see Figure 8. Figure 8 is a trajectory of the computer model relative to the wave for a 
selected cycle of motion. The computer model behaves very much as expected. On the left- 
hand side of the figure, the craft is planing down the crest of the wave and, as it approaches 
the wave trough, comes very close to leaving the water before slamming and submerging 
itself deeply into the front of the oncoming wave crest. 
Figures 9 through 14 show comparisons of the computed and experimental pitch and 
heave motions at VIS L = 6.0 through a range of wavelengths and at a constant wave height 
of 2.54 centimeters (1 inch) for deadrise models with 10, 20, and 30 degrees. The data have 
been plotted with respect to the coefficient C), defined by Fridsma as L/A [Ca/(L/2b)7] M3) 
Note that in our notation, b is the half-beam. 
Comparisons of heave and pitch for the 10-degree deadrise model shown in Figures 9 
and 10, respectively, show excellent results. The computer model accurately predicts the 
secondary peaks in the pitch and heave responses at C, = 0.19. At this condition, the physical 
experimental model rebounds so as to fly over alternate waves. The computer model oscillates 
at half the wave-encounter frequency and comes close to leaving the water at alternate 
encounters with the wave. It does not quite leave the water to fly over alternate wave crests; 
nonetheless, it is a good representation of the actual motion. 
The heave and pitch comparison for the 20-degree deadrise model at WH TE = 6.0 is also 
excellent as can be seen in Figures 11 and 12, respectively. No experimental phase data for 
the condition were reported for C) greater than 0.072; however, extrapolated results (not 
shown) are in line with the computed results. The pitch and heave results shown in Figures 
13 and 14 for the 30-degree deadrise model are good; however, responses at C) = 0.048 and 
C) = 0.072 are higher than the experimental results. 
For practical considerations a computational scheme for planing boat motions should be 
valid for a range from approximately Wale = 4.0 to Vis = 6.0. Computations of the 
motions were made for W/E = 4.0 for the 20-degree deadrise model; see Figures 15 and 16. 
Again the comparison of the computed heave and pitch response with experimental results is 
excellent. 
Comparisons of the computed and experimental impact accelerations (or largest negative 
values) are presented in Figures 17 through 20. Figures 17 and 18 show bow and CG 
accelerations for the 10-degree deadrise model; Figure 19 shows similar results for the 20- 
degree deadrise model; Figure 20 shows the results for the 30-degree deadrise model. In all 
cases, the comparison appears to be fair to good. In the shorter wavelengths, A/L = 1.0 and 
A/L = 1.5, the computed accelerations are higher than the corresponding experimental values. 
This is most pronounced for the 10-degree deadrise angle model. 
12 
a 
