Natural Fibre Rope — A Complete Guide to Choosing, Using and Preserving Rope at Sea

Collection: Field Notes - Regenerative Materials | 

Series: Natural Ropes | 

The VAKA guide to choosing, preserving, using and inspecting natural fibre rope at sea

How this began

There is a moment, familiar to anyone who has worked seriously with traditional materials, when a simple practical question opens into something considerably larger than you expected. The question I started with was this: what should I treat the standing rigging with on a small traditionally rigged sailing boat? Stockholm tar was the obvious answer. I had used it. It worked. But I wanted to understand why it worked, how well it worked relative to alternatives, and whether the ecological cost of the treatments that worked better was one I could justify.

That question led to a 1936 paper by two researchers at the Plymouth Marine Laboratory — W.R.G. Atkins and J. Purser — who had immersed natural rope in Plymouth Sound for twelve months and measured what happened to it under different preservation treatments. It led further back to a 1928 paper by Atkins alone, working on fishing nets rather than rope, accumulating the evidence base that the rope trials would eventually extend. It led to Charles Bushell's Rigger's Guide of 1874, a professional manual for naval riggers written with the precision of someone who understood that a failing shroud loses a mast and a lost mast can lose a ship. It led to Hervey Garrett Smith's Marlinspike Sailor, written for working yachtsmen in a voice that assumed intelligence and experience, mourning the passing of natural fibre while acknowledging the practical reality of synthetics in 1971. And it led to the Handbook of Fibre Rope Technology by McKenna, Hearle and O'Hear — an engineering text that provides the chemical and mechanical framework within which the older sources make complete sense.

These are the interlocutors for this series. Not sources to be cited and set aside, but books to be argued with, tested against practice, found right in some places and incomplete in others. The 1936 trials are the most useful single piece of evidence I have found for what actually happens to natural rope in seawater under different treatment conditions. They are also ninety years old, conducted on rope from suppliers who no longer exist, at a site contaminated in specific ways that may or may not represent current conditions, and published with the kind of honest methodological caveats that make them more trustworthy rather than less. Reading them carefully — which is different from mining them for convenient data points — is what this series has been trying to do.

What the Natural Fibre Rope series is

This is not a how-to guide, though it contains practical guidance throughout. It is an investigation in progress — here is what the old sources say, here is what the trials found, here is where those things agree with each other and where they do not, here is what I tried and what happened. The Compendium is where experiments that have held up long enough to be trusted will eventually be distilled into conclusions. These field notes are where that work is being done.

The investigation covers the whole life of natural rope on a small sailing boat — from choosing it, through understanding how and why it fails, to the preservation and maintenance systems that extend its useful life, to the question of when to retire it and what to do with it after. That arc is longer than it might appear, because each stage reveals something that changes how you think about the others. Understanding why natural rope fails — the four mechanisms that operate simultaneously and accelerate one another — changes what you do about preservation. Understanding the trials evidence for which treatments actually work changes which of those treatments you reach for and why. Understanding the ecological cost of the best-performing treatments changes whether you choose them at all.

The materials themselves

The starting point for any serious engagement with natural rope is knowing what you actually have. Six fibres matter for rope on a small sailing boat: manila, hemp, sisal, cotton, coir, and jute. Each has different chemistry, different mechanical character, different responses to salt and moisture. Manila's reputation for seawater tolerance has a chemical basis in its high lignin and extractives fraction — but the 1936 trials found untreated hemp and manila reaching zero retained strength at the same rate in contaminated water, which complicates the received wisdom considerably. The chemistry explains initial behaviour. The trials explain what happens over a year. Neither is the complete picture.

What the fibres are made of leads directly to how the rope is constructed — the lay, the strand geometry, the difference between three-strand and plaited, and why these things matter not just for how the rope handles but for how well it accepts treatment, how it fatigues under working loads, and whether it will hockle when coiled without attention. Construction type is decided at manufacture and cannot be changed. It is the first choice, which means it belongs at the beginning of any serious engagement with the material rather than being taken for granted.

Buying well is harder than it sounds, and the difficulty is not just about price. The hemp rope department of the firm that supplied Atkins and Purser with test rope sent them manila. The label is a starting point rather than a reliable description. What to look for — the surface character of the fibre, the consistency of the lay, what the interior reveals when a section is opened, what the rope smells like inside — is learnable, but it requires knowing that the investigation starts before you apply any treatment.

Failure and preservation

The mechanisms that destroy natural rope are not mysterious once you understand them. Bacterial cellulase activity works from outside the fibre inward, breaking cellulose chains, leaving no surface signature until the process is well advanced. Internal abrasion cuts fibres against one another under working loads, accelerated by the salt crystals that hygroscopic sodium chloride deposits throughout the bundle on every wet-dry cycle. UV radiation degrades the lignin fraction that gives the fibre its partial natural resistance. These mechanisms interact — each worsening the conditions for the others — which is why the rope that fails suddenly after appearing sound has usually arrived at that state through the combination rather than through any single cause.

The preservation response is where the old sources and the trials converge most usefully. Stockholm tar is hydrophobic, biocidal through its phenolic fraction, and lubricating — it addresses the bacterial, moisture, and abrasion mechanisms simultaneously. The trials found it retained 57% of original strength in hemp rope after twelve months in contaminated seawater against zero for the untreated control. It is not the highest performer in the evidence base, but it is the most defensible treatment that is genuinely effective, and it dries — a practical advantage over coal tar that matters for working rope in storage.

The wider range of dressings — linseed oil, tallow, beeswax, cutch, aluminium stearate, the copper and iron soaps — each has its place and its limits. The most useful distinction the trials establish is between the lubricant function and the biocidal function, which are separate requirements that the best treatments address simultaneously. A treatment that deposits a biocide without lubricating leaves the rope protected against bacteria while still cutting itself from the inside. This is not an obvious point, and I missed it on first reading the trials. It changes which treatments you choose and how you combine them.

Making an iron soap preservative is the current edge of the investigation — the attempt to close the performance gap between Stockholm tar alone and the copper-tar combinations that performed best in the trials, without introducing copper's ecological burden. The chemistry is sound, the preparation is achievable, and the preliminary results are encouraging without being conclusive. The exposure testing that will eventually give a more definite answer is ongoing.

Protection and maintenance

Worming, parcelling, and serving is the mechanical complement to the chemical preservation system — the three-stage process that fills the strand grooves that channel water into the rope core, wraps the filled surface in tarred canvas applied in the direction that prevents water penetrating between the layers, and binds the whole assembly in a tight spiral winding applied against the lay so that tension in the rope tightens the service rather than loosening it. Smith's mnemonic encodes the sequence and the directions. Bushell explains why. The directions are not convention — they follow from the geometry, and the geometry is the argument.

How rope is handled between uses turns out to matter as much as how it is treated. The storage interval is where most of the damage happens — not under working loads, but in damp lockers over winter. The salt that hygroscopic sodium chloride pulls back into a rope that was not rinsed before drying maintains internal moisture levels that support bacterial activity continuously. The rope that fails in spring is usually the rope that was put away without attention in autumn.

End treatments and seizings are where the logic of the system extends to the fittings. A cut end sealed with tar before whipping, the whipping material matched to the rope's treatment chemistry, closes the most exposed point of the rope against water ingress and the bacterial entry it enables. A throat seizing followed by a quarter seizing on a shroud eye — Bushell's standard practice — distributes the stress concentration that a single seizing would create across the combined length of both, reducing fatigue at the eye's bending point. These are not decorative details. They are the system extended to its extremities.

Grommets and strops and deadeyes complete the picture of a rig built from rope and wood rather than metal. The grommet that holds a wooden block to its spar distributes the block's working load around the full circumference of the block shell rather than concentrating it at a single bolt. The deadeye and lanyard system that tensions the shrouds allows adjustment without tools, fails gradually through visible deterioration rather than suddenly through metal fatigue, and can be made at sea from available materials. Whether these fittings belong on every small traditionally rigged boat is a genuine question — the answer depends on how the boat is used, how frequently it is rigged and de-rigged, and how much the maintenance commitment is acceptable. That question is more open than I expected when I started making deadeyes for the first time.

Knowing when to stop

Inspecting and retiring rope is perhaps the most uncertain part of the investigation, because the gap between observable condition indicators and actual retained strength is one that the trials literature does not fully bridge. The powder test, the smell test, the softness test when a suspect section is opened — these tell you that degradation has occurred and at what apparent severity. They do not tell you precisely how much strength has been lost. The Handbook is clear that retained strength in rope at any point in its service life cannot be reliably estimated from appearance alone, particularly for rope in wet service. The implication is conservative retirement criteria and systematic inspection rather than visual optimism.

Rope that has genuinely reached the end of its working life can be composted. This is not a trivial point against the background of the broader problem that conventional boating creates — tens of thousands of end-of-life GRP vessels with nowhere to go, microplastic fragmentation from synthetic rope and antifouling throughout the water column. A rope that returns to soil when it is done is a genuinely different relationship with material than the synthetic alternative offers.

Where the investigation stands

The series has reached the point where the evidence base is established, the practical methodology is in place, and the open questions are identifiable. The ecological ranking of the treatments places Stockholm tar with iron soap as the best available option that balances preservation performance against environmental impact — a position held with appropriate uncertainty until the exposure testing provides better data. The inspection methodology is a working practice that is better than what I started with and probably not finished. The deadeye question is genuinely open for boats that are frequently transported and re-rigged.

The Compendium is where the conclusions that survive this investigation will eventually live. These field notes are where they are being tested. The distinction between those two things is the difference between knowledge that has been claimed and knowledge that has been earned, and the earning is still in progress.

Sources:

 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). 

W.R.G. Atkins, The Preservation of Fishing Nets by Treatment with Copper Soaps and Other Substances, Journal of the Marine Biological Association of the United Kingdom (1928). 

H.A. McKenna, J.W.S. Hearle and N. O'Hear, Handbook of Fibre Rope Technology (Woodhead Publishing, 2004). 

Charles Bushell, The Rigger's Guide and Seaman's Assistant (Griffin & Co., 1874). Hervey Garrett Smith, The Marlinspike Sailor (International Marine, 1971).

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