A former is an object, such as a template, gauge or cutting die, which is used to form something such as a boat's hull. Typically, a former gives shape to a structure that may have complex curvature.
A former may become an integral part of the finished structure, as in an aircraft fuselage, or it may be removable, being using in the construction process and then discarded or re-used.
Here, a former is a structural member of an aircraft fuselage, of which a typical fuselage has a series from the nose to the empennage, typically perpendicular to the longitudinal axis of the aircraft. The primary purpose of formers is to establish the shape of the fuselage and reduce the column length of stringers to prevent instability.  Formers are typically attached to longerons, which support the skin of the aircraft.
The "former-and-longeron" technique (also called stations and stringers) was adopted from boat construction,  and was typical of light aircraft built until the advent of structural skins, such as fiberglass and other composite materials. Many of today's light aircraft, and homebuilt aircraft  in particular, are still designed in this way.
A former may instead be a temporary shape over which a structure is built, the former subsequently being discarded in whole or part, as follows:
A fixed-wing aircraft is a heavier-than-air flying machine, such as an airplane, which is capable of flight using wings that generate lift caused by the aircraft's forward airspeed and the shape of the wings. Fixed-wing aircraft are distinct from rotary-wing aircraft, and ornithopters. The wings of a fixed-wing aircraft are not necessarily rigid; kites, hang gliders, variable-sweep wing aircraft and airplanes that use wing morphing are all examples of fixed-wing aircraft.
Monocoque, also called structural skin, is a structural system in which loads are supported by an object's external skin, in a manner similar to an egg shell. The word monocoque is a French term for "single shell".
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 include medium-density fibreboard (MDF), oriented strand board (OSB) and particle board (chipboard).
A cantilever is a rigid structural element that extends horizontally and is supported at only one end. Typically it extends from a flat vertical surface such as a wall, to which it must be firmly attached. Like other structural elements, a cantilever can be formed as a beam, plate, truss, or slab.
In aeronautics, the fuselage 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 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 the control and stabilization surfaces in specific relationships to lifting surfaces, which is required for aircraft stability and maneuverability.
The mechanical structure of an aircraft is known as the airframe. This structure is typically considered to include the fuselage, undercarriage, empennage and wings, and excludes the propulsion system.
Boat building is the design and construction of boats and their systems. This includes at a minimum a hull, with propulsion, mechanical, navigation, safety and other systems as a craft requires.
Strip-built, or "strip-plank epoxy", is a method of boat building. Also known as cold moulding, the strip-built method is commonly used for canoes and kayaks, but also suitable for larger boats. The process involves securing narrow, flexible strips of wood edge-to-edge around temporary formers. The temporary formers are usually created via a process called "lofting" whereby a set of tables is used to generate the shapes of the formers. The strips are glued edge-to-edge with epoxy. It is effectively a modern form of carvel which needs no caulking and which is both stiffer and more watertight. In a small boat, there will be just one layer of strip-planking, but larger vessels may have two or three layers which,, forms a light, strong, and torsionally stiff monococque.
The term semi-monocoque refers to a stressed shell structure that is similar to a true monocoque, but which derives at least some of its strength from conventional reinforcement. Semi-monocoque construction is used for, among other things, aircraft fuselages, car bodies and motorcycle frames.
Homebuilt aircraft, also known as amateur-built aircraft or kit planes, are constructed by persons for whom this is not a professional activity. These aircraft may be constructed from "scratch", from plans, or from assembly kits.
A geodetic airframe is a type of construction for the airframes of aircraft developed by British aeronautical engineer Barnes Wallis in the 1930s. Earlier, it was used by Prof. Schütte for the Schütte Lanz Airship LS 1 in 1909. It makes use of a space frame formed from a spirally crossing basket-weave of load-bearing members. The principle is that two geodesic arcs can be drawn to intersect on a curving surface in a manner that the torsional load on each cancels out that on the other.
In engineering, a longeron and stringer is the load-bearing component of a framework.
Steel frame is a building technique with a "skeleton frame" of vertical steel columns and horizontal I-beams, constructed in a rectangular grid to support the floors, roof and walls of a building which are all attached to the frame. The development of this technique made the construction of the skyscraper possible.
Formwork is temporary or permanent molds into which concrete or similar materials are poured. In the context of concrete construction, the falsework supports the shuttering molds.
In a fixed-wing aircraft, the spar is often the main structural member of the wing, running spanwise at right angles to the fuselage. The spar carries flight loads and the weight of the wings while on the ground. Other structural and forming members such as ribs may be attached to the spar or spars, with stressed skin construction also sharing the loads where it is used. There may be more than one spar in a wing or none at all. However, where a single spar carries most of the force, it is known as the main spar.
In mechanical engineering, stressed skin is a type of rigid construction, intermediate between monocoque and a rigid frame with a non-loaded covering. A stressed skin structure has its compression-taking elements localized and its tension-taking elements distributed. Typically, the main frame has rectangular structure and is triangulated by the covering.
Luft-Fahrzeug-Gesellschaft, also referred to as LFG, was a German aircraft manufacturer during World War I. They are best known for their various "Roland" designs, notably the Roland C.II Walfisch (whale), Roland D.II haifisch (Shark) and Roland D.VI, although they also produced a number of airships and many experimental designs.
The Bennett Aircraft Corporation Bi-motored Transport Commercial Number One (BTC-1) Executive was a 1930s American eight-seat light transport aircraft built by the Bennett Aircraft Corporation. In the ten-year span of its known life, the Bennett BTC-1 was identified in print by four different names: the Bennett, the Breese Bennett, the Bowlus Bennett and the Globe BTC-1.
The Boulton & Paul P.10 was a two-seat, single-engined biplane built just after World War I to develop techniques for the construction of all steel aircraft. It is also notable for its first use of plastic as a structural material. Only one P.10 was built and it attracted much attention; but it probably never flew.
The LFG Roland D.XV was a World War I German single seat fighter aircraft, ordered as a test-bed for engine comparisons. It was distinguished from earlier Roland biplane designs by the elimination of flying wires. Two later aircraft, also called LFG Roland D.XV, were completely different designs with slab sided fuselages.