ROPE & CORDAGE

Shock Cord

Elastic bungee cord for holding, tensioning and absorbing small movements — never for load-bearing duty.

INSPECT BEFORE LOAD · NEVER EXCEED WLL

Rope, splices and hardware are only as good as their condition. Inspect before every use and retire on evidence.

Shock Cord — nautical chart line drawing

Specification

Construction	Rubber filament core, braided sheath
Elongation	100–150% usable
Typical diameter	4–10 mm
UV resistance	Sheath dependent — poor once breached
Load rating	Not a rated rigging element
Typical use	Covers, gear retention, light tensioning

Technical parameters

Diameter 6 mm	Working tension ≈ 8 kg
Diameter 8 mm	Working tension ≈ 15 kg
Diameter 10 mm	Working tension ≈ 25 kg
Elongation	≈ 120% before set
Duty	Securing only — never overhead

SelectMaintain

Overview

Shock cord is a core of many thin rubber filaments inside a braided synthetic sheath. The rubber does the stretching, the sheath protects it and gives the cord its shape and colour. It will extend to roughly twice its length without damage, which makes it useful for holding covers taut, securing light gear and absorbing small movements.

It is a securing device, not a rigging element. The filaments are many small strands rather than one continuous load path, so the breaking strength is modest and the failure is progressive rather than clean. A shock cord that parts tends to do so one filament at a time, but it also tends to be under tension when it goes.

The sheath is what fails first in service. Ultraviolet light and abrasion break the braid, the filaments then see direct sun, and the cord loses its stretch long before it loses its shape. If a cord no longer retracts, the rubber has perished and the cord is done.

Safety notes

Shock cord is not rated for lifting, towing, climbing or any overhead load. Do not substitute it for a rated line.
A tensioned shock cord that releases can strike an eye. Hook ends should be taped or whipped closed.
Discard any cord whose sheath is frayed to the core — the filaments underneath are degrading from that point on.

Using it well

Cut with a hot blade so the sheath fuses and the filaments do not unravel.
Store relaxed, not stretched, or the rubber takes a set and the cord loses tension.
Use a ball or knot rather than a metal hook where the cord may whip loose.

Suited to

Boat coversGear retentionFender adjustmentLight tensioning

Typical applications

Securing gearCover tensionLight duty

Figures are typical catalogue values for new equipment, quoted for comparison and planning. They are not a guarantee for any specific product or any specific load. Always work to the manufacturer’s stated working load limit and to the regulations that apply where you sail.

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