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National Advisory Committee for Aeronautics, Technical Notes - The Planing Characteristics of a Surface Having a Basic Angle of Dead Rise of 40° and Horizontal Chine Flare

In order to determine the effects of increasing the angle of dead
rise on the planing characteristics of horizontally flared prismatic
surfaces, an experimental investigation has been conducted with a surface
having a basic angle of dead rise of 40° and horizontal chine flare.
Wetted length, resistance, center-of-pressure location, and draft were
detenmined for speed coefficients up to 25.0 and trims up to 30°. Beam—
loading coefficients ranged frdm 0.85 to 87.33 and keel-weeted—length——
beam ratios extended generally to 7.0 and, in some cases, to higher values
whenever conditions of load and spray permitted.

The data show that for.a given trim the planing characteristics
depend principally on lift coefficient. The experimental variation of the
difference between chine and keel wetted lengths with trim has the same
general trend as theory. An increase in angle of dead rise from 20°
(NACA TN 2804) to #00 decreased the ratio of center-of—pressure location
to mean wetted length and the extent of the pile-up of water but increased
the friction drag. At trims of 2&0 and greater, friction drag is negli—
gible and the resistances for those trims may be assumed equal to the load
times the tangent of the trim angle.

A general program of research on the planing characteristics of a
series of related prismatic surfaces has been undertaken by the National
Advisory Committee for Aeronautics and is described in reference 1. The
primary Objective of this program is an extension of the range of experi—
mental data on planing surfaces to cover the high trims and loads of
significance in the design of high-speed water-based aircraft.

The detailed scope of the program was established to include basic
angles of dead rise up to #00, trims up to 30°, wetted—length~—beam
ratios up to 7.0, and Froude numbers based on beam up to 25.0. The prin-
cipal planing characteristics to be determined for appropriate combinations
of speed, load, and trim were resistance, center of pressure, draft, and
wetted length.