Here are some sketches from the stern–the business end of the United States. In number 1, I’m just trying to get the scale of everything right as I show some of the key elements such as the propellers, bossings, and rudder. The bossing is the wing-like structure that supports the propeller shaft. Since there are two propellers on each side of the ship, there are also two bossings on each side. The structure is partly disassembled here to show some of the subassemblies that make up the structure around the rudder. The space between the steel plates, depending on exactly where they are, is filled either with seawater or fuel oil.
In sketch number 2, you can see some of the sections of one of the bossings. The end piece, the one that looks a little like a jet engine, is the stern tube. The propeller shaft projects from the sterntube to receive its propeller. The pieces of framework that carry the weight of the shaft, propeller, and bossing plates are called spectacle frames. It probably looks like I draw these things over and over. The reason is I do draw these things over and over until I either convince myself I understand what I’m looking at and how it all goes together or I just lose interest.
In sketch number 3,we have a finished view of the five bladed, port side, aft propeller ( I hope you’re impressed with the specificity of that last phrase-I’ve practiced it a lot). It is not unlike, in fact it’s identical to the propeller that now appears on a tee shirt and seems to be weightless. Why not? These cast objects really are pieces of sculpture. Beautifully finished. My favorite so far is still attached to a piece of shafting and is displayed outside the Mariners Museum in Newport News, Virginia. Worth the trip just for the screws that hold the pieces together. The screw driver must be enormous!—David Macaulay