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The video at the bottom of this post shows the Mod 1 version of the jackline / tether system that I have been thinking through. Before watching it, you may wish to review this post for background.


  1. Key design consideration is to prevent the person that is clipped in from hitting the water. While I have yet to test this by actually hanging overboard, I believe that the objective is met in all but one or two spots.
  2. The line being used for the jackline in the video is just an old sheet that I found on board. It is just for planning purposes. The actual material that we will use has yet to be determined.
  3. The tethers shown are climbing slings. Again, used only for planning purposes to work out the length.
  4. I chose to fix the jacklines at the mast to minimize overall stretch, and keep them close to the center line of the boat. While this does necessitate a tether change to go forward to the bow, I believe that the number of times this would be required (when sailing on a boat with a roller furling headsail) is much less than the times required to go to the mast to reef, etc. It is a worthwhile tradeoff IMO.
  5. I opted to use a remote tether at the mast instead of a two-part tether.
  6. While it may have appeared to be cumbersome to make the switch at the mast, this was the first time that Rebecca had run through it, and the tethers being used were just improvised from climbing slings and carabiners. I’m confident that with practice, using the finished product, the result would be much more streamlined.

Working out a jackline / tether system for Frost. Key requirement is to prevent the person who is clipped in from hitting the water. I think this does a pretty good job of it.

Posted by Zero to Cruising on Tuesday, December 15, 2015

In just a few minutes, Rebecca and I will be heading off to hike to one of Grenada’s many waterfalls. Feel free to add your thoughts to this post while we’re out getting sweaty and muddy.


  1. The jacklines look good, but why not use a shorter tether?

    Ideally, it would always keep you on deck. Hanging over the side and banging against the hull, even if not in the water, is still beyond reasonable recovery without injury in rough seas.

    I use two tethers – short and less short. In reality I only use the short tether because things need to be taken care of at the mast or bow, never at the toerail – at least not yet.

    Either way, it’s still a huge improvement, and you can always use the jackline like a handrail while walking along the coachroof.

  2. It might just be my computer but I am not seeing the video.

  3. Thanks for sharing this info, and we look forward to reading about the materials you choose. We’re new to all of this and your set-up looks great! I really don’t want a MOB!

  4. Have looked at any fall protection companies. I think Miller Fall Protection has information to help you calculate the forces you need to address. This will ensure the product you choose is strong enough to withstand the forces you potentially will apply.

  5. Oh yeah, use two (2) tethers or lanyards that way you’ll always be tied off when you’re unclipping from one area/line you can already be clipped to another.

  6. I doubt you’ll need the jack-lines when your little cockpit tent is up, so we should disregard any gymnastics necessary to get in/out of the cockpit. I think the tether should be shorter. There will be times when you’ll want to crawl on your “hands and knees” to get to the pulpit. I’m also questioning the need for a tether on each side of the boat. Could you possibly get by with just one down the middle? On the other hand, I think I prefer shorter runs, where you have to re-hook, to long runs – because there is much less stretch in the jack-line, stretch that could have you over the side….

  7. A few thoughts, recognizing that we are looking at trail rigging:

    * One reason for 2 lines is that if there are 2 people up front (could happen) a single line will be structurally overloaded. Additionally, if there are 2 up front and one needs to go back, if they are on a single line they are sharing a single “track.” Having 2 close together is an elegant way to avoid both problems.

    * I like rope. It is a better handhold and it can be rigged full time. It does not appear to be underfoot.

    * Polyester is a fine material choice for those short runs. Remember that ultra low stretch materials will put fierce loads on the anchor points. Thus the hard top part cannot be an ultra low stretch material (a fall would damage the hard top).

    * I don’t know what the forward anchor point is, but I would not use the bow cleat. If these are rigged full time, that would get in the way. I would probably end them ~ 4′ aft of the bow; if you need to clip further forward, either have a separate short tether or second leg, and clip something like the pulpit.

    * I like the Kong Trango biners. Very easy to clip and will open wide enough to clip railings. They do require regular lubrication to prevent corrosion, but that has not been a problem yet.

    * Harness fit is always a question. The ONLY place you want to take a hit is up under the armpits. Anywhere else is looking for separated or broken ribs. Hanging from any other location causes suffocation. Without leg loops, no matter how fit your shoulders, you can still wiggle out under load; I do 3 sets of 15 weighted dead hang pulls as part of my climbing training, and I can still worm out of any harness fit I could tolerate all day. But comfort matters. to make matters worse, the strap on an inflatable PFD is even lower because of it’s function as a PFD. A puzzlement for which I have no answer. Personally I feel safer in a well-fitted harness than a poorly fitted PFD (all PFDs are poor harnesses IMHO), since I doubt anyone is coming back for me soon enough to matter.

    Overall, I love the concept.

    • PS: I also meant to add the note about crotch straps. If you are going to wear a harness, then you NEED and WANT crotch straps. Regards

      • I understand the purpose of crotch straps, I have taken thousands of rock climbing falls on both seat harnesses and swami belts so I know about falling… I do not wear them sailing.

        Comfort matters, and the ONLY way you will fall out of a chest harness is if you raise your arms. Never, never, never raise your arms when being lifted by a horse collar or Lifesling. Rescue crews tell people that and they have learned that people never listen (they instinctively grab the rope). Thus, for any lift the crews must fit the person with a harness or lift with them.

        Keep your elbows down!

  8. This may be too complex:

    When you mentioned using a sheet for the jackline, I got turned sideways and thought – what about combining a jackline and tether with a halyard? The objective is to stay out of the water, and a halyard would do exactly that, even if you were to fall.

    Here’s the whole thought.

    I’ve thought of tethering to both the jackline and to the lifelines / pulpit/pushpit with adjustable-length tethers in order to help keep a more secure position. In addition to that (like I said, this may be too complex or even overkill, a free halyard with both ends fed back to your harness would allow you to adjust your vertical position and also to keep from getting hung out over (or under) the lifelines. You’d need to adjust the halyard length as you went fore and aft.

    Just an idea…

    • I tried that once–I was writing an article and someone suggested it.

      *If tight it can easily pull you off your feet. If the boat is heeling that will really suck. Not as bad as dragging beside the boat, but close (you probably will be part in the water–consider the geometry of a leaning boat–and hanging from a harness can easily cause suffocation in a few minutes).
      * If loose it will get wrapped around the spreaders, if there is enough seaway that you needed it in the first place.
      * Someone needs to continuously adjust the slack.

      Like I said, I tried it. Your mileage may differ,

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