Dry Dock 1 How it Works Sign

Sign with text and images about how Dry Docks work.

NPS Photo/MWoods

Quick Facts

Location:

Dry Dock 1

Significance:

Sign with text about how dry docks work.

Amenities

1 listed

Historical/Interpretive Information/Exhibits

Description of Sign

Low-profile wayside that is 24 x 24 inches. It has a black semi-cylindrical base with two rectangular pillars supporting the panel. The panel is framed in black metal. The wayside is located by the flag poles facing Dry Dock 1.

Layout

The panel is all black with white text and black and white diagrams. At the top of the panel is the title for the text in all capitalized letters. Below the title, the panel is divided into two sides: in a column to the left are four diagram images; in a column to the right is corresponding text for each image.

Title

Dry Dock #1: How it Works

Text 1 (top right)

1. The large gate at the harbor end of the dry dock is a caisson, partially filled with water. The dry dock is filled with sea water by opening pipes through the caisson which allow water to flow from the harbor into the dry dock.

Image 1 (top left)

A cutaway of a dry dock is to the left of the diagram. Visible along the bottom of the dry dock is a row of seven black beams. At the entrance of the dry dock (right) is a tall object (called a caisson in the text). The caisson is between the dry dock and the ocean water. The ocean water is almost at the caisson’s height. It is split in half horizontally, letting water into the dry dock. A ship with three masts is in the ocean to the right.

Text 2 (second from top, right)

2. Water is pumped out of the caisson, allowing it to float and be towed away.

Image 2 (second from top, left)

The dry dock is full of water and the ship is at the entrance of the dry dock. The caisson floats in the water behind the ship to the right of the diagram.

Text 3 (second from bottom, right)

3. A ship is brought in and lined up above the keel blocks.

Image 3 (second from bottom, left)

The ship is floating in the dry dock over the beams (identified as keel blocks in text). Caisson remains floating to the far right.

Text 4 (bottom, right)

The caisson is replaced and flooded to seal the end of the dry dock. The water in the dry dock is pumped out, and the ship is left cradled and dry.

Image 4 (bottom, left)

The dry dock is empty and the ship rests on the 7 black beams (keel blocks). The caisson is at the entrance to the dry dock blocking the water from entering and is partly filled with water.