In July 2008, Practical Sailor looked at products for docking, anchoring, or mooring in a storm. Among those mentioned was the Synergy docking line, an abrasion-resistant polyester braid with a short length of industrial-grade rubber in the core. Synergy also makes a stretchy, floating tow-rope for dinghies.
We put Synergy dock lines into use for six months on a fixed dock and during a two-week Mississippi River delivery cruise. They held up as well as similar braided lines and proved to be more convenient to use than its nearest comparison, a dock line with a rubber snubber. One drawback noted was that the woven cover was more prone to snagging than more tightly braided lines.
In controlled tests, Practicla Sailor applied a 900-pound load to a 10-foot long, half-inch Synergy line ($42.50) and observed about 15 inches of stretch. The line, which has a 9-inch length of rubber in the core, began visibly stretching at loads of about 10 pounds but returned to its original length once the load was released.
We will add the line to an upcoming line-abrasion test. For now, our preferred choice for most docking and mooring duties is good quality, three-strand nylon with chafe gear, a tough team to beat. Check out our used 3-strand nylon rope endurance test here.