The iconic HDML

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    invisible officer

    For me the Harbor Defence Motor Launch was ever a bit iconic.

    I have a special liking for the HDML since visiting HDML ML1387 on a sailing trip.

    More than 460 got built by various yacht builders in UK and Commonwealth harbors. 22 meter long it had two Diesel engines that gave it a maximum speed of 12,5 kts.

    Crew was 2 officers, two Petty officers and 8 ratings. A bit top heavy for such a small vessel. Many German Vorpostenboot of triple the size had a Bootsmann as CO, no officer on board.

    The first boats of 1941 got 1 x 1 or 2 pdr QF gun and two twin .303 Vickers K guns. And up to 8 DC. In Late 1941 a 2cm was added aft. And in late war the QF gun was replaced with another 2 cm. Some Australian launches got .50 MG.

    Design was around the idea to have a vessel that would be capable of turning inside the turning circle of a submerged submarine. That resulted in problems to hold on a straight course. In order to lessen the chances of the boat sinking in the event of damage to the hull, they were divided into six watertight compartments.

    Some HDML were built by US yards. They are delivered under Lend-Lease to RN. Post war they went via USA to other navies.
    The helmsman position was on the open bridge where the two engine room telegraphs were fitted. There was also an inside steering position.

    Two men served the engine. There was no direct control of the engine from the bridge. A ship telegraph transmitted the orders. The settings for the engine governor controls were “slow” 250 RPM, “half” 600 RPM, “full” 800 RPM and “emergency full” 900 RPM.
    An auxiliary power unit provided motive power for electrical generation and to operate the fire and bilge pump.

    invisible officer

    HDML had been surprisingly seaworthy so they got not just used for harbor defense. They got used in jobs like escorting convoys along the African coast, chasing submarines around Iceland or in covert operations with commandos.

    In SEA some had been doing raids behind Japanese lines. At D-Day HDML operated in Operation Taxable to give the impression of another landing area.

    At first HDML were initially transported as deck cargo of freighters but soon they started sail alone. For example HDML 1301 sailed to Malta with extra deck fuel tanks. Three even got a second mast for sailing.

    A lot got lost. Some by typical sea accidents like foundering in a hurricane or running aground. One exploded in Beirut harbor.
    Others are lost as deck load with torpedoed freighters.

    The last war loss, 1163, was hit by a torpedo. No hazard in cruel sea game for such a small vessel. Gunfire, mines and air attacks destroyed other launches.

    One (1381) was taken 25.8.44 by the Germans, it became a vessel of Küstenjägerkompanie Rhodos (formed 4.1944). A unit related to the Brandenburger. They did many clandestine operations in the area. The boat became KJ 25. The CO of the area, Generalmajor Dr.Wagener, went in Mai 45 on it to Symi. There he signed on board of HMS Active his capitulation. The HDML brought a first small British unit to Rhodos. There the launch was taken back into RN service.

    Shown here with two Warlord Vospers for size comparison.

    invisible officer

    And a big pic


    Great work once again.

    Just makes me think, how much more i would have loved to see an HDML instead of 3 different Fairmile Ds. Not that the Fairmile are bad models, but its more or less the same model 3 times. A HDML would have been something really different and useful.

    (and yes i bought all of the Fairmile Ds…)

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