Boatnerd Discussion Forum

As mentioned, the early "stovepipe" looking stacks were just that- hollow pipes connected directly to the boilers that helped create a strong draft for the fires due to their relatively large height to diameter ratio. Once later forced-draft watertube boilers came in, the stack design itself became less critical for the function of the boilers- they used smaller exhaust pipes that didn't need to be as tall and whose location wasn't as strictly dictated by the boiler arrangement. At this point the "stacks" were no longer exhaust pipes themselves, but rather a housing that enclosed the actual exhaust systems; they became more about tradition and providing a central, elevated point for intake and exhaust functions for various ships systems (not just boilers). So you saw more variation in design from the 50s on, as the shape and proportion of the stack could be driven by cost or aesthetics vs engineering requirements.

Diesels were even more flexible in terms of exhaust venting, and stacks became increasingly vestigial. In some cases the diesel exhaust from converted ships bypassed the stack altogether- the post-diesel conversion George A Sloan/Mississigai is an example of this. She simply had a diesel exhaust pipe poking through the deck astern of the original stack, not run through the stack at all. In some cases in recent years, the room available in the "stack" has been used to house exhaust after treatment equipment.

Stack design of the tall stovepipe did indeed serve a design purpose in that it provided updraft for the coal fired boilers to operate effectively in pulling the exhaust ( smoke ) from coal fired boilers out of the vessel. Later designs along with efficient power plants served simply to allow the exit for either boiler exhaust ( now with forced draft versus natural updraft) and the diesels exhaust. The physical size also served to house auxiliary equipment such as HVAC units etc. on the some of the later vessels.

First off, I should say that I have very minimal knowledge of ship design, and this is purely speculation…. But the Blough is amongst the last of the fore and aft lakers built, and I’d guess was an “in-between” from the mid-century design (think Sykes, Ryerson) and the more modern, economical design. I’d have to imagine building polygon stacks is way cheaper than elliptical ones.

Over the years there has been a wide range of stack designs with the earliest renditions being mainly stovepipe like styles that apparently served little purpose other than to contain the uptake from the engine. During the 1950s stacks seemed, for the most part, to become larger with some like those used on the Republic Steel C-4 conversions, Joseph H. Thompson, and McKee Sons being quite large. I’m assuming that some of this evolved from a stylistic standpoint but also that the extra space inside of the larger casing was used to place auxiliary equipment. I was wondering if anyone has any further insight into this and how these stack designs evolved to the large rectangular structures seen on modern vessels.

Also, for some reason the United States Steel’s Bradley fleet went with a conical stack design for its’s reboilering/diesel repowering conversions such as the Cedarville, Myron C. Taylor, and Calcite II done during the 1960s. This general style was later carried over to the building of the Roger Blough in the early 1970s. Was there any real reasoning behind this, or was this more just a way to update the stacks (of the older vessels) to a more modern appearance?