“Over-sized” Anchor?

by · January 27, 2016

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Excerpted from Anchoring: A Ground Tackler’s Apprentice by Rudy and Jill Sechez

How conservative one should be when computing the load on the ground tackle is a personal decision. At one end of the spectrum would be day sailing in a small, limited area and only in pleasant conditions and where well-protected anchorages or ready access to mooring or a slip are plentiful. At the other end of the spectrum is a boat which spends every night at anchor in widely differing locations, wherein the anchorages are quite varied in protection, high winds may occur, and many, if not all, of these additional load factors may be encountered.

Fortunately, there is one rule that reigns supreme—those who “oversize” their gear, seldom have the problems which often plague those who don’t. But first, stop and think about he term “over-sized” for a moment—if the gear did not bend or break or if the anchor did not drag, is the gear really “over-sized”? Since the term “over-sized” often imparts a negative connotation, maybe we should, instead, start using the term “big enough.”

So you see, the loads on ground tackle, even for modestly sized boats, can be huge. So, when loads like this are anticipated, it is no wonder that the use of big, hefty gear comes highly recommended. If the boat can be located so as to not receive the full force of the wind or surge, so much the better, though it should not be depended upon that this can always be arranged.

Have you been wondering why that anchor, mentioned at the beginning of this chapter, bent? This anchor had dug in so deep that it could not come around sufficiently to stay “in-line,” as the boat changed direction, thus had a side load imposed on it. This anchor had a tensile strength that was more than adequate in straight-line pull, but as we discovered, it did not have the strength that it needed when when the boat veered and a side load developed on the anchor; thus it bent. Since bent anchors are not reliable anchors, we immediately switched to using a different anchor. Eventually we were able to return that anchor into service, but only after it was straightened back to its original shape…however, this anecdote does not end here.

For years we had been seeing reference to the idiosyncrasy for items to bend or break with less force when side-loaded than what it takes for them to bend or break in straight-line pull. Thus, about a year later we had an epiphany while perusing a tensile strength chart provided by the manufacturer for this, as well as other size of anchors. We noticed that the anchor one size up had more than twice the tensile strength than the anchor we had been using.

It was at this point it dawned on us that this idiosyncrasy of things to bend or break with less load when side-loaded can easily be overcome simply by up-sizing that piece of gear. Once the implications of this simple alternative sunk in, we replaced the now know-to-be-too-weak main bower with another anchor, one of the same design, only bigger, one strong enough to resist the side loads our boat can impose on the anchor in 60-knot winds.

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