Hydrofoil Size and Seaworthiness 193 
Similarly, the amplitude of the static roll angle is found to be 
Po = — nn (r 28122) : (3) 
The vertical movements of the center-of-gravity of a hydrofoil craft can also be deter- 
mined: The dimensionless static amplitude of the center of gravity is (see Fig. 2) 
5p Fh cool D) . 
Ze 
Coosy 
A 
Fig. 2. Static amplitude of the center of gravity 
Both values are shown in Fig. 3 as a function of wavelength divided by craft length. 
The scales for wy and Z,/% are valid for o = 0.05. For other values of o the scales have 
to be adjusted. 
The roll angle @ will not be discussed in more detail, because experience has shown 
that rolling is not a critical factor. Moreover it can be treated in the same way as the pitch 
angle. 
Figure 3 shows both the static pitch amplitude wy and the dimensionless static verti- 
cal amplitude of the center of gravity Z)/as a function of the relative wavelength 
\/tcos y. If 
r Dee Dn joe 
Wiss 2 De aE , etc., then Wo = 0 
but Z,/ 4, shows an extreme value, while if 
re : 
Le eee erc., then Dafa = 0 
and wy attains its extreme values. The effect of these parameters on the craft’s behavior 
will be discussed later. 
It should be noted that the values of the excitation frequency resulting from Eq. (1) 
should be regarded with some reserve. Practice has shown results to be sufficiently accu- 
rate when going against or with the waves, but when going along the waves higher values of 
@ are actually found due to the irregularity of the seaway [8]. 
