Proceedings Of The Marine

FALL 2011

Proceedings magazine is a communication tool for the Coast Guard's Marine Safety & Security Council. Each quarterly magazine focuses on a specific theme of interest to the marine industry.

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In a July 2007, USCG Marine Safety Center mem- orandum, investigators took into account a wide range of factors to analyze the effect of ice on the vessel's stability to better understand how the vessel capsized so rapidly. The technical evaluation arrived at a relatively straightforward conclusion based on environmental conditions, vessel geometry, and vessel loading. The evaluation stated that the vessel, in its assumed loading condition "would only have been able to sustain a maximum of 2.25 inches of ice uniformly distributed about [its] surfaces and still remain upright." 1 The evaluation found that the vessel was likely experiencing heavy icing at the rate of .75 inches per hour, and that these icing conditions exceeded the amounts of ice that the vessel was required to be evaluated to by the Code of Federal Regulations. Marine Safety Center computer model in iced condition (green surfaces denote ice). antennae." Put simply: Ice accumulation increases the rate of ice accumulation. According to the analysis, the critical air temperature for icing is between zero and 32 degrees, and studies indicated that the vessel would begin to accumulate ice in wave heights of 3.9 feet with winds of about 14 knots. Furthermore, the effects of sea spray in icing were a key factor. Sea spray increases ice accumula- tion on a vessel, and is generated mainly by wind and spray blown from wave caps. Sea spray also occurs in others ways—from various aspects of severe cold weather conditions to the different characteristics of a vessel—all of which affected the ill-fated ship. Sea spray can also become more intense if the domi- nant sea state wavelength approaches the vessel's length. Additionally, as stated in the memorandum, "ice already formed increases the effective cross- sectional area of exposed rigging, mast, rails, and Icing curves for two sea water temperatures. The naval architect who was hired in July 2006 to make stability calculations in order for the ves- sel to be outfitted as day-scallop fishing boat was able to provide computer models of the vessel as well as a report of inclining and stability calcula- tions. The vessel was carrying several tons of newly added scalloping equipment aboard, in addition to an approximated 15,000 lbs. of fish and 13,000 Ibs. of ice in its hold that night. It was also outfitted with a roll-dampening system consisting of two 40-foot pin-connected masts, one port and one starboard, mounted outboard and aft of the pilothouse. The vessel's assorted surface areas and added weight provided a range of metrics and called for a variety of calculations and model analyses before investigators arrived at the conclusion that the vessel could only have handled 2.25 inches of ice before it would cap- size. It was evident based on eye-witness accounts and environmental conditions that there were most likely far heavier amounts of ice on certain portions of the vessel. The report went on to conclude that: "When compared with the required icing loads used in the naval architect's calculations, this number rep- resents a case that is nearly 12 times more severe than the anticipated amount of icing required by 46 CFR 28.550." 2 Endnotes: 1. United States Coast Guard Memorandum, "Subj: Request for Stability Evaluation of the Sinking of the F/V Lady of Grace, O.N. 599517," From: S.P. McGee, To: L.W. Clayborne, LCDR, July 18, 2007. 2. Ibid. www.uscg.mil/proceedings Fall 2011 Proceedings 65

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