Panel Discussion 



A contribution was received from F. R. Miller and S. N. Gyves of Hydro- 

 nautics on tests of a self-propelled 1/2 scale model (20 ft long) of a high-speed 

 inverted v or sea-sled-hull amphibious vehicle. All tests were conducted in 

 Chesapeake Bay and measurements were made of resistance, trim, and wave 

 impact acceleration in various sea conditions up to upper 3 (significant wave 

 height = 2.5 ft). In addition, self-propulsion tests were conducted on a 1/6 

 scale wood model at the National Physical Laboratory, England. Full-scale 

 tests were conducted by the Marine Corps Landing Force Development Center, 

 Camp Pendleton, California. The correlation between model and full-scale 

 data varies from excellent to a maximum difference of 15% lower full-scale 

 SHP in the speed range from 15 to 20 knots. Data were presented on the mo- 

 tions and impact accelerations of the sea- sled and qualitative comparisons 

 were made with v bottom hulls. 



2. TESTING PROCEDURES FOR PLANING-HULL MODELS 



Professor C. Falkemo of Chalmers University of Technology described a 

 new outdoor facility for model tests in calm water, regular waves, and also at 

 sea in natural waves. The test basin is 300 ft long, 45 ft wide, and 15 ft deep. 

 It is formed by a natural crevice which has been dammed and blown out. 

 Planing boats can also be tested in full-scale on measured miles in sheltered 

 water and outside the belt of rocks. 



J. T. Everest and D. Bailey of National Physical Laboratory, England, 

 described experiments made to determine the total power requirements of a 

 systematic series of high-speed displacement craft. Measurements were made 

 of the total resistance and wavemaking resistance by the method of Eggers 

 based on wave-pattern analysis. Tests were limited to a maximum speed of 

 15 ft/sec, which, in turn, limited the wave-pattern measurements to a maxi- 

 mum Froude number based on water depth (v/vgd) of approximately 0.55. The 

 measured values of wave drag formed well-defined curves, although there was 

 a discontinuity at a ship Froude number of approximately 0.53. At this speed, 

 a tumbling wave existed at the stern of the craft falling on to the transom — it 

 is speculated that this effect could likely cause the discontinuity in wave- 

 resistance measurements and also invalidate the assumptions made by Eggers 

 in his method of estimating wave drag. Viscous drag was estimated using the 

 ITTC formulation and measured wetted areas with an allowance for a form fac- 

 tor. It was found that the summation of wave drag and estimated friction drag 

 was as much as 40-50% less than the measured total drag. Several possible 

 reasons for this large discrepancy are discussed, and it is suggested that the 

 complete lack of pressure recovery at the stern caused by complete flow sepa- 

 ration at the transom is the most significant effect. 



Consideration is also given by the author to wavemaking resistance of high- 

 speed catamaran hulls. The estimation of this resistance was based upon the 

 linear superposition of experimental wave-pattern data for a single hull in or- 

 der to calculate the wave pattern and, hence, the wave resistance of multi- 

 hulled ships. The results show that wave interference effects between hulls 

 can be of some importance for Froude numbers less than 0.5, although adverse 

 influences exceeding 25-30% are unusual. Some slight beneficial influence is 



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