tag:blogger.com,1999:blog-5399150767029697926.post317305853667986318..comments2024-03-18T07:50:55.198-04:00Comments on Sail Delmarva: Via Ferrata Tethers--Some Good Ideas, But Not for SailingDrew Fryehttp://www.blogger.com/profile/06013965677534522281noreply@blogger.comBlogger2125tag:blogger.com,1999:blog-5399150767029697926.post-79826760353207173272013-12-25T15:48:05.355-05:002013-12-25T15:48:05.355-05:00Jacklines and energy absorption. I wrote a long po...Jacklines and energy absorption. I wrote a long post on this subject here (http://sail-delmarva.blogspot.com/2010/04/sample-calculations-for-jack-line.html). In a nut shell, there seem to be 3 points:<br />1. There are very few recorded injuries and failures related to sailors clipped to jacklines. Unless the lines are very short and made of steel cable, there is generally enough stretch in the system to control forces. Rope or webbing are fine for boats under 40 feet.<br />2. More stretch could be bad, increasing the chance of going over the side.<br />3. The greatest injury risk has proven to be getting rinsed the full length of the deck. More of a Volvo Ocean Race issue.<br /><br />How much stretch is allowable depends on deck layout. I have a catamaran and run the lines well inboard. This allows for a stretch line, which is good, because I have a big tramp which allows for long slides. On a narrow boat I would use polyester line, but probably not Amsteel; too much impact load.<br /><br />Jackline attachments need to be VERY strong as the tight rope effect multiplies forces. Even for casual sailors, the 5000-pound figure is a minimum. For larger competitive boats, 10,000 pounds is a better design value, easily managed with today's fibers; this is significantly because it is more likely for a fully crewed boat to have 2 sailors on the jackline.Drew Fryehttps://www.blogger.com/profile/06013965677534522281noreply@blogger.comtag:blogger.com,1999:blog-5399150767029697926.post-84207163068420379032013-12-25T14:36:29.867-05:002013-12-25T14:36:29.867-05:00Thanks Drew, much appreciated. Another question I...Thanks Drew, much appreciated. Another question I had was whether it would be useful to have the jack line attachments have some energy absorption capability (think rubber snubber on a rode). Happy Holidays.rwchttps://www.blogger.com/profile/02197021303656418287noreply@blogger.com