Gearing
The oar acts as a lever, pivoting around the gate, which acts as a fulcrum. The oar's button sets the leverage ratio between the inboard and outboard portions of the oar and therefore sets the gearing.
Moving the button towards the handle reduces the inboard and increases the outboard, making each stroke harder but more effective. Such a gearing might be used for sprint racing.
The distance of the gate from the boat's centerline is usually adjustable by 3 to 4 cm (2 to 2.5 inches).
The gearing is usually set the same for all rowers in a crew, though a particularly tall or strong oarsman may have a different gearing to accommodate them.
The gear ratio is calculated slightly differently for sculling and sweep boats.
Sculling:
Sweep:
where is the overall oar length, is the inboard length, and is the spread
The reason for two formulas is that spread is typically measured as the distance between port and starboard pins in a sculling boat and the distance between the keel and the pin for a sweep boat. Common gear ratios for sculling are between 2.4 and 2.6; for sweep common gear ratios are between 3.0 and 3.2.
Read more about this topic: Boat Rigging (sport Rowing)
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