Project 204 Poti Class - Design
The Tactical-technical specification (TTZ) for the design of the small anti-submarine ship of Project 204 was approved April 10, 1956. The task for the development of such a vessel was issued to Zelenodolsk PKB. Chief Designer was appointed A.V.Kunahovich, but mostly watching from the Navy - Captain 2nd rank N.D.Kondratenko. Standard displacement rose to 440 tons, but at the same time significantly increased and armament antisubmarine vessel. After the final test the creators were awarded the Lenin Prize.
The TTZ for the ships was designed to fight in coastal areas with enemy submarines, having an underwater speed of travel more than 30 knots. TTP was issued to CDB-340 (later Zelenodolsk design - Design Bureau), which had previously designed the large (122bis project) and minor (draft ML - 200bis, 199 and 201), submarine-chasers.
It should be noted that in 1955, the same CDB received TTZ on drafting anti-submarine ship of the project 159, destined to change the large hunters 122bis and utilization project in more remote coastal seas. On housing architecture, location of residential and office space, both projects somewhat repetitive. Project 159 ships were built almost on the same plants in the same period of time.
The sketch and technical projects were developed during 1956-1957. Technical patrol ship project was approved, together with the project of small anti-submarine ship March 18, 1958. Development of the project was carried out under the supervision of the chief designer, watching from the Navy carried out by the same person.
The superstucture, housing construction in comparison with the anti-submarine boats Project 201 was essentially not much changed. The superstructure configuration is almost the same in both projects. However, the stern appeared characteristic "hump", for which he was called in the Fleet "humpback" project, which housed gas turbine compressors and air intakes. Magnesium alloys (AMG) were used in a large amount with aluminum to reduce the displacement. Even for protecting personnel from bullets and shrapnel, the pilot house was made of AMG alloy 15 mm thick. As time has shown, AMG alloy had a tendency over to continuous exfoliation corrosion, which required a large amount of work with the use of argon welding.
The total displacement of the ship was 555 tons, main dimensions:.. The greatest length - 58.6 meters, width - 8.13 meters, draft average - 2.8 meters.
To solve the problems of anti-submarine warfare (ASW) the design installed on a ship 4-tube 400mm anti-submarine torpedoes, two jet bomb installation RBU-2500 (installed only on the first two orders), on production vehicles it was replaced by two RBU-6000, with bombs stock, control system devices torpedo and bomb fire. The Omnidirectional sonar "Hercules - 2M" was installed. It should be noted that the multi-barreled bomb reactive depth charges and management systems were united in complexes taken into service in 1962-1964 for fighting qualities superior to the installation of similar purpose, applied to foreign fleets.
For self-defense ship from enemy aircraft and boats there were installed two AK-725 57 mm cannon gun mount. The radar control system CS MP - 103 "Bars" was placed in the middle part of the ship. The gun mount AK-725, due to its high rate of fire - 200 rounds per minute per barrel, was an effective weapon against the boats and low-flying targets. The location gun mount and antenna control system was certainly not the best. This was due to the fact that the bow position was occupied by RBU, and air intakes to feed gas turbine compressors. As the radar detection of air and surface targets used radar MR-302 "Deck", and signals intelligence system "Mizzen".
The power plant was developed in two versions - diesel, and diesel-gas turbine with the original use of the gas turbine. The need for variation was motivated by the desire to find an optimal solution for the ship when searching for the submarine. Based on these considerations, the diesel - gas turbine version was chosen, even though it was more difficult to use, leading to higher fuel consumption and, consequently, to a decrease in the range of navigation and autonomy. In addition, this option also had serious shortcomings which had been revealed, unfortunately, during the operation.
The technical nature and the constructive design of the variant engines were as follows. At the aft end of the ship on each side in the underwater hull there by hydraulic motor, consisting of a tube with nozzles. The tubes are propellers driven in rotation, as in the conventional power plant, propeller shafts, in turn driven in rotation diesel engines arranged in an engine room. On the upper deck at the poop superstructure was placed gas turbo-compressor (SCC) that fed air pressure of 1.5 kg / cm2 in the pipe for the hydraulic propellers. As a result, the created additional thrust in addition to the thrust generated by screws when driving gas and water mixture through the nozzle.
The installation could operate in two modes: in diesel mode (working only diesel engines), and the joint operation (operation of diesel engines and gas turbine compressors). This two-stage setup is basically a new type of propulsion system. IT was developed originally by Professor of the Physics Department of the Moscow Aviation Institute, later under the leadership of B.K.Elias.
The works were provided by two diesel engines M504A (later M504B) with a capacity of 4750 hp each, and two gas turbine compressors SCC D - 2B with a capacity of 15,000 hp each. When using only diesel vehicle developed as speed of 17 knots, while working together GDGD and SCC teh speed was 35 knots. There is evidence that the first building built Khabarovsk GCC, during sea trials during the delivery of the Navy developed a speed of about 41 knots.
The choice of this very complex propulsion system was due to the fact that from this anticipated substantial reduction in their own acoustic field of the ship and reducing interference to their own sonar (SAS). Unfortunately, in practice, this was not confirmed. Due to the structural features of the motor installation, screws at a speed of 16-17 knots started to work in the conditions of the developed cavitation. Hydraulic pipes only screened noise in traverse directions, but in the same axial directions screw noise was not quenched. This directional noise unmasked the ship and created more interference with its own sonar.
In addition, the propulsion coefficient (ie efficiency), which characterizes the perfection of hydrodynamic screws complex - housing and represents the ratio of the towing capacity to a total gross capacity (power GDGD) ship with motor installation was low and was at the maximum speed about 30%. While at the fastest ships navigating in the design mode, it was 60-70%. From this it follows that the power consumed would be enough for the movement at a higher speed and at normal layout.
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