Harbour Defence Motor Launch
Sussex Thorsen, Ellsworth, Maine, USA
12 May 1944
24 October 1945
Dimensions & Displacement
Displacement 36 tons
Length 72 feet
Beam 15 feet 6 inches
Draught 4 feet 3 inches
Speed 16 knots
Crew 10 - 12
Machinery Twin Hercules DNX6 diesels, 390 BHP each, twin screws and twin rudders
Guns 1 x 20mm Oerlikon gun, 2 x twin .303 machine guns
Other Armament Depth charges, small arms

HDML 1340 was one of a class of thirty motor launches built for the Royal Australian Navy during World War II. Nine were constructed in Australian shipyards, three in the United Kingdom and eighteen in the United States. They were originally classified as Harbour Defence Motor Launches (HDMLs) and those that remained in service following World War II were subsequently redesignated Seaward Defence Motor Launches (SDMLs) in the early 1950s and Seaward Defence Boats (SDBs) in 1957.

HDML 1340 was one of four vessels built for the RAN by Sussex Thorsen boat builders of Ellsworth, Maine, USA. The four Sussex Thorsen built HDMLs for the RAN were numbered 1340/1341/1342 and 1343. The US built HDMLs originally had the designator ‘Q’ rather than ‘HDML’ as shown in the picture above at launching.

HDML 1340 under construction at the L.S. Thorsen Boat Works, Ellsworth, Maine, 28 March 1943.
HDML 1340 under construction at the L.S. Thorsen Boat Works, Ellsworth, Maine, 28 March 1943.

Following delivery to Australia HDML 1340 commissioned into the RAN at HMAS Rushcutter on 12 May 1944 in Sydney under the command of Lieutenant Christopher Cundell, RANR, who remained in command throughout the vessel’s commission. Sub Lieutenant Arthur Chapman, RANR, served as Executive Officer until 6 August 1945.

A period of fitting out and trials for the newly delivered boat followed from May through to October 1944. It appears she may have originally been earmarked for patrol activities in Burma; however, this never eventuated. Instead, on 21 October, in company with HDML 1352, she departed Rushcutter for Western Australia to undertake patrol operations. The two launches called in at Eden on the NSW south coast on 23 October as a result of heavy weather and arrived in Melbourne on 24 October. 

The two boats were slipped in Melbourne to rectify defects that had not been able to be completed in Sydney. Replacement wireless telegraphy sets were also fitted. Time was taken for a cricket match with the combined crews of 1340 and 1352 playing the undefeated HMAS Platypus side and inflicted upon them their first loss.

Following extended time for repairs and maintenance, the ships sailed from Melbourne on 3 December and proceeded at 10.5 knots towards Adelaide, South Australia, arriving on 5 December. Both vessels were again slipped in Adelaide, HDML 1340 for inspection only but HDML 1352 was suffering a hot propeller bearing. The two vessels departed Adelaide on 24 December and soon encountered rough weather and a severe sand storm forcing them to shelter at Wedge Island for three days. They got underway again in calmer conditions on the 28th. They conducted an un-scheduled refueling and storing stop in Port Lincoln, South Australia, later that day and departed again on the 31st.

An injury to the eye of a petty officer necessitated a return to Port Lincoln for medical attention and the two boats remained alongside until 2 January 1945 due to inclement weather. Luckily the injured sailor was able to sail with vessels having been discharged from Port Lincoln hospital.

They made port visits to Ceduna on 3 to 6 January, and Albany on 11 January 1945. The range of the launches was such that a refueling stop was necessary in between Ceduna and Albany at Israelite Bay in Western Australia where fuel carried as deck cargo in drums was transferred to the main fuel tanks. The end of the long trip approached with periods in heavy weather and the welcome arrival at Fremantle on 18 January 1945 with HDML 1340 in a less than ideal state, the voyage across the Great Australian Bight having revealed numerous issues with the boat’s build.

HDML 1340 was slipped on 19 January and the subsequent inspection found that her ASDIC dome had been damaged and rendered unserviceable, and that her shaft bearings were defective as were the chain-driven superchargers which bought the power of the engines up to required levels.

She conducted one anti-submarine patrol with other HDMLs in Gage Roads off Fremantle on 4 February before the issues with her superchargers became untenable. The vessel was declared non-operational on 5 February and she was placed in dockyard hands to repair numerous defects. This included efforts to place painted canvas over the decks to remedy serious leaks into the accommodation and galley areas. Extra shoring and beams of wood, up to 15 feet long (4.6 meters), were placed inside the vessel to strengthen the decks, prevent warping and shore up the leaks. Deck strength proved to be an issue across the class and investigations were conducted in both Fremantle and Brisbane to address the problem. 

In addition to these issues there remained defect with her main engines. Replacement chains for the superchargers had to be sourced from the USA and there was no indication that this would happen in a reasonable timeframe, so it was decided to conduct trials running the engines without superchargers. The trails yielded promising results but the boat could not be considered to be at an operational standard.

In June Lieutenant Cundell reported the crew to be somewhat disheartened by the long period of defect maintenance. He also noted that during engine trials there was considerable vibration in the ship’s hull and ‘working’ of the vessel in a seaway. This was another indication of the weaker construction of the boat, and further maintenance, dockings and realignment of propeller shafts and bearings continued. The ordeal came to an end, however, in July 1945. Parts arrived and were installed, trials were conducted and the boat was finally considered operational on 18 July 1945 with ASDIC fitted and working. With repairs to both HDML 1340 and HDML 1352 complete after a long period, the force available for patrol activity at Fremantle amounted to six vessels. 

The responsibilities of the Fremantle based MLs included anti-submarine exercises with Allied submarines, guiding new arrivals into port and conducting daily patrols outside the Harbour. Splash targets were towed for submarine gunnery and coastal battery exercises. A whole of flotilla activity, including HDML 1340, was conducted on 16 July 1945 screening units of the British Pacific Fleet.

Anti-submarine training for officers and sailors from the flotilla was conducted on the ‘Attack Table’ at HMAS Leeuwin. Communication branch ratings carried out wireless and visual signalling exercises each day that their boat was in harbour and was conducted by the Chief Telegraphy NCO from Leeuwin. Visits to the Silo Signal Station at North Quay for all ML signalmen were conducted under the charge of the Chief Yeoman. 

HDML 1340’s primary operational commitment was comprised of anti-submarine patrols off the West Australian coast, the general pattern being to sail 0815 in the morning and return alongside Leeuwin at about 0840 the next day upon relief by another unit. Hall Bank, a 5 meter high rock about 2.5 nautical miles to the North West of Fremantle, was the centre of the patrol effort. HDML 1340 conducted six patrols in July and 11 in August covering some 105nm. As the expectation of enemy activity reduced in the latter half of 1945, so did patrol operations. HDML 1340 remained on standby for the majority of September only conducting one trip to ferry an officer to Rottnest Island on the 19th.

HDML 1340’s operational service came to an end in October 1945. The boat was de-stored and de-ammunitioned, and the crew were accommodated at Leeuwin prior to demobilisation. Her armaments, gun mountings, ASDIC, radar wireless gear, engines, propellers and electrical gear were all removed ashore.

HDML 1340 was decommissioned was on 24 October 1945 having sailed 3576nm in 17 months of service with 476 hours underway. She was sold in 1948

Commanding Officer of HDML 1340

12/05/1944-24/10/1945 LEUT CR Cundell, RANR