598 W. J. Marwood and A. Silverleaf 
[2] Saunders, H.E., “Hydrodynamics in Ship Design,” Vol. 2, p. 408 
[3] DuCane, P., “The Planing Performance, Pressures and Stresses in a High-Speed 
Launch,” Trans. I.N.A. 98:469 (1956) 
[4] Crewe, P.R., “The Hydrofoil Boat; Its History and Future Prospects,” Trans. I.N.A. 
100:329, Oct. 1958 
APPENDIX A 
NPL Small Portable Torsionmeter No. 1 
This torque meter (Fig. Al) was designed to be readily portable, and to fit shafts 
having diameters from 1 to 6 inches without any need for removing any part of the propeller 
shaft. To meet these requirements a strain-guage-type meter was designed, with the gauges 
mounted directly on the shaft and their output leads taken through a readily dismountable 
slip ring assembly. 
Four small resistance strain gauges are bonded to the shaft by an appropriate strain 
gauge cement at a position close to, and inboard of the stern gland. The gauges lie on 45- 
degree helices on the shaft surface, so placed that there is symmetry relative to the shaft 
axis and also to a plane normal to the shaft. Hence gauges respond only to torsion in the 
shaft and the gauge output is not affected by bending or thrust in the shaft. The gauge 
Fig. Al. Torsionmeter No. 1 
