sailing - page 2
2.2 Masts and Mast words
While you are standing on the foredeck, start looking up. Notice that cabled wire extending from the point of the bow to the top, or near the top, of the mast. This is headstay. Its job is to support the mast against forces in the sails that want to push the mast backward, or aft. Notice that the headstay has a colleague at the back of the boat, a wire running from the top of the mast to the transom.
This is the back-stay. Sails, even in the rather light wind, exert significant stress on the mast that most could not withstand without additional support. When the wind blows from over the front of the boat, the stress in the sails exerts an aft-ward force on the mast, in which case the headstay helps support the mast. And when the wind blows over the back of the boat, the backstay takes over to support the mast, as common sense would suggest.
But the mast also needs side-to-side, athwartships support. So step aft to one side or the other of the mast and look at the wires stretching from one or more points along the top and sides of the mast down to the side decks. These wires are the shrouds. Though their configuration, their geometry, will vary from boat to boat depending on size, shrouds counteract the lateral forces generated on the mast particularly when sailing to windward-that is, when the wind blows over the front of the boat.
Collectively, the stays and shrouds constitute the standing rigging.
The obvious basic purpose of the mast is to hold up the sails, but a glance around any mooring field will show that all masts are not created equal, even those on similar-sized boats. Some masts are short and syubby, while others tower over the deck. Some are as stout as bridge abutments, others beanpole-thin. A mom-and-pop cruising boat 34 feet long will naturally carry less sail area on a shorter, stouter mast than a 34-foot dedicated race boat meant to carry movable ballast in the form of human bodies.
The height of the mast and the lenght of boom determine the size of the mainsail in square-foot area; and the relative lenght of the mast and boom determine the shape of the mainsail. The thinner and taller the mast, the more standing rigging you need to support it, along with the additional hardware required to attach shrouds and stays to the mast and deck.
As you peer up the mast, notice those appendages protruding horizontally perpendicular to the mast. These are called spreaders because that's what they do-they spread the load on the mast. The farther from the base of the tower you can anchor the wires, the greater the support they will affort. But of course on a sailboat, the shrouds can't be anchored any farther out-board than the width of the beam.