Small update to this old thread.
Finally I am able to fill the most significant gap in it's content - the submarine chaser ORP Bitny (S-72).
German conquer of vast areas of the Soviet Union in 1941 created a demand for a riverine combat vessel that could be used by
Wasserschutzpolizei (Water Security Police, subordinated to SS) for counter-insurgency operations in those areas that had extensive net of inland waterways. Such vessel was to wield significant firepower and be land-transportable. Initial demands called for a boat armed with 1 tank turret with 37mm cannon (from LT-38 tanks or alternatively the 4cm Flak.28 Bofors) and 1 quadruple 20mm AA gun, 10mm-thick armor of important part of the vessel, speed of 18,5-21 knots, range of 240 NM and production time not exceeding 3 weeks. Design works were entrusted to
Gebruder Sachsenberg shipyards and initial plans called for a series of 250 cutters called
Zerlegbares Polizei-Kampboot (Demountable Police Combat Boat), mainly to be used in the Dnepr area (by the
Wasserschutzpolizei-Kommando Dnepr). In 1943 the much-reduced order for 50 cutters was placed, 40 of which were to be built in Hamburg shipyard of Gebr. Sachsenberg company, and several each in
N.V. Holland Nautic in Haarlem (Netherlands; EDIT: according to ALVAMA, the actual name of the shipyard at the time could possibly be
Scheepswerf Conrad N.V.) and in
Weichselwerft GmbH in Schroettersburg (which was German name of Płock in Poland). In June 1944 the order was further reduced to 22 or 28 cutters.
Cutters could be transported in parts on 6 heavy truck trailers and were powered by two aircraft engines Hispano-Suiza 12Y (900hp power) adapted for car fuel. First cutter, ZPK-1 was completed in December 1943 and until 1944 was undergoing trials in Kiel. It's further fate is unknown.
Next two cutters, ZPK-2 and ZPK-3 were completed in February 1944 and around July 1944 were attached to
4. Artillerie-Flotille of Kriegsmarine, operating on Lake Peipus. Their combat career there was rather short - ZPK-2 ran aground on 25 of August and was destroyed by its own crew, while ZPK-3 was sunk by Soviet Air Force.
ZPK-4 (first of cutters built in Haarlem) was initially planned to be attached to the same unit as previous two cutters, but eventually was sent to
Wasserschutzpolizei-Kommando Danemark.
ZPK-5 was a trials unit, propelled by experimental Schottel SRP azipods but despite promising results of trials it wasn't accepted for wide used.
Fate of ZPK-6 and ZPK-7 (both built in Hamburg) is unknown.
ZPK-8 (second Haarlem-built) was completed in May 1944 and immediately transferred to
Wasserschutzpolizei-Kommando Westliche Ostsee and after the war was taken over by British in Flensburg.
Cutters ZPK-9 and ZPK-10 were probably completed but no details are known.
Cutters ZPK-11 and ZPK-12 (both Haarlem-built) were initially earmarked to
4. Artillerie Flotille but because of the Soviet advance they were in October commissioned to Kriegsmarine as submarine chasers Uj-124 and Uj-125, only to be transferred in December to
Wasserschutzpolizei-Schule in Lauterbach (on Rugen island). At least one of them was captured on 6 May 1945 in Maasholm (Schleswig) by British.
Besides above mentioned vessels that were completed, at least several were in the various stages of completion when the war ended (or their shipyards were captured).
One of the incomplete Płock-built ZPK's was found shortly after the war in Toruń and after much deliberation, around 1950 it was decided to complete it for the Polish Navy as a training cutter. The hull was transported by rail (in sections) to
Stocznia Marynarki Wojennej (Navy Shipyard) in Gdynia, where reconstruction plans were made in early 1951 uder the work name ST (
Ścigacz Toruński - Toruń Chaser) and it's purpose changed to patrol boat.
During the construction process the sections were connected permamently. Finished cutter was armed with 2 37mm 70-K cannon, single DShK machine and two depth charge launchers. ORP Bitny (pennant number S-72) was officially commisioned into service in the Polish Navy on 18 July 1953 and sent to naval base in Świnoujście. From the beginnig the HS 12Ydrs engines (particularly the starboard one) caused lots of troubles and greatly contributed to Bitny's short period of service, which ended formally on 8 January 1957. Shortly later the cutter was scrapped.
Because of Bitny's service coincided with most secretive period in the history of the Polish Navy (namely the era of stalinism - or, as it was called in the Party newspeak after it's denounciation "period of errors and distortion"), Bitny remains very little known vessel, of which only
two photographs are known.