The overall objective of the eISR is to encourage innovative design in submarine engineering. Past teams have designed a wide variety of exciting machines, propelled either by standard rotating propellers, or by novel non-propeller thrusters. Regardless of the propulsion system selected, the basic design and build process boils down to five components: hull, propulsion, transmission, pilot safety & ergonomics, and control. The levels of sophistication applied to all of these components are up to each team - it is possible to do well with just a hull, some fins, and a recycled bicycle, but to really excel requires some serious thought and careful manufacturing. Here are some examples of the boats that participated in one of the previous races.
The rate-determining step for most teams is the hull manufacture. The process starts with some research into appropriate design, then proceeds through a CAD model (and often some CFD) to the actual build. Different teams have done things a variety of ways, but the most common procedure is to shape a foam and plywood block, then cover it in fibreglass to make a mould, which is then used to make the final hull. Modern 3D printing techniques are now beginning to show up in some teams´ designs. Buoyancy, reinforcement, attachment points, ports and hatches are then built into the hull halves before they're joined. The whole process can be done in two weeks by a dedicated team working some serious overtime, but to budget a month is more realistic.
The rest of the components then get fitted to the submarine. The simplest submarines use a set of bicycle cranks, fixed into the sub on a support column of some kind, with a bevel gearbox driven by a chain. The propeller is then driven by a shaft supported by a set of bearings fastened either to a shaft log, or directly to the hull. More sophisticated biomimetic machines have oscillating wings or undulating fins driven by complex mechanisms which harness the pilot’s muscle power to produce forward thrust. Control systems range from simple joysticks and bicycle brake cables, to sophisticated electronic systems, which are sometimes even computer controlled.