We next come to consider the stability, or sail-carrying power, of Jullanar. Here again it is interesting to note that the fortuitous com bination of conditions rendered the condition on which Jullanar's stability mainly depends a possible one. Hitherto all attempts to evade the effects of the Y. R. A. tonnage rule, by increasing the proportion of length to beam, had been limited by the fact that a consequent increase in depth involved an excessive area of immersed surface. But Jullanar, like a well designed yacht with a much rockered keel, has great depth of middle body as well as length, and consequently carries her ballast low. At the same time the area of her immersed surface is small, for the reason which has been sufficiently pointed out.
The stability of Jullanar is of a satisfactory character; but it is not of so potent a nature as it might have been with a little more beam. Mr. Bentall, in his letter heretofore quoted from, does not say why he gave Jullanar so little beam. He says his object was to get the longest vessel on the load-line with the smallest area of immersed surface. Lengths and areas are not directly comparable, and possibly Mr. Bentall meant that his object was to get the longest vessel on the load-line in ratio to length of keel. At any rate, the proportions of the linear dimensions of length, breadth, and depth of Jullanar exemplify in a certain manner the truth of what those who have made yacht naval architecture a study have long contended, that the best sea-going craft is one of long body in proportion to her breadth of body, accompanied with great depth of body and small initial stability. A vessel with a faint bilge, small initial stability, and great depth will not have violent lateral motion among waved water, such as rolling, lurching, and lifting of the whole mass ; and one that is long and deep will have, compared with short vessels, no violent fore-and-aft motions, especially if her displacement is so apportioned that her weights are necessarily concentrated in the middle of the vessel. The disadvantage of small initial stability is that, even with low wind pressures, the vessel will take an excessive heel ; her deck will be a difficult one to walk upon, and so will be her cabin floor. However, the discomfort of a steep platform may be considered
compensated by the fine behaviour of the vessel that has it among dis turbed water. [The stability of Jullanar compared with some other yachts will be found referred to on page 46.] It is beyond doubt that speed is proportional to length, other things being equal ; and Jullanar affords a string example of the deficiency of length alone for speed purposes where no equality in other essential qualities exists. For instance, Florinda is 14ft. shorter on the load-line than Jullanar, yet is her speed, under what may be considered as the most favourable circumstances for developing the same, equal to the speed of &thanes. We have not far to look for the reason of this. The initial stability of Florinda is much greater than that of Jnllemes, and consequently, in moderate whole sail breezes and smooth water, she can carry her canvas much more effectively—or, in other words, she then commands a greater propelling force. This will be easily under stood by reference to the diagram showing the curves of stability of the yachts (page 47).
Florinda, like Jullanar, has a small area of immersed surface ; but she has comparatively little draught of water, and her keel has but a moderate upward rake. Now Jullanar's excellence in a good whole sail breeze depends on her weatherliness, and speed. Florinda has equal, perhaps superior, speed under such conditions ; but she compares un favourably for weatherliness. In the first place, her form—she having very little depth of body, and an expanded V form of section—is not so suitable as Jullanar's for lateral resistance; and, secondly, her small rake of keel renders her dead wood less effective than it would be if she had the same area differently disposed. If her sternpost were given more rake—without increasing her length of load line—and if the piece removed were placed along and under her keel aft, and if some of the dead wood forward were removed, there is not much doubt that her weatherly qualities would be improved.