Jackline Installation Tips

High on many to-do 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 last report on jacklines (see “Jackline Materials Evaluation,” PS November 2015) we try revisit the ideal materials for jacklines-webbing, rope, wire, or a combination. This follows up on a prior test (see “Sailboat Jackline Test,” PS April 2007) with a focus on how elasticity can dramatically impact the jackline’s effectiveness, and how ignoring the amount of stretch in your jackline can be dangerous to sailors.  One of the most intriguing conclusions of our current test was that although the International Sailing Federations (ISAF) takes a generalized one-size-fits-all 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, you should add both of those prior reports to your reading list.

• 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 wont 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 wont 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.