Hydroplane
- This article is about the hydroplane motorboat used in sport of hydroplane racing. See seaplane for the airplane that can land on water.
A hydroplane (or hydro, or thunderboat) is a very specific type of motorboat used exclusively for racing.
One of the most unique things about these boats is that they only use the water they're on for propulsion and steering--when going full speed they are primarily held aloft by a principle of aerodynamics known as "hydroplaning", with only a tiny fraction of their hull actually touching the water.
Hydroplane design
The basic principle of the hull design of most hydroplanes has remained much the same since the beginning of the sport: two sponsons in front, one on either side of the bow; behind the wide bow, is a narrower, mostly rectangular section housing the driver, engine, and steering equipment. The goal is to keep as little of the boat as possible from touching the water, since water gives more drag than air.
One of the few significant attempts at a radically different design was referred to as Canard. It reversed the width properties, having a very narrow bow that only touched the water in one place, and two small out-rigger sponsons in the back.
Early hydroplanes had mostly straight lines and flat surfaces, other than the uniformly curved bow and sponsons. The curved bow was eventually replaced by what is known as a pickle fork bow, where a space is left between the front few feet of the sponsons. Also, the centered single, vertical tail (similar to the ones on most modern airplanes) was gradually replaced by a horizontal stabilizer supported by vertical tails on either side of the boat. Later, as fine-tuning the aerodynamics became more important, the bottoms of the main hull have subtle curves to give the best lift.
Unlimited hydroplane engines
The aerodynamics industry has been the main source of engines for the boats. For the first few decades, they used surplus World War II-era internal-combustion airplane engines. The manufacturers of the two most commonly used engines are Rolls Royce and Allison Engine Company (part of General Motors). The loud roar of these engines earned hydroplanes the nickname thunderboats.
Starting in 1980, they have increasingly used Vietnam War-era turbine engines from helicopters (actually, in 1973-1974, one hydroplane used turbine engines in races to test the technology). The manufacturer of the most commonly used turbines is Lycoming.
Efforts have occasionally been made to use automotive engines, but they generally haven't been proven to be competitive.
