Choosing, Knotting and Testing Cord for Field Repairs

Which knots hold a load and which ones jam?

Three knots cover most field repairs: the bowline, the figure eight on a bight, and the Prusik. Each holds a load in a different way, and each fails in a different way.

The bowline makes a fixed loop that does not slip under steady tension and unties easily after heavy loading. It is the standard choice for a loop around a stake, a tree or a pack strap. Its weakness is side loading and cyclic shaking: a bowline can work loose if the line is repeatedly jerked without tension on the standing part, so it needs a stopper knot or a backup.

The figure eight on a bight is the more secure fixed loop. It is bulkier, it consumes more cord, and it can be stubborn to untie after a hard pull, but it does not shake loose the way a bowline can. For a repair that will be loaded and unloaded many times, such as a guy line or a pack compression cord, it is the safer default.

The Prusik is a friction hitch, not a fixed loop. Wrapped around a thicker host line, it grips when loaded and slides when slack, which makes it useful for tensioning a ridgeline or improvising an adjustable tie. It holds best on cord of similar or slightly smaller diameter than the host, and it releases cleanly when the load comes off.

Knots that jam are the ones tied tight against themselves under load: the overhand, the water knot in flat webbing, and most double fisherman's variants. They hold well but may need tools to undo. That is acceptable for a permanent repair and a poor choice for anything you expect to adjust.

A short length of cord is a tool, and the way it is knotted and used is a craft in its own right. A magazine such as paracord knots and projects covers the lanyard, cobra and fishtail family in step-by-step form, which is useful background before tying anything that will carry weight.

How is cordage chosen and rated?

Cordage is chosen by material, construction and stated strength, in that order. The number printed on a package is a laboratory figure, not a field guarantee, and it applies to the cord, not to the knot.

Nylon and polyester are the two common materials. Nylon stretches more, absorbs shock better and loses strength when wet. Polyester stretches less, resists UV and water better, and holds a more predictable length. For a repair that must stay tight, polyester is usually the better pick. For anything that takes a sudden jerk, nylon's give is an advantage.

Construction matters as much as material. A kernmantle cord has a braided sheath over twisted core strands: the sheath takes abrasion, the core takes load. A solid braid is uniform throughout and tends to be more abrasion resistant but less strong for its diameter. Paracord sold as type III is commonly rated around 550 pounds, type IV higher, and the lighter types I and II much lower. Those ratings describe new, dry, undamaged cord pulled in a straight line.

Diameter is a rough guide, not a rating. Two cords of the same thickness can differ by a factor of two in strength depending on core count and material. Read the specification, or test a sample.

Every knot weakens the cord it is tied in. A bowline typically retains around 60 to 70 percent of the line's strength, a figure eight on a bight around 75 to 80 percent, and a sharp bend over a small radius can cut that further. A repair rated at 550 pounds with a bowline at each end is realistically a 350 pound assembly. Size the cord so the derated figure still exceeds the load, with margin for shock, wear and age.

Inspect before use: run the cord through your hands, look for glazing, flat spots, embedded grit and sheath damage that exposes core. Cut and discard damaged sections rather than tying around them.

How is a field repair checked before it is trusted?

A repair is checked in three stages: visual, gradual load, and observation under working load.

Visual first. Every knot should be dressed, meaning the strands are arranged so the knot sits in its intended shape with no crossed turns and no slack tail. Leave a tail of at least ten diameters beyond the knot, and more on slick or stiff cord. Look at the whole run of the cord: no sharp bends around a metal edge, no contact with a hot surface, no path where it will chafe against rock or a pack frame.

Then load it gradually. Pull the repair by hand to roughly half the expected working load and hold for a few seconds. Watch the knots: they should tighten and settle, not creep or change shape. A knot that continues to migrate under a steady pull is telling you the tail is too short or the knot is wrong for the cord.

Then load it fully, in a controlled place. If the repair is a guy line, tension it as it will be tensioned in use. If it is a pack strap, load the pack and lift it. If it is a ridgeline, hang weight on it while you stand clear. Nothing critical should be tested for the first time over a person, a fire or a drop.

After the first real use, inspect again. Look for sheath fuzz, a tail that has shortened, or a knot that has rotated. Retie rather than retighten if anything has moved.

What changes the answer in wet or cold conditions?

Wet nylon loses roughly 10 to 15 percent of its strength and stretches more, so a repair that was marginal dry becomes unreliable wet. Polyester holds up better in rain and repeated immersion. Cold makes cord stiffer, knots harder to dress and hands less able to tie them properly, which is why a repair tied in the dark at low temperature deserves a second look in daylight.

Ice and grit are the other variables. A knot loaded while frozen can cut itself as the strands shift. A knot with sand in it abrades from the inside. Rinse and retie when conditions allow.

What belongs in a repair kit?

A small kit covers most field repairs: two or three lengths of cord in different diameters, a lighter for fusing cut ends, a small knife or cutter, and a short length of tape for whipping. Fusing the end of a synthetic cord stops it fraying and takes seconds.

Carry cord slightly longer than you think you need. Knots consume length, and a repair that is too short cannot be retied. Store cord dry, out of sunlight, and inspect it before each trip rather than after a failure.