Airboat

Airboating has become a popular ecotourism attraction in the Florida Everglades in the USA

An airboat

Hovercraft.

An airboat, also known as a fanboat, is a flat-bottomed vessel (jon boat) propelled in a forward direction by an aircraft-type propeller and powered by either an aircraft or automotive engine.^[1] Airboats are a very popular means of transportation in the Florida Everglades, parts of the Indian River Lagoon, the Kissimmee and St. Johns Rivers, as well as Louisiana Bayous, where they are used for fishing, bowfishing, hunting, and ecotourism, and in other marshy and/or shallow areas where a standard inboard or outboard engine with a submerged propeller would be impractical.

Overview

The engine and propeller are enclosed in a protective metal cage that prevents objects, e.g., tree limbs, branches, clothing, beverage containers, passengers, or wildlife, from coming in contact with the whirling propeller, which could cause devastating damage to the vessel and traumatic injury to the operator and passengers. The propeller produces a rearward column of air that propels the airboat forward. Steering is accomplished by forced air passing across vertical rudders. There must be a forceful airflow in order for the vessel to be steered. Airboats do not have brakes and are incapable of traveling in reverse, unless they have a reversible propeller. Stopping and reversing direction are dependent upon good operator/pilot/driver skills. Some designs use a clam shell reversing device but it is intended for braking or backing up very short distances. These systems are not commonly used.

Aft view of safety cage during operation

The operator/pilot/driver and in most instances the passengers, are seated in elevated seats that allow visibility over swamp vegetation. The improved visibility permits the operator and passengers to observe floating objects, stumps and animals in the airboat's path.

The characteristic flat-bottomed design of the airboat, in conjunction with the fact that there are no operating parts below the waterline, permit the vessel to be navigated easily through shallow swamps and marshes; in canals, rivers, and lakes; as well as on frozen lakes. The airboat's design makes it the ideal vessel for flood and ice rescue operations.

Steering the airboat is accomplished by swiveling vertical rudders positioned at the rear (stern) of the vessel. The propeller produces a column of air that produces forward momentum. That column of air passes across the rudders, which are directed through the forward and backward movement of a vertical "stick" located on the operator's left side. The "stick" is attached to the rudders via Bowden Cable or linked rods. Overall steering and control is a function of water current, wind, water depth, and propeller thrust.

The Army Corps of Engineers uses an airboat to collect herbicide-resistant hydrilla from Lake Seminole in northern Florida

The sound produced by an airboat's propeller and engine can be loud; the majority of the sound is produced by the propeller. Modern airboat designs and modern technology have significantly reduced the sound that an airboat produces. Modern airboat engines are equipped with mufflers and multi-blade carbon-fiber propellers that greatly reduce the sound emitted by the airboat.

Airboats vary in size from standard, 10-foot (3.0 m)-long hunt/trail boats, with a two- to three-passenger capacity, to large 18-passenger and greater tour boats.

History

An early form of the air boat

The first airboat, called the Ugly Duckling, was built in 1905 in Nova Scotia, Canada by a team led by Dr. Alexander Graham Bell. It was used to test various engines and prop configurations. An associate of Dr. Bell, Glenn Curtiss (of airplane manufacturing fame) is reported to have registered the first airboat in Florida, USA in 1920. It was called the Curtis Scooter^[2] and it had a closed cockpit design.

A story in the Nov/Dec 2009 issue of Airboating Gazette showed an airboat called a Free Bottom Craft that was built in the mid to late 1920s, using a wood hull, a Curtiss aircraft engine and was on exhibit at a New York boat show. The airboat was built by Charles Post and Herbert Ballantine in Huntington, NY and tested on the Long Island's Hewlett Bay.

By the 1930s homemade airboats began appearing in the swamps and marshes of Florida and Louisiana. One company in Florida claims to have been providing airboat rides as entertainment since the mid-1930s. Over the years a variety of designs were tried and through trial-and-error, the standard design used today arose: an open, flat bottom boat with an engine mounted on the back, the driver sitting in an elevated position, and a cage to protect the propeller from objects flying into them. One well documented case of a homemade design (though not the first) was an airboat built by staff at the Bear River Bird Refuge near Brigham City, Utah in the 1940s. It appears to have involved collaborative efforts by three employees of the refuge - Leo Young, G. Hortin Jensen and Cecil Williams.

A 1987 story in Ducks Unlimited magazine mentioned Young and Jensen and dated the building of the first boat in 1950. Refuge records, however, show the first boat came into use in 1943, with several photos of running air boats dated 1947. Prior to the introduction of the airboat, refuge biologists had to either walk through shallow water and deep, sticky mud or push unpowered flat-bottom boats with long poles. Staff had experimented with a boat called the "Mud Queen," which had small paddle wheels on either side that pushed the boat. They built their first airboat nicknamed "Alligator I" from a flat-bottom boat pushed along by an aircraft engine purchased for $99.50. Young reported that he called the first airboat an "air-thrust boat." Once word got out about the boat, Leo Young built and sold boats all over the world.

Propulsion

Airboats are powered by either an air-cooled, 4- or 6-cylinder aircraft or water-cooled, large-displacement, V8 automotive engine, ranging from 500 to over 600 horsepower (450 kW). Readily-available replacement parts make the automotive engine preferred in some cases, although an opposed, 4- or 6-cylinder (O4 or O6) aircraft powerplant is usually preferred due to ease of repair and lighter weight (a reciprocating aircraft engine contains fewer moving parts than a standard automotive engine). High octane automotive gas is less expensive than aviation gas (usually 100LL), although most reciprocating aircraft powerplants can be derated to burn 87-octane autogas.

Safety

Knowledge of operational safety is essential when operating an airboat.

The average airboat produces a 150-mile-per-hour (241 km/h) prop wash behind it and if a tree branch gets into a propeller the spray of material could be devastating, causing damage to the vessel and injury to the boat's occupants.

Modern commercially manufactured airboat hulls are made of aluminum or fiberglass. The choice of material is determined by the type of terrain in which the vessel will be operated.

Airboat manufacturers tend to be small, family run businesses that assemble built to order boats; airboats are also manufactured in Russia and Australia. There are also airboat manufacturers in Europe, Airboat Italy and Hi Tech International which produces the Arctic Airboat used for ice transport. Normally a truck or airplane engine is positioned on the back of the boat with a wood or carbon fiber propeller.

Also, in 1998-99 the U. S. Fish & Wildlife Service's National Conservation Training Center, located in Shepardstown, West Virginia, and in cooperation with the U. S. Corps of Engineers in Jacksonville, Florida, produced a 70-minute training video entitled Airboat Safety - Design-Operation-Maintenance. The video also includes an early history of airboats and interviews with two airboat manufacturers in Florida. It was considered to be the only airboat video of its kind and purpose in 1998-99, and may still be the only one with the range of airboat subject matter ever produced. Since it was produced by a Federal Agency, it is in the public domain, and is not copyrighted. 500 copies of the video were produced.

Rescue

A resident is transported by Airboat after Hurricane Katrina.

In recent years airboats have grown in popularity in the area of public safety. Airboats have proven to be indispensable for flood, shallow water, and ice rescue operations. During the flooding of New Orleans following Hurricane Katrina, August 29, 2005, airboats from across the United States rescued thousands of flood victims. Thirty airboats evacuated over 3,000 patients and medical staff from four downtown New Orleans hospitals in less than 36 hours.

Numerous articles have been published in fire-rescue trade journals, such as Fire Engineering and National Fire and Rescue Magazine, describing the advantages, capabilities, and benefits of using airboats for water rescue operations, and providing in-depth description of actual water rescue incidents, including the flooding of New Orleans.^{[3][4][5][6][7][8]}

Airboats are also used by U.S. Military and U.S. Coast Guard. In Vietnam the Hurricane Aircat airboat was used to patrol areas where larger boats could not get to and used by the U.S. Special Forces.^[9] They are also used in Iraq for border patrol. The Nov/Dec 2007 issue of Airboating Magazine had an article on airboats used in Vietnam and in Iraq and has had numerous articles on airboats used by U.S Coast Guard and other state and county EMS unitis for rescue of ice fisherman and rescue in floods and after hurricanes.

See also

• Aerosani
• Hovercraft
• Hydrocopter
• Paddle steamer includes comment regarding animal drive ships
• Rotor ship, a same type of ship using a vertical "pipe" to propel the air

Notes

External links

• On the propulsion of ships by air propellers