Written by Jen Finn
March 6, 2013
What's in the hold should tip the scales, not your boat
Based on U.S. Coast Guard reports.
Vessel stability must be a concern at all times and during all operations, particularly if you have not had your vessel assessed or tested and you don't have a stability book or stability instructions for your vessel. The best way to understand the limits of your vessel is to be trained in stability, and if possible, get training specific to your vessel.
Improper loading, failure to prevent catch from shifting in holds, failure to control free-surface effect, adding permanent ballast without a proper analysis, adding gear and equipment without assessing its effects, not accounting for vessel modifications, and inability to control progressive flooding can all contribute to a significant change to the center of gravity and righting arm on your vessel. These types of vessel alterations and vessel loading will affect the ability of your vessel to recover from a roll or list whether underway or tied up.
All of these factors came into play and contributed to the sinking of a 51-foot steel seiner built in 1970 and fishing out of Neah Bay, Wash. It was about 32 gross tons and had a draft of about 6 feet.
The seiner had interconnected fuel tanks outboard of the engine room, amidships. The pilothouse was located on top of the cabin forward, and there was a large removable purse seine net power reel on the deck astern.
Aft of the engine room, there was a single hold with dividers, and the crew normally used bin boards. Because the vessel was less than 79 feet long, it was not required to have a stability analysis, so there were no stability instructions for the vessel.
The vessel had been modified over the years, and equipment and gear had been added for use in various fisheries. The original owner added a significant but unknown amount of concrete ballast after the vessel capsized when attempting to lift a heavy load of fish aboard, amidships.
The owner at the time of the incident added the power reel on the stern. The drum was about 8 feet wide and about 8 feet in diameter. The center of the drum was about 5 feet above the deck. The reel, seine net, and stern roller added approximately 2,500 pounds of weight to the vessel.
Several years later, an enclosed pilothouse was added onto the cabin top forward. This added at least 1,000 pounds more than 6 feet above the deck.
The boom and rigging were apparently unchanged over the years except that the power block used for traditional purse seining may have been part of the original equipment. Other miscellaneous gear and equipment was removed and added as needed.
The owner indicated he had operated the vessel in Washington's Puget Sound and in Alaska waters for more than 10 years without unusual stability problems.
On this November evening, the skipper and crew of three had completed some salmon fishing in Puget Sound's Hood Canal. They had about 30,000 pounds of salmon in the hold, so it was approximately three-quarters full. The crew rendezvoused with a tender to offload their catch.
En route to the tender, they pumped off a minor amount of surface water in the fish hold and removed the top layer of bin boards. This allowed the fish to spread out evenly in the hold to facilitate manual unloading of the fish.
After mooring alongside the tender, the skipper saw that there was equipment to suction the fish from the hold. He had unloaded catch by this method before and had no problems. Had he known this method would be used ahead of time, he probably would not have removed the bin boards.
The fishing vessel had a slight port list, so the skipper vanged the seiner's boom to starboard, away from the tender, to compensate for the list. Seawater was added to the hold to help suction the fish. The system's dewatering return box was placed in the hold pointing to the fishing vessel's starboard side, while the suction tube was at the centerline.
When unloading commenced, the skipper was surprised by the power and capacity of the vacuum system. Water from the return lines jetted toward the vessel's starboard side, destabilized the surface layer of fish, and caused a list to starboard. The boom was repositioned to port, but the starboard list continued to increase.
The load continued to shift, the vessel heeled over, and water began coming over the gunwale and flooding the fish hold. Progressive downflooding occurred through the open galley and pilothouse doors. In short order, the bow spaces filled, and the vessel sank bow first.
The three crew members were able to climb aboard the tender, and the skipper got into the seine skiff. He was able to release the tender's suction and return hoses from the fishing vessel before it completely sank.
A salvage team was called in, and divers sealed the vents to reduce pollution. A crane barge raised and dewatered the vessel. The net and reel were removed from the vessel to increase its stability, and a tug then towed the vessel to a shipyard.
The initial list to port when tied to the tender, countered by positioning the boom to starboard, and the subsequent uncontrollable roll to starboard, indicate a vessel in a tender condition of stability. This was likely because of the upward migration of the center of gravity from the addition of the pilothouse and the power reel, and complicated by the addition of water to the hold, enabling the cargo to exhibit free surface effect from removal of the upper bin boards.
A stability assessment or test and stability book and instructions could have prevented this casualty. Additionally, measures to prevent cargo shifting and free surface effect in the hold could have been enhanced by leaving the bin boards in place. Proper loading and unloading procedures are critical.
Make sure you understand your vessel's stability issues. Seek assistance from a naval architect or marine surveyor. And ensure your vessel meets all the safety requirements. For more information and assistance, contact your local Coast Guard fishing vessel safety examiner. Also, visit www.fishsafe.info.
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