MTB Vosper (Family)

Description

MTB Vosper, or more accurately, the 70 ft Vosper MTB, was a class of 28 Royal Navy motor torpedo boats built between 1938 and 1942. After World War II, several were sold to the Italian Navy who continued to operate them in small number.

Vehicles

Rank I - Coastal Fleet

• MTB Vosper
• MTB Vosper(2)
• GIS 811

History

During the 1930s, the Admiralty began to reestablish the coastal boat flotillas it once commanded during the First World War. British boatbuilding company Vosper & Company competed for the contract but lost both times in 1935 and 1936, the lucrative contract to build the first coastal boats since WWI going instead to their rival, British Power Boat Company. In response to this, Vospers developed plans for a faster and more seaworthy design than that of their rivals'. In the following months, Vospers proposed their new design to the Admiralty multiple times, but ultimately, they could not secure a contract to build a prototype. Around this time, though, the Admiralty officials had unofficially suggested that future contracts would only be awarded for vessels that could surpass 40 knots in speed and that were armed with two 21-inch torpedoes as well as an assortment of light anti-aircraft guns. Additionally, it was known from previous specifications that the Admiralty wanted a vessel capable of operating in open waters in at least Force 5 winds and that was fast enough to cross the English Channel during the night. With these unofficial specifications, Vospers preemptively began development on a new vessel as a private venture at the company's own expense.

Immediately, it was decided that the private venture vessel had to be larger than the existing 60 ft British Power Boat MTB in order to meet the specifications. Additionally, engines more powerful than the Napier Sea Lion engines used in the BPB design were required. With none available domestically, Vospers looked to the Asso 1000 engine by Italian manufacturer Isotta-Fraschini. Though in limited supply, the Asso 1000 was specifically designed for marine craft and provided the necessary power: 1150 bhp at 1500 rpm maximum and 950 bhp at 1660 rpm continuous. In late 1936, Vospers completed their design. It called for three Asso 1000 engines and two in-house 75 bhp auxiliary engines, the latter of which could be coupled to the outer shafts to give a total maximum power of 3600 bhp. The hull-form was a hard chine planing design and was 69½ ft in length with a displacement of about 33 tons. The prototype was laid down before the end of the year and completed in May 1937.

Upon completion, the prototype underwent internal trials where she achieved a top speed of 47.8 knots unloaded and 43.7 knots loaded. Satisfied with these results, Vospers presented the prototype to the Admiralty for official trials against the 60 ft British Power Boat MTB. The prototype fared favorably, and after much deliberation, the Admiralty decided to purchase the vessel from Vospers. She was commissioned in May 1938 as MTB 102 and sent to HMS Vernon for further evaluation. Up to this point, MTB 102 had not actually been fitted with torpedoes, so during her time at HMS Vernon, many torpedo configurations were tested. These included the tried-and-true yet outdated stern projection systems, as seen on the 60 ft British Power Boat MTB and earlier WWI designs, as well as a unique arrangement of a single launcher in the stem of the hull with a reload carried internally. These all had their own issues, and none were found to be satisfactory. Ultimately, it was decided that MTB 102 should have two torpedo tubes mounted on either side of the bridge, pointed forwards with the nose angled outwards, an uncommon configuration for the time. Around this time, the gun armament had also not yet been decided, so various configurations were also experimented with, including combinations of 0.303 in and 0.50 in machine guns and a 20 mm autocannon.

Impressed with MTB 102, the Admiralty placed an order for four more vessels on 15th August 1938, Vospers' first-ever Admiralty contract. These vessels, and any ordered after, all shared the same overall design as MTB 102, although with several minor changes such as the hull being lengthened to 70 ft 3¼ in. After 1940, with the entrance of Italy into the war, Isotta-Fraschini engines could no longer be obtained, and subsequent boats had to be fitted with much weaker American Hall Scott engines—only 1800 bhp total—as a stopgap measure until they could be upgraded with more powerful Packard engines, although this wasn't until 1941 as supply was limited. Of the 32 planned 70 ft Vosper MTBs, 28 were completed and are as follows:

• MTBs 20-23: Ordered 15th August 1938, all were completed by December 1939. MTBs 20, 21, and 23 were sold to the Romanian Navy. MTB 22 served with the 4th MTB Flotilla. She survived to the end of the war and was sold in 1945.

• MTBs 29-30: Ordered on 8th September 1938—including a Thornycroft design, MTB 28—as replacements for the three boats sold to Romania, all were completed by July 1940. Both MTB 29 and 30 served with the 4th MTB Flotilla. MTB 29 was lost in a collision with a German E-boat on 6th October 1942, and MTB 30 struck a mine and was lost on 18th December 1942.

• MTBs 31-40: Ordered on 27th September 1939, six were completed by May 1941. MTBs 33, 37, 39, and 40 were bombed by German aircraft while under construction in 1940-41. The completed boats survived to the end of the war and were sold in 1945-46.

• MTBs 57-66: Ordered on 26th February 1940, all were completed by April 1942. MTB 61 was stranded during an attack on 9th May 1943, and MTBs 63 and 64 were lost after collisions with friendly MTBs on 2nd April 1943. The remaining boats were sold in 1944.

• MTBs 69-70: Ordered in April 1940, both were completed by June 1940 and received only two engines. Both were stationed at HMS Beehive, Felixstowe. They both survived to the end of the war and were sold in 1945-46.

• MTBs 218-221: Ordered on 7th December 1940, all were completed by September 1941. MTB 218 struck a mine and was lost on 18th August 1942, and MTB 220 was sunk by German E-boats on 13th May 1942. MTBs 219 and 221 survived to the end of the war. MTB 221 was sold in 1945, and MTB 219 was transferred to the Sea Cadet Corps at Staines in 1945 and was converted to a houseboat in 1948.

The 70 ft Vosper MTB design continued to receive many improvements and modifications order-to-order and would lead to the development of the 72 ft Vosper MTB and 73 ft Vosper MTB.

External links

• [Coastal Forces Veterans] Boat Database
• [ww2ships.com] 70' Vosper Motor Torpedo Boat
• [Unit Histories] Royal Navy Coastal Forces 1940-1945
• [naval-history.net] British vessels lost at sea in World War 2 - MGB, MTB, SGB, ML, etc - originally published in British Vessels Lost at Sea, 1935-45, His Majesty's Stationary Office, 1947

Bibliography

• Lambert, J., & Ross, A. (1993). Allied Coastal Forces of World War II Volume II: Vosper MTBs & U.S. Elcos (pp. 21-32). London, England: Conway Maritime Press. ISBN 0-85177-602-7.