Member Gavin wants to get to the bottom of why his Spade anchor, that had served him well for six years, failed so catastrophically.
AAC contributor, engineer, and experienced sailor Eric Klem and I both got interested in:
- What the cause might have been.
- The lessons all of us can learn from this incident.
So we both followed up in the comment stream with some questions that Gavin answered promptly and well.
And then we both independently came up with some thoughts about what might have happened, which correlate well, although Eric's include a deeper engineering understanding than mine.
A big thank you to Eric for much of what follows. That said, I have built on some of the things Eric told me and in so doing could have made errors. If so, they are all mine.
I'm also hoping that both Eric and Matt come up in the comments to this article, as they so often and so generously do, to correct any engineering mistakes I have made and/or postulate different theories.
Before we get going, this is a long article at over 3000 words, and then I plan to follow up with a second on the many lessons I learned from this incident. That said, it's worth your time.
This is not just about one spectacular failure, but rather about things we can learn from this that can make us safer going forward.
Here's Gavin's original comment, lightly edited:
I am interested in opinions on my recent catastrophic failure of my SPADE anchor S160. I am particularly hoping to hear from John, and Steve Goodwin of SV Panope.
I have a 46 foot catamaran, 14 ton displacement. I have lived on my boat full-time since 2016. When I started out, I had a Spade S140. I upgraded to an S160 in 2017 in Cherbourg.
I have sailed this boat from Florida, to Newfoundland, and on to Greenland, Iceland, UK, the Baltic, the Med, the Caribbean, and across the Pacific and I am now in Fiji.
I have about 50,000 miles of ocean sailing miles logged and we anchor approximately 320 days per year.
I have been in my current anchorage now for 48 hours with lots of wind.
I am with 6 other boats. They are using Manson, Sarca, Excel, Rocna, and Delta anchors. I was using my Spade S160.
It is a very gusty anchorage with winds from different directions 10 knots gusting to 33 knots. I was anchored in sand, 3 meters depth water from sea bottom to sea surface at high tide on 20 meters (65 feet) chain, 7 meter (23 feet) nylon snubber bridle.
I had set the anchor as per my normal routine with 1800 rpm in reverse with two engines. I had checked the anchor by snorkelling and it was buried in sand.
In these sorts of conditions we have never dragged. But this time we did. My SPADE bent 90 deg where it meets the scoop (see photo above).
I snorkelled the anchorage again and confirmed there is nothing but sand. The damage occured while anchored, and not during retrieval.
I also recommend that we all read the whole thread since Gavin expands a lot on the above. (I have closed said thread to comments since it will be more useful if further discussion occurs on this article.)
Let's take this step by step: