hydroplane(redirected from Drag boat)
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hydroplane,small, high-powered racing boat designed to skim along the surface of the water. Its hull is so shaped that at high speeds the bow is tilted up out of the water, reducing the effect of frictional drag. Hydroplanes are commonly powered by outboard motors.
a light, high-speed vessel. Because of the special shape of its bottom, during mption the hydroplane gains hydrodynamic thrust, which lifts the nose part and causes a significant general up-floating of the vessel. (It appears to slip or glide along the surface of the water.) As a result, the area of contact between the bottom and the water is reduced, resistance to movement decreases, and the traveling speed increases. Light internal combustion engines and gas turbines are mounted on hydroplanes. Propellers (less often, airscrews) and water jets serve as propelling devices. Hydroplanes are used to carry passengers, for guard duty, in sport races, and for pleasure.