All Rodes Lead to Where I Stand
I travelled to Victoria a few weeks ago to buy a stash of used charts for the Inside Passage, and the fellow who sold them to me recounted the story of the worst night of his life. Anchored in a cove out of the 50 knot winds in one or another strait, he found himself at the mercy of 70 knot katabatic winds -- Williwaws. As a landmass cools at night, the air cools, grows heavier, and slides down towards the water, converting potential energy to kinetic energy. His 40 foot steel sloop was sailing on her anchor, describing smiles on the chart plotter, a pendulum on a 300 foot tether, rolling through 90 degree arcs. THUNK. His anchor let go, but mercifully reset itself. More than once. Those smiles were getting closer to the lee shore, until finally when all was said and done, his margin of safety was a scant 6 feet.
I've been boning up on ground tackle ever since.
The guidebooks to the Inside Passage talk about 15 fathom anchorages in some places. Multiply that by even modest scope, and you're talking serious rodes. My 7.5 kg Bruce anchor, 20 feet of G3 chain, and 200 feet of 1/2 nylon just aren't up to this trip. Terry, my sailing partner of recent years, directed me to an article that makes a convincing argument that beyond a boatlength of chain, there is no particular advantage to all-chain rodes, which is great, as I have no windlass. Its hand-over-hand for me.
An additional argument in the analysis is that, after 8:1, increases in scope don't buy you much. But 15 fathoms is 90 feet, and I won't have more than 400 feet of scope to draw on, so in a real blow... well, it will be a long and anxious night.
The article that I'm quoting is on the Rocna Anchor site. They are in the business of selling anchors, but there is independent data that lends credence to their claims, and I drank the KoolAid. The standard Rocna anchor doesn't work with a bowsprit, so I decided on the Rocna Vulcan, a design that purports to retain the features of the Roll-bar Rocna with a configuration that fits a boat like mine.
So, today, I replaced my 7.5 KG Bruce claw anchor with a 9 KG Rocna Vulcan. I will attach 400 ft. of nylon rode, and ride the rode to a better night's sleep. Till those Williwaws make me smile.