Device For Taking Off Lines 

 From Half-Model. A piece of 

 pencil lead projects through the 

 small, spring-loaded block under 

 the forefinger of the user'sleft hand. 

 The vertical bar is held against the 

 model by a slight pressure from the 

 forefinger of the user's right hand. 

 As he slides the frame across the top 

 of the rack, the pencil point traces 

 a line on the paper e.xactly parallel 

 to the vertical sliding bar point rest- 

 ing on the model. The photograph 

 shows one section completed and 

 another being drawn. {Smithsonian 

 photo 46597-a.) 



when it is necessary to measure with staffs or foot 

 rules over or around deck structures and where 

 measurement points must be plumbed. The diffi- 

 culty in identification is made greater by the rather 

 common practice of wooden-ship builders of adding 

 frames amidships in order to lengthen a hull over the 

 designed length. This was particularly common 

 among New England builders. In some models the 

 process of adding length by inserting frames required 

 refairing the middle body, with the result that the 

 beam might also be slightly increased in real measure- 

 ment. Hence one cannot be sure whether the varia- 

 tion betw^een dimensions scaled from the half-model 

 and those of the register require allowance for in- 

 serted frames or merely represent inaccuracy in the 

 latter. 



A practical example of the difference between real 

 and register dimensions can be shown in the case of 



the American clipper ship Challenge, built at New 

 York in 1951 by William H. Webb. The mould-loft 

 offsets of this vessel exist and also a plan made with 

 great care in England, while the vessel was in dry- 

 dock. The registered length of the ship, by the old 

 method in force when she was built, was 230 feet 

 6 inches and the beam 43 feet 2 inches. The loft 

 dimensions and takeoff drawing show that the length 

 of the \essel by the measurement system used at New 

 York in 1857, had it been possible to measure accu- 

 rately, was actually 227 feet and the beam 42 feet 10 

 inches. 



Note should be made that another method of length- 

 ening hulls under construction was sometimes used; 

 the frame spacing was increased to give the desired 

 increase over the design length. It seems possible that 

 this was used in a few ships, fishing schooners, and 

 coasters. 



