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National Advisory Committee for Aeronautics, Report - Water Pressure Distribution on a Flying Boat Hull

The investigation reported herein was conducted by the
National Advisory Committee for Aeronautics at the
request of the Bureau of Aeronautics, Navy Department.
1 his is the third in a series of inrestigations of the water
pressures on seaplane floats and halls, and completes the
present program. It consisted of determining the water
pressures and accelerations on a C'urtiss H—16 flying
boat during landing and tazying maneurers in smooth
and rough water.

The results show that the greatest water pressures occur
near the heel at the main step, where the maximum pres-
sure is approximately 15 pounds per square inch. From
this point maximum pressures decrease in magnitude
toward the bow and chine. Pressures of approximately
11 pounds per square inch were experienced at the keel
slightly forward of the middle of theforebody when taking
of in rough water. The area of the forebody subjected
to considerable pressure is roughly a triangle having its
base at the step and its apex on the keel at the load water
line forward. 0n the bottom between steps, a maximum
pressure of 8 pounds per square inch is nearly uniform.

A tertical acceleration of 4.79 is the greatest calue encoun-
tered in landings, and is considerably greater than any
other value recorded. It was found that 39 is approxi—
mately the maximum to be expected in take-ofs in rough
water, and that this. value was exceeded during only a few
landings. A longitudinal acceleration of 0.9g was once
attained in. a landing in rough water and 0.79 is not
'unusual for take-ofis in rough water. The maximum
lateral acceleration attained in cross-wind landings is
approximately 0.59. The results show that the landing
loads were usually borne by an area near the main step,
and that rough water may cause large loads to be applied
near the middle of the forebody.

When considering the water reaction on a seaplane
float, the designer should know the magnitude of the
total water force, the manner in which the water load is
distributed, and the magnitude of the maximum local
pressures on all parts of the float bottom. The latter
item may be a separate consideration because high
local pressures are not necessarily associated with large
totalloads. For this reason data on the distribution of
maximum pressures should be correlated with total
loads if possible.