Halyards, sheets, guys and other control lines are the boats sinews, they transfer the load from the muscles to the site of the work. They hoist and trim the sails that move the boat.
There are two basic construction methods for boat line – three-strand and braided. Three-strand is used for docking and anchor lines and by traditionalists who want a classic look to their running rigging. Braided line is the mainstay of the modern boat’s running rigging.
For many years double braided polyester has been the line of choice for cruisers – it’s durable, strong and uv resistant. Easy on the hand and it knots well – a superb all-rounder.
But in this high tech racy world there is a plethora of more purpose-specific options. Because each rigging application requires a slightly different emphasis on the lines qualities – strength, flexibility, stretch and abrasion resistance – the rope manufacturers have obliged with a bewildering array of specifications.
Within the braided line category we find single braided line and double braided line. Single braided line is just that, a line comprising twelve strands of fibre woven together with no cover. This line is very flexible, quite strong with moderate stretch and abrasion resistance.
Double braids are lines with a braided core within a braided cover. They are strong, reasonably flexible, low stretch and quite resistant to abrasion. They represent the most widely used form of construction for running rigging. A variation of double braid construction is parallel core line in which the core comprises parallel fibres running all the way through the line and covered by a braided outer sleeve. These lines are a bit stiffer than double braid but have lower stretch characteristics.
Within each construction category we find different man-made fibres being used, often blended together. These include the well-known polyester and polypropylene. Then we have high modulus polyethylene such as Dyneema and Spectra which display great strength to weight ratio and low stretch. They knot poorly and have a low melting point but their great strength and low stretch make them popular on racing boats. We also have aramid fibres such as Kevlar and Technora and liquid crystal polymers such as Vectran.
These various fibres bring specific characteristics to the table which, combined with the appropriate construction method, permit the very precise selection of the right line for the job.
So, you can choose a special line for each task or, like me, you can just use double braided polyester for all your running rigging.