When the builder has made the four ribs, he should proceed to construct the lower deck, which consists of a single piece of wood nicely planed and finished, measuring 14-1/2 inches long by 8 inches wide and 1/8 inch thick. This piece must be nailed to the bottom of each of the ribs, one at each end, and the other two containing the holes at equal distances apart. Tiny nails, similar to those used on cigar-boxes, will be found very suitable for this work. Some old cigar-boxes may be broken apart to obtain the nails for this purpose. Before nailing on the board it should be marked out to present ordinary deck-boards. The reader is referred back to Chapter 9 which describes this process, using a straight-edge and knife.
When this board is nailed in place, the next requirement will be two pieces for the sides the bottom edges, of which must rest on the top of the deck-board. These boards are the same length as the deck. They should reach to the top of the ribs, and be fastened in the same way as the bottom deck. It is good practice, when doing this, to place a little white lead on the bottom edge before finally driving the nails in place. This will tend to produce a water-tight joint. This done, three pieces of wood 5/8 inch square must be screwed in place, flush with the bottom ends of the ribs, to form a flat keel. They should be firmly fixed since a lead keel is afterward screwed on the bottom of the boat. Attention should now be directed to fitting the two middle decks. These are placed 4 inches from the top and are 4 inches wide. In this space the engine and pumps are placed. Therefore, the top deck is made in the form of a lid, and the outside plate made to draw out. In this way the mechanism below the deck can be made very accessible.
The framework of the dry-dock is now completed, and the builder can proceed to fix on the side plates. These are made from sheet tin with a width of 14-1/2 inches. The length must be sufficient to reach from the top of one side, around the bottom of the hull, to the top of the other side. Having cut the tin to the required size, one side is put in place with small nails, spacing them an equal distance apart.
Before securing the opposite side, the builder must first arrange the inlet-valve. This particular member is constructed as follows. First, obtain an old gas-pipe union which measures about 5/8 inch in diameter and 3/4 inch long. With a hacksaw this is cut off in a sloping direction with an angle to correspond with the slope in the bottom of the dry-dock. When this is done, a lid must be fitted to the top by means of a long rod, as clearly shown in Fig. 122. On the under side of this lid a small piece of sheet rubber should be glued, so that when the lid is screwed down the valve will be made water-tight. The valve must now be soldered to the inside of the hull. It is placed in such a position that it will rest just under the center of one of the upper decks when the controlling rod is upright.