Ailanthus - class net laying ship The " Ailanthus " class were a group of 40 wooden - hulled net laying ship s of the United States Navy built during World War II as part of the huge building programs of late 1941 and early 1942 for small patrol and mine warfare vessels . Five of the class were transferred to the British Royal Navy under Lend - Lease , and another five were converted while at their shipyards into Auxiliary Fleet Tugs , the " ATA - 214 " - class . Construction . Originally ordered on 30 September 1941 as Yard Net Tenders ( " YN " ) , the first twenty ships ( YN 57 - 76 ) were to be constructed for the British under Lend - Lease , while a further twenty ( YN 77 - 96 ) were for the United States . However , after a major redistribution of small combatant contracts this order was cancelled . Finally in May 1942 contracts for twenty vessels were awarded , with orders for YN 57 - 66 going to the Everett Pacific Shipbuilding & Drydock Company of Everett , Washington , and for YN 67 - 76 to the Pollock - Stockton Shipbuilding Company of Stockton , California . In July , 14 more ships were ordered from four shipyards ; four ( YN 77 - 80 ) from the Barbour Boat Works in New Bern , North Carolina , five ( YN 81 - 84 and 86 ) from Snow Shipyards Inc . in Rockland , Maine , one ( YN - 85 ) from the Canuelette Shipbuilding Company of Slidell , Louisiana , and four ( YN 87 - 90 ) from the American Car and Foundry Company of St . Charles , Missouri . Finally , in September , the final batch of six ships ( YN 91 - 96 ) were ordered from the Canuelette Company . On 19 February 1943 , after a review of requirements , the first twenty ships were reallocated to the United States . In January 1944 the ships were reclassified as Auxiliary Net Layers , redesignated " AN " and renumbered . Ultimately the British allocation was reduced to five vessels ( AN 73 - 77 ) , and in British service they were called Boom Defence Vessels . On 9 August 1944 five of the ships that were still at their yards were ordered to be converted to Auxiliary Fleet Tugs , and AN - 64 , 65 , and 70 - 72 were reclassified as ATA 214 - 218 on 12 August 1944 . Armament . In the original design , in addition to the 3 - inch gun mounted forward of the bridge , there were two single 20 mm guns mounted on top of the bridge . In September 1944 , as a trial , a third 20 mm gun was installed on a small elevated platform mounted on a pedestal between the bridge and the smokestack on " Terebinth " ( AN - 59 ) , but it was found that the arc of fire was restricted , that the platform was too hot to permit the storage of ready ammunition , and that the gun crew became ill from engine fumes . Instead two additional single 20 mm guns were installed at the after end of the deckhouse on AN 39 - 63 and 66 - 69 . In April 1945 the four single mounts were ordered to be replaced with four twin mounts , but this change does not seem to have been made . Losses . Two ships of the class were lost during the war ; Disposal . In early 1946 six of the ships , " Cliffrose " ( AN - 42 ) , " Cinnamon " ( AN - 50 ) , " Silverbell " ( AN - 51 ) , " Torchwood " ( AN - 55 ) , " Catclaw " ( AN - 60 ) , and " Shellbark " ( AN - 67 ) , were transferred to the Republic of China ' s Maritime Customs Service at Shanghai , while the remainder were disposed of in 1947 in a Maritime Commission sales program for small vessels .