The buoy has a special form to meet its requirements
as a lightship, and the conditions of its employment is the fast tidal
current of the river. It was designed by Mr. C. Berthon, of Westminster,
and is intended to carry a six months' supply of gas, the burner,
regulator, and lamp being on the well known Pintsch system. The hull is
formed of 3/8 inch plate, 24 feet 3 inches total length, and 9 feet beam
at the line of flotation. The laps of the plates are 4 inches wide, and
riveted with 3/4 inch rivets, spaced 2-1/4 inch apart center to center.
The keel and stem are both in one piece, as shown, and to this the
garboard strake is to be fastened. The bilge pieces are riveted on to the
bilge, and made of 9 inches by 4-1/2 inches by 9/16 inch T-iron. A wooden
fender, 4 inches by 4 inches wood, is fitted on both sides of hull,
running from stern to stern, by 3 inches by 3-1/2 inches by 7/16 inch
L-iron top and bottom with the sheer as shown. The hull from water line
falls in as shown, so as to describe at midships an arc of 4 feet 6
inches, and a circular deck of 1/8 inch plate is riveted on the hull.
There are two man-holes, each 16 inches diameter in the clear, placed in
end plates of the circular deck as shown, and provided with covers 3/8
inch thick, secured by twenty screws 3/4 inch diameter.
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