Shockcord, or bungee, is used on small sailboats to secure daggerboards, centerboards, hiking straps, and more. This stretchy line is useful anywhere you need give in an attachment point. Polypropylene is a floating line commonly used as a bow line on small boats such as Optimists and Lasers.
Shockcord is a unique type of line that stretches and then recovers back to the original length. The core is comprised of parallel strands of round latex rubber yielding 85% to 100% elongation and recovery, with a polyester cover. West Coast Sailing offers a high quality shockcord in a range of diameters.
Polypropylene is a thermoplastic polymer material that has a wide variety of uses. For sailors, it offers a line that is tough, flexible, and strong yet lightweight enough to float which makes this ideal for dinghies and small keel boats. It is commonly used as a dinghy tow rope, an economy dinghy mainsheet, or even as a spinnaker take down line on larger keel boats.
If you are replacing an existing line, the easiest way to determine what diameter you need is to match what you already have. This can be done with a caliper or by close estimation with a tape measure. If you've previously used a 7mm sheet and it has performed well, another 7mm line is likely a great choice. In most applications, there is some flexibility in the exact diameter that can be used. Most blocks, for example, have an 'ideal' diameter (ie, the line diameter that runs most effectively though the block's sheave) but also have a range so that you can run a slightly thinner or slightly thicker line. If you have a sheet that is getting hung up in your rig, stepping down 1-2mm might help the sheet run more efficiently. If you have a larger boat or rig and want to run a thinner sheet, consider a double braid line that features a Dyneema or spectra core for strength.
1mm = 3/64 inch | 2mm = 5/64 inch | 3mm = 1/8 inch
4mm = 5/32 inch | 5mm = 3/16 inch | 6mm = 1/4 inch
7mm = 9/32 inch | 8mm = 5/16 inch | 9mm = 3/8 inch
10mm = 25/64 in | 11mm = 7/16 in | 12mm = 1/2 in
