Which sheet and halyard diameter to choose by boat size

Diameter follows hull length

The simplest guide is hull length. For halyards and sheets we recommend 8 mm on boats up to 8.5 metres, 10 mm up to 11 metres, 12 mm up to 14 metres, 14 mm up to 17 metres and 16 mm on larger yachts. Control lines, that is the kicker, outhaul, cunningham or reefing line, are thinner: 6 mm up to 11 metres, 8 mm up to 17 metres, 10 mm above that. These bands correspond to the normal loads of cruising sailboats and are the ones our Boat selector uses.

Halyards: strength and minimal stretch

For a halyard, stretch matters more than diameter. A rope with a Dyneema or Nexsteel core carries far more at the same diameter than polyester and, above all, does not stretch, so the sail keeps its shape. On racing boats this even allows going one size down and saving weight aloft. For cruising boats, however, we recommend staying within the bands above for comfortable handling and reliable holding in the stopper.

Sheets: grip comes first

You hold the sheet in your hand at every tack and lead it over the winch. So it is not only about strength but about a diameter that fits the hand well and that the winch and stopper grip reliably. Too thin a sheet cuts into the palms and slips on a self-tailing winch; too thick does not fit the stopper and runs badly through blocks. For genoa and spinnaker sheets, allow two pieces of the same diameter.

Check the hardware

Before ordering, look at the documentation of your stoppers and blocks: every stopper has a range of diameters it holds safely. If your stoppers are rated 8 to 12 mm and the boat is on the edge of a band, pick a diameter in the middle of the range. The same applies to self-tailing winches, which have a manufacturer-recommended diameter range.

When to deviate from the table

Go one size up on boats with a large sail area for their length, on heavy cruising yachts and where the crew is less experienced and comfortable grip matters more than weight. Racing crews with Dyneema ropes and boats with modern hardware designed for thinner lines can go one size down. If in doubt, contact us and we will advise for your specific model.