The Book of the Sailboat: How to rig, sail and handle small boats

by A. Hyatt Verrill

Shaded portions indicate leverage of hull against sail. Outlined rectangles show relative stability areas.

Thus the farther a boat tips over the less force can the wind on the sails exert, for with every inch that the boat heels the length of the lever decreases, as will be seen by the accompanying diagram. For this reason a boat tips much more easily when upright than after it has heeled over a bit and for the same reason a shallow or flat-bottomed boat tips more readily than a deep hull.

It would be perfectly feasible to build a boat so deep that it would not tip at all, and likewise a boat could be built so heavy, or with so much ballast, that the leverage of the sails would be unable to heel it in the least. But neither of these schemes would be practical. If the boat was built too deep it would offer so much resistance to the water that the sails could not drive it forward and if built too heavy or if it carried too much ballast, it would be slow, clumsy and the sails and masts might be carried away before the boat moved.

Moreover it is not desirable to prevent a boat from tipping to a certain extent. Many boats sail at their best while heeled at a sharp angle and the tendency to tip also serves as a sort of safety valve by spilling the wind from the sails and warning the sailor that too much sail is being carried and thus serving a very useful purpose. Hence, in order to make boats safely stable without making them heavy, slow or clumsy, various forms of hulls and various methods of ballasting are adopted.

For example, if a boat is made very broad and shallow the result, when tipped, will be almost the same as if the hull was made very deep and narrow but the resistance to the water will be overcome. As the hull is tipped up by the leverage of the masts the upper side acts as a weight which must be lifted, and exerts just as great a counter-leverage as if the weight was under water. But instead of presenting a large surface with its attendant friction to the water the area of the boat’s surface is reduced the more it is tipped.

Such broad, flat hulls are very stiff, up to a certain point, and boats built in this manner are usually very fast when heeling far over, but when they are tipped a single inch beyond a certain point the weight of the raised side acts with the lever and flops the boat over in an instant. When a hull thus shaped is provided with a centerboard or a weighted keel it becomes far more stable. Many of the fastest racing boats are of this type, a form designed to sail the very best when heeled far over with half the bottom out of water. To add to the stability under such conditions the bows and sterns are cut away for a long distance so that when sailing on a level keel the surface in contact with the water is very small, while the further they tip to one side or the other the greater the length is increased.

But in every case, whether stability is obtained by great breadth or beam, by extreme depth from deck to keel, by ballast inside or outside, by fin-keel or otherwise, you should remember that the further under water the ballast is placed the less will be required. Always bear in mind that ballast or weight on the downward or lee side aids the boat in tipping, whereas the same weight, on the upper side, prevents it and that the weight placed on the high side will exert many times the force of the same weight in the center of the boat.

Often by sitting far out on the upper or weather edge of a boat, she may be sailed in safety through winds that would capsize her if you sat inside the cockpit. If a plank or board was extended out from the weather side and you perched upon that the boat would be still harder to upset and it is by such methods that the natives of the South Seas sail their catamarans and proas at terrific speed and with huge sails out of all proportion to the hulls. Sometimes one may see a “flying proa” tearing along in a perfect gale with half a dozen persons hanging on to the slender outrigger extending from the weather side, and by their weight alone preventing the queer craft from turning turtle.

All the above remarks refer to stability, but there is another factor which must be considered and which is known as lateral resistance, or in other words, the resistance offered to the water when moving sideways. A boat might be very stable and yet it might be worthless if it did not possess lateral resistance, for in that case it would merely slide sideways instead of going ahead and a properly designed boat must combine both stability and lateral resistance to the highest possible degree.

When sailing in any direction, save directly before the wind, there is a strong sideways pressure against the sails and unless the boat is provided with some means of overcoming this she will slip sideways or diagonally or will make “leeway,” as a sailor would say. Deep, narrow boats have great lateral resistance but their resistance to the water when moving forward is also great and hence the lateral resistance is usually obtained by means of deep, narrow keels, centerboard or leeboards. The knife-like keel offers little resistance to the water when moving forward but great resistance when moving sideways, while the centerboard may be pulled up entirely when moving forward with a wind from the rear, thus still further reducing the friction against the water.