488 SEC. 12. APPLIED MECHANICS. 



them through the water at the required speeds, and automatically recording 

 the leading phenomena of the trial, namely, the speed, the resistance, and 

 the change of level induced by the speed at each end of the model. 



The several processes are illustrated by the accompanying series of seven 

 photographs and two specimens, which may be explained as follows : 



No. 1. The designer. 



This consists of a pile of adjustable templates, the thicknesses of which 

 represent the horizontal intervals between the successive water-lines of the 

 intended models, shown on a reduced scale. One edge of each template is an 

 elastic steel band held to a wooden base-piece by adjustable ordinates hinged 

 to the band and sliding through mortices in the base-piece fitted with hinged 

 metal clamps. One of these templates (No. 8) set up as for use is sent to aid 

 this explanation. 



The photograph shows them in combination ; when thus placed they 

 represent the intended model on a reduced scale, by a series of water-lines 

 in steps, which, if either filled up solid and fair to the salient angle of each, 

 or trimmed off fair to the re-entering angle, would constitute the finished 

 form. 



No. 2. The moulding box, the mould, and the core. 



L. B. D. 



The former is a rectangular wooden box 16' x 2' 9" x I' 10". containing 

 plastic clay. 



In the clay the external form of the full sized model is moulded by help of 

 a series of rough cross sections deduced from the small scale designer, and into 

 the mould is fitted the core, which constitutes the figure of the inside of the 

 model. The core is framed on a series of internal cross sections made good 

 to a surface and rendered coherent, first by a series of laths nailed to them 

 externally, and, secondly, by a skin of calico drawn tight over the lathed 

 surface, and then coated with plaster-of-paris and clay. Between this " core " 

 and the " mould " there is, of course, a space, equal to the intended thickness 

 of the model, into which space the melted paraffin is run, and there allowed 

 to remain until by cooling it has become solid enough to bear removal. 



Nos. 3 and 4, the shaping machine. 



This is what has sometimes been termed in technical phrase a " copying 

 machine." The model, bottom upwards, and adjusted successively to a series 

 of different levels, travels longitudinally between a pair of revolving cutters, 

 which are caused by means of a hand lever to so recede and approach one 

 another, as the model passes, as to cut upon the model the horizontal section 

 or " water-line," correctty appropriate to the level at which the model is set. 

 At the side of the machine, in full view of the operator, there is a vertical 

 board, which carries either a drawing of the intended model, showing the series 

 of water-lines to be cut, or one of the " designer " templates already described. 

 In front of this board is a " tracer," and the board and the " tracer" severally 

 imitate upon the appropriate scales (the former by longitudinal motion, the 

 latter by vertical motion) the longitudinal motion of the model and the lateral 

 motion of the cutters. Thus the drawing (or template) passing along beneath 

 the tracer, is practically a small scale picture of the model travelling past the 

 cutters, and if the tracer be made to follow the correct line on the drawing 

 (or to follow the edge of the template) the revolving cutters will cut the 

 correct water-line on the model. 



The model is then finished by hand with spokeshaves and scrapers, an 

 operation which takes a man about three hours. 



No. 5. The hauling engine. 



This is the instrument by which the required motion through the water at 

 definite speed is given to the model. The dynamometric truck to which the 

 model is attached, is connected by a wire rope with a winding drum, driven by 

 a small stationary double-cylinder steam engine. The engine is regulated by 



