FIRST RECORDER 465 



fixed in cast brackets, were placed large triangular vanes at a downward angle, each 

 vane being like half of a child's kite. These were the diving planes designed to give a 

 downward thrust to the machine. Below the front of the body was a lead keel to bring 

 the centre of gravity of the machine well forward. In its first form the recorder was 

 designed to be towed from a shackle joining three chain bridles from three stout eyes, 

 one on each side of the front end of the cylindrical body and one on the top of the 

 cylinder towards its rear end. (In Plate I these chains are not shown, but the machine 

 is hung for photographing from the above-mentioned eyes by wires.) 



This design of planes had proved successful in a model but failed in the full-sized 

 machine to give stability at speeds over 4 knots. In the completed machine the me- 

 chanism turned out to be heavier than was expected, with the result that the lead keel 

 had to be larger than was originally intended to bring the centre of gravity sufficiently 

 far forward. This enlarged keel being placed so far forward upset the lateral stability 

 and made the machine veer sideways at high speeds. I then consulted Commander 

 (now Sir Charles) Burney, the inventor of the paravane, who kindly put me in touch 

 with the Department of Mine Design at H.M.S. 'Vernon', Portsmouth. From the 

 staff of H.M.S. 'Vernon' I received invaluable help; stability tests were carried out 

 and a new system of planes and fins designed which gave perfect stability up to speeds 

 of 15 knots. 



The modified Type I machine is shown in Plate II. The original planes, keel, and 

 towing points were abandoned and in their place was fitted the following system. Below 

 the front of the cylindrical body was placed a curved steel plane having a span of 36 in., 

 breadth of 9 in., and angle of incidence of 12J . This was heavily loaded with lead. 

 Above the part of the cylindrical body and over the centre of pressure of the plane just 

 described was fixed the single point for towing : a shackle linked to an eye in a steel bar 

 and frame connecting the old towing eyes. The small movable tail planes were replaced 

 by much larger ones fixed horizontally. The vertical fin was greatly enlarged and fitted 

 with a small movable inset rudder ; above all this was fixed a large streamlined buoyancy 

 chamber to give lift to the rear end of the machine which was very heavy on account of 

 the internal machinery being placed so far back. This arrangement gave the machine 

 a very ungainly appearance but remarkable stability in the water. Apparently the 

 turning of the propeller tends to throw the machine slightly to starboard ; this can be 

 corrected by setting the inset rudder a few degrees to port. 



Internal Mechanism 



The arrangement of the internal mechanism will be best understood by reference to 

 Fig. 1 and the photograph in Plate I where the machine is shown opened but unloaded, 

 and in Plate II where it is loaded with a gauze banding ready for use. In this brief 

 description the reader is assumed to have read the preceding section on general prin- 

 ciples employed. The letters here refer to those in Fig. 1 which is a simplified diagram 

 representing a longitudinal section through the machine. The water enters and leaves 

 by the circular openings A and B, passing through a rectangular water tunnel made of 



