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National Advisory Committee for Aeronautics, Technical Notes - Water Pressure Distributions During Landings of a Prismatic Model Having an angle of Dead Rise of 22.5° and Beam Loading Coefficients of 0.48 and 0.97

Smooth-water landing tests of a prismatic model having an angle of
dead rise of 22% 'were made as part of a landing investigation being con-
ducted at the Langley impact basin to determine the distribution of water
pressure on seaplanes. Landings were made for beam-loading coefficients
of O.h8 and 0.97 at fixed trims between 0.29 and 30.30 for a range of
initial flight-path angles from h.6° to 25.90 and also for 90°.

Initial impact conditions, over-all loads and motions, and maximum
pressures are presented in tables and figures for all the landings,
together with instantaneous—pressure-distribution and wave—rise data.

The experimental wave rise, peak pressures, and pressure distribu-
tions are found to be in fair agreement with the predictions of the
available theory; however, better agreement is obtained by modification
of the theory.

In order to obtain information regarding the magnitude and distribu-
tion of the water-pressure distribution during seaplane landings, an
experimental program is being conducted at the Langley impact basin on
various prismatic models. The results of investigations on heavily
loaded prismatic models having angles of dead rise of 0° and 30° have-
been reported in references 1 and 2, respectively. The present investi-
gation was made on a lightly loaded prismatic model having beam-loading
coefficients of 0.h8 and 0.97, an angle of dead.rise of 22% , and a beam
of 3.39 feet. Fixed-trim landings were made in smooth water for a large
range of trims, velocities, and flight-path angles. During each landing,
time histories of the pressures, velocities;_draft, and over—all loads
were recorded.

The purpose of this paper is to present the experimental pressure:
distribution, velocity, draft, wave-rise, and over-all-loads data obtained
from this investigation and to use these data to evaluate and extend the
existing knowledge of the wave rise and pressure distribution on V-bottom
seaplanes. Pressure distributions are compared to show the effects of
flight-path angle and beam loading, and experimental wave—rise and pres-
sure data are compared with the available theoretical and empirical pre-
dictions that are summarized in references 3 and h. In addition these
theories are modified in order to obtain better agreement with the experi-
mental data.