page_title: H1 Unlimited
section_title: Today
hierarchical_section_title: H1 Unlimited / Today
caption_attribution_description: English: Seafair 2017 H1 Unlimited Final. First Turn after the start.
context_page_description: H1 Unlimited is an American Unlimited Hydroplane racing league that is sanctioned by the American Power Boat Association. 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 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 - 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.
context_section_description: The H1 Unlimited (prior to the 2009 Oryx Cup, known as ABRA Unlimited (American Boat Racing Association) since 2004) class is sanctioned by APBA, its governing body in North America and UIM, its international body.
  Unlimited Hydroplanes are fast boats capable of more than 320 km/h (200 mph) on the straights and running average lap speeds of 209–266 km/h (130–165 mph). They are 8.5–9.1 m (28–30 ft) in length and weigh a minimum of 3,060 kg (6,750 lb).
  The modern turbine-powered unlimited hydroplane is derived from the 3-point prop-riding hydroplanes of the 1950s. These were the first boats to ride on a cushion of air trapped between "sponsons" mounted on the sides of the front of the boat, and the bottom half of the propeller, which were all that touched the water.
  They were called "Unlimited" because they were the only class of boat racing the APBA that had no restrictions on the displacement size of their piston engines. The designation Unlimited has stayed with the class in the turbine era, even though there are restrictions on the turbine engine and its fuel.
  The Lycoming T55 L7C, originally used in Chinook helicopters, is the only turbine engine currently allowed in the sport.
caption: First turn after the race started at Seafair during the final race.
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