Archimedes' screw pipe does not need to be perfectly watertight, as long as the amount of water being scooped with each turn is large compared to the amount of water leaking out of each section of the screw per turn. If water from one section leaks into the next lower one, it will be transferred upwards by the next segment of the screw. In some designs, the screw is fused to the casing and they both rotate together, instead of the screw turning within a stationary casing. The screw could be sealed to the casing with pitch resin or other adhesive, or
SS Archimedes 1836 patent. Following the ship's entry into service, the propeller would subsequently undergo a number of modifications, the most important of which were an alteration to a double threaded/half turn format, and a division of the original 360° screw into two separate blades. The propeller had the unusual feature of being fully retractable in order to reduce drag when the ship was under sail—a task that took about 15 minutes. "Archimedes" made her maiden voyage, from London to Sheerness near the mouth of the Thames, commencing 2 May 1839. On the 15th, she commenced her first sea voyage, from Gravesend