American Boat Racing Association
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| Category | Unlimited hydroplane racing |
|---|---|
| Country |
 United States
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| Inaugural season | 1946 |
| Drivers | 12 |
| Teams | 12 |
| Engine suppliers | Lycoming Engines |
| Drivers' champion |
Jimmy Shane |
| Teams' champion |
Miss Madison (U-6) |
| Official website | www |
 Current season
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H1 Unlimited is an American Unlimited Hydroplane racing league that is sanctioned by the American Power Boat Association (APBA). Until 2009, the series was known as ABRA Unlimited Hydroplane, in turn renamed from APBA Unlimited Hydroplane in 2004. The H1 Unlimited season typically runs from July through September, consisting of five races.
A hydroplane (or hydro, or thunderboat) is a very specific type of motorboat used exclusively for racing. One of the unique characteristics about hydroplanes is that they only use the water they're on for propulsion and steering (not for flotation) - when going at full speed they are primarily held aloft by a principle of fluid dynamics known as "planing", with only a tiny fraction of their hull actually touching the water.
The unlimited hydroplane racing series was founded in 1946 when the unlimited class of boats was allowed to compete following World War II and the subsequent availability of surplus aircraft engines. It had been disbanded in 1922 in favor of the newly introduced "Gold Cup Class".
The world's first sanctioned unlimited hydroplane race was held in 1903 at Queenstown, Ireland and was very modest by later race standards. That race was won by Dorothy Levitt, driving a 11 metres (35 ft) boat powered by a 56 kilowatts (75 hp) Napier engine, totaling an average speed of 31.43 km/h (19.53 mph).
The boats were initially restricted to engines of a maximum of 10,240 cm3 (625 cu in), later increased to 12,000 cm3 (732 cu in). Hulls with "steps" or "shingles" on the underside were prohibited.
One reason for the rule change was to end the domination of its star driver, Gar Wood, who had won five consecutive Gold Cups from 1917. One win in 1920 in his twin Liberty L-12 powered Miss America, averaged 113.317 km/h (70.412 mph) in the 48-kilometre (30 mi) race over a 8.0-kilometre (5 mi) course and set a race record that stood until 1946. "King Gar" had entered fifteen Gold Cup heats during those pinnacle years. He finished first twelve times and second three times. Throughout the years, only two boats showed up to challenge Miss America; one of those was piloted by George Wood, Gar's younger brother, in Miss Chicago. Another reason for the rule change was to make racing more affordable.
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Wikipedia