Formulae for estimating the forces in seaplane-water impacts without rotation or chine immersion

Abstract

This report presents formulae and curves for estimating the maximum forces, together with the times and drafts associated with these forces, in main-step landings of seaplanes, provided that there is no rotation and that the chines do not become immersed. It also compares the values estimated by these formulae with the results of model tests made by the N.A.C.A. under controlled conditions in their Impact Basin, when good agreement is found. The basic formulae and curves given are considered to be the simplest and most accurate which can be evolved at present from the many proposed in various reports in recent years and reviewed in R. & M. 2720. They involve the use of a new basic 'impact parameter' and a new estimate for associated mass, which is based on three- rather than on two-dimensional concepts. It was convenient to split the report into two parts. Part I contains a statement of the formulae recommended for use in design estimates, together with numerical examples. Part II contains the comparison with experimental data. A simplified theoretical treatment and all mathematical details relevant to both parts is given in Appendix I.