The Offshore Voyaging Reference Site

Q&A: How To Design A Shorefast System

We have now replaced this article with three in depth chapters in our Anchoring Online Book on shorefast gear and use. Membership required.

Question: We’re about to build a shoreline system. We have two reels from Easyroll that can take about 150 m of 12 mm line each. I’ve seen the system used by Polaris, and it looks very solid, but my concern is, obviously, the cost of using Dyneema [Spectra].

As far as I can see the only alternative to Dyneema will be polyamide [Nylon]  lines, less cost, but also by far less strength. 12 mm gives about 3,4 metric tones breaking load, versus 10 mm Dyneema with 9 tons.

  • How strong (breaking load) should a shoreline be to be sufficient to suit our 20 ton boat?
  • What kind of, and how much shore line do you guys carry?
  • Are they often used (normal anchorage situations during cruising season)?
  • If you were about to make a system, like we are, which system would you choose, money taken into consideration?

Answer: Let’s start with our shorefast usage and then move on to our system on Morgan’s Cloud.

Despite the amount of information about shorefasts on this site—put “shorefast” in the Google Search box (above right) and you will see what I mean—we don’t use shorefasts ourselves very often at all, perhaps once or twice a season. Our reasons are:

  1. We have an oversized 55 kg (120 lb) SPADE anchor that we have huge confidence in that sets in almost any bottom type, so we  don’t feel the need for shorefasts to replace or backup the anchor.
  2. We don’t like to anchor really close to the shore since such positioning would give us very little time and space to manoeuvre if anything went wrong. In fact, if we are expecting a really nasty blow, we often look for a larger anchorage than many people might choose, say half to a quarter mile across, and anchor well off the shore—it’s not the sea that kills sailors (and boats) but the hard bits around the edges.
  3. Shorefasts prevent the boat from swinging to face the wind, which puts huge strains on the shorefasts themselves and any anchor that’s down.

Having said that, there are times when only a shorefast(s) will do: Usually when the only available anchorage, like the one above in East Greenland, is too small to safely anchor in, or we are trying to get into very shallow water in the high latitudes to get away from ice. Incidentally, shorefasts can be a real pain if there is any ice drifting around since it tends to get hung up on the lines, producing truly frightening loads.

Our shorefast system consists of one 300 foot (91 meter) length of 1/2 inch (about 12 mm) Spectra single braid and a further 900 feet of 7/8 inch (22 mm) Nylon single braid in three lengths that double as secondary anchor rode(s) and for streaming a Galerider drogue.

All the lines have thimbles spliced into both ends so that they can be joined using shackles—knots would reduce the strength of the rope too much and will slip in Spectra—or be shackled to the two 50 foot (15 meter) 7/16 inch (11 mm) stainless steel wires with soft eyes spliced into each end that we use to go around boulders on the shore.

All of the lines are kept flaked, never coiled since that will cause tangles, in bags. The bags work fine, although line reels would be more convenient. However, we don’t like the clutter of reels, and since we don’t use shorefasts that often, bags are a good compromise.

In all our years of cruising we have always been able to get secure with this system, although there was one time when every dock line on the boat got co-opted as well; however,  that was when we were still anchoring with a CQR, which was, as usual in the high latitudes in our experience, refusing to set properly.

We plan to replace one of the Nylon lines with a second Spectra line simply because my aging back is starting to object to dragging over a hundred pounds of wet Nylon rope around. The Spectra will, as you point out, cost a bundle, but less than a back operation!

By the way, you can reduce the cost dramatically by sourcing Spectra or Dyneema from a commercial supply house rather than a yacht shop. We got ours from Machovec and they even custom dyed the rope high visibility red and spliced it for us.

As to a recommendation on the appropriate strength for shorefast lines, it’s hard to be precise. But given that the loads can be huge when the boat is caught on the beam by storm force winds—as was graphically brought home to us on Polaris last winter when we had winds gusting to well in excess of 50 knots on the beam—and the penalty for a shorefast failure close to land may be loss of the boat, we have sized our entire system for our 52,000 pound (23 metric ton) boat for a minimum break-load of  17,000 pounds (8 metric tons), including the shackles.

Your boat is a bit lighter than ours, but unless you can come up with some really good engineering to support it, I would not want a shorefast system that was much lighter, in relation to the boat’s weight and windage, than ours.

If you have a shorefast system that works well for you, or any other thoughts on the subject, please leave a comment. We would be particularly interested in hearing from any reader with an engineering background that could make a stab at calculating the loads on a shorefast with the boat caught abeam in storm-force winds.

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