When making a sharpy to sail in, a trunk and centre-board should be built when the keel is laid so that the cumbersome and unhandy lee-board may be done away with. The centre-board is housed in the trunk, through which it can be raised or lowered as occasion requires.
The arrangement of the trunk in the boat is shown in Fig. 19, and it is located so that the front of the trunk is three feet from the bow. For a centre-board one inch and a quarter in thickness the trunk should be one inch and three-quarters wide between sides, five feet long, and eighteen inches high. It is made of tongue-and-grooved boards one inch and one-eighth in thickness, and these are attached by stout screws to posts one inch and three-quarters square at bow and stern. The trunk is mounted on the keel, set in white-lead, and securely fastened with screws. A slot is cut in the keel the same size as the inside opening of the trunk—that is, two inches wide and about five feet long. The bottom planking is butted against the sides of the trunk at the middle of the boat as shown in Fig. 20.
An inner keel is laid over the bottom planking through the centre of the boat from stem to stern, and where it fits around the trunk it is cut out. Both the inner and outer keels are six inches wide and the exposed edges are bevelled with a plane. A sectional or end view of the trunk and its location in the keels is shown in Fig. 20, where the shading and lettering will designate each part.
The centre-board is four feet and nine inches long, thirty inches wide at the back, and twenty-four inches at the front. It is attached to the trunk with a hard-wood pin located near the forward lower end, and when it is drawn up it will appear as shown in Fig. 21 A, but when lowered it will look like Fig. 21 B.
The centre-board is made of hard-wood, several boards of which are pinned together with galvanized-iron rods three-eighths of an inch in diameter and driven through from edge to edge of the boards in snug holes made with a long bit or auger. The rods are riveted at both ends over washers to prevent the boards from working apart.
Fig. 16 Fig. 17 Fig. 19 Fig. 20 Fig. 21 A CENTRE-BOARD SHARPY ]
It would be better to let a boat-builder or carpenter make this board the proper size and shape to fit the trunk, for it is the most difficult thing to construct about a boat and somewhat beyond the ability of many boys. A large galvanized eye and a rope made fast below the middle of the board at the rear edge will provide the means for raising and lowering the centre-board.