The following plan for the construction of a centerboard is illustrated in Plate XVIII.:
The sailing canoes of the Royal Canoe Club, of England, frequently carried centerboards of thick iron plate, weighing fifty or sixty pounds. Several canoes, chiefly "Pearls," have recently been built to carry similar heavy centerboards on this side of the Atlantic. A heavy iron centerboard forms most excellent ballast when lowered, but it has some disadvantages. It is unhandy to lift in and out of the canoe, especially if the latter is bobbing about on broken water by a wharf. When fully housed in the centerboard box, it makes a good deal of top-heavy weight, and helps the canoe to roll. Acting on a hint given to me by Mr. W. P. Stephens, at Lake George last August, I have designed, and have had constructed a centerboard loaded with lead, in which the greater part of the weight is concentrated in the lower part of the board. A skeleton frame of bar iron is first made, and on each side of this is riveted a sheet of iron 1/16 in. thick. This makes a hollow centerboard of a total thickness of 5/8 in., and weighing 23 pounds. Two light iron frames, 7/16 in. wide, with long handles, are made to fit into the lower part of the inside of the centerboard. These frames are loaded with lead, and each then weighs 13 pounds, thus making the total weight of the centerboard 49 pounds when fully loaded. This new board will, I think, be found to possess the following advantages:
The weight being concentrated in the bottom of the center board gives better ballasting power with less actual weight. I hope that my 49-pound board will give as much sail carrying power as a 65-pound iron plate would.
The lead-loaded board will act as ballast even when housed in the canoe, and will not make the canoe roll, as the greater part of the weight is then within 5 inches of the bottom line of the keel.
For the same reason, most valuable help is afforded in righting the canoe when capsized, even if the board should slip back into the box or had not been lowered. A button across the slot on deck will prevent the board being unshipped in the event of the canoe turning bottom up.
When sailing in shallow water the whole weight of the lead can be got below the keel by lowering the centerboard 8 in. only.
It is much easier to handle in removing it from the canoe or putting it on board. Instead of one heavy lift of 50 pounds, you first remove 13 pounds of lead, then lift another 18, and finish with a lift of 23 pounds.
When a light centerboard only is wanted, leave the lead at home. This will in some cases save the necessity of a man keeping two centerboards.
In the accompanying drawing, at figure 1, the board is shown with one side removed, so as to bring the internal economy to view. Starting at F, the frame is continued to E, thence to D and L. It is not continued up to the top corner at C, but is taken across to M, continuing to I, it doubles back in a sort of loop, and is welded at N. This gives doubled strength at M. and Bb, where the greatest strain is. The dotted line A B shows the line of the keel when the board is lowered. The portion of the frame from E to about M is made of bar iron 7/8 deep by 1/2 in. thick. From E to L it is chamfered off to an edge, as shown by the line R R R, so as to cut the water easily. A hook is welded on at P, which hooks on to the king bolt. Where the sheet iron is, the frame is 1/2 in. thick; where not covered with sheet iron - G, I, A, and F to O - it is 5/8 thick, so as to give a uniform thickness throughout.
The sheet iron is shown by the lightly shaded part. Starting at P, its outer edge passes H, and Aa to G where it is level with the outer edge of the centerboard. It continues past M and C to L, where it takes a jog inward for half an inch to the line R R R. It follows the chamfer along the bottom of the board to near E and up to P again. The upper corner L C M is composed merely of the two thicknesses of sheet iron, and is only an eighth of an inch thick, except where it widens out as it approaches the bar L M. This, while giving plenty of strength, gives room for the chain shackle at C without thinning down and weakening the frame, and it also reduces somewhat the top-heavy weight of frame at the corner. These two sheets of iron, 1/16 in. thick, are riveted to the frame by copper rivets as shown, and are chamfered off from L to D and D to E, to correspond with the chamfer of the frame. From C to L the edges of the sheets are brought together so as to continue the sharp edge. Figure 2 gives a full-sized section at one of the rivets. The two frames which contain the lead are made of 1/2x3/16 in. iron, hammered on the edge down to 7/16, which increases the thickness slightly. They are shown at S, T, U, V, and X, Y, Z, 0. The lead is held by pieces of stout wire which are riveted in the frames before the melted lead is poured into them. These wires are shown by dotted lines. The frames are fitted with long handles V I and 0 J, which terminate in eyes I and J. Above the eye J is a button K, working on a bolt F, secured by two jammed nuts below. This makes it impossible for the lead to fall out if the centerboard is upside down. The eyes I and J project above the deck.
To take out the lead when the board is housed in its box, turn the button K, put your finger in the eye J, and lift out the forward lead frame, then by means of the eye I, drag the aft frame forward, and lift it out.
Robert Tyson, Toronto Canoe Club.
The smaller sketch is a suggestion of Mr. King's, in connection with the same design.