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Some Observations of Actual Trials Under Varying Conditions and Some Unlooked for Results—Measurements Carefully Made HE: QUESTION of the be- I havior of ships under certain conditions, such as backing at full speed in case of impending col- lision or stranding, is not new. It has arisen frequently in admiralty cases and in numerous instances of damage, actual or claimed, which do not reach court. There appears to be practically no authentic record of any observations, nor, in fact, accu- rate information of any sort, on the subject. Having occasion recently to look into the question, and being unable to find anything beyond com- mon report, or verbal statements of an exceedingly general character, and usually based upon incidents bound to affect the interest of the observer, the writer decided to do some experi- menting where the only conditions were the making of obsérvations as accurately as possible. Diagrams and data are herewith pre- sented from two steamers. They rep- resent both easy and medium lines, the block coefficient of A being 75 per cent and of B 80 per cent. Both are fairly high powered ships, the power available for backing in A being about 0.35 horsepower per ton of full load displacement, and in B, about 0.25 horsepower. These compare with Snip Ap Lawt Huron, Avg23/is Leviarh OA. 301 S' Beam 390 Displacement 2953 Tous Wearher ~ Fine, about 0.13 to 0.15 horsepower in the average bulk freighter. The trials were made at two differ- ent displacements in each case. The objectives were: 1—To determine the time required to bring the ship to a stop from nor- mal full speed. 2.—To determine the distance cov- ered (a) on, or parallel to, the nor- mal course, and (b) the actual dis- tance covered by the ship’s head. 3.—To observe the change in head- ing, if any, while bringing ship to rest, and its effect upon the ship’s position. Weather Conditions The intention was to make obser- vations under three different condi- tions, in other words, full, half and slow speeds. In the case of ship B, however, the trials, Figs. 7 and 8 with the ship nearly light, were made in a stiff head breeze which not only reduced the normal speed materially and probably exercised considerable influence upon the backing period and distance, but made the slow speed trials of doubtful value. The other trials of both ships were all made in clear fine weather. Since the experiments were all made in the open lake the ship herself was % * ae Fig \. Full Speed, \ZA Miles Ea lan 400Fr. Time re a Te Ee eS 6é HE way of a ship in the midst of the sea,’ is well exemplified in these observations. The difficulty of making them with- out any -visible fixed objects or ranges and with no assistance from the outside seems to have been over- come by causing the ship to serve as her own scale and protractor. The author deserves credit for his willingness to publish his results. 27 \ | Sowrae a +], awe aes DISFT Tyme 2 mine BSH REE OL ‘ By Henry Penton employed as the unit of measurement of distance. A man was_ stationed forward with a number of markers; an observer was placed at the taffrail in view of the bridge; at an agreed visual signal from the latter. the master shifted his telegraph to “Full Astern” and at the same instant repeated the signal to the man forward who threw a marker overboard. The whole op- eration occupied not over two sec- onds. As the marker came abreast of the taffrail the observer repeated his signal and another marker was put over, this being repeated as often as necessary, the observer noting the distance from the ship as they came aft and finally moving forward to meet the last one, and, when the ship’s headway appeared entirely gone, not- ing position, distance from ship and elapsed time. It will be observed ‘that. this distance is very important, in conjunction with the ship’s heading, in establishing her position and drift. By the latter term is meant the set- ting or reaching of the ship bodily along a line parallel to her course even with her head swinging at a consid- erable angle. An inspection of the diagrams will show that this heading did occur to a considerable extent. In plotting it was assumed that the SHip A. LAKEHURON Sept isis Displacement 3719 Tous. Weather. Fine Fig 4. FullSpeed. 11.6 mites \ ‘ Si ye eves MILE noe a . | Mme 90sec. -——— Fig.G. Slow. Speed 8.7 Miles. A25r. TWime WOsec.