LESSONS LEARNED WHILE CRUISING Jamie & Behan Gifford

Simple Machines

What cruisers should know about levers, pulleys, wheel and axles and screws.

To less salty sailors and shore birds

alike, sailing vernacular must seem absurd. String together a group of nautical words, add inflection, and dash it with a four letter word and those who master sailor-speak can wield leverage on board any boat. For example, “Ease the vang to twist the roach,” or “The damn lazy guy is wrapped around the sheet,” is meaningless, confusing, or even intimidating if one is insecure in this parlance. Perhaps the power of language is unique to sailing because I’ve never felt nervously naïve when a knitter bellows out, “Damn, I’ve dropped a stitch,” despite my never finding a single stitch on the floor. For many reasons, knowing sailor-

speak is essential to cruising but it takes awhile to learn and that’s alright. After all, a sailboat is a very complex machine evolved over centuries with much of the terminology rooted in that history. The genius of technology continually adds new lingo, such as broadband radar and personal locator beacon (PLB). Keeping up with technology or not is a personal choice, but all sailors will do well to understand the non-wired, old world genius of “simple machines”. There are four types of simple

machines commonly found on every sailboat: lever, pulley, wheel and axle, and screw. So many examples exist aboard that you could say a sailboat exists only as a collection of simple machines. Many simple machines on board are

intentional devices designed to make sailors stronger. A steering system is a great example of mechanical muscle

48° NORTH, JUNE 2010 PAGE 40

using a wheel and axle. The rudder post is an axle and the tiller or quadrant and steering wheel create the mechanical advantage. To truly appreciate the affect, try to steer while holding the tiller near the rudder or the steering wheel spokes near the center. Other simple machines enhance human strength and also replace the effort required by humans. For example, a shroud turnbuckle is a screw enabling a person to exert a relatively small amount of force tightening the turnbuckle to create much higher force in the shroud to support the mast. From the system of pulleys that make up a mainsheet or vang to the lever handle used on a mechanical windlass or used to pump the head, intentional simple machines give humans super strength. Still other simple machines on

board exist in contrary ways, creating higher forces when we would prefer the opposite. Wouldn’t it be great if monohulls didn’t have to lug thousands of pounds of ballast around in light air when that amount was engineered to counter the weight and wind forces exerted on mast, rigging, and sails in extreme conditions? The mast-keel lever is a physical reality of monohulls that our friends with catamarans like to remind us about. Another example is mid-boom sheeting. The benefit of mid-boom sheeting is to keep the mainsheet and traveler controls clear of the cockpit and companionway.

The challenge is that the boom is a lever where the load transferred from the mainsail clew to the end of the boom is doubled if the mainsheet is at 50% of the boom length. The boom, mainsheet, traveler, and deck structure are engineered to accommodate this amplification of load. Still, shock loading from flogging or slating can cause tremendous stresses on those components.

Unfortunately, many items on

board are simple machines in disguise that amplify forces in ways that can damage gear and injure crew. Lifelines may be the most common safety feature found on board a cruising boat. Yet, due to poor design/manufacturing, a lack of maintenance, or misuse, in addition to the reality that each stanchion is a lever capable of inflicting tremendous forces into the deck, can make for a bad combination. Hold the stanchion at the base (fulcrum) and push hard. There should be no sign of flex or movement. Now, push at the top of the stanchion: and it doesn’t take much exerted force to cause flex in the stanchion base. Fenders attached Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84  |  Page 85  |  Page 86  |  Page 87  |  Page 88  |  Page 89  |  Page 90  |  Page 91  |  Page 92  |  Page 93  |  Page 94  |  Page 95  |  Page 96  |  Page 97  |  Page 98