Hydroplane (boat)

A hydroplane (or hydro, or thunderboat) is a fast motorboat, where the hull shape is such that at speed, the weight of the boat is supported by planing forces, rather than simple buoyancy.

A key aspect of hydroplanes is that they use the water they are on for lift rather than buoyancy, as well as for propulsion and steering: when travelling at high speed water is forced downwards by the bottom of the boat's hull. The water therefore exerts an equal and opposite force upwards, lifting the vast majority of the hull out of the water. This process, happening at the surface of the water, is known as ‘planing’.

Early designs of the 1920s were often built by amateurs, who employed the lightest materials available to them at the time, which were often glued timber boarding or plywood on the floor, 4-millimetre (0.16 in) plywood topsides, and varnished canvas decks. Most were about 4 metres (13 ft) long and stepped hulls were employed with a 75-millimetre (3.0 in) step to induce air under the hull, to enable the boat to float on air bubbles. The concept of 'planing' was not fully understood. Thus, hulls were flat bottomed with an upward curve at the bow and the step 2/3 of the way aft. The sheer weight of a 100 hp. engine was enough to keep the bow from digging in. In Ireland the sport was managed by the Motor Yacht Club of Ireland which had a base at the Lough Ree Yacht Club near Athlone.

One of the earliest examples can be seen in the Popular Mechanics issue, Vol. 63, No. 5, May 1935. the story of "Mile A Minute-Thrills of the Water" tells the story of the "No-Vac" by LeRoy F. Malrose Sr. aka. Fred W. McQuigg (pen name). LeRoy was the lead design illustrator for Popular Mechanics magazine, which at the time was located in Chicago, Il. The No-Vac design and build actually began in 1933, when LeRoy Sr. conceptualized an airfoil hull surface design which proved to produce far less drag than conventional "V" style boat hull designs of the time. In June 1933 the No-Vac was put the test with professional racing driver Jimmy Rodgers at the helm. That day the No-Vac set the world water speed record for an outboard powered boat of 78 miles per hour (126 km/h).

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