LENGTH OF SPARS FOR YAWLS AND KETCHES.
The bowsprit of a yawl is generally about •4 of the length on the load water-line, and rarely is as long as the bowsprit of a cutter of similar size. The first impression would be that a yawl, owing to her mizen being stepped so far aft, would require a longer bowsprit than a cutter, but in practice this is not found to be the case. In fact, as a rule, a yawl carries a very slack helm on a wind in moderate breezes, and the reason is that the eddy wind from the mainsail strikes the fore cloths of the mizen sail from the leeward, so that all the fore part of the sail generally lifts, and this unsteadiness in turn disturbs the currents of air that are approaching the mizen sail from to windward, the final result being that for close-hauled sailing the mizen is a much less effective sail than is generally supposed. In sailing "along" the wind one, two, or three points free, the mizen is generally sheeted somewhat flatter than the mainsail, so that the eddy wind from the latter does not disturb it. The mizen then does its full share of work.
The mainmast of a ketch in length, deck to hounds, is about times her beam. The mizenmast of a ketch, deck to hounds, is about •8 of the mainmast.
The ketch rig has seldom been adopted for yachts, one reason probably being that, the mizen mast being stepped forward of the sternpost, it comes very much in the way of the tiller, and the boom has to be kept a great height above the deck. Another objection to the ketch rig is that the sails are necessarily narrow in proportion to their height, and for this reason their heeling movement for any given area is greater than is the heeling movement of the squarer sails of a cutter or yawl.
It must be clearly understood that the rules given for finding the dimensions of spars are only applicable to racing yachts ; for cruising yachts the spars should be at least 8 per cent. less ; or l ft. should be
taken off every 12ft. 6in. of the proportions found by any of the rules. For example, if the beam of a cutter yacht be then her mast would be three times her beam, or x 3 = 24-99ft. = length of mast deck to hounds. This would practically be 25ft., and as there are two lengths of 12ft. 6in. in 25ft., the mast for cruising would require to be reduced exactly 2ft., that is to say, to 23ft. The other spars would be reduced in proportion.
In determining upon the length of main boom, the designer of the sail plan will be almost wholly guided by the figure of the sails; neverthe less, it must be always borne in mind that the shorter the boom is, the lighter it will be, and the more the weights—which are necessarily above the centre of gravity—can be reduced, the stiffer the vessel will be. Some confusion, however, occasionally appears to exist about this matter in con sequence of the erroneous supposition that the quarters of a vessel bear the weight of the boom by some independent support, and sailors frequently say of a vessel, " She'll never bear the weight of that great boom with those lean quarters." It has already been pointed out that any weight a vessel carries has its support through the common centre of gravity of the vessel (Fig. 3); and lean quarters will no more interfere with a vessel carrying a long and heavy main boom than a lean bow will. But a long, heavy boom, the same as a long, heavy bowsprit, will tend to increase the momentum acquired during pitching and wending in a sea way; and, moreover, it will also tend to increase this momentum because a main boom is somewhat free in its action, and is not stayed in an immovable position, the same as a mast or a bowsprit is. Then, again, a main boom is always more or less off the lee quarter, and thus assists in heeling a vessel ; and, of course, the heavier a boom is, the more potent this assistance will be. But a " leanness " of the quarters has nothing to do with this matter, further than that lean quarters affect the general question of stability.