Funded by BuShips maintenance funds (1942 for YDG-1, 1943 for others). YDG-1 was acquired as a district patrol vessel, YP-404, but her YP conversion was cancelled when she was found to be in bad condition. After her owner refused to take her back the Navy decided to use her as a mobile deperming barge. On 30 Jun 42 and 1 Jul 42 CNO asked the Joint Merchant Vessel Board in the 11th Naval District to nominate for acquisition three wooden hull vessels capable of carrying about 40 tons of degaussing gear. Initially only one, CIPANGO (designated YP-504) could be found, but two more were soon added as YP-522 and YP-528. The class designation Degaussing Vessel and symbol YDG were created for these four vessels on 18 Dec 42, although they were also referred to as Mobile Degaussing Units. YDG-5 was the former HMAS NAMBUCCA, a 162-foot wooden coaster or river steamer used by the Australian Navy as an auxiliary minesweeper.
The conversions of YDG 1-4 included a large battery installation in a hold, a diesel generator for charging the battery, a ventilation fan for the battery compartment, an electrical switchboard, cable reels, stowage for portable range equipment, and a plotting room. YDG-5 had a less comprehensive degaussing installation, and YDG-3 was found to be too small to make full use of hers. Each ship was designed to go to an advanced base, lay her cables to form a degaussing range, then position herself where her battery could power the cables and she could provide degaussing services to ships that came to use her range. As necessary she could recover her gear and move to another location.
||Ex YP-404 18 Dec 42, ex merc. THOMAS C. McNEAL. Menhaden fishing vessel, 219 tons gross, 127.75' reg. x 21.1' x 9.7', armament cancelled, 300hp, 20 men, wood hull. CNO directed purchase 22 Apr 42. Arrived at conversion yard 11 Apr 42 but conversion as YP cancelled 9 Jun 42 due poor material condition. Selected 1 Jul 42 for use as a mobile deperming barge, assigned to Guantanamo Bay 15 Nov 42. Converted by Old Dominion Marine Railway Co., Norfolk, between 28 Jul 42 and 18 Dec 42. Guantanamo reported on 24 Feb 44 that her engine was in very bad condition and she returned to Charleston, S.C., in August 1944 for disposal.
||Ex YP-504 18 Dec 42, ex merc. CIPANGO. Tuna boat, 177 tons (gross?), 103' oa, 95.3' reg. x 24.75' x 9.25', 375hp, 9kts, 2-20mm. VCNO directed acquisition 9 Jul 42. Converted by Campbell Machine Co., San Diego, between 27 Jul 42 and 14 Dec 42. In service 10 Nov 42, comm. 5 Dec 42. Arrived in Australia 3 Feb 43 still designated YP-504 and received her YDG-2 designation there 9 Feb 43. Reclassified back to YP-504 on 15 Feb 44 and converted to cargo and mail carrier. In bad condition by the end of the war, stripped and sunk off Manus 7 Dec 45.
||Ex YP-522 18 Dec 42, ex merc. CHICKEN OF THE SEA. Tuna boat, 295 tons gross, 436 tons light, 600 tons full load, 122' oa, 113.25' reg. x 28.3' x 12.4', 500hp, 1-6pdr (removed 1944) and 2-20mm. wood hull. CNO directed acquisition 23 Jul 42. Ordered equipped for deperming 26 Aug 42. Converted by Campbell Machine Co., San Diego, between 12 Aug 42 and 14 Dec 42. In service 30 Oct 42, comm. 5 Dec 42. Based at Noumea from April 1943 to September 1944. Found unseaworthy at San Diego 8 Mar 45 due to storm damage and dry rot. AM-359 (which became YDG-11), under construction at Willamette, Ore., was designated to replace her, and YDG-3 arrived at Willamette on 3 May 45 to transfer her deperming gear.
||Ex YP-528 18 Dec 42, ex merc. SANTA MONICA. Wooden freight vessel, 497 tons gross, 1,500 tons full load (?), 186' oa, 166' reg. x 34' x 12.8', 35 men, 1-6pdr (changed 1943 to 1-40mm) and 4-20mm, 400hp, steam propelled. Built 1902, inactive since 1938. VCNO directed acquisition 7 Aug 42. Ordered equipped with deperming and range gear 26 Aug 42. Converted by United Engineering Co., Alameda, Calif., between 15 Oct 42 and 7 Mar 43. Grounded on reef at New Caledonia 1 Oct 43 and quickly broke up. The entire crew was saved and some gear was salvaged including 4-20mm guns.
||Ex HMAS NAMBUCCA (misspelled in U.S. sources as NAWBUCCA or NAUBUCCA), ex merc. NAMBUCCA, wooden coaster or river steamer, launched 1936, 489 tons gross, 900 tons full load, 162.5' oa, 154' pp x 34.5' x 8.3', 2 screws, 2 compound steam engines (built circa 1899), 396 shp, 8.25 kts, 28 men, 1-12pdr 2-20mm (changed in American service to 4-20mm). Requisitioned by RAN 7 Nov 39, comm. 10 Jan 40, served as auxiliary minesweeper, and paid off and transferred to USN 19 Apr 43. Acquisition directed by BuShips and the Bureau of Supplies and Accounts on 23 Oct 42. Conversion to degaussing ship by Evans & Deakin, Brisbane, completed 31 Jul 44 and vessel placed in service. Inspected at Okinawa in November 1945 by USS BLACK HAWK (AD-9) which reported that she required major machinery repairs, her main propulsion plant was obsolete, her capabilities as a degaussing barge were limited, her wooden hull was old and in need of recaulking, and she was not safe for sea under her own power. The Board's recommendation to strip locally and dispose of was approved by SecNav on 19 Dec 45. She was declared a total loss as of 30 Dec 45, decommissioned on 7 Feb 46, and destroyed on 8 Feb 46.