Choosing rope: material and size

Rope for a sailing boat: which line goes where

The lines on a sailing yacht do very different jobs. Halyards hold a sail up and should stretch as little as possible while they do it. Sheets pass through your hands and round the winch all day, so they need grip and must hold well in a clutch. Mooring lines and the anchor rode, on the other hand, are meant to give. Keep those three groups apart and you have already made the most important decision.

Low stretch matters for halyards and outhauls, because a halyard that creeps under wind pressure changes the shape of the sail. For sheets the hand comes first: too thin and it cuts into your fingers, too thick and it no longer fits the clutch or the self tailer. Control lines such as reefing lines, outhaul and traveller sit in between, and a good polyester line usually does the job.

Look at your deck gear before you buy rope. Clutches, blocks and winches are designed for a particular range of diameters, and the hardware maker states it. A line outside that range will either slip or jam, however good it is otherwise.

Mooring line size and length

For the diameter of a mooring line, many sailors go by the rope makers' charts, which are graded by boat length and weight. As a rough rule of thumb those charts often suggest around 12 to 14 millimetres for yachts of eight to ten metres and 14 to 16 millimetres for ten to twelve metres. Heavy boats and berths with a lot of surge justify going up a size.

The cleat sets the upper limit. It has to take a round turn, two or three figure of eight turns and a locking hitch. If that no longer fits, the line is too thick for that cleat, and a heavy warp that is badly made fast holds less than a slightly thinner one that sits neatly.

For length, there is another rule of thumb: bow and stern lines about one boat length, springs about one and a half. For unfamiliar harbours, locks or rafting up, carry at least one considerably longer line. You can always shorten a line in a hurry, but lengthening it means a knot that is hard to undo under load.

Dyneema on board: strengths and limits

Dyneema is the brand name of a high strength polyethylene fibre. Diameter for diameter it is far stronger than polyester, barely stretches and weighs very little. That is why it now often forms the core of halyards and turns up in strops, soft shackles and lashings, where strength for low weight counts.

Its limits are just as clear. The fibre is very slippery, many knots hold poorly or slip in it, and strength drops sharply at a knot, so Dyneema is spliced rather than knotted. It also tolerates little heat, for example from friction on a fast running winch, and it can slowly lengthen under a constant load. It is the wrong choice for mooring lines and anchor rodes, which need exactly the stretch it lacks.

In a cover and core line with a Dyneema core, the core carries the load and the polyester cover gives grip in the clutch and the hand. If the clutch only grips the cover, the cover can slide over the slick core. Make sure line and clutch suit each other, and if in doubt have splices in such lines done by a rigger.

Anchor rode: material, chain leader and length

An anchor rode ought to stretch, because it has to absorb the snatch that waves create in an anchorage. Nylon is therefore the usual choice, either three strand or eight plait, which stows neatly in the locker and hardly kinks. Polyester stretches less and is only a second choice here.

Between anchor and rope belongs a length of chain. It protects the rope from chafe on the seabed and lowers the angle of pull on the anchor so it digs in better. As a rule of thumb, use at least one boat length of chain, and more does no harm. The join between chain and rope is best spliced; a shackle with a moused pin will also do, provided it passes through the bow roller and the gypsy.

Length depends on depth. A common rule of thumb says: at least three times the depth with all chain, and at least five times with rope and a chain leader, more in wind and waves. If you plan to anchor in deep bays you need a correspondingly long rode, and that has to be thought about when you buy it.

Construction: cover, core and lay

Construction matters as much as material. Laid rope, twisted from three strands, is easy to splice by hand and stretches well, but tends to kink. Braided rope with a cover and core lies more quietly, runs better through blocks and is now the standard on deck for sheets and halyards.

When buying, read what the maker says about breaking load, stretch and intended use. The breaking load applies to a new line without knots, and both a knot and age take a noticeable share away from it. If you are torn between two sizes, choose the larger for mooring lines and anchor rodes, and for sheets the one that sits better in your hand.

Colour coded lines pay off in a manoeuvre. When every sheet, halyard and reefing line has its own colour, even a new crew finds the right one faster. It is not decoration, it stops the wrong line being let go at the wrong moment.

Frequently asked questions