526 Edward V. Lewis and John P. Breslin 
The development of the submarine puts a new light on the problem of surface ship de- 
sign. During World War II, the submarine and the destroyer were evenly matched. This is 
no longer true. Submarines have distinct advantages in speed and maneuverability, partic- 
ularly when seas are rough. In addition, submarines have added advantages in evasiveness 
because they operate in a three-dimensional realm. To meet the challenge of the submarine, 
naval architects must develop high-performance surface ships. This problem has frequently 
been viewed with pessimism. It has been said that the only way to cope with the submarine 
is to go above the surface, as with a hydrofoil craft, or to go below it with another subma- 
rine. In this view, ships on the surface can only be fast if they are large, which increases 
cost. 
There is another viewpoint, however, that suggests the need to give serious attention 
to the possibilities of more radical types of small surface craft that might be able to attain 
high speed even in rough seas. 
POWER REQUIREMENTS 
Figure 1 shows three directions for seeking higher ship speed than can be obtained with 
a conventional surface ship — for example, a destroyer. One direction is to go well below 
the surface to eliminate surface-wavemaking resistance. Another is to stay on the surface 
but to reduce surface-wavemaking resistance drastically with a longer and more slender hull. 
The third is to raise the hull above the surface with either a planing-type hull or hydrofoils. 
In addition, Fig. 1 shows that there are a multitude of different possible types of craft, 
with successively larger submerged volumes, that can be designed to operate at the air- 
water interface. Other possibilities have been suggested by Boericke [1]. 
It is of interest to consider the comparative powering problems of these diverse water- 
borne craft. Because it is difficult to determine reliable figures for the propulsive coeffi- 
cients, the comparison of the power required for these craft (Fig. 2) is based on effective 
horsepower (EHP). Displacement is a reasonably good index of size; therefore, EHP’s have 
been estimated for the craft shown in Fig. 1. Each craft is assumed to have a displacement 
of 2844 tons, which corresponds to the displacement of a DD-692 class destroyer. This dis- 
placement was selected as the desirable maximum displacement for high-speed craft. 
Figure 2 is a rough comparison of the calm-water resistances of these waterborne craft 
at speeds up to 70 knots. The craft that has the lowest resistance is an ideal, deep-running 
submarine with a minimum of appendages, optimum hull form, and an assumed length-to- 
diameter ratio of 7.0. Not only is a deeply submerged submarine the lowest in resistance of 
any type of craft, but even at 60 or 70 knots the EHP is far from astronomical. 
For an ideal submarine form (H) running with its center 1-1/4 diameters below the sur- 
face (that is, the upper surface of the submarine is 3/4 diameter below the surface) there is 
a pronounced hump in resistance that corresponds to the maximum wavemaking speed. The 
submarine is close enough to the surface to produce a surface wave that causes this rise in 
EHP. As the speed of the submarine increases further, the wavemaking resistance becomes 
a decreasingly important part of the total resistance. 
For an ideal submarine (about 210 feet long) with a strut (about 30 feet long) piercing 
the surface (G) there is a sizable increase of EHP, which rapidly goes up with speed. Infor- 
mation is still rather sketchy on the resistance of struts piercing the surface, but the plotted 
values are believed to be roughly correct. The disturbance of flow by the strut is not 
