What are typical purchase systems for the IC control lines?
Purchase systems vary in purchase power and arrangement. I like to cascade the purchase whenever possible. This practice minimizes weight, hardware and friction. Most boom vang systems use an 8:1 with a 4:1 cascading to a 2:1. You could also use a 2:1 to a 2:1 to a final 2:1 cascade to get 8:1. I have seen 12:1 vang systems, but I don’t think anything more than an 8:1 is really necessary. Cunningham systems are usually 2:1, but I prefer a 4:1 system to give precise finger-tip control. The forestay purchase should be at least 4:1 and preferably 6:1. The increased purchase puts less tension on the cleat holding the forestay. Under mainsheet tension, the forestay can get to over 300 pounds and I have seen poorly designed 2:1 forestays slip through the cleat. A 6:1 forestay also lets you make fine adjustments more easily. Outhauls are usually 2:1 and I would recommend 2:1 or 3:1.
