Page 101 - Theory and Design of Air Cushion Craft

Classification of drag components 85

obtained by adding the residual drag of the ship to the main components of ship drag
which can be determined by calculations.
In general, the total drag of craft can be written as follows:
R
R m
or

where R, dcv is the ACV total drag; R SK the SES total drag; R w the wave-making drag
the aerodynamic profile drag; R m the aerodynamic momen-
due to the air cushion; R d
tum drag; R sk the skirt drag for ACVs and bow/stern seal drag for SESs; R swf the fric-
tion drag of sidewalls; R. dp the underwater appendage drag (e.g. rudders, air ingestion
fences, propeller brackets); R mw the hydrodynamic momentum drag due to the cooling
water of engines and R a the drag due to the differential air momentum leakage from
bow and stern skirts.
Fig. 3.1 shows the various components of drag of the SES-100A built in the USA.
The principal dimensions and parameters of the SES-100A are LIB = 2.16, p c/L c =
19.5 kgf/m, v max = 76 knots.
The following sections of this chapter outline the methodology for determination
of each drag component listed above.

24 ^
wave making drag

sidewall drag

underwater appendage drag

air profile and momentum drag

Fig. 3.1 SES-100A drag as a function of Froude number.