Former

Aformeris an object, such as a template,gaugeorcuttingdie,which is used to form something such as aboat'shull.Typically, a former gives shape to a structure that may have complexcurvature.

A former may become an integral part of the finished structure, as in an aircraftfuselage,or it may be removable, being used in the construction process and then discarded or re-used.

Aircraft formers

Interior of an F-16B with the engine removed showing frames or formers

Formers are used in the construction of aircraftfuselage,of which a typical fuselage has a series from thenose coneto theempennage,typically perpendicular to thelongitudinal axisof 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 tolongerons,which support the skin of the aircraft.

The "former-and-longeron" technique (also called stations and stringers) was adopted fromboat construction,and was typical oflight aircraftbuilt until the advent ofstructural skins,such asfiberglassand othercomposite materials.Many of today's light aircraft, andhomebuilt aircraftin particular, are still designed in this way.

Disposable formers

Plywood formers awaiting the application of strip planks on a strip-built catamaran.

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:

• Strip-builtboat construction uses formers over which thin plank strips are applied and glued.In some cases, some of the formers may be incorporated as structural ribs.
• Incivil engineering,bridge building,andarchitecture,arches may be built upon a wooden former, which is removed once thekeystoneis securely in place.