DROP COLLARS
For ships’ boats and the early small torpedo boats (rated second-class), the weight of a torpedo tube and its compressed-air launch system posed severe weight problems. The lightweight drop collar seemed to provide the answer. This seemingly simple solution had two drawbacks: the early drop collars give the impression of being very flimsy devices, considering the weight of the torpedoes and the lively motion of these small craft; second, before the introduction of the gyro, to start the motor of an early torpedo and drop it in the water was a somewhat hit-and-miss affair, compared with giving it a healthy push out of a launch tube in the direction you hoped it would continue to run. The drop collar would, however, survive to be carried into action in two world wars.
Italian drop collars were much more substantially-constructed devices. Drop collars were mounted on the barchino saltatore. On MAS 15 the system allowed Rizzo to carry out a successful stealth attack on the Austro-Hungarian dreadnought Szent István. With no flash from a powder charge the Austrians remained unaware of his attack until it was too late.
The early Second World War British MTBs and US Navy PT-boats were fitted with lightweight torpedo tubes. Even so, the weight of the tubes limited the other armament they could carry, so roll-off racks were substituted. In mid 1943, on US PT-boats the Mark 8 torpedoes and the Mark 18 tubes were replaced by four lightweight 22.5in Mark 13 torpedoes, carried on lightweight Mark 1 roll-off torpedo launching racks. They were then able to carry four shorter torpedoes as well as a heavy gun armament of 20mm, 37mm and 40mm cannon in addition to their original armament of .50-cal machine guns. As with the Italian MAS boats, the racks had the added advantage of requiring no black powder launch charge, thus avoiding giving away the boat’s position at the moment of launch.
LAUNCH TROUGHS AND RAILS
As torpedoes grew bigger and heavier, and their speed increased dramatically, designers searched for ways to launch them effectively from small craft. As early as the 1880s the Polyphemus was at risk of running down a torpedo launched from her bow tube — after all, once in the water the torpedo motor had to accelerate the weapon up to its set speed. In the Great War period, the internal combustion motor and hydrodynamic developments in hull design were producing torpedo-capable boats of modest dimensions but able to reach 40 knots or more.
The solution was to carry the torpedo in a trough located at the rear of the torpedo boat, using a pusher rod to throw it backwards into the water. Even travelling at high speed, the motorboat would then have to take immediate avoiding action to escape from the path of its own torpedo. The system was brought to a state of operational efficiency and went to war in the CMBs, or coastal motorboats, built by Thornycroft.
Simple and efficient as the launch system was, it had one fatal drawback. A small motor torpedo boat, built of wood and loaded with petrol, was extremely vulnerable to defensive fire from its intended target. The best chance of success lay in being able to approach the victim unseen and unheard, preferably at a modest speed to avoid creating a bow wave. At the moment of launch, the throttles were opened full, the motors accelerated with a deafening noise, and the boat created the unwanted bow wave. She was thus revealed, and exposed, and the enemy could not only open fire but also commence avoiding action.
Despite these drawbacks, the economy of the arrangements meant that Thornycroft’s designs continued to be built up until the Second World War, and they were the direct inspiration for the Soviet G5s, usually depicted dashing at high speed in formation.
In 1935 the government of the Philippines decided to form an offshore patrol squadron of fast motorboats, controlled by the army as an element of coast defence. Thornycroft delivered one 65ft CMB which was numbered Q 111, armed with two 21in torpedo tubes mounted at either side of the wheelhouse. A further boat, Q 112, was delivered in sections and re-erected in the Philippines. This second boat was a 55-footer, armed with two 21in torpedoes in stern troughs in the classic CMB configuration. Faced with an embargo on further sales, due to the onset of the Second World War, the Philippine army copied the design of the 55-footer and built a third boat, Q 113. All three Q-boats took part in the struggle against the Japanese invasion forces, and on one occasion they shot down three Mitsubishi Zero fighters attempting to strafe them (a real-life exploit similar to the opening action scene in the John Ford movie They were Expendable).
Having suffered from the attentions of the Thornycroft CMBs in the Baltic, it was only natural that the young Soviet navy should turn to this type of torpedo craft. They had captured or salvaged several examples, and the Tupolev aircraft design bureau undertook to improve on the basic Thornycroft design. The G5 (G for Glissiryuschchy, or hydroplane) was designed in 1933, and built of aluminium. Armed with two 21in torpedoes in stern troughs, production boats were capable of speeds of up to 56 knots, depending on the type of engine fitted.
