The Casco Class vessels were built asseaplane tenders by the USN. They were designed to operate out of small harbors and atolls and had a shallow draft. The fact that the class were very seaworthy with good habitability and that the diesel plant gave it good range made this class well suited for ocean-station duty.

A number of changes were madeto these ships to better suit them for OS duty. A balloon shelterwas added aft, there were spacesdevoted to oceanographic equipment, and a hydrographic winch was added.

Displacement (tons) 1791 (light)
Length 311'7" (oa)
Beam 41' (max)
Draft 13'1"

4 Fairbanks Morse 1600 hp coupled to twin screws through reduction gears
Max sustained speed 17 knots (11,000 miles)
Ecconomic speed 10 knots (209,000 miles)

Fuel oil 170,000 gallons

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