What is a sea anchor

Myboatplans 518 Boat Plans

Build Your Own Boat

Get Instant Access

he concept of a sea anchor for small vessels in storms is as old as seafaring itself.

The idea seems to have come from the notion that if all else fails, the crew can tie a bundle of oars, masts, poles, awning battens, and anything that's handy on deck to the end of a long line. Then if the people on board toss this collection of odds and ends over the side and lead the line to the bow, the boat, being larger and with more wind resistance, will blow downwind faster than the sea anchor. The floating sea anchor will tend to hold the narrow bow of the vessel up into the wind. The idea is that the whole procession will then slowly drift downwind directly in-line with the axis of the storm.

In theory, if the smooth and streamlined bow is headed into the wind and is held in this position by the sea anchor, the boat will be set up in the best possible manner to ride out the storm. The efficiency of this scheme depends on the drag of the sea anchor, which is just awash or a little below the surface.

As far as I can find out, the use of sea anchors on yachts and fishing boats in modern times is largely due to a book written by Captain J. C. Voss in 1913. Voss was a professional Canadian sailor who in 1901, when he was 47, took one crewman and spent a little over 3 years sailing a small boat from Victoria, British Columbia, west-about to England, three-quarters of the way around the world.27

Voss's vessel was a long, slim, decked-over log canoe (with slightly built-up topsides and a cabin) named Tilikum that was driven by a small three-masted gaff rig with a total sail area of just 230 square feet. (The four sails ranged in size from only 39 to 79 square feet.) The boat was 38 feet long (including the figurehead); her beam was an

Tilikum Boat
The jaunty Tilikum in Apia, Western Samoa, in 1901, with Captain Voss at the tiller. It had four very small sails.

ultra-skinny 5 feet 6 inches, and she drew just 2 feet. Tilikum was hacked out of a red cedar log, stiffened with oak frames, floors, and a keelson. She was ballasted with 1,700 pounds of sandbags and lead.

During his trip, Voss dealt with gales by tossing out a cone-shaped canvas sea anchor (22 inches in diameter with a bag 4 feet long) from the bow of Tilikum and striking all sail except for a small riding sail hoisted astern. According to Voss's book, Tilikum lay nicely with her head to the wind and stayed within a range of 21/2 points (28 degrees) of the wind's direction. Meanwhile the Canadian captain and his crewman went below to rest and smoke their pipes.

Tilikum lay successfully to her sea anchor dozens of times during the voyage. Much has been made of Voss's technique, and his name is always brought up when sea anchors are mentioned to prove how good they are. Unfortunately this argument is quite specious today because the designs of modern sailing yachts—whether long-keeled or with a fin keel—are completely different from the shallow-draft, narrow-beamed, low-rigged Tilikum of a century ago.

Voss's boat had the hull form of a canoe or a lifeboat, which have the same windage and draft forward as aft, whereas the hulls of practically all modern high-performance yachts are significantly different. Today's boats have (1) more underwater area aft than forward, and (2) their tall rigs have greater windage forward than aft. The combination of (1) and (2) tends to turn a boat at right angles to the wind and exposes her vulnerable

Rnli Sailing Lifeboat
Tilikum had a long straight shallow hull form topped by a small sail plan. Her windward performance was poor, but according to researcher Nicol Warn (who made this fine drawing) she could reel offlOO to 150 miles per day in a moderate sailing breeze off the wind.

side to the fury of a storm. This is about the same orientation as when lying a-hull, as discussed in Chapter 6, only we're now considering storm management in stronger winds.

Captain Voss's concept and rules were useful for the yachts and long-hulled sealing schooners of his era, but in the 21st century the designs of our sailing yachts are quite different.

W. A. Robinson, another sailor of vast experience, points out that Voss unwittingly gives innumerable arguments against sea anchors, which a careful analysis of the latter part of his book will reveal: "Not the least of these is the fact that after all his experience with Tilikum—which never met the ultimate storm—he was unable to provide a sea-anchor that would stand up when he finally did meet it years later in Sea Queen, a yacht of only 19 feet water-line."28

The authority Eric Hiscock agrees that Voss's Tilikum, with her balanced hull form and windage and a small riding sail at the stern, will ride well to a sea anchor.

"A normal [modern] yacht," writes Hiscock, "drawing more water aft than she does forward, and having greater windage forward than she has aft, will not lie like that. No matter how large the sea-anchor, she is bound to make sternway; her bow, having less grip than her stern on the still, deep water, is more affected by the wind, breaking crests

The 2006Swedish Malo designed by Hans Leander. A typical modern design with three times the draft of Tilikum. With no sails up, this yacht will turn away from the wind, pivoting on her underbody because of the resistance of the mast and forward rigging.

and surface drift, so that it falls off to leeward; the hull pivots on its heel, and eventually [the boat] takes up a position more or less beam on to wind and sea, just as it will when lying a-hull. If a riding sail is set aft and sheeted flat, the position may be improved, but even then the yacht will not lie head to wind, though she may come up occasionally and fall off on the other tack, the sail flogging dreadfully at times, and the strain on the rudder caused by sternway being great."29

Sailors can help their cause by setting a small riding sail on a mizzenmast, or they can hoist a tiny storm jib immediately forward of the mainmast backstay to help turn the ship's head toward the wind. But if the ship's heading changes with passing seas, such a sail may flog itself to death while the noise threatens the crew's sanity.

Earl Hinz suggests a better idea: a wedge-shaped riding sail that will always exert some sideways force no matter how the yacht moves in relation to the wind. The head of this small sail can be held in place with a shackle around the backstay and hoisted with the main halyard. The tack can be secured to the main boom or fittings in the cockpit or on the coachroof. The port and starboard clews of the V-shaped sail can be held apart with a boathook or a scrap of wood. Two short lines from the clews downward to aft mooring cleats or elsewhere complete the job.30

small, flat-cut riding sail backstay downhaul to keep tension on leech

Sailing Lateral Winds

This scheme for a storm-riding sail employs a single small sail. In strong winds the problem is to keep the sail from flogging and destroying itself. It may be useful to reinforce the luffwith nylon tape and to use two sheets. Area? Take three-quarters of the length of the yacht and use this number as the square footage. This means 38 square feet for a single sail for a 50-footer, etc. For a V-shaped sail, double the figures.

small, flat-cut riding sail shackles instead of hanks backstay downhaul to keep tension on leech

This scheme for a storm-riding sail employs a single small sail. In strong winds the problem is to keep the sail from flogging and destroying itself. It may be useful to reinforce the luffwith nylon tape and to use two sheets. Area? Take three-quarters of the length of the yacht and use this number as the square footage. This means 38 square feet for a single sail for a 50-footer, etc. For a V-shaped sail, double the figures.

In New Zealand, the firm of W. A. Coppins in Motueka has sold large numbers of these wedge-shaped riding sales to commercial squid fishing boats. "The sails are set at 30 to 40 degrees to the centerline of the boat," says Bill Coppins. "The two sails create a wedge shape that kicks the boat back into the wind as soon as the vessel wants to point off."

John Armitage wrote me about a wedge-shaped riding sail that he made in Norway for his 38-foot sloop in 1979. "I first tried using an ordinary storm jib," says John, "but

idealized alignment practical alignment alignment with riding sail

Modern yachts lying to a cone-shaped fabric sea anchor. Left: The optimum position, head to wind, is seldom achieved. Middle: Normally a sailing yacht will take up a position at 70 degrees or so to the wind. This puts the vessel in a poor position relative to waves. Right: The addition ofa riding sail improves the angle, but the yacht is still vulnerable. The small sail at the stern has a hard life in strong winds as the boat dances around on passing seas.

found that it slammed badly when the wind went from one side to the other. The sail shook the whole boat. Really bad. Overall, it seemed worse than no riding sail at all.

"Then I noticed that the Norwegian fishing boat riding sails were built like a V-shaped wedge, with the sharp edge of the V into the wind. I sewed a V-wedge sail of heavy sailcloth with strong edge taping. I hoisted this little sail with its V-luff—stiffened to be about 2 inches broad—low on the backstay, with the two clews leading outboard to the port and starboard quarters. I used a generous roach on the leeches and feet. When I tightened everything, the little sail sat there in all winds without a twitch. The slamming was gone and my new riding sail made a miraculous reduction in sheering back

Anchor Riding Sail

An alternative to the Hinz sail (above) might be to construct a riding sail entirely ofthin plywood with the blades held in position with a wooden crosspiece. The plywood sail could be hoisted and kept in position the same way as the Dacron sail in the illustration. The wooden sail would be cheaper than a cloth sail, more durable, and when not in use could be knocked down and stored flat in a locker. In an emergency, extra plywood could be a godsend.

An alternative to the Hinz sail (above) might be to construct a riding sail entirely ofthin plywood with the blades held in position with a wooden crosspiece. The plywood sail could be hoisted and kept in position the same way as the Dacron sail in the illustration. The wooden sail would be cheaper than a cloth sail, more durable, and when not in use could be knocked down and stored flat in a locker. In an emergency, extra plywood could be a godsend.

and forth at anchor in gusty winds. The sail not only reduced the load on the anchoring system, but it made the entire ride much calmer and less worrisome."

Fishing boats, motor vessels, and multihull sailing yachts that have long straight keels present more balanced hulls to the sea and have a greater chance of heading into the wind and waves, particularly if they use a bridle with a parachute sea anchor. Earlier I mentioned that more than half of a modern sailboat's lateral area below the water is aft of amidships, particularly when you consider the rudder.

Additionally, a sailing yacht has lots of windage up forward because of her single forward-located mast (sloop or cutter) and bulky roller-furled jib at the bow, something that 90% of sailboats carry today. The combination of the aft keel area and forward windage combine to turn the sailing yacht away from the wind. This exposes the vulnerable sides of the yacht to a breaking wave.

"Then," writes the veteran Maurice Griffiths, the long-time editor of Yachting Monthly, "the merry, sparkling sea—which tops the scales at 64 pounds for each cubic foot, or 35 cubic feet to the ton—can be about as friendly as a ton of wet concrete when it chooses to break over a small vessel."31

"This is exactly what happened to me during a violent Pacific storm," said New Zealand sailor Ross Norgrove when I saw him in Tortola in 1985 and talked with him about his experiences with the sea anchor that he deployed from his 11-ton sailboat

John Armitage's Hale Kai in Norway showing the V-shaped riding sail he devised after talking with local fishermen. Although John speaks of hoisting the riding sail on the ship's backstay, this photograph shows the head raised by the main halyard and the tack of the sail held in position by a line to the mast.

John Armitage's Hale Kai in Norway showing the V-shaped riding sail he devised after talking with local fishermen. Although John speaks of hoisting the riding sail on the ship's backstay, this photograph shows the head raised by the main halyard and the tack of the sail held in position by a line to the mast.

White Squall. "As soon as we streamed the sea anchor at the bow, the yawl turned sideways and I knew it was a disaster."

Since today's typical long-distance cruising yacht is 42 or 43 feet long, a suitable conical sea anchor would have a mouth about 30 inches in diameter and a bag 5 feet long. It would be made of heavy Dacron, and the mouth would be supported by a stainless steel ring hinged for folding so the sea anchor could be collapsed for stowage. Six or eight small lines would be spliced around the circumference of the metal ring and led to a heavy thimble to take the line from the boat.

Today's experts who have read over the last page say that Ross Norgrove's problem was certainly caused by using a V-shaped conical bag that was much too small. The companies that deal in these devices make their sea anchors of large parachute designs. For a sailing yacht 42 to 43 feet long, they recommend diameters from 12 to 18 feet— far greater than the Voss model.

This sea anchor would probably have a small float on a short line attached to the metal ring at the front of the parachute (where the shroud lines collect) to keep the

Jangkar Apung

2" opening at point

1/4" dia. s/s hinge pin to allow ring to collapse for stowage bag 60" long., made of 9-10 oz. Dacron

2" opening at point

Voss-type fabric sea anchor with hinged metal ring that collapses for storage.

device from sinking. In addition there might be a light floating trip line and small buoy tied to the far end of the parachute canopy to help with recovery after the storm.

Although the latest marine catalogs are filled with seemingly unlimited offerings, you won't find a sea anchor of the Voss type shown above. These days there are better control techniques—parachutes and drogues—for yachts and fishing boats caught out in horrendous storms.

Which scheme is better? Or are they both good? Read on.

Was this article helpful?

0 0
How To Have A Perfect Boating Experience

How To Have A Perfect Boating Experience

Lets start by identifying what exactly certain boats are. Sometimes the terminology can get lost on beginners, so well look at some of the most common boats and what theyre called. These boats are exactly what the name implies. They are meant to be used for fishing. Most fishing boats are powered by outboard motors, and many also have a trolling motor mounted on the bow. Bass boats can be made of aluminium or fibreglass.

Get My Free Ebook


Post a comment