The RFB X-113 Aerofoil Boat was an experimental

ground effect vehicle A ground-effect vehicle (GEV), also called a wing-in-ground-effect (WIG), ground-effect craft, wingship, flarecraft or ekranoplan (russian: экранопла́н – "screenglider"), is a vehicle that is able to move over the surface by gainin ...

intended to work over water. It was one of three such aircraft designed by

Alexander Lippisch Alexander Martin Lippisch (November 2, 1894 – February 11, 1976) was a German aeronautical engineer, a pioneer of aerodynamics who made important contributions to the understanding of tailless aircraft, delta wings and the ground effect, and a ...

in the 1960s and early 1970s. The X-113 first flew in 1970; only one was built.

Design and development

Lippisch's development of his Aerofoil Boat, a

for use over water, began whilst he was working in the aviation division of the

Collins Radio Company Rockwell Collins was a multinational corporation headquartered in Cedar Rapids, Iowa, providing avionics and information technology systems and services to government agencies and aircraft manufacturers. It was formed when the Collins Radio Comp ...

Cedar Rapids, Iowa Cedar Rapids () is the second-largest city in Iowa, United States and is the county seat of Linn County, Iowa, Linn County. The city lies on both banks of the Cedar River (Iowa River), Cedar River, north of Iowa City, Iowa, Iowa City and north ...

, US. The first test of concept was the

Collins X-112 The Collins X-112 was an experimental two-seat ground-effect vehicle, designed by Alexander Lippisch in the United States in the early 1960s to test his thick reverse delta wing concept. Design and development Lippisch's development of his Aerof ...

, flown in the mid-1960s. In 1967 development was continued in collaboration with

Rhein-Flugzeugbau Rhein-Flugzeugbau GmbH (RFB) was a German aircraft manufacturer. The company was established at Krefeld, Germany in 1955, and later moved to Mönchengladbach. Aircraft *1955 Rhein Flugzeugbau RW 3 Multoplan *1960 Rhein-Flugzeugbau RF-1 *1970 RFB ...

(RFB) in

Germany Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwe ...

, funded by the German government. This resulted in the X-113. The X-113 was an inverse delta aircraft; that is, it had a wing which was triangular in plan but with a straight, unswept

leading edge The leading edge of an airfoil surface such as a wing is its foremost edge and is therefore the part which first meets the oncoming air.Crane, Dale: ''Dictionary of Aeronautical Terms, third edition'', page 305. Aviation Supplies & Academics, ...

. Combined with strong anhedral, this layout produces stable flight in ground effect. Specifically, it is claimed that it is stable in pitch and also that it can fly in ground effect at altitudes up to about 50% of its span, allowing it to operate over rough water. This contrasts with the lower aspect ratio square wing of the Ekranoplans which leaves ground effect at only 10% of span, limiting them to the calmer waters of lakes and rivers. The Aerofoil Boat was built using

glassfibre Fiberglass (American English) or fibreglass (Commonwealth English) is a common type of fiber-reinforced plastic using glass fiber. The fibers may be randomly arranged, flattened into a sheet called a chopped strand mat, or woven into glass cloth ...

sandwiches with foam or tube cores. Its wing was set

high High may refer to: Science and technology * Height * High (atmospheric), a high-pressure area * High (computability), a quality of a Turing degree, in computability theory * High (tectonics), in geology an area where relative tectonic uplift ...

on the

fuselage The fuselage (; from the French ''fuselé'' "spindle-shaped") is an aircraft's main body section. It holds crew, passengers, or cargo. In single-engine aircraft, it will usually contain an engine as well, although in some amphibious aircraft t ...

, with swept fins at the tips inclined at about 60°, carrying short

aileron An aileron (French for "little wing" or "fin") is a hinged flight control surface usually forming part of the trailing edge of each wing of a fixed-wing aircraft. Ailerons are used in pairs to control the aircraft in roll (or movement around ...

s. The tips also carried long, wide planing floats which projected a long way forward of the leading edge to support the fuselage stably above the surface when on water. Forward of the wings the fuselage was flat sided and quite shallow, so the pilot was semi-recumbent under a long canopy. Aft, a long dorsal fin extends to a T tail with

rudder A rudder is a primary control surface used to steer a ship, boat, submarine, hovercraft, aircraft, or other vehicle that moves through a fluid medium (generally aircraft, air or watercraft, water). On an aircraft the rudder is used primarily to ...

and horizontal stabiliser. The Aerofoil Boat was powered by a Nelson flat four engine derated to , driving a two blade, wooden,

tractor A tractor is an engineering vehicle specifically designed to deliver a high tractive effort (or torque) at slow speeds, for the purposes of hauling a trailer or machinery such as that used in agriculture, mining or construction. Most common ...

propeller A propeller (colloquially often called a screw if on a ship or an airscrew if on an aircraft) is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear thrust upon ...

. The engine was mounted uncowled over the fuselage near mid-

chord Chord may refer to: * Chord (music), an aggregate of musical pitches sounded simultaneously ** Guitar chord a chord played on a guitar, which has a particular tuning * Chord (geometry), a line segment joining two points on a curve * Chord ( ...

on a pylon constructed from three pairs of narrow angle V- struts. The first flight was made in October 1970 on

Lake Constance Lake Constance (german: Bodensee, ) refers to three Body of water, bodies of water on the Rhine at the northern foot of the Alps: Upper Lake Constance (''Obersee''), Lower Lake Constance (''Untersee''), and a connecting stretch of the Rhine, ca ...

and the initial tests to explore the performance of the Aerofoil Boat were also done there. These were deemed satisfactory and later flights over the

North Sea The North Sea lies between Great Britain, Norway, Denmark, Germany, the Netherlands and Belgium. An epeiric sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian S ...

showed that it could be operated over rough water. It also demonstrated its ability to fly out of ground effect, reaching at least . Flight tests continued at least until 1974 and possibly later. The X-113 was displayed in public at the Paris Salon in May 1973.

Specifications (X-113 Am)

Video

"The aerofoil Boat", Lippisch research Corporation (https://www.youtube.com/watch?v=gnflnBF7jWk)

References

*Patent US3190582, 1965 {{Lippisch aircraft Ground effect vehicles RFB aircraft 1970s German experimental aircraft Single-engined tractor aircraft High-wing aircraft Aircraft first flown in 1970 T-tail aircraft