The Effect of Beam Loading on Water Impact Loads and Motions

An investigation of the effect of beam loading on impact loads and motions has been conducted in the Langley impact basin. Water impact tests of flat-bottom 5-inch-and 8-inch-beam models having beam-loading coefficients C(sub Delta) from 62.5 to 544 and a 30 deg dead-rise 5-inch-beam model A having beam-loading coefficients from 208 to 530 are described and the results analyzed to show trends of these heavy-beam-loading data with initial flight-path angle, trim angle, dead-rise angle, and time through- out the impact. Data from flat-bottom model tests, C(sub Delta) = 4.4 to 36.5, and from 30 deg dead-rise model tests, C(sub Delta) = 0.58 and 18.8, are included, along with the heavy-beam-loading data; and variations of these data with beam-loading coefficients are shown. Each of the load and motion coefficients is found to be directly proportional to a power factor of C(sub Delta). For instance, the maximum impact lift coefficient is found C(sub L,max) to be directly proportional to C(sub Delta, exp 0,33) for the flat-bottom model and C(sub Delta, exp 0,45) for the 30 deg dead-rise model. These variations of C(sub L, max) with C(sub Delta) are found to be in agreement with theoretical variations. Finally, an empirical equation for the prediction of C(sub L,max) is presented and is shown to give good agreement with experimental C(sub L, max) for about 500 fixed-trim smooth-water impacts. The range of variables included dead-rise angles from 0 deg to deg, beam-loading coefficients from o.48 to 544, trim angles from 3 deg to deg, and initial flight-path angles from about 2 deg to about deg.