Much of the history of the City of Sturgeon Bay has been shaped by the comings and goings of all manner of ships and boats. The marine propeller played an important role as these vessels transitioned from sail to steam as their primary means of propulsion. Propellers continue to be an essential component in the propulsion system of most ships and boats plying the Great Lakes today.
A propeller is essentially a type of fan that transmits power by converting rotational motion into thrust. A pressure difference between the forward and rear surfaces of the blade create thrust as water is accelerated behind the propeller. A marine propeller is commonly referred to as a screw propeller or screw.
Components of two very different size marine screw propellers are exhibited here. A single blade from the enormous propeller that once moved the massive lake freighter Hon. James L. Oberstar towers on your left. Launched on November 22, 1958, the Oberstar is 806 feet long and can carry over 32,000 tons of cargo. The blade you see here was one of five that bolted to a central hub to create a propeller over 19 feet in diameter. It was donated by The Interlake Steamship Company, owner and operator of the Oberstar.
The smaller propeller to your right is cast from bronze as a single piece. This propeller is from the "bow-thruster"
of U.S. Coast Guard barge CGB-12002. A "thruster" is a small propulsion propeller specially designed to push a vessel from side to side. Rather than being at the rear of the vessel, these smaller propellers are typically located in a tube-like structure built into the hull facing the side of the vessel.
The small propeller was donated by the U.S. Coast Guard cutter Mobile Bay. This powerful 140-foot icebreaking tugboat is configured to fit into a notch at the stern of CGB-12002 to form one of the Coast Guard's largest buoy tenders.
The generosity of Interlake Steamship Company, Bay Shipbuilding Corporation, the Door County Maritime Museum, and the U.S. Coast Guard helped to create this exhibit.
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