Directional Stability Tests of Two Prismatic Planing Hulls

摘要

The first of four reports on research designed to obtain basic hydrodynamicinformation about planing hulls through the use of captive model tests. The information is to be used for the general study of dynamic stability while underway, course keeping, turning and maneuvering, etc. The models tested were of idealized patrol boats having an LBP of 100 ft., a beam of 20 ft., and a displacement of 100 long tons. The models had prismatic hull forms with 10, 20 and 30 degrees of deadrise. The report presents the results of tests on the 10 and 20 degree of deadrise hulls. Most of the data is for unappended hulls. Straight course and rotating arm tests were conducted at three speeds C V = 1.5, 3.0, and 4.0 three angular velocities L/R = 0, 0.117, and 0.234 and a single beam loading C delta = 0.4375. The tests covered the following angular parameter ranges. Trim: -2 to 6 degrees, roll: -10 to 20 degrees, and yaw: -15 to 15 degrees. Twin rudders were fitted during the straight course tests at zero roll and yaw angles, and the effect of rudder deflection from -20 to 20 degrees investigated. Measurements were made of the drag and side forces, and the roll, pitch, and yaw moments. Draft was recorded. Underwater photographs were taken, and the wetted lengths and areas determined from these photographs. Video recordings were made of all runs. The data are presented in extensive tables, in wind axes and body axes, and in both dimensional and non-dimensional form. Planing boats, Transverse stability, Prismatic hulls, Course keeping, Turning tests, Maneuvering, Directional stability.