Posted by Darrell Nicholson with Drew Frye at 07:45AM - Comments: (13)
The “to-do” list begins to swell in October, a month when many northern hemisphere sailors start preparing their boats for offshore passages to warmer climates. High on many lists is the job of installing jacklines—the lines running along the deck to which we attach our safety tethers. Jacklines have been in use aboard ships for centuries, and materials have evolved from traditional woven hemp to braided Dyneema, a strong, stiff (high modulus) fiber that is pound-for-pound stronger than steel.
In the our recent report on jacklines, we try revisit the ideal materials for jacklines—webbing, rope, wire, or a combination. We carried out a similar comparison in 2007, but this time around we're looking more closely at how elasticity can have a dramatic impact on the jackline's effectiveness. One of the most startling conclusions of our current test was that despite the International Sailing Federation’s (ISAF) generalized approach to jackline standards, the best material for a jackline varies as boat length increases.
Material selection is just one of many details regarding jacklines that deserves careful thought. If you are re-installing your jacklines or installing for them for the first time, be sure to read our upcoming test report. In the meantime, you can read our 2007 report and review some of the following tips that came out of our ongoing jackline research.
- Although you can use existing hardware for anchoring jacklines to your deck, finding adequate anchors on light boats can be difficult, since the deck and fittings might not be very strong. Whatever hardware you use must be strongly reinforced and capable of supporting the anticipated loads.
- Confirm that the entire system is of known minimum strength. ISAF standards recommend 4,500 pounds minimum breaking strength for webbing, although we recommend more for boats greater than 40 feet in order to provide an adequate safety factor. The minimum safety factor is 2.4:1, based on dynamic loads. This means that whatever gear you use should be capable of supporting 2.4 times the amount of force generated by a falling body (or bodies), or by a person who is dragging in the water at maximum boat speed.
- Nylon stretches a great deal when it is wet, so nylon jacklines should be tensioned when wet.
- Webbing jacklines should be twisted—not laid flat. This way they are easier to clip into when wet and they won’t flap in the wind.
- Outboard-powered boats should never have jacklines or tethers so long that a sailor who has fallen overboard could be towed behind the boat near the prop.
- Jacklines should stop well short of the bow. Fast boats, multihulls in particular, can hurl a person forward when the bow stuffs into a wave.
- The cockpit should have at least one dedicated fixed point for clipping into. Consider installing dedicated clip-in points (padeyes) at other work stations—i.e. at the mast, or at the bow.
- Rope jacklines can be acceptable on boats with higher coachroofs that allow the lines to be routed off the deck where they won’t fall underfoot. Rope is more durable that most other choices, it is also easier to clip on and off with carabiners.
- When Dyneema or stainless cable are used on the deck, sheathing them in tubular webbing can reduce the chance that the jackline will roll under foot. However, some of our testers preferred exposed Dyneema because the carabineers slipped along the jackline more easily.
- Jacklines must be clearly distinguishable from running rigging, so that there is no chance of clipping into the wrong line. Color is not enough, as the typical side deck is littered with similar control lines and colors are indistinguishable in the dark.
- Jacklines should be permanently rigged during a passage. It takes time to become accustomed to their use, and sailors have often gone overboard in benign conditions.
- Jacklines should be rigged under sheets and over deck-routed control lines so that a sudden tack or jibe does not grab the tether.
- If you rely on stainless steel hardware, use only the highest quality. (Wichard is one company whose hardware has consistently done well in our tests.) During our field research we came across a 46-foot boat with very tight 3/16-inch stainless jacklines attached with 3/16-inch stainless shackles. Our tester grabbed the jackline at the centerpoint with gloved hands, gave it a maximum effort jerk, and one of the shackles exploded, the cable whipping about. Stainless-steel jacklines must be very conservatively sized to account for hidden corrosion.
For more on jacklines see our eBook Man Overboard Prevention and Recovery.