Auxiliary Sail Vessel Operations for the Aspiring Professional Sailor - Hardcover

Chase, G. Andy

Hardcover

ISBN 10: 087033493X ISBN 13: 9780870334931

Publisher: Cornell Maritime Press, 2009

Synopsis

Initially created as a course curriculum for classes in sail vessel operations at the Maine Maritime Academy, this work has been developed to provide a firm foundation for men and women working toward earning U.S. Coast Guard licenses to operate auxiliary-powered sailing yachts and vessels. The book addresses seamanship aboard sailing vessels, relevant hydrodynamic and aerodynamic theory, basic and advanced sailing maneuvers, planning and managing for crew and vessel safety, meteorology for sailors, heavy-weather sailing, emergencies at sea, and vessel administration as related to Coast Guard rules and regulations. Designed to accompany the sailor as a study guide and point of reference, the work, in both theory and practice, calls attention to the myriad constant and critical elements of professional yacht and vessel management.

About this title

About the Author

G. Andy Chase, author of Auxiliary Sail Vessel Operations for the Aspiring Professional Sailor, made his first offshore voyage from the Caribbean to Maine via Bermuda at age ten. At sixteen he worked as a deckboy on a Norwegian merchant ship on a five-month voyage that took him around the world. During that voyage he taught himself celestial navigation and developed an interest in going to sea commercially. Chase graduated from Maine Maritime Academy with a bachelor’s degree in nautical science, an unlimited third mate’s license, and a 100-ton auxiliary sail captain’s license. Over the following eight years, he sailed on a number of merchant ships and sailing vessels. In 1987, he returned to Maine Maritime Academy to teach, and took command of the schooner Bowdoin. He developed a sail-training program for the academy that quickly evolved into an ambitious northern waters sailing program. Chase is now a professor of marine transportation at Maine Maritime. He holds an unlimited master’s license for steam and motor vessels and an auxiliary sail master’s license for vessels up to 1,600 tons.

Excerpt. © Reprinted by permission. All rights reserved.

Balance

Picture a wind vane. There is an arrow with a small head and large feathers at the tail. When the wind blows it will point into the wind. Why? Because the head is small, presenting little wind resistance, catching little wind, and the tail feathers are large, presenting a great deal of wind resistance, catching a great deal of wind. The wind pressure is then greater at the tail than the head and overcomes the wind pressure at the head, blowing the tail downwind. This causes the head to point upwind. If the tail broke off, the vane would spin around and point downwind.

This simple concept must dominate every maneuver you attempt in a sail vessel, and you will do well to utilize it in powerboats as well. You must always identify where the greatest amount of wind resistance or sail force is, and what effect it is having on your vessel.

Picture your vessel sailing comfortably on a beam reach. She is a ketch, with jib, main, and mizzen set and drawing well. She is well balanced you need very little attention to the helm to maintain your course. Suddenly, without warning, the mizzen blows out and disintegrates. Before you can react, the vessel's head falls off to leeward. Why? Intuitively, you may know why, but let us look at the principles involved.

Center of Lateral Resistance and Center of Effort

The center of lateral resistance (CLR) is the pivot point of the wind vane. It is a complicated point to describe accurately, as it moves around in obedience to various hydrodynamic principles, but it is sufficient to say that it is the longitudinal, geometric center of the vessel's underwater area. The simplest way to find this is also the best way to describe it. Take a profile drawing of your vessel and with scissors cut out the underwater shape of the boat (see figure 4-4A).

This will include the hull (below the waterline), keel, and rudder. (The rudder should really count only partially, since you can manipulate it, but this will be good enough for our purposes.) Crease the cutout lengthwise, parallel to the waterline, so it is stiff enough to hold its ends out straight (fig. 4-4B). Now place the crease gently down over the head of a pin, moving the pin forward and aft until the cutout balances (fig. 4-4C). Mark that point, unfold the cutout, and draw a vertical line (perpendicular to the waterline) that passes through that point (fig. 4-4D). That is, more or less, the center of lateral resistance of the vessel. In approximate terms that is the pivot point of the vessel and is comparable to the pivot point of the wind vane.

Next, look at the sail plan and think about which sails are in front of, and which are behind, the CLR (fig. 4-5). On a ketch, the jib is out front, the mizzen out back; the main straddles it. In very approximate terms then the sail plan should balance. If the mizzen were much too big, it would act like the tail feathers of the wind vane and the boat would head up. If the jib were too big and the mizzen too small, the vessel's head would be blown off, downwind.

Suppose we let the jib carry a luff, so that it is not drawing well. The mizzen will now be having more effect than the jib. The power of the sail plan, taken as a whole, will be shifted aft. What we are now talking about is the center of effort (CE) of the sail plan. This could be found by mathematically averaging all the force vectors from all the sails and finding the one resultant force of the whole plan. But we do not need to know it so accurately. It will serve us well simply to understand that as we de-power the jib by letting it luff, we shift the CE aft, whereas if we de-power the mizzen, we shift the CE forward.

As the CE moves forward and aft (as we change the trim, or power, of each sail), we alter the balance of the vessel. If we allow the jib to luff and sheet in the mizzen, the boat heads up. This is because the CE moves aft of the CLR, creating a moment about the pivot point. The mizzen forces the vessel's stern to leeward and the slack jib allows her bow to come up into the wind. You can look at it in two ways, and you should grasp both. Letting the jib luff has taken some pressure off the bow, allowing it to head up into the wind. Or, letting the jib luff has shifted the CE aft, allowing the mizzen to take charge and forcing the stern to leeward. You may need to utilize either of these two viewpoints. If you suddenly need to get the bow to head up, slack the jib. If you need to get the stern to move to leeward, again let the jib luff. All maneuvers under sail are assisted by these moves. Maneuvering by rudder alone is inefficient and sometimes will prove to be impossible. The power of the rudder to steer can easily be overcome by the sails own power to steer.

So what happened to the vessel who blew out her mizzen? Initially, she was well balanced because her designer balanced the sail plan so that the CE was very close to the CLR. The mizzen was doing its part to maintain the overall balance, so when it blew out, the CE suddenly shifted well forward of the CLR. This produced a powerful moment which allowed the jib to take charge, blowing the bow to leeward. Simultaneously the sudden release of pressure from the mizzen allowed the stern to jump to windward. The vessel took a quick swerve to leeward.

Edition details

• Publisher: Cornell Maritime Press
• Publication date: 2009
• Language: English
• ISBN 10: 087033493X
• ISBN 13: 9780870334931
• Binding: Hardcover
• Edition number: 1
• Number of pages: 328