Propeller Shaft Tunnel Architecture


Tim C

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Jul 20, 2018
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I'm quite ignorant of ship construction so this may be a silly question.
I'm trying to understand the architecture of the propeller shaft tunnel. I'm looking at a tank top deck plan, from WTB "N" and aft. Starting at WTB N, this deck plan starts showing regularly spaced vertical line segments extending from the port and starboard sides inward. Between WTB N and O, an uninterrupted floor area is still obvious. Aft WTB O, the uninterrupted floor space is reduced and appears to disappear 2/3 of the way oft through this compartment.

What do these vertical lines represent? I'm guessing they are stringers extending from the hull into the center of the ship to provide structure? They also appear in the No 1 cargo hold. Some terminate in straight longitudinal lines, others in sequential curved lines - I'm not sure what that significance is?

In the first watertight compartment aft of the dynamo room, with these additional vertical lines shown, it's not clear to me if there are other longitudinal walls in place. Is this compartment open the entire breadth of the ship (ie, over 40') with all three propeller shafts residing in one "room"? Or are there additional longitudinal walls isolating each propeller shaft (forming multiple parallel tunnels)? This area is described as a "tunnel" but if it's a single open room it's not quite the claustrophobic environment I associate with "tunnel". I see, e.g., immediately prior to WTB O the longitudinal lines stop, which sort of suggests to me a side corridor but maybe I'm reading too much into this.

Aft of WTB "O", I see two shaft bearings for the central shaft on the flat floor. I assume greasers would have to access these. I also see one last bearing farther back (could they have reached this one?) with a thick black line immediately aft of it. I assume this thick black line is an external seal and that the greasers couldn't go any farther aft than this? A vertical cross section of the ship in this watertight compartment would be really enlightening since it's not clear to me how the vertical location of the two side shafts interacts with the hull contours.

Finally, greaser Frederick Scott's testimony involves retrieving a colleague trapped in one of these two tunnel compartments. Are we certain which of the two he was in?
 
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Tim Aldrich

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Jan 26, 2018
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There's some nice photos of Olympic's fore and aft propeller bosses that might help you wrap your head around how those areas may have looked. You just have to imagine how the hull plating wraps around the bosses.
 

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