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National Advisory Committee for Aeronautics, Technical Notes - An Experimental Study of Water Pressure Distributions During Landings and Planing of a Heavily Loaded Rectangular Flat Plate Model

As part of a landing investigation being.conducted at‘the Langley
impact basin to determine the distribution of water pressure on sea-
planes, a rectangular flat-plate model, 1 foot wide and 5 feet long,
was subjected to smoothrwater impact and planing tests. Landings were
made at fixed trims of 6°, 9°, 12°, 15°6 30° , and h5° for a range of
flight-path angles from approximately 2 to 20°, with beam—loading
coefficients of 18.8 and 36.5. Planing runs were made at trims of 6°,
15°, 30°, and A50.

Initial impact conditions and maximum pressures are presented in
tables and figures for all impacts, together with time histories of the
pressure distribution, draft, vertical velocity, vertical acceleration,
and wetted length.

The pressure coefficients based on the equivalent planing velocity
appeared to be substantially independent of the deceleration of the model
normal to the plate. The peak pressures were substantially equal to the
dynamic pressure corresponding'to the velocity of the peak-pressure
point, for which velocity an approximate equation was derived. For.
wetted-length — beam ratios greater than approximately 1.5, this velocity
was equal to the equivalent planing velocity for all flight—path angles;
for wetted-length - beam ratios less than approximately 1.5, the ratio
between this velocity and the equivalent planing velocity was unity for
planing (0o flight-path angle) and increased with increase of flight-
path angle.

In order to obtain information regarding the magnitude and distri—
bution of the hydrodynamic loads occurring during seaplane landings, a
large amount of theoretical and experimental research has been conducted
(references 1 to 18), most of which has dealt with the problem of a
V—bottom prismatic surface having a finite angle of dead rise (refer-
ences 1 to 10). For the limiting case of 00 angle of dead rise (the
rectangular flat plate), some research has been conducted but the avail-
able information is hardly adequate to describe completely all practical
conditions.