The authors present a simplified method of stability analysis applicable to tugboats which must be reviewed by the U. S. Coast Guard for load line assignment. The paper includes a brief review of tugboat stability leading up to the present criteria applied by the Coast Guard. The present criteria are included. The proposed method consists of two or three conditions which, upon satisfactory analysis, provide considerable leeway to the tugboat captain in the manner in which he operates his vessel. The method of analysis and necessary definitions and interpretations are presented. The authors have made note of especially troublesome areas of design and some good design practices which will improve the stability of tugboats.

This paper presents a simplified method for the preparation of stability information for offshore supply vessels. The paper reviews the current methods used by the Eighth Coast Guard District Merchant Marine Technical Office for preparation of stability information and compares these with the proposed "simplified" method. The simplified stability letter incorporates a loading diagram which will make it easier for the vessel operator to use. The recommended letter will allow designers to obtain a higher maximum amount of deck cargo, provide more flexibility in the manner in which cargoes are carried, allow operators to exchange consumables for additional below-deck cargo, and simplify the calculations necessary for preparation of the stability information. It should be cautioned that the method presented is only the opinion of the authors. Approval should be obtained from the cognizant Coast Guard technical office before employing this or any other proposed method. It should also be noted that the stability criteria presented in Appendix I are not yet included in regulations and are subject to change.

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