SAIL CARRYING POWER OF CANOES.
Paddling demands an upright position of the man's body, but sailing equally demands a lowering of the weights, and consequently a reclining position; and further, when running dead before a strong wind under a press of sail, even though a spinnaker be set, the head of the lug will get forward of the right angle, and cause violent, if not dangerous, rolling. Comfort, combined with safety, will be obtained under these circumstances by lying back, and firmly wedging one's shoulders between the two sides of the after well-coamings. To obtain this the bulkhead is placed six inches further aft than it would be for the ordinary back board, and the back board is supported for paddling by a shiftable beam, which can be removed when sailing, and then the back board is inclined against the bulkhead.
A British sailing canoe, of racing build and equipment, is undoubtedly the most delicate of all sailing craft in the world to handle. Her sail carrying power almost entirely depends on the artificial shifting of her centre of gravity to windward by moving her ballast and crew. She is the craft par excellence, in which " crew" and " craft" are linked together, and form one working machine. The small depth of body and keel allowed by the club rules, coupled with the necessary large proportion and weight of crew, spars and sails, to the small hull, cause a far higher position of centre of gravity in a canoe than would be found in any other class of vessel.
The beam allowed by the club being very trifling for sailing purposes, it will be readily understood that the "righting couple" (see page 9) must be very short at any angle of heel, unless the weights are moved rapidly over to windward as the vessel heels; consequently, righting force or stability will be limited to comparatively small angles of heel, and there will be a point at which stability will vanish and the craft capsize.
As soon as the canoe begins to heel, the weather bilge is lifted out of water, and a large bulk of body is immersed on the lee side, and consequently the centre of buoyancy is rapidly shifted out to leeward. Supposing, then, that her weights remain in midships (Fig. 125), there would be a considerable and gradually increasing righting power, till, practically, the deck is awash, or about at a heel of 25°; but the centre of gravity is now being lifted, as it were, and some of the weights, such as that of the man's body, is coming into the vertical in which is the centre of buoyancy, and that of the spars and sails is shifting out to leeward. This is rapidly shortening the righting lever, and therefore
the vessel is nearing the capsizing point, and at 45° she has brought them into the same vertical, and then a capsize must follow. But before this point is reached the man's balancing power, aided by that of ballast trimmed to windward, comes into play, and the craft receives a new lease of righting life, as in Fig. 126; the only danger then remaining is that of the lee well-coaming getting under water, or of the ballast or man suddenly falling to leeward.
In Figs. 125 and 126 the positions of the centres are slightly exaggerated, in order to show the movements more clearly : b in each drawing represents the centre of buoyancy (through which a force is always acting upwards at right angles to the surface of the water) ; g, the centre of gravity, is the mean centre of gravity of all the weights, such as ballast, man, spars, sails, centre-board, and weight of hull; a force is always acting downwards, in a vertical direction through g. Each of these two forces is equal to the exact weight of the canoe and all she contains. The horizontal distance between the verticals of g and b is the "righting couple," and, so long as g has any horizontal distance to windward of b, there is stability ; but in Fig. 125, g and b have been brought into the same vertical line, the meta-centre (tn, in Fig. 126) has been brought to coincide with the centre of gravity, and consequently the vessel is in equilibrium, and a cockroach walking across the deck might settle the question of " capsize" or "right" The centre of gravity of the separate parts of the canoe may be considered individually : a is the centre of gravity of the canoeist; d the centre of gravity of the ballast ; c the centre of gravity of the centre board. The arrow 8 reminds the reader that spars and sails are heavy, and have a centre of gravity.