The Shawmut having broken her stern-post, a new forging was ordered from the East and shipped to Seattle, where it was desired to remove the old stern-post and fit the new, and no dry-dock being available for the work the following mode of procedure was adopted:
The Moran Bros. Company have a small floating dry-dock capable of docking a vessel of about 3000 tons, while the Shawmut is a large vessel belonging to the Boston Steamship Company of the following dimensions:
Length between perpendiculars 488 feet.
Length, over all 505 feet.
Beam, molded 58 feet.
Draft, loaded 27 feet 3 1/8 inches.
Displacement, loaded 17,200 tons.
Water bottom capacity 2,100 tons.
It was decided to form a cofferdam around the stern and to utilize therefor the floating dry-dock.
The ship being light, the forward tanks were filled so as to bring her down by the head as shown on the accompanying sketch. This gave her a draft forward of 13 feet it inches, and aft of 13 feet 3 inches.
Across the floor of the floating dock, and at such a distance from the end that the upper corners of the sides of the dock would clear the ship's side, the ship's extreme beam being in excess of the width of the dock, was located a bulkhead, so in dined that when the dock was in its final inclined position this bulkhead would be practically vertical. The shape of the bulkhead was determined from the plan of the lines of the ship, the shape being taken at the section on which the bulkhead would rest.
The ship was hauled in place, her stern projecting into the sunken dock and the dock was pumped out, thus lifting until the bulkhead came in contact with the ship's bottom and sides, after which the dock lifted at one end only.
As the dock lifted against the ship, the keel blocks shown on the sketch came into play, the stern of the ship thus being lifted, which was continued until the proper position of the dock was reached; this position being such that the inclined floor of the dock and the bulkhead across the dock formed a triangular-shaped space with sides projecting above the water line sufficiently to insure safety in fairly rough weather.
After the dock had reached the desired position, the water on the floor of the dock, held in place by the inclination of the floor and the bulkhead at the end, was partly drained through the floor of the dock into the tanks below, and the remainder pumped by improvised steam pump connections.
When this space was emptied of water the stern was thus supported by the keel blocks and left projecting into the improvised cofferdam, and the work of fitting the stern-post was proceeded with, satisfactorily concluded, and the floating dock removed.