Saturday, 26 January 2008

Sea anchors

And drogues got me thinking about sea anchors. Also known as para-anchors they are small parachutes that function underwater and are deployed, again via a long rode, from the bows of a boat. Their function is to keep the boat head to wind and waves. They differ from drogues in that they should stop the boat in the water.

One day I may be caught out by the weather. With successive reefs, I suspect Onawind Blue can take quite a lot of wind and on small bodies of water with minimal fetch I don’t think she’d have much trouble. The Mediterranean, though not a huge body of water, virtually tide-less and often calm, can become blisteringly violent with little or no warning. The western Med can throw its entire gamut of conditions at you in one 24-hour period but luckily, unless you’re in the Gulf of Lions and the Tramontana or Mistral is blowing (or in the Straits of Gibraltar with the Levanter), nothing lasts too long.

Marauding thunderstorms roam the seas in late summer and conditions that would seriously compromise my little boat can quickly grow from nothing. What may be a fresh breeze for a 52 footer is a gale for OB. Judging from what I’ve seen while windsurfing in strong winds, and knowing that this light, narrow, shallow hull is tender, I think that somewhere around a force five the waves will get too big for Onawind Blue to continue sailing. A breaking wave will capsize a boat that is broadside to the weather if that wave is as high or higher than the boat’s beam. In our case that’s 1.2m or
4ft. Not very much.

I could heave-to or try keeping OB’s head to wind with a scrap of mizzen, she would move downwind backwards, punched about until she swamped or rolled. It would be tantamount to lying ahull, which, although once accepted as a heavy weather tactic, is now considered to be courting disaster. In the drink with strong winds and large seas we’d have trouble recovering.

Of course my primary heavy weather tactic should be to stay on the land when there’s a poor forecast and my secondary tactic should be to sail sufficiently near the coast to give me time to run for cover. But, as Web Chiles, who sailed many thousands of miles in an open, 18ft Drascombe lugger, said, ‘Land is a mixed blessing’. Meaning that many boats have been wrecked on the same shores on which they hoped to find shelter, when they may have been safer keeping to the sea. In a force five or more a dash for a beach, cove, headland or port would still be the first option, but it would depend on the beach, cove, etc. in question. In a strong winds OB’s home beach rapidly closes out with up to ten lines of surf forming and a vicious current running parallel to the shore much in the manner of a swollen river. An unfamiliar beach could bring all sorts of unquantifiable problems in the form of rocks, reefs, shorebreak and currents. A port on a lee shore can also be hazardous. The waves created by an easterly force six break across the entrance to the local marina and once the Guardia Civil, rather embrassingly (for them), were rolled while putting to sea. The boat was wrecked on the rocks but fortunately there were no casualties.

Sea anchors generally form part of the serious offshore cruiser’s heavy weather armoury and this is reflected by manufacturers who don’t make sea anchors for boats under seven metres (23ft). Obviously I’m not thinking about serious (or lighthearted) offshore cruising in Onawind Blue but if I’m lucky enough to have the time then prolonged coastal cruising is on the agenda this spring. If my destination is 10 or 15 miles away and the wind isn’t favourable I may well be beating three or four miles offshore—and I’ll admit I do like to get some distance on the land. Were the weather to deteriorate dramatically and the sea state to preclude sailing, were a dash for safety not an option, then I could only hope to sit out the weather. In this worrying scenario I could deploy a sea anchor and crouch down in the bottom of the boat with a baler in each hand, praying that the blow would be short lived. But at least knowing that Onawind Blue could reliably sit head to wind taking the waves where she’s best designed to receive them—on the bow.

Another use would be that of simply stopping at sea, to bale, to picnic, to effect a repair or to reef without losing any of that valuable ground made to windward as one does when hove-to.

But lets hope that however far a field OB and I go I always double check the weather forecasts, the signs in the sky and sea, and that I never get into a situation where I may need to use a drogue or sea anchor. But, for cruising, I still want to carry both, just in case.

Here is an interesting article on reefing small boats.

And here are some general ones about heavy weather tactics. Though they refer to
larger sailing boats the principles apply.
Fitz Henry Lane, "A Smart Blow (Rough Sea, Schooners)," 1856

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