ROPE & CORDAGE

Dyneema Rope

Ultra-high-molecular-weight polyethylene — the strongest line by weight, with almost no stretch at all.

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.

Dyneema Rope — nautical chart line drawing

Specification

Fibre	UHMWPE (HMPE), e.g. SK78
Construction	12-strand braid, often with a cover
Specific gravity	0.97 — floats
Elongation at 20% MBL	3–5%
Wet strength loss	None
UV resistance	Poor without a cover
Abrasion resistance	Good, but heat-sensitive
Typical use	Halyards, runners, weight-critical rigging

Technical parameters

Diameter 6 mm	MBL ≈ 4,000 kg
Diameter 8 mm	MBL ≈ 6,800 kg
Diameter 10 mm	MBL ≈ 10,500 kg
Diameter 12 mm	MBL ≈ 14,500 kg
Safe working load	MBL ÷ 5, then derate for creep
Creep	Significant under sustained load

SelectLoad

Overview

Dyneema is a brand of ultra-high-molecular-weight polyethylene, abbreviated HMPE. By weight it is around fifteen times stronger than steel and roughly three times stronger than polyester, which means a line the thickness of your finger can carry a load that would need a much heavier polyester line. It also floats, because its specific gravity is below one.

Its elongation is the other headline: three to five per cent at a working load, and it barely recovers. That makes it the right choice for halyards on a racing boat, where a stretched halyard shows up immediately as a slack luff, and for any application where weight aloft or bulk matters.

The weaknesses are real. HMPE has poor resistance to sustained load — it creeps — so it should not be used where a permanent static tension must be held for months. It also has a low melting point, so a line running fast through a clutch or around a winch can heat, glaze and fail. It is slippery, which makes knots unreliable in it, and it degrades under ultraviolet light.

Safety notes

Do not hold a permanent static load on HMPE — it creeps and will slowly lengthen under a steady tension.
Never rely on a knot in Dyneema. It is too slippery; a splice, ideally a locked Brummel, is the only sound termination.
Heat kills it. A fast running line through a clutch can reach the melting point and part without warning.

Using it well

Always use a covered version where the line sees sunlight or abrasion.
Splice rather than knot, and use a class-approved splice pattern for the construction.
Set the line under load once, then re-check the splice tail before trusting it.

Suited to

HalyardsRacing riggingWeight-critical workWinch lines

Typical applications

RacingHigh loadWeight critical

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.

Related tools

Halyard

The line that hoists a sail — low stretch, spliced at both ends, sized to the winch.

Sailing & Lines Select

Eye Splice

A permanent loop spliced into the line itself — the strongest way to terminate a rope.

Knots & Splices Tie

Shackle

The universal metal connector — a bow or Dee shackle with a pin, rated by working load limit.

Rigging Hardware Select

Block & Tackle

Sheaves and rope combined into a system that trades distance for force — with friction taking its cut.

Rigging Hardware Select

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