“THE C.M.B.’S”

Dominion, Volume 15, Issue 154, 25 March 1922, Page 14

“THE C.M.B.’S”

A LESSON OF THE WAR MOTOR BOATS EMBODIED IN THE NAVY The development of the coastal motor boats was a phase of the naval war in which New Zealanders played a part. A Wellington officer, Dr. C. F. V. Anson, was ono of the men responsible, for the initial experiments that led to the creation of a new and important branch of the Navy. The motor boats have now become a permanent arm of the service, and they are being adopted by some foreign Powers.

So jealously was the secret guarded by the authorities that it was not until some considerable time after the close of hostilities that the general public had an opportunity of learning something of the remarkable services rendered during the war by that invaluable addition to the British Navy—-the fleet of high-speed coastal motor boats (C.M.B.’s or “scooters”) by which name they have now become familiar. In recalling briefly the record of their achievements, from the penetration of minefield of enemy bases for reconnaissance work and counter-mine laying, the hunting out and destruction of submarines, the triumphant exploits during the memorable Zecbrugge raid, to the daring attack on .Kronstadt harbour and the torpedoing of numerous Bolshevik cruisers, some idea may be gained of the extraordinary efficiency and invulnerability .of these little vessels, constructed of timber less than half an inch in thickness, armed with two or, in some cases, three torpedoes, in addition to depth charges and machine guns, and capable of speeds of over 40 knots. Considering this list of successes., the subsequent decision of the British Admiralty to adopt this class of boat as a permanent arm of the service came as no great surprise to those more closely associated with their operations during the war. That foreign Powers have not been backward in realising the immense possibilities for these “mosquito craft” is indicated by the announcement of the delivery to the French Navy of a second boat recently completed by John I. Thornycroft and Co., Ltd .> who are responsible for the design and. construction of these boats, while similar boats will .shortly be running trials prior to delivery to the United States Navy Department, i Having regard to the fact that these are probably the first naval contracts to be placed bv the United States Government with any firm in Great Britain, or for many years by the French Government, a few particulars illustrating brieflv the general characteristics and armament will, no doubt, prove of interest. /As an example may be taken the boat destined for the French. Navy, which lon her recent’ trials attained a speed of 41.6 knots, while carrying .a load of over ten tons. This boat is 55 feet in length, with a beam of 11 feet and . draft 3 feet 3 inches. The hull is built of two skins of Honduras mahogany, the inner planking being laid diagonally and fastened, to elm frames with the outer planking running fore and aft. Oiled canvas is stretched between the two skins to ensure water-tightness. A third skin worked in from the fore portion of the boat and extending to amidships, forms a step of about 3|. inches in depth, on which the boat rises as she gathers speed, and so obtains a skimming action over the surface of the water. The after construction is such that v-then travelling at full speed ’the boat is supported solely by this step and the stern portion, and on a cushion of air formed between these two points. Despite their light construction and apparent fragility, the safety and, seagoing capabilities of these boats in all but the roughest of seas have been conclusively proved; the special construction providing for considerable flexibility and enabling the craft satisfactorily to withstand “pounding” in a heavy swell. The forward portion of the boat, decked over, is devoted to the machinery space. In ibis' there are. fitted, “en echelon,’ two sets of Thorny croft 12-cvender engines, each developing 375-h.p. at 1500-1600 revolutions. For starting up. a small auxiliary single cylinder engine of xahont 23-h.p. is provided, driving a worm shaft through a clutch which engages the starboard engine. This auxiliary can be utilised independently when required for charging accumulators for electric lighting, etc. Four hundred gallons of petrol carried in two tanks provide sufficient fuel for a radius of action of about 200 sea miles. As regards armament, the .55 feet boats are fitted with two 18-inch torpedoes carried in troughs in the after portion of the boat, two depth charges, and four machine-guns. .