The Offshore Voyaging Reference Site

Getting Tether Length Just Right

As we have discussed at length in our Online Book on Crew Overboard Prevention, tether length is critical to a safe system, which is why I roll my own.

Too long and we up the risk of being drowned by dragging, but too short will make it impossible to sail the boat properly and/or result in an excessive number of tether changes—our system has multiple tethers that stay attached to the boat.


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Mike House

Nice approach John. Another great knot for that application is an alpine butterfly because a single knot can tune the tether to an exact length. It’s adjustable in a way that a fig 8 is not. Not a common sailing knot, but used a lot in climbing as it allows a 3 way load.

Floris Tichler

Why not use a length adjustable system like used in mountaineering. For example the Petzl „connect adjust“?

Drew Frye

Another good article.

I had custom length tethers on my cat; the 2-meter length wouldn’t reach everywhere I needed to go, and the 1-meter length was too long for the side decks. Yes, my trial tethers were all knotted, until I got the lengths right. On the other hand, the standard 1- and 2-meter legs are perfect for my trimaran … depending, of course, on how you run the jacklines and place the hard points!

I have used adjustable tethers in climbing and rope access situations. I think they are too fiddly for sailing. I also like to actually use both legs to different points in some situations, like when the bow is playing submarine

A tip for 2-leg tethers. Clip the 2-meter leg behind your back, like a belt, when not in use. This keeps it out from under foot and out of the way of grinding. Also, remember that if you clip the spare leg to the harness instead of the tether (add a small parking loop if needed) you have defeated the quick release feature; this practice was implicated in one fatality I know of.

I’m due to make or buy a new tether. The elastic in the long leg of my favorite has died. I hate buying one, when I have so many good clips. Time to re-think construction methods again. On the other hand, the Kong Double is a good value.