Natural Rope Fibres — Manila, Hemp, Sisal, Cotton, Coir & Jute Compared

Collection: Regenerative Materials | Series: Natural Ropes |

Subject: The character, chemistry and saltwater behaviour of six natural cordage fibres

The fibres worth knowing

There are six natural fibres that matter for rope on a small sailing boat: manila, hemp, sisal, cotton, coir, and jute. Each comes from a different plant, processed differently, with different chemistry, different responses to salt and moisture, and different practical characters on deck. They are not interchangeable, and the received wisdom that "natural rope" is a single category does more harm than it resolves.

I'll work through each in turn, then give a comparative table and some thoughts on which fibre suits which job aboard a working boat.

Manila

Manila — properly abaca — comes from the leaf stalks of Musa textilis, a relative of the banana grown almost exclusively in the Philippines. It is the benchmark hard fibre for marine rope, and it earned that position honestly.

The chemistry helps explain why. Manila fibre contains around 64% cellulose but carries a significantly higher proportion of lignin and natural extractives than hemp or flax — roughly 22% combined, against hemp's 13%. Lignin is hydrophobic. It resists water uptake, slows bacterial penetration, and gives the fibre a waxy surface that sheds moisture rather than absorbing it immediately. This is the source of manila's reputation for seawater tolerance, though I'd characterise it more accurately as a delay than a defence. Once the natural oils leach out — and they do, steadily, through salt cycling and UV exposure — that advantage narrows considerably.

Manila has a large central lumen in each fibre cell, which makes individual fibres more flexible than sisal and gives the finished rope a pleasant, lively hand. It floats when dry, which matters for sheets and halyards on a traditionally rigged boat. It knots well, splices cleanly, and the Handbook of Fibre Rope Technology rates it as giving excellent knot retention — better than any synthetic tested.

The weakness is that manila is not especially strong for its weight compared to hemp, and it will deteriorate if stored damp. The Marlinspike Sailor's description of old manila — soft, limp, colour faded from gold to grey — is an accurate picture of a fibre that has lost its oils and begun to rot from the inside. Treat it, dry it and store it properly, and it will last. Neglect it, and it goes faster than you'd expect.

Best for: sheets, halyards, docklines, decorative ropework, any application where good hand and moderate seawater resistance matter and the rope will be maintained.

Hemp

Hemp — Cannabis sativa — is a bast fibre extracted from the stem of the plant, produced historically across Russia, Italy, and northern Europe. It is the rope fibre of European maritime tradition, the material of standing rigging, bolt ropes, and deep-sea cables for several centuries before manila displaced it in the nineteenth century.

Chemically, hemp sits close to flax: around 77% cellulose, 9% moisture, roughly 13% combined lignin and extractives. It is finer and stronger than manila for equivalent weight, with a higher tensile modulus — meaning it stretches less under load, which historically made it the choice for standing rigging where stretch is undesirable. The Handbook notes that flax and hemp are "the most suitable natural fibres for strong, fine cordage," and by the numbers that holds up.

Hemp absorbs moisture more readily than manila on initial wetting, which contributed to its reputation as inferior in seawater — a reputation that the 1936 Atkins and Purser seawater immersion trials in Plymouth Sound largely failed to support. In heavily contaminated water, untreated hemp and manila reached zero retained strength at essentially the same rate. The difference in water uptake is real; the difference in practical rot resistance, once both fibres are thoroughly saturated in bacterially active water, is negligible. What matters far more is whether the rope has been treated, and how well it is dried and stored.

Hemp has a strong revival following in the natural materials community, partly on ecological grounds — it is a low-input crop with good carbon sequestration — and partly because quality hemp rope is again becoming available from European producers after decades of scarcity. It takes Stockholm tar exceptionally well, better than any other fibre in this list, which is why it was the traditional material for tarred standing rigging.

Best for: standing rigging on traditionally rigged vessels, bolt ropes, applications requiring low stretch and high strength, any context where the rope will be tarred or served.

Sisal

Sisal comes from the leaves of Agave sisalana, a plant native to Central America and now grown extensively in East Africa, particularly Tanzania and Kenya. It is a hard fibre, extracted and processed similarly to manila, but with a distinct chemical profile: higher cellulose content (around 77%), lower moisture, and a lignin and extractives fraction of roughly 15%.

Sisal is stronger than manila by most measures and sinks in water immediately — a consequence of its higher density and lower lumen volume. This is not a trivial point on a boat. A line that sinks is a line that can foul a propeller, and on a sailing boat under engine it is a genuine hazard that manila, which floats when dry, does not present in the same way.

The Atkins and Purser trials found that untreated sisal outlasted both hemp and manila in seawater exposure — 18% retained strength at twelve months against 0% for the others. This is sometimes cited as evidence that sisal is superior for marine use. I'd read it more carefully: 18% retained strength is still close to useless, the superiority is marginal in absolute terms, and sisal's tendency to give widely varying results under repeated bending makes it less predictable than either hemp or manila in dynamic applications. Properly treated sisal — copper resinate in coal tar held it at 80–97% strength over twelve months in the same trials — is a different proposition, and worth considering where the preservation question has been addressed properly.

Where sisal genuinely earns its place is in applications where high strength, low cost, and biodegradability matter more than seawater tolerance — agricultural use, temporary lashings, baler twine. On a sailing boat I find it most useful for short-term applications ashore or in the yard, unless it has been thoroughly treated.

Best for: temporary lashings, yard work, agricultural and utility cordage, and — when properly preserved — standing rigging on tight budgets. Less suited to permanent running rigging aboard.

Cotton

Cotton — Gossypium — is the outlier in this group. It is a seed fibre rather than a leaf or stem fibre, with around 90% cellulose and very low lignin content. The near-absence of lignin means cotton has no inherent rot resistance, absorbs water readily, and is highly vulnerable to bacterial degradation in marine conditions — the same mechanisms that destroy any untreated natural fibre at sea act on cotton faster than on any other fibre in this list.

Cotton rope has a very soft, pleasant hand — genuinely the most comfortable natural fibre to handle for extended periods — and it is the traditional choice for signal halyards, bell ropes, decorative lanyards, and any application where contact with skin matters more than structural performance. It dyes well, which is why it dominates in decorative ropework.

For anything load-bearing on a boat that will get wet, cotton requires either treatment or acceptance that it will be short-lived. Cutch and tannic acid treatments can extend cotton's life considerably, and aluminium stearate gives useful water repellency without stiffening the fibre unduly, but treated cotton in marine use is still a maintenance commitment rather than a set-and-forget solution.

Cotton does have one structural advantage: it stretches significantly before breaking, which gives it good shock absorption. In a fender lashing or a snubber, the stretch works in your favour. For running rigging the same stretch is a problem — a halyard that gives 10% under load is not a halyard you can trust to hold a sail position accurately.

Best for: decorative work, signal halyards, bell ropes, lanyards, fender lashings where shock absorption is wanted. Not for standing rigging, anchor rodes, or any permanent marine application without serious treatment and regular inspection.

Coir

Coir is the fibre of the coconut husk — the outer shell of Cocos nucifera — and it is in almost every measurable respect the weakest of the six fibres discussed here. It has low tensile strength, poor abrasion resistance, and limited durability in sustained seawater immersion. The Atkins and Purser trials showed untreated coir at 6% retained strength after twelve months, slightly better than hemp and manila only because the contaminated Plymouth Sound conditions were so severe.

None of that matters much, because coir's value aboard a boat is not in its strength. It matters for three things: buoyancy, elasticity, and price.

Coir floats exceptionally well — better than any other natural rope fibre — and it has a springy, extensible character that absorbs shock loads without transmitting them as hard jerks. These properties make it the traditional material for towing hawsers, where the rope is used in great thickness and the function is partly to absorb dynamic loads between towing vessel and tow. The Handbook of Fibre Rope Technology notes this explicitly: the breaking of a coir towing hawser could lose a ship, and properly preserved coir towing ropes in service had often deteriorated well below their rated strength without anyone knowing. Inspect coir working ropes regularly — the consequences of not doing so are disproportionate to the effort.

For fender making, coir is close to ideal. The buoyancy keeps it positioned correctly, the elasticity absorbs impact, and the texture grips the hull side rather than sliding. It is cheap enough to use in quantity, and a well-made coir rope fender will outlast a cheap foam fender with reasonable maintenance — and unlike the foam, when it finally fails it does not shed microplastic fragments into the water.

Best for: fenders, towing hawsers, temporary mooring springs where shock absorption matters more than strength, any application where buoyancy and elasticity are the primary requirements.

Jute

Jute comes from the stem of Corchorus species, grown principally in Bangladesh and India. It is a bast fibre like hemp, but lower in quality — higher lignin content gives it a brown colour and a harsh, bristly texture, and its moisture absorption is high while its rot resistance is low. The Handbook of Fibre Rope Technology categorises jute plainly as "a lower-quality fibre," and that is a fair summary.

Jute rope has almost no place aboard a sailing boat. It weakens significantly when wet, degrades quickly in marine conditions, and offers no particular advantage over hemp or sisal that would justify its use in a marine context. It appears here for completeness and because it is sometimes sold cheaply in chandleries and garden centres alongside better fibres without clear labelling. If you have bought brown, slightly scratchy natural rope without checking the label, there is a reasonable chance it is jute. It is fine for the garden. I would not rely on it at sea.

Best for: horticultural and packaging uses. Not for marine applications.

Comparative table

Fibre	Typical breaking load (3-strand, 20mm)	Seawater durability untreated	Hand	Floats?	Notable behaviour
Manila	~7 kN	Moderate	Excellent	Yes (when dry)	Loses natural oils over time; shrinks slightly when first wetted
Hemp	~9 kN	Moderate	Good	Yes (when dry)	Absorbs moisture faster than manila initially; takes tar exceptionally well
Sisal	~8 kN	Moderate–poor	Rough	No	Sinks immediately; inconsistent under repeated bending; strong when treated
Cotton	~5 kN	Poor	Excellent	No	High stretch; no inherent rot resistance; good dye uptake
Coir	~3 kN	Poor–moderate	Coarse	Yes	High elasticity; best natural shock absorber; inspect frequently
Jute	~4 kN	Very poor	Rough	No	Weakens significantly when wet; not suited to marine use

Strength figures are indicative for comparable construction and diameter. Actual values vary by manufacturer, construction type, and condition. For any structural application use manufacturer data and apply appropriate safety factors.

Which fibre for which job

The table gives the numbers. The practical summary is shorter than it looks.

For running rigging — sheets, halyards, control lines — manila is the default. It handles well, floats, and responds well to dressing and preservation. Hemp is stronger and lower-stretch but absorbs moisture faster on first contact; on a boat where the rigging will be properly tarred that moisture uptake is largely moot, and hemp is the better choice.

For standing rigging on a traditionally rigged vessel, hemp served and tarred is the historical standard and still the right answer. It is low-stretch, strong, and takes worming, parcelling and serving better than any other natural fibre. The Bushell Rigger's Guide of 1874 specifies hemp throughout for standing rigging, with wire as the newer alternative; the logic has not changed even if the materials landscape has.

For fenders, mooring snubbers, and towing, coir. The elasticity is the point. Everything else is secondary.

For decorative work, lanyards, and any application where the rope lives mostly dry and handling comfort matters most, cotton.

For temporary lashings in the yard, sisal. It is strong, cheap, and biodegradable. Do not leave it on a boat over winter expecting it to be usable in spring.

Jute: not at sea.

Sources: H.A. McKenna, J.W.S. Hearle and N. O'Hear, Handbook of Fibre Rope Technology (Woodhead Publishing, 2004). Hervey Garrett Smith, The Marlinspike Sailor (International Marine, 1971). Charles Bushell, The Rigger's Guide and Seaman's Assistant (Griffin & Co., 1874). W.R.G. Atkins and J. Purser, The Preservation of Fibre Ropes for Use in Sea-Water, Journal of the Marine Biological Association of the United Kingdom (1936).

At VAKA I design skin-on-frame sailing craft built throughout from natural materials — the rope choices aboard follow the same logic as the hull choices: honest assessment of what each material does well, and where its limits are.

Plans at VAKA Boatplans | Full knowledge base at Field Notes