by Richard Jenkins » July 19, 2018, 2:35 pm
The Supers were ordered before the US got involved in the war, and were the largest vessels designed for the iron ore trade. They were also quite advanced for the time. They made extensive use of welding in their construction, and were powered by 4,000-horsepower reduction-geared steam turbines fed by water tube boilers - about twice the average horsepower of most lakers of the time.
The Maritimers were designed as a wartime measure, to boost steelmaking capacity during the war, but also to serve as post-war replacement tonnage for older lakers that were traded in as part of the program. (A fleet would trade in an equivalent tonnage of older vessels in exchange for a new Maritimer, and continue to operate the older vessels along with the new one for the duration of the war, then hand over the trade-in ships for disposal at war’s end). With that in mind, they were designed to be modern vessels for their time, and were based closely on the design of the Pittsburgh Supers. To better fit the needs of a variety of fleets, the design was reduced in size somewhat (620/621 feet long x 65 feet wide vs. 639.5 x 67). Also, because there was a limited number of steam turbine manufacturers who were busy supplying engines for warships and fast transports, the Maritimers (like the ocean-going Liberty Ships) were powered by old-fashioned reciprocating steam engines with 2,500 horsepower, that were built by the shipyards. The six examples built by the American Shipbuilding Company (L6-S-A1 class) were given four-cylinder double-compound engines with Lentz-Poppet rotary-cam valve gear, while the ten that were built by the Great Lakes Engineering works (L6-S-B1 class) had more traditional three-cylinder triple-expansion engines with Stephenson valve gear.
In terms of spotting features, in addition to the difference in size, the Supers had a rounded front to the forward cabin, a tall stack mounted towards the front of the boat deck (the bunkering hatch was behind the stack), the rear mast behind the stack, and a counter stern. The A1 Maritimers has a similar round-fronted forward cabin, but a somewhat shorter stack that was mounted aft of the bunkering hatch, the mast behind the stack, and a cruiser stern. The B1 Maritimers had a square-fronted forward cabin, the rear mast mounted towards the front of the boat deck, with the bunkering hatch behind it and a tall stack mounted aft of the bunkering hatch, and a counter stern.
For surviving examples, see Alpena (Super), Cuyahoga (A1 Maritimer), and Mississagi (B1 Maritimer).
The Supers were ordered before the US got involved in the war, and were the largest vessels designed for the iron ore trade. They were also quite advanced for the time. They made extensive use of welding in their construction, and were powered by 4,000-horsepower reduction-geared steam turbines fed by water tube boilers - about twice the average horsepower of most lakers of the time.
The Maritimers were designed as a wartime measure, to boost steelmaking capacity during the war, but also to serve as post-war replacement tonnage for older lakers that were traded in as part of the program. (A fleet would trade in an equivalent tonnage of older vessels in exchange for a new Maritimer, and continue to operate the older vessels along with the new one for the duration of the war, then hand over the trade-in ships for disposal at war’s end). With that in mind, they were designed to be modern vessels for their time, and were based closely on the design of the Pittsburgh Supers. To better fit the needs of a variety of fleets, the design was reduced in size somewhat (620/621 feet long x 65 feet wide vs. 639.5 x 67). Also, because there was a limited number of steam turbine manufacturers who were busy supplying engines for warships and fast transports, the Maritimers (like the ocean-going Liberty Ships) were powered by old-fashioned reciprocating steam engines with 2,500 horsepower, that were built by the shipyards. The six examples built by the American Shipbuilding Company (L6-S-A1 class) were given four-cylinder double-compound engines with Lentz-Poppet rotary-cam valve gear, while the ten that were built by the Great Lakes Engineering works (L6-S-B1 class) had more traditional three-cylinder triple-expansion engines with Stephenson valve gear.
In terms of spotting features, in addition to the difference in size, the Supers had a rounded front to the forward cabin, a tall stack mounted towards the front of the boat deck (the bunkering hatch was behind the stack), the rear mast behind the stack, and a counter stern. The A1 Maritimers has a similar round-fronted forward cabin, but a somewhat shorter stack that was mounted aft of the bunkering hatch, the mast behind the stack, and a cruiser stern. The B1 Maritimers had a square-fronted forward cabin, the rear mast mounted towards the front of the boat deck, with the bunkering hatch behind it and a tall stack mounted aft of the bunkering hatch, and a counter stern.
For surviving examples, see Alpena (Super), Cuyahoga (A1 Maritimer), and Mississagi (B1 Maritimer).