Davis and Oates 



1/8 Scale Foil Models 



Bow and main foil models have been tested in the N.P.L. towing tanks at 

 Feltham. Using special dynamometers provided by N.P.L., trials data included 

 foil unit lift, drag, sideforce, pitching moment, yawing moment, and rolling mo- 

 ment over a range of Froude speeds and depths of immersion. Both subcavi- 

 tating and supercavitating bow foil models were evaluated. The effect of bow 

 foil downwash on the main foil was measured and found to be small. The main 

 foil model was fitted with pressure taps at the centre section and power pod to 

 obtain foil and foil to pod interference pressure distributions to verify theoret- 

 ical predictions. N.P.L. developed a scanning valve to read up to 90 taps. 



Finally, the bow and main foil model were coupled to a beam representing 

 the hull, free to heave and trim. The results of towing trials in calm and rough 

 water were scaled up to 1/4 size and are shown in Figs. 5 and 6 in comparison 

 with the predicted response of the 1/4 scale RX craft in sinusoidal seas. 



1/4 Scale Fully Cavitating Bow Foil Model 



The 1/4 scale bow foil was built for the RX manned model. The size of the 

 N.P.L. towing tank and dynamometer provided the opportunity to compare the 

 data from tank trials with the simulation and with the measured response of the 

 RX test craft. 



1/4 Scale RX Craft 



The craft is owned and operated by the Naval Research Establishment of 

 the Canadian Defence Research Board. The RX equipped with the 1/4 scale foil 

 system designed and built by De Havilland weighs about 3-1/2 tons. The hull 

 and forward boom are not representative of the FHE-400; neither is the propul- 

 sion system, consisting of a gasoline engine 'Vee' drive and single propeller. 

 Because of the 'Vee' drive the hull clearance is only 2/3 of the FHE-400 design 

 clearance. 



In addition to providing the craft and test crew, N.R.E. have fitted instru- 

 mentation to record the following data: 



(a) Linear acceleration angles and angular rates at the C.G., vertical accel- 

 eration at the bow foil. 



(b) Main foil lift, drag and sideforce and bow foil lift. 



(c) Main and bow foil element stresses through strain gauges. 



(d) Bow foil steering loads and helm angles. 



(e) Velocity, engine RPM and propeller thrust. 



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