From 0° up to 30° it will be seen that the shallow vessel has much the longer length of righting lever ; but it is quite possible that the deeper vessel would have as much actual righting power as she would have a greater weight acting on the lever; but, assuming the weight, or displace ment, of the two vessels to be equal, the shallow one would have the greater righting power up to 30°, when some portion of the deck would be immersed.
Now, it is this greater stiffness at initial angles of heel which, whilst it is of the utmost advantage for speed, forms the element of danger in shallow vessels. It can be supposed that a vessel, B, is sailing at an angle of 15°, and that a sudden acceleration of wind force heeled her to 30°, the point where her maximum stability would be reached ; then, if the wind force were not instantly removed the vessel would increase her heel if she got the least beyond the 30° until she finally lost all stability, or righting power at 80° and capsized. But if a similar force were applied to a vessel with a curve of stability like A, when she reached 30° inclination there she would stick, and it would take a very large increase of wind to carry her to 50°, the point where her maximum stability would be reached ; and even then there need be little danger of capsizing, as the decrease in the length of the righting lever is so slow, that at 90° there is nearly as much righting power as the shallow boat has at 30°. (As a matter of fact, no wind force could lay a yacht, with such a curve of stability as represented by A, fiat on her beam ends, inasmuch as long before she reached 90° the wind would have lost nearly all its effect upon the sails.*) The curve B, no doubt, very accurately represents the curve of stability of such a vessel as the American yacht Mohawk, which was blown over during a squall off Staten Island last summer. The vessel was at anchor, and, no doubt, from this cause felt the force of the squall more severely. Her maximum stability would be reached say at 30°, and then the squall that put her over so far would take her to the vanishing point in less time than it takes to write it. But it is quite possible that the Mohawk would not have gone clean over on her beam ends if her ballast and heavy cabin furniture had not shifted, inasmuch as when she got to 60° the wind must have had decreased effect on the sails ; and, as the squall passed over very quickly the Mohawk might have righted but for the reason stated. However,
beyond the accident of the ballast and heavy furniture shifting, the Mohawk was subject to another condition, which rendered her righting quite impossible : she had a very large " well " or cockpit aft, into which the main cabin opened, and soon after the deck became immersed the water rushed into the cabin, and then, of course, her chance of righting was gone. Now, from the manner of stowing the ballast in a deep yacht, there would be little chance of its shifting until the vessel got beyond her beam ends, when it might certainly come tumbling through the sky lights. However, deep yachts, such as the Vanessa, Kriemhilda, Seabelle, or other similar yachts, are in no danger, even if hove down on their beam ends, providing water is not allowed to get inside their hulls. The case, however, is very different with shallow vessels and with some steamers, which have their centres of gravity high ; and it is necessary for their safety that they should never be sailed very near the angle of heel where their maximum stability is reached. In practice, in small shallow boats, this is well understood, and the helmsman throws his little craft in the wind directly she is struck by a squall, or lets go sheet or halyards, whichever comes readiest to hand.
The stability or stiffness of a yacht under canvas will principally interest English yachtsmen as a matter affecting speed ; and every novice knows that the more canvas a boat will carry at any given angle of heel, the faster she will be, all other things being equal. To demonstrate that power to carry canvas affects speed, it will be con venient to take two vessels of very opposite types, such as the American centre-board schooner Columbia and the English schooner Seabelle. The linear dimensions of the Columbia are 98ft. on the load line, and beam ; her displacement is 150 tons, and her area of lower sail 8770 square feet. The Seabelle is on load line, beam 19ft., displacement 155 tons, and area of lower sails 5780 square feet.