Über die Autorin bzw. den Autor

John Vigor has sailed more than 15,000 ocean miles in boats 11 to 40 feet. He is the author of The Practical Mariner's Book of Knowledge and The Boatowner's Handbook.

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All sailors want to believe their boats can go anywhere and stand up to anything. Who knows when you might get caught by bad weather? It's enough to worry about your own responses without worrying about the safety of your boat. The Seaworthy Offshore Sailboat explains feature by feature how you can refit your boat for worry-free bluewater voyaging.

Take the unique diagnostic questionnaire to determine whether your boat is capable of offshore sailing, then let John Vigor show you step by step how to get there, as he covers everything from structural modifications and reinforcements to rigging, engines, systems, and gear. Whether you're planning an offshore voyage or just dreaming of one, The Seaworthy Offshore Sailboat is the perfect guide.

"An invaluable resource. Vigor's practical wisdom gives you the know-how and confidence to prepare your boat for the sea."--Cruising World

"Not only hands us practical advice in a clear format but also the hope that an offshore voyage is fully within our grasp if we are willing to follow his roadmap."--Good Old Boat

"Vigor's questionnaire offers hard-to-find, honest evaluations of whether or not a boat is bluewater capable. . . . This clear, objective reference will make fearless, prudent skippers."--Mariner

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THE SEAWORTHY Offshore Sailboat

McGraw-Hill

Contents

Chapter One

Most mass-produced sailboats are based on the coastal cruiser philosophy. Their design and construction is governed by the theory that they will not stray far from a safe port and that their owners will seldom want to be at sea for more than a couple of nights. This philosophy calls for a light, fast, stiff, weatherly boat with spacious accommodations, plenty of auxiliary power, and sufficient crewmembers to handle her.

An ocean cruiser, on the other hand, must look after herself and her shorthanded crew in all types of weather for extended periods of time far from land. This calls for sturdier construction, stronger spars and rigging, more stowage, less need for weatherliness, and more need for seakindliness. In short, an oceangoing sailboat needs to be more seaworthy than a coastal cruiser.

That statement would border on the banal were it not for the fact that seaworthiness is poorly understood and difficult to define. If seaworthiness were merely the ability to stay afloat in the worst conditions of wave and weather, then a corked bottle, an empty eggshell, or a scrap piece of plastic foam all would qualify as supremely seaworthy.

Unfortunately, that's not a practical definition for our purposes, although it does illustrate that seaworthiness has more to do with design and construction than with size. It is a fact that a good big boat is more seaworthy than a good small boat, but size alone is not a reliable indication of seaworthiness. Many very small boats, including at least one less than 6 feet (1.83 m) long, have crossed oceans. But without going to that extreme, it is safe to say that boats of 20 feet (6 m) in overall length have proved themselves seaworthy enough to sail around the world.

There are two more important characteristics of a seaworthy boat: the ability, even in extremely heavy weather, to maneuver clear of dangers such as rocks and shorelines; and habitability, the ability to accommodate human beings. And there is a very desirable third characteristic: the ability of a sailboat to right herself quickly from the upside-down position and to continue her voyage.

There is no guarantee that even the largest yachts are immune from capsize, since (according to tests carried out at Southampton University, England) they can be turned turtle by a breaking wave with a height equal to 55 percent of their overall length. Thus, a 35-foot (10.7-m) boat would be capsized through 180 degrees by a 20-foot (6-m) wave, which could be generated by a 40-knot wind blowing for about 40 hours. Even a breaking wave with a height equalling only 35 percent of the boat's length (a 12-foot wave for a 35-footer or a 3.7-meter wave for a 10.7-meter boat) will roll her 130 degrees—from which position she may recover or turn turtle. And a 12-foot (3.7-meter) wave can be generated by a 24-knot wind blowing for 24 hours. Even large ocean liners and tankers have fallen victim to freak waves off the South African Wild Coast, between Durban and East London, where the swift-flowing Agulhas Current rears up in frenzy when confronted by southwesterly gales.

Development of a plunging breaker. Because of the rapid change in the steepness of the wave, a small boat caught between stages 2 and 7 would have little or no chance of avoiding capsize.

It is prudent, in any discussion of seaworthiness, to take it for granted that a boat may be rolled upside down at some stage. The chances of this happening depend on the size of the yacht, where she is sailed, the experience of her crew, and the time of the year. Along the well-used trade wind routes during the recommended times of passage, the likelihood of capsize is extremely small. Around Cape Horn in winter, it is infinitely greater.

A seaworthy boat, therefore, is one that is:

• Able to recover from the inverted position without serious damage to her hull, deck, rig, rudder, or interior, and without shipping substantial amounts of water.

• Strong enough to look after herself while hove-to or lying ahull.

• Seakindly—that is, free of violent, extravagant, jerky rolling and pounding.

• Well balanced, docile on the helm, and easily handled under sail at all times.

• Agile downwind, to maneuver out of the way of plunging breakers.

• Able to beat to windward, or at least hold her ground, in all but the heaviest conditions.

• Habitable—able to carry ample crew with good headroom and comfort, plus water and supplies, for extended periods.

• Capable of good average speeds on long passages.

No boat can fulfill all these requirements to perfection, since many are mutually exclusive. For instance, the long keel that makes a boat hold her course well also makes her less maneuverable. The widely spread-out sail plan that helps with helm balance also makes her less efficient to windward. Everything in boat design is a matter of trade-offs. One desirable feature must be sacrificed for another. But the most successful designs spring from a kind of mysterious resonance that occurs when sacrifices, judiciously made, add up to a net gain.

The requirement for a boat to be self-righting from a capsize would also disqualify most multihulls, because they are just as stable upside down as they are standing the right way up. Although some multihulls may be able to regain their feet by methods such as flooding one hull or inflating a masthead float, this is often more difficult than it sounds—especially under the conditions likely to cause a capsize. In their favor, it can be said that, without a heavy ballast keel, multihulls will not sink; but they will not be capable of going anywhere. Even if their crews are capable of finding shelter on board, they will be totally dependent on outside help for rescue.

A properly designed and built monohull yacht, however, is capable of righting herself and continuing toward land under her own power, even if that power is a jury rig. Many have done it, some more than once. Again, the likelihood of a multihull's capsizing is small if she is in the right places at the right times: There are many well-documented accounts of catamarans and trimarans weathering prolonged storms without damage.

In the end, it boils down to making choices. Does the lack of heeling and the inherent positive flotation of a multihull compensate for the risk of remaining upside down after a capsize? Many people think so, and who can say they are wrong?

How Design Affects Seaworthiness

The yacht designer's vocabulary is full of moments, righting arms, lines of buoyancy, centers of gravity, and so forth. But simply put, two things counterbalance the overturning force of the sails: beam and keel weight.

Wide beam gives a boat initial stability—it's hard to get her started heeling.

Keel weight gives a boat ultimate stability, the ability to right herself from a 180-degree capsize. Keel weight starts to work only after the boat has begun to heel, and its maximum efficiency occurs when the keel is sticking straight out sideways. The deeper the keel and the farther it sticks out, the more effective it is.

Incidentally, the pressure of the wind in the sails, even the sudden blast of an unexpected squall, is unlikely to cause a 180-degree capsize. The sails spill wind as they become more horizontal, and the...