T&R Bulletins & Reports

A new theory and computer program to predict the resistance of a sailing yacht with keel and winglets ace presented. While established ship-motion and added-resistance theories have been shown to give reasonable results for conventional ships, they do not satisfactorily predict the rough water behavior of a yacht sailing to windward. This is partially due to an inability to accurately account for the effects of the keel and other lifting appendages, including winglets as found on most modern International Twelve-Meter Class Yachts. Theories for evaluating both steady and unsteady lift, and the associated thrust and drag, due to body motions and waves must be included in order to obtain useful results. These theories have been incorporated into existing motion and added resistance prediction programs and can be used to determine the behavior in waves of a yacht sailing to windward at a specified angle of heel and yaw. Computer results for yachts with and without winglets are presented and compared with experimental results, which include the recent model experiments conducted by Gerritsma in Delft.

Single-skin glass-reinforced plastic (GRP) was the first craft in the early 1940s. Sandwich construction - a pair separated by and bonded to a thicker, lightweight core - is used in small marine Of thin, strong skins relatively new in the marine industry. Sandwich construction in general was introduced at about the same time as GRP in other industrial areas, namely aircraft, and structural engineering. Today, fiber-reinforced plastic (FRP) single-skin construction is employed in almost 80 percent of marine small craft design. Sandwich construction with balsa or foam cores is a much smaller percentage but is used almost exclusively in the construction of larger power vessels both private and commercial. The largest cored sandwich vessels built to date in North America are LOA 130 feet in length and are built of FRP skins and foam-cored construction.

The Society of Naval Architects and Marine Engineers has requested Tracer Hydronautics to perform a Trials - Model Test Correlation study for a 769 Foot Containership, Marad designation C8-S-85d. This report presents the findings of that study, performed under SNAME Purchase Order Number 0823. Tracer Hydronautics gratefully acknowledges the cooperation of Bethlehem Steel Corporation in providing trial data and trial calculation worksheets for this analysis.

This paper explores the application of magnetohydrodynamics (MHD) to marine ship propulsion plants. The paper first examines the theory behind and the history of magnetohydrodynamics, specifically with applications to seawater thrusters, and follows with an assessment of the state of the art and an evaluation of current MHD research efforts. The paper concludes with an annotated bibliography of a large body of published technical papers and research work in the field of MHD.