Ogee

An ogee is a curve (often used in moulding), shaped somewhat like an S, consisting of two arcs that curve in opposite senses, so that the ends are parallel. It is a kind of sigmoid curve.

The term has uses in architecture, mathematics, and fluid mechanics, as well as marine construction, clock design and plastic surgery.

Construction
Plastic-shaped keel bows usually have an inner and an outer arch; these may be uniform, but in many cases the inner (lower) arch is a round or pointed arch, whereas the outer (upper) arch is formed as a donkey back. Overall, a variety of variations can be observed.

The centers of the two lower circular arcs lie within, those of the upper circular arcs outside the arch field. If both lower circle centers coincide in one point, a common shape of the keel arch is created; if they lie apart, the arch receives a more compressed form. Conversely, if the arch is constructed to be a variant of the pointed arch having only a small counter- arch at the tip, it is called "donkey's back" or "donkey's arch"; the name derives from the outstanding backbone of the donkey.

History

Origin
The keel arch seems to have its origin in India, where already since the 3rd century BC. Entrances to the Buddhist cave monasteries were designed in this way. The background of such a design form is unclear, but similarities to the leaves of the Bodhi tree or to a prayer position prevalent in India with raised hands and pressed over the head obvious; it could, however, also be a purely architectural-aesthetically understood "center emphasis" or "exaggeration". In later times, such entrance designs were in any case converted to windows (kudus) and even later developed from it blind decorative elements (chandrasalas), which were often combined to larger decorative panels (udgamas).

Development
In Islamic architecture, keel bows did not come into use until around 1100. In the Persian and Egyptian architecture, they experienced first highlights, but they occasionally appear in the 12th century in the Maghreb and Andalusia.

In Central and Northern Europe Kielbögen came - with a few exceptions in book paintings - only from the 13./14. Century in Late Gothic in use - the earliest examples are commonly some of the Eleanor crosses in England. Keel bows are particularly often found at the top of a portal or window frame, either as suitably shaped archivolts, lintels or ornamental gables in the form of roofs or crowns. Accordingly, these components are referred to as 'keel bow window' or 'Kielbogenportale'.

Use in architecture

Ogee arch
In architecture, the principal use of the term is to describe an arch composed of two ogees, mirrored left-to-right and meeting at an apex. Ogee arches were a feature of English Gothic architecture in the later thirteenth century.

Moulding
A building's surface detailing (indoors or out) may have a moulding with an ogee-shaped profile, consisting (going from low to high) of a concave arc flowing into a convex arc, with vertical ends; if the lower curve is convex and higher one concave, this is known as a Roman ogee, although frequently the terms are used as if they are interchangeable and for a variety of other shapes. Alternative names for such a true Roman ogee moulding include cyma reversa and talon.

The cyma reversa form occurs in antiquity. For example, in ancient Persia, the Tomb of Cyrus featured the cyma reversa. The cyma reversa is also evident in ancient Greek architecture, and takes its name from the cymatium. The ogee shape is one of the characteristics of the Gothic style of architecture, especially decorative elements in the 14th and 15th century late Gothic styles called Flamboyant in France and Decorated in England. Ogee windows and arches were introduced to European cities from the Middle East. The ogee curve is an analogue of a "cyma curve", the difference being that a cyma has horizontal rather than vertical ends.

The ogee and Roman ogee profiles are used in decorative moulding, often framed between mouldings with a square section. As such it is part of the standard classical decorative vocabulary, adopted from architrave and cornice mouldings of the Ionic order and Corinthian order. An ogee is also often used in the "crown moulding" frequently found at the top of a piece of case furniture, or for capping a baseboard or plinth, or where a wall meets the ceiling. An ogee moulding may be run in plaster or wood, or cut in stone or brickwork.

Other uses
Ogee is also a mathematical term, meaning an inflection point.

In fluid mechanics, the term is used for an ogee-shaped aerodynamic profile. For example, a wing may have ogee profile, particularly on supersonic aircraft such as the Concorde. Also, the downstream face of a dam spillway is usually formed in an ogee curve to minimize water pressure.

An "ogee washer" is a heavy washer with a large bearing surface used in marine timber construction to prevent bolt heads or nuts from sinking into the face of timbers. The term ogee is used due to the ogee shape in radial symmetry around the centre. Due to the size and shape, they are generally manufactured as a cast iron product in accordance with ASTM A47 or A48.

An "ogee clock" is a common kind of weight-driven 19th-century pendulum clock in a simplified Gothic taste, made in the United States for a mantelpiece or to sit upon a wall bracket. It is rectangular, with ogee-profile moulding that frames a central glass door that protects the clock face and the pendulum. The weights fall inside the ogee moulding supported by pulleys and hidden from view. The door usually carries a painted scene in the area beneath the face. Ogee clocks are one of the most commonly encountered varieties of American antique clocks. The design is usually attributed to Chauncey Jerome.

In aesthetic facial surgery, the term is used to describe the malar or cheekbone prominence transitioning into the mid-cheek hollow. The aim of a mid-face rejuvenation is to restore the ogee curve and enhance the cheekbones. This enhancement is also commonly a part of a routine facelift.

In distillation, an ogee is the bubble-shaped chamber of a pot still that connects the swan neck to the pot. It allows distillate to expand, condense, and fall back into the pot.

Examples

India
Barabar Caves (Lomas Rishi Cave),
3rd century BC Chr.
Udayagiri and Khandagiri caves, about 2nd century BC Chr.
Udayagiri and Khandagiri Caves (Ranigumpha)
Vestibule of the Bedsa Cave, 1st or 2nd century AD
Ajanta (Cave 36), about 4th century
Ajanta (Cave 9)

Islam
Quwwat-ul-Islam Mosque, Delhi, India (around 1225)
Mihrab of the mosque of Qus, Egypt (around 1250)
Koran Niche, Lodi Gardens, Delhi, India (15th c.)
Mihrab of Dilawar Khan Mosque, Mandu, India (15th c.)
Arch in Dilawar Khan Mosque, Mandu, India (15th century)
Jama Masjid, Delhi, India (around 1650)

Europe
Eleanor Cross, Hardingstone, around 1300
Bow-shaped keel arches at the Porte de la Craffe in Nancy, France
Kielbogen portal of a church in Dumfries, Scotland
Late Gothic seating niche portal with five-fold keel arch (1506) at the Peter Ulrich House in Pirna
Kiel bow window at a house in La Garriga, Spain
Kiel bow window at Palazzo Corvaja in Taormina, Italy

Source From Wikipedia