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National Advisory Committee for Aeronautics, Technical Notes - Impact Loads Investigation of a Chine-Immersed Model Having a Longitudinally Curved Bow and a V-Bottom with a Dead-Rise Angle of 30°

As part of a program to study the effects of transverse and longi-w
tudinal curvature on impact loads of chine-immersed models, a V-bottom
model having a dead-rise angle of 30° and the forward half longitudinally
curved upward on a radius of 10 beams has been tested at the Langley
impact basin. Impacts were made in smooth water at a beam-loading coef-
ficient of 18.8 with the trim angle held fixed throughout each impact.
Impacts with forward speed were made OVer a range of trim angles from
—50 to 30° and initial flight-path angles from 5.50 to 27°, and a few
impacts without forward speed were made at a trim angle of 00 for several
vertical velocities.

The data are presented and analyzed to determine the extent of bow
immersion during the impacts. The curved bow was found to be not immersed
at the high trim angles (15° and 50°), only slightly immersed at trim
angles of 6° and 9°, and almost totally immersed at trim angles of 5° and
below. The impact loads and motions obtained are presented in coefficient
form as variations with trim and initial flight-path angles. The maximum
impact loads are shown to be in substantial agreement with loads predicted
by theory for the non-bow—immersed case; however, comparisons at 5° trim,
where the bow is immersed, show maximum loads that are less than the loads
predicted by theory for a straight-keel model.

At the Langley impact basin a program has been underway to determine'
the relations of model configuration to hydrodynamic impact loads of
chine—immersed bodies. This program has dealt primarily with transverse
shapes, the effects of longitudinal shape having been included only in
tests of a single concave—convex transverse shape (reported in ref. 1).
The investigation reported herein was concerned with impact loads expe-
rienced by a Vsbottom model having a dead-rise angle of 50° and a longi-
tudinally curved bow of approximately half the model length.