. Wrongly handled, gripped, or tied, rope can kill, maim, or burn. You could be the victim! Handle rope with care, inspect and test any knot you tie, and respect any rope subject to a heavy load, e.g., a rope controlling a large sail, a mooring rope when you are docking or berthing, and especially your own climbing rope.

Control

Never try to control a heavily loaded rope or fishing line with your bare hands. Take two or more turns round a post, winch, or cleat, and use appropriate equipment for fishing line. The danger associated with heavily loaded rope or fishing line is commonly learned by experience, which is often very painful and could be lethal.

Knots Weaken Rope

To repeat what we already said on the Home Page, assume that even brand new rope will perform at no more than 50% of its rated breaking strength. And, when dealing with critical loads, it is vital to understand the magnitude of a sensible Safety Factor:

Working Load or Safety Factor

The National Fire Prevention Assoc. advises the following: To lift non-critical loads, e.g., equipment, a rope's breaking strain should be seven times the load (7:1).

For live or critical loads the rope's breaking strain should be fifteen times the load (15:1). To lift an average man, a breaking strain of over a ton is indicated.