Design and development
The Sunderland MOBA 2 was entirely one man's glider. In the 1970s Gary Sunderland was an Australian Department of Aviation engineer and a glider pilot who wished to compete the Australian National Championships in his own design of glider, "my own bloody aircraft" or MOBA for short, in his phrase. It was intended as an aircraft of high, Standard class performance, but capable of low cost, home assembly. By 1970 his efforts had converged onto the MOBA 2 and some outline drawings and trial metalwork produced. The single seat glider was to have a 15 m Standard class span wing but with a retractable undercarriage and flaps, not then allowable in that category. [1] [2]
Competition classes in gliding, as in other sports, mainly exist to ensure fairness in competition. However the classes have not been targeted at fostering technological development as in other sports. Instead classes have arisen because of:
Landing gear is the undercarriage of an aircraft or spacecraft and may be used for either takeoff or landing. For aircraft it is generally both. It was also formerly called alighting gear by some manufacturers, such as the Glenn L. Martin Company.
Two versions, driven by a competition held by the Australian Glider magazine, did not get off the drawing board: though accounts differ in detail, it seems the MOBA 2A had a 15 m span and the final competition entrant MOBA 2B a 13 m span as required. [1] [2] [3] The MOBA 2B was one of two potential winners selected by the judges in 1972, but unfortunately they could not agree on a final choice and no prize was awarded. [1] The MOBA 2C, the sole version to be built though later modified into the MOBA 2D, differed only from the MOBA 2B in having a 15 m span wing, taller fin and fabric covered rudder. [3]
A fin is a thin component or appendage attached to a larger body or structure. Fins typically function as foils that produce lift or thrust, or provide the ability to steer or stabilize motion while traveling in water, air, or other fluids. Fins are also used to increase surface areas for heat transfer purposes, or simply as ornamentation.
Aircraft fabric covering is a term used for both the material used and the process of covering aircraft open structures. It is also used for reinforcing closed plywood structures, the de Havilland Mosquito being an example of this technique, and on the pioneering all-wood monocoque fuselages of certain World War I German aircraft like the LFG Roland C.II, in its wrapped Wickelrumpf plywood strip and fabric covering.
A rudder is a primary control surface used to steer a ship, boat, submarine, hovercraft, aircraft, or other conveyance that moves through a fluid medium. On an aircraft the rudder is used primarily to counter adverse yaw and p-factor and is not the primary control used to turn the airplane. A rudder operates by redirecting the fluid past the hull (watercraft) or fuselage, thus imparting a turning or yawing motion to the craft. In basic form, a rudder is a flat plane or sheet of material attached with hinges to the craft's stern, tail, or after end. Often rudders are shaped so as to minimize hydrodynamic or aerodynamic drag. On simple watercraft, a tiller—essentially, a stick or pole acting as a lever arm—may be attached to the top of the rudder to allow it to be turned by a helmsman. In larger vessels, cables, pushrods, or hydraulics may be used to link rudders to steering wheels. In typical aircraft, the rudder is operated by pedals via mechanical linkages or hydraulics.
The MOBA 2C was of mixed construction. Its wing was in three sections, with a constant chord centre piece mounted high on the fuselage and straight tapered outer panels. It was built around a single metal, rectangular, PVC plastic foam filled box spar, with GRP/plywood sandwich ribs. The space between the ribs was also filled with PVC foam, which was then shaped to the Wortmann FX 67-K-150 section and covered with glass cloth. The outer panels carried long span ailerons and the inner sections full span, metal skinned flaps, which could be set at angles between +20° and -15°. They were lowered for landing, increasing lift at lower speed and acting as airbrakes. [1] Aerodynamically, the wing was designed to operate at speed, a natural choice for soaring in Australia with its strong thermals and long inter-thermal distances. [2]
The fuselage is an aircraft's main body section. It holds crew, passengers, and cargo. In single-engine aircraft it will usually contain an engine, as well, although in some amphibious aircraft the single engine is mounted on a pylon attached to the fuselage, which in turn is used as a floating hull. The fuselage also serves to position control and stabilization surfaces in specific relationships to lifting surfaces, which is required for aircraft stability and maneuverability.
Plywood is a material manufactured from thin layers or "plies" of wood veneer that are glued together with adjacent layers having their wood grain rotated up to 90 degrees to one another. It is an engineered wood from the family of manufactured boards which includes medium-density fibreboard (MDF) and particle board (chipboard).
Glass cloth is a textile material, originally developed to be used in greenhouse paneling, allowing sunlight's ultraviolet rays to be filtered out, while still allowing visible light through to plants. The cloth is usually woven with the plain weave, and may be patterned in various ways, though checked cloths are the most common. The original cloth was made from linen, but a large quantity is made with cotton warp and tow weft, and in some cases they are composed entirely of cotton. Short fibres of the cheaper kind are easily detached from the cloth.
The MOMBA 2C had a pod and boom type fuselage. The pilot's seat was just forward of the wing leading edge, placing him in a reclining position under a long, single piece canopy, shaped from an uncut Slingsby Kestrel moulding. The cockpit had some unusual features, principally that access to it was by rolling the whole nosecone and canopy forwards along a rail from a join around the fuselage ahead of the wing. This provided an aerodynamically very clean and well sealed forward fuselage, as well as easy access for instrument panel servicing. The control column was side mounted on a raised side beam on the right; flap and undercarriage levers were similarly mounted on the other side. This arrangement avoided underfloor control cables, keeping the fuselage cross section low and simplifying the control linkages. The cockpit was narrow and low and would not have been comfortable for bigger pilots than Sunderland. The nosecone was skinned with glass cloth over balsa. Instrument panel, controls, seat and the retractable monowheel undercarriage were supported by a central, sturdy, sheet alloy frame linked to the wing. The fuselage tapered from the leading edge aft, an area covered glass cloth over PVC foam. Behind this the boom was a roughly oval metal tube, with flat top and bottom plates for ease of construction. Tail surfaces were all straight edged; the tall, metal skinned fin had a slightly swept GRP leading edge and carried a tapered, fabric covered rudder. The MOMBA 2C had a T-tail, with a metal surfaced, high aspect ratio, tapered tailplane and a plywood surfaced elevator. There was a small, semi-recessed tailwheel below the fin. [1] [3]
The leading edge is the part of the wing that first contacts the air; alternatively it is the foremost edge of an airfoil section. The first is an aerodynamic definition, the second a structural one. As an example of the distinction, during a tailslide, from an aerodynamic point of view, the trailing edge becomes the leading edge and vice versa but from a structural point of view the leading edge remains unchanged.
The Slingsby T.59 Kestrel is a British Open class glider which first flew in August 1970. Of fibreglass construction, it features camber-changing flaps, airbrakes, and a retractable main wheel.
A T-tail is an empennage configuration in which the tailplane is mounted to the top of the fin. The arrangement looks like the capital letter T, hence the name. The T-tail differs from the standard configuration in which the tailplane is mounted to the fuselage at the base of the fin.
Though Sunderland had hoped to have the MOMBA 2C ready for the World Gliding Championships held in Australia in 1974, particularly after changes to Standard Class rules allowed retractable undercarriages and flaps, he was unable to complete flight testing before 1980. It handled well and performed as expected, competitive with Open Class whilst climbing in thermals but slower across country. Landing behaviour led to the addition of spoilers halfway out along the central panels and of tapered, rather than parallel chord flaps, which added 51 mm (2.0 in) to the overall chord at the wing root, slightly increasing the wing area. This revision was named the MOMBA 2D. [1]
The World Gliding Championships (WGC) is a gliding competition held every two years or so by the FAI Gliding Commission. The dates are not always exactly two years apart, often because the contests are sometimes held in the summer in the Southern Hemisphere.
In aeronautics, a spoiler is a device intended to intentionally reduce the lift component of an airfoil in a controlled way. Most often, spoilers are plates on the top surface of a wing that can be extended upward into the airflow to spoil it. By so doing, the spoiler creates a controlled stall over the portion of the wing behind it, greatly reducing the lift of that wing section. Spoilers differ from airbrakes in that airbrakes are designed to increase drag without affecting lift, while spoilers reduce lift as well as increasing drag.
The wing root is the part of the wing on a fixed-wing aircraft that is closest to the fuselage. On a simple monoplane configuration, this is usually easy to identify. On parasol wing or multiple boom aircraft, the wing may not have a clear root area.
Operational history
The MOBA 2C had its first competitive outing at the 1980 Australian Championships at Benalla. Sunderland judged its performance as between the 15 m class and the Standard Class gliders there, perhaps rather closer to the latter. He could out-turn the 15 m aircraft in thermals but they, 100 kg (220 lb) heavier flew faster at the same glide angle. He estimated that the MOBA 2C approximately achieved its 1:38 design glide angle. [3]
As the MOBA 2D aged, the foam filling that determined its wing profile began to destabilise and expand. The outer glass fibre covering was removed, the profile restored and the aircraft was flown again after the wing was recovered, but further development was abandoned. [1]
