Fast Attack Boats

Briefing
written by
James Davies

Key Information

Overview

The French fast attack boat programme began after the end of the First World War, influenced by the success of the Italian and the British boats. In France these boats are known as Vedette Torpilleur, commonly shortened to VT, and with an ‘A’ appended for smaller boats and ‘B’ for larger boats they are classified as either VTA or VTB.

They began in 1921 by buying two boats from the British, one 45’ boat (VTA1) and one 55’ boat (VTB1) made by Thornycroft, to use for trials, and these boats were the basis for the first French series of boats (VTA2 to 4 and VTB2 to 7).

The three small VTA boats were built by three different French yards (Excelsior, Jeannin and Wisner) in 1929, and were very similar to the Thornycroft 45’ boat bought in 1921. They made 37 knots with a 500 hp Lorraine aircraft engine on a 5.4-ton hull, and carried one stern-launched 45-cm torpedo. They were not a success, particularly with respect to their seakeeping, and no more ‘A’ boats were built.

As with the VTAs, the six larger VTB boats were similar to the 55’ Thorneycroft boat. They were developed by two French yards (Ateliers et Chantiers de la Loire and Wisner) and entered service in 1930. The boats built by the Wisner yard had two 500-hp Lorraine engines, but at 10.1 tons they were nearly twice as heavy as the VTAs and their top speed was an identical 37 knots. The Ateliers et Chantiers de la Loire boats were similar, but used 1100-hp Lorraine engines, giving them 44 knots on trials. The increased size of the VTBs brought with it a greater punch, and they carried two 45-cm torpedoes. Unfortunately, as with the smaller ‘A’ boats, the French naval authorities were not happy with their seakeeping and the design was not continued.

Abandoning their previous reliance on designs based on British boats, the French went for a new home-made design from Société Silbur. Two boats were built (VTB8 and 9) with a similar specification, designed for 46 knots on Lorraine engines and with two side-dropping torpedoes. Unladen, VTB8 made nearly 52 knots on trials, although VTB9 broke up and sank when travelling at full speed off Barfleur in August 1939, raising questions about whether too much strength was sacrificed for speed. Problems also existed with their torpedo dropping equipment, and no more boats were built on these designs.

To date, all the French boats had been planing vessels, with a stepped hull. A stepped hull form has a round bottom with a sharp discontinuity (step) in the bottom, where the depth of the hull behind the step is several inches less than the hull in front of the step. The British, Germans and Italians had begun experimenting with a ‘hard chine’ hull form. A hard chine hull has a ‘V’ shape, with a sharp edge where the side of the hull meets the top of the ‘V’ (there are thus two sharp edges – one at the side of the boat and one on the bottom of the ‘V’). The hard chine form slightly reduced the maximum speed of the boat, but significantly improved the seakeeping qualities and manoeuvrability.

An Anglo-French prototype boat, 40K, used the hard chine design and several were sold to the Spanish Republicans during the Civil War. These made 40 knots, and were armed with two 20-mm cannons, two 53.3-cm torpedoes and 12 depth charges. The French navy considered buying some, but decided not to as the engines, although a French design, were no longer being made in France (they were made in Britain under licence).

VTB10 was designed and built by Ateliers et Chantiers de la Loire, and intended to make 45 knots at 21 tons with four 650-hp Hispano-Suiza engines and two side-dropping torpedoes. Unladen, the boat made 55 knots on trials. VTB11 and 12 were similar, apart from their engines which were dual 1100-hp Lorraine engines.

The final series of French designed and built boats, VTB13-22, followed the same basic design as VTB10. These were to be built by Ateliers et Chantiers de la Loire, Chantiers Navals de Meulan, and Chantiers Jouett, but the armistice interfered and only VTB13 and VTB14 were laid down.

18 boats were also ordered from the British, VTB23-40, and these were a British Powerboat Company design. These boats had four 45.7-cm torpedo tubes, two 13.2-mm machineguns (one each side of the bridge), eight depth charges and a smoke generator. They made 42 knots with three 1100-hp Rolls Royce Merlin engines.

The characteristics of the French-designed boats were defined by their stepped hull form – very fast in calm water, but not suited to operations in any other weather.

Units

Specifications

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