A coxed four is a rowing boat used in the sport of competitive rowing. It is designed for four persons who propel the boat with sweep oars and is steered by a coxswain. 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 Originally made from wood, shells are now almost always made from a composite material (usually carbon-fibre reinforced plastic) for strength and weight advantages.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 b
rigged for either as fours or quads. "Coxed four" is one of the classes recognized by the International Rowing Federation. It was one of the original events in the Olympics but was dropped in 1992. Carbon-fiber-reinforced polymer or carbon-fiber-reinforced plastic (CFRP or CRP or often simply carbon fiber), is an extremely strong and light fiber-reinforced polymer which contains carbon fibers. The polymer is most often epoxy, but other polymers, such as polyester, vinyl ester or nylon, are sometimes used. The composite may contain other fibers, such as Kevlar, aluminium, or glass fibers, as well as carbon fiber. The strongest and most expensive of these additives, carbon nanotubes, are contained in some primarily polymer baseball bats, car parts and even golf clubs where economically viable. Although carbon fiber can be relatively expensive, it has many applications in aerospace and automotive fields, such as Formula One. The compound is also used in sailboats, rowing shells, modern bicycles, and motorcycles, where its high strength-to-weight ratio and very good rigidity is of importance. Improved manufacturing techniques are reducing the costs and time to manufacture, making it increasingly common in small consumer goods as well, such as certain ThinkPads since the 600 series, tripods, fishing rods, hockey sticks, paintball equipment, archery equipment, tent poles, racquet frames, stringed instrument bodies, drum shells, golf clubs, helmets used as a paragliding accessory and pool/billiards/snooker cues. The material is also referred to as graphite-reinforced polymer or graphite fiber-reinforced polymer (GFRP is less common, as it clashes with glass-(fiber)-reinforced polymer). In product advertisements, it is sometimes referred to simply as graphite fiber for short.