The crew consists of four rowers, each having one oar, and a cox. There are two rowers on the stroke side (rower's right hand side) and two on the bow side (rower's lefthand side). The cox steers the boat using a rudder and may be seated at the stern of the boat where there is a view of the crew or in the bow (known as a bowloader). With a bowloader, amplification is needed to communicate with the crew which is sitting behind, but the cox has a better view of the course and the weight distribution may help the boat go faster. When there is no cox, the boat is referred to as a "coxless four".
Racing boats (often called "shells") are long, narrow, and broadly semi-circular in cross-section in order to reduce drag to a minimum. Originally made from wood, shells are now almost always made from a composite material (usually carbon-fibre reinforced plastic) for strength and weight advantages. Fours have a fin towards the rear, to help prevent roll and yaw and to help the rudder. The riggers are staggered alternately along the boat so that the forces apply asymmetrically to each side of the boat. If the boat is sculled by rowers each with two oars the combination is referred to as a quad scull. In a quad scull the riggers apply forces symmetrically. A sweep oared boat has to be stiffer to handle the unmatched forces, and so requires more bracing, which means it has to be heavier than an equivalent sculling boat. However most rowing clubs cannot afford to have a dedicated large hull with four seats which might be rarely used and instead generally opt for versatility in their fleet by using stronger shells which can be rigged for either as fours or quads.
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