Excerpts from Edmund Fitgerald NTSB Report
The National Transportation Safety Board determines that the probable cause of this accident was the sudden massive flooding of the cargo hold due to the collapse of one or more hatch covers. Before the hatch covers collapsed, flooding into the ballast tanks and tunnel through topside damage and flooding into the cargo hold through non-weathertight hatch covers caused a reduction of freeboard and a list. The hydrostatic and hydrodynamic forces imposed on the hatch covers by heavy boarding seas at this reduced freeboard and with the list caused the hatch covers tocollapse.
Contributing to the accident was the lack of transverse weathertight bulkheads in the cargo hold and the reduction of freeboard authorized by the 1969, 1971, and 1973 amendments to the Great Lakes Load Line Regulations.
The FITZGERALD was a conventional "straightdecker" Great Lakes bulk cargo vessel. (See figure 2.) It was 729 feet long, 75 feet in breadth, 39 feet in depth, 13,632 gross tons, and 8,686 net tons. It was propelled by a 7,500-hp, 
steam turbine and was built as Hull 301 at Great Lakes Engineering Works, River Rouge, Michigan, in 1958. The vessel was owned by Northeastern Mutual Life Insurance Company and operated by the Columbia Transportation Division of the Oglebay Norton Company
The vessel had a 860,950-cubic-foot cargo hold divided by two nonwatertight transverse "screen" bulkheads. Outboard and below the cargo hold were eight ballast tanks divided at the centerline into port and starboard tanks. The forward deckhouse contained the pilot house and accommodations for the deck crew. The engine room was located aft, above which were the rest of the accommodations and the crew’s messing facilities. Below the weather deck and above the ballast tanks were two tunnels, one port and one starboard, used for access between the accommodation areas during adverse weather. The sheer strake extended 15 3/8 inches above the weather deck at side and was connected to the stringer plate by a riveted gunwale bar.
There were 21 cargo hatch openings. Each opening measured 11 feet longitudinally and 48 feet transversely and had a 24-inch coaming above the weather deck. Each opening was made weathertight by a single-piece steel hatch cover. The hatch covers were made of 5/16-inch stiffened plate with a 9/16-inch rubber gasket around the underside of the plate’s perimeter. Each hatch cover was secured by 68 manually operated "Kestner" clamps arranged on 2-foot centers. Each clamp had an adjustment bolt which determined the force applied by the individual clamp and therefore controlled the deflection of the hatch cover, the compression of the rubber gasket, and the weathertightness of the hatch opening. There were no written procedures concerning maintenance or adjustment of the hatch clamps or gaskets. An electrically operated hatch cover crane which ran on rails outboard of the cargo hatch openings was used for lifting the hatch covers.
Between 1958 and 1973, the FITZGERALD was permitted three reductions in the minimum freeboard required by 46 CFR Part 45. (Freeboard on the FITZGERALD was the distance from the maximum draft permitted to the weather deck at side.) A comparison of the requirements for Great Lakes cargo vessels and those for vessels operating on the oceans shows that for vessels of similar dimensions, the freeboard required for a Great Lakes Load Line and that required for ocean service would be approximately the same. However, the longitudinal strength required for a Great Lakes vessel is approximately one—half that required for a vessel in ocean service.
46 CFR 45.5 states that midsummer freeboard applies May 1 through September 15; summer freeboard applies April 16 through April 30 and September 16 through September 30; intermediate freeboard applies October 1 through October 31 and April 1 through April 15; and winter freeboard applies November 1 through March 31.
[when the Fitzgerald was built in 1958 her required minimum winter freeboard was 14 feet, 9-1/4 inches. This was reduced to 14 feet, 3-1/2 inches in 1969; 13 feet, 2 inches in 1971 and 11 feet, 6 inches in 1973]
The FITZGERALD was last inspected by the Coast Guard and the ABS on October 31, 1975. Four minor structural defects in way of the hatches were noted and the Coast Guard ordered these defects to be repaired before the 1976 shipping season. The structural defects consisted of: A 1-inch notch in the plate in way of hatch No. 13; a 1-inch gouge in the plate in way of hatch no. 15; a 10-inch crack in No. 16 hatch end girder; and a 1-inch crack at the intersection of No. 21 hatch coaming and hatch end girder. All four defects probably resulted from damage from off loading equipment and did not affect the strength of the hull girder.
The wreckage lies approximately 17 miles northwest of Whitefish Point, Michigan. The wreckage consists of an upright bow section, an inverted stern section, and debris from a missing 200-foot midship portion. The bow section is 276 feet long, inclined 15 degrees to port from the upright, extends from the stem to a location between hatches Nos. 8 and 9, and is buried in mud up to the 28-foot draft mark.
There was extensive damage to the forward deckhouse and there were several holes in the bow shell plating. The rest of the shell plating extending back to the rupture was intact. The No. 1 hatch cover was entirely inside the No. 1 hatch and showed indications of buckling from external loading. Sections of the coaming in way of the No. 1 hatch were fractured and buckled inward. The No. 2 hatch cover was missing and the coaming on the No. 2 hatch was fractured and buckled. Hatches Nos. 3 and 4 were covered with mud; however, one corner of hatch cover No. 3 could be seen in place.
Hatch cover No. 5 was missing. A series of 16 consecutive hatch cover clamps were observed on the No. 5 hatch coaming. Of this series, the first and eighth were distorted or broken. All of the 14 other clamps were undamaged and in the open position. The No. 6 hatch was open and a hatch cover was standing on end vertically in the hatch. The hatch covers were missing from hatches Nos. 7 and 8 and both coamings were fractured and severely distorted. The bow section abruptly ended just aft of hatch No. 8 and the deck plating was ripped up from the separation to the forward end of hatch No. 7.
The stern section was upside down and inclined 10 degrees from the vertical away from the bow section. All bottom plating was intact from the stern to a location between hatches Nos. 17 and 18 where the vessel had separated.
The rudder and propeller were undamaged with the rudder positioned no more than 10 degrees from centerline. There was mud—covered wreckage extending out from the ruptured end of the stern section, but no identification of what part of the ship it came from can be determined. Three hatch coamings and a hatch cover were lying next to the stern section. One of the hatch coamings bore the numeral 11.
An analysis of the wreckage itself did not give any conclusive evidence as to the cause of the sinking of the FITZGERALD. However, an analysis of the final events in conjunction with the wreckage indicated that the FITZGERALD experienced massive flooding of the cargo hold just before she sank.
When the master of the FITZGERALD first reported topside damage to the vessel at 1530 on November 10, he stated he had a fence rail down, had lost two vents, and had "both" pumps going. Flooding was occurring in one or more ballast tanks, the tunnel or a combination of ballast tanks and the tunnel. At the same time, because of the severe sea conditions, water was entering the vessel’s cargo hold through nonweathertight hatch covers. Between 1530 and the sinking, the FITZGERALD’s deck was awash with green water. Since the sheer strake extended 15 3/8 inches above the weather deck for the entire length of the vessel at side, water would have been trapped on deck. The combined effect of the water in the ballast tanks, the tunnel, the cargo hold, and on deck would have decreased the vessel’s freeboard, permitted more water to enter the cargo hold, and increased any trim or list initiated by the ballast tank or tunnel flooding.
The Safety Board determined through its structural analysis of the hatch covers that the sea state, combined with the loss of freeboard and the trim caused by flooding, could have imposed sufficient hydrostatic loads to cause a hatch cover failure and collapse under static loading.
The Safety Board calculations assumed a wave height of 25 feet. This was based on the ANDERSON’s observations of significant wave heights from 18 to 25 feet. A significant wave height of 25 feet means that the average height of the one-third highest waves is 25 feet. The Safety Board also calculated that, by 1915 on November 10, sufficient water had entered the hull of the FITZGERALD to reduce its freeboard to near zero at hatch No. 1. With zero freeboard, a wave of 25 feet in height would yield a static head of 12.5 feet. This static head was sufficient to cause hatch cover failure. 46 CFR 45.145 required that hatch covers be designed assuming a minimum 4-foot head of water
The quartering seas would cause a piling" effect in the area behind the forward deckhouse and thus increase the static head. Any stresses caused by the dynamic forces of the boarding seas would have added to the static stresses and would have accelerated the hatch cover failure.
The hatch cover failure would have been severe enough to allow rapid massive flooding of the cargo hold. Since there were no watertight bulkheads within the cargo hold, the flooding water would have progressed throughout the hold within minutes, causing the vessel to sink bow first to the bottom of the lake. Upon impact with the bottom, the midship portion disintegrated and the stern section rolled over, coming to rest upside down.
Safety Board investigators considered the possibility that flooding resulted from a grounding which ruptured the hull plating in the area of some ballast tanks, but rejected this possibility for the following reasons: A reconstruction of the FITZGERALD’s most probable trackline shows her path to be about 3 miles from the nearest position where grounding could have occurred.
No gouges, scrapes, fractures, indentations, or other indications of grounding were visible on the exposed bottom plating on the after section of the wreckage. These observations were made during a close examination of the exposed bottom plating by underwater television from the CURV III. Damage to the bottom plating of a vessel from grounding on boulders in the rocky shoal north of Caribou Island during the severe sea conditions would probably have extended into the bottom plating of the stern section.-
Is it a ship or a boat ?
(nautical lingo on the Lakes!)
There is often confusion over nautical lingo on the Great Lakes. You might say that people connected with the Great Lakes shipping industry have kind of become bilingual since the opening of the St. Lawrence Seaway in 1959. It's no secret that the nautical lingo of the Great Lakes differs considerably from that on the high seas.
While the saltwater seafarer thinks of "going to sea" a Great lakes seaman thinks of "going sailing" or "steamboating" - and on a "boat" rather than a "ship". A lakes seaman similarly thinks of seagoing as "sailing on saltwater' or "sailing down the coast".
An oceangoing vessel, regardless of its size, should always be referred to as a "ship". To the saltwater sailor, a "boat" is simply the lifeboat hanging in its davits on the "boat deck".
Lake freighters, on the other hand, have been called "boats" for more than 100 years, even though their lengths have reached 1,000 feet. It has also become tradition throughout the Great Lakes - seaway region to identify oceangoing ships as "salties" and lake freighters as "lakers".
The term "master" is appropriate on the high seas, but is rarely heard on the lakes. And, the duties of the senior officer are to "command" his ship. On the lakes, the senior officer is almost always referred to as "captain" and he "sails the boat" or "has a boat to sail". Both master and captain are commonly called "old man" by their respective crews, but never when within earshot.
On the lakes, the "helmsman" or "quartermaster" is known as the "wheelsman". The "lookout" is a "watchman" and lesser deck ratings are "deck hands". Thus the deck crew spends the season "wheeling", "watching" or "decking". As for the engine room, the terms "oiling" or "firing" apply to both salties and lakers. All freighters sailing the lakes are either "upbound" or "downbound" On the "trip" (the term voyage is seldom heard on the lakes) from Lake Erie to Lake Superior and return, this is easy to visualize. But other lake trips are more confusing, especially if you attempt to correlate status of upbound and downbound with the status of whether a vessel is light and going after a cargo, or whether it is loaded and coming back. For instance, a "light" vessel to Lake Superior for iron ore or grain is always upbound, and coming back loaded is always downbound. But a light vessel sailing from Buffalo to Chicago for cargo is upbound while sailing westward and sometimes southwestward on Lake Erie. The vessel is also upbound while sailing northward on Lake Huron, but is downbound on the same trip sailing southward on Lake Michigan.
On most ocean vessels, both the deck and engine departments are housed in on main superstructure. On lakers, the deck department is known as "forward end" and the engine department as the "after end".
To all saltwater seamen, ocean vessels have their "main deck" at "deck line", or at the level of the top of the sheer strake. On the lakes, however, this is the "spar deck". The "main deck" of a laker is at a level of the tops of the side tanks, or one deck below the spar deck. While the bottom of the cargo hold on salties is the "cargo deck" or "hold deck", this deck on lakers is simply the "tank top".
Ocean ships have "passageways" and "ladders" while lakers have "hallways" and "stairs". There is one exception, lakers have a "boarding ladder" while the salties have a "gangway".
In contrast to the ancient sailing concept of going to the right and passing port-to-port, the recommended courses are so laid out in Lakes Huron and Superior that upbound vessels are close to the U.S. shore and downbound vessels are 10 miles or so further out in the lake, creating the impression, at least to the newcomer, of passing to the left, or starboard-to-starboard. However, the reason for keeping the heavy laden vessels out in deeper water is readily apparent.
In narrow channels or rivers, vessels keep to the right and pass port-to-port, or, as lake sailors say, "pass on the one-whistle side".
Finally, we can advise that it is entirely appropriate to ask oceangoing seamen about rough weather sailing on the high seas and to ask sailors about a good blow on the lakes. On the other hand, never attempt to tell lake sailors about how tough sailing may be "on the coast" or North Atlantic, save your breath!