"Flush-deck" Conversions
The first group of APDs (APD-1 through APD-36) were converted from one Caldwell class, 17 Wickes class, and 14 Clemson class "flush-deck" destroyers built during and after World War I. Some of these had been previously converted to aircraft tenders or other uses.
In the conversion, the two forward boilers (out of four) were removed with their smokestacks (reducing speed to 25 knots). Accommodation for 200 troops was installed in the former engine spaces. The original armament of four 4" guns, one 3" AA gun, and twelve torpedo tubes was replaced with three modern 3" AA guns, one 40 mm AA gun, and five 20 mm AA guns. Two depth charge racks and six anti-submarine mortars were carried. In place of the torpedo mounts, four davit mounted LCPLs (landing craft) were shipped.
Read more about this topic: High Speed Transport