(ii) upholstery should be ‘firm’ rather than ‘soft’ (it is sometimes said that a heavy user should not deform it by more than 25 mm);
(iii) covering materials should be porous for ventilation and rough to aid stability.
The traditional wooden ‘Windsor’ chair can be surprisingly comfortable in spite of its total absence of upholstery. Its basic form was probably developed by the craftsmen of the Chiltern beechwoods sometime around the beginning of the eighteenth century.
A critical feature seems to be the subtle contouring of the seat known as its
‘bottoming’. This was hand carved, using first an adze then a variety of shapers, by a man known as the ‘bottomer’, whose specialized trade was considered the most skilled of all the activities that contributed to the chair-making process. He worked by eye without recourse to measurements; contemporary machine-made versions are said to be less satisfactory.
4.3.10 Seats for more than one
When considering benches and other seats in which users sit in a row, it is necessary to bear in mind that the breadth of a 95th %ile couple is less than twice that of a 95th %ile individual. (The chance of two people, each 95th %ile or more, meeting at random on a bench is only 1 in 400.) In general, n people sitting in a row have a mean breadth of nm and a standard deviation of √n, where m and s are the parameters of the relevant body breadth—which will usually be that of the shoulders. Table 4.3 gives values based on male data and including a clothing correction of 15 mm.
However, if the row of seats is divided by armrests the problem is more complex.
Assume each user sits in the centre of his seating unit—a little reflection will tell us that the minimum separation of seat centres will be determined by the distribution of pairs of half-shoulder breadths: 480 [40] mm; 95th %ile=545 mm. Since in the presence of armrests the minimum seat breadth is 500 mm (see above), and an armrest cannot reasonably be less than 100 mm wide, 600 mm between seat centres will satisfy all criteria.
follows naturally from these functions and from the considerations of the previous section.
Grandjean (1973) recommends a seat tilt (ß) of 20–26° and an angle between seat and backrest of 105–110°. This gives a backrest rake (a) of as much as 136°, which is really only suitable for ‘resting’ and requires a degree of agility for standing up and sitting down. Le Carpentier (1969) found a tilt of 10° with a rake of 120° to be suitable for both reading and watching television. The present author inclines to the latter view with the caveat that for elderly users a rake of more than 110° may cause problems. Difficulties of standing up and sitting down will be reduced if the space beneath the front of the chair is unimpeded, allowing the user to place his feet beneath his centre of gravity, hence achieving a more vigorous upward thrust and a more controlled descent.
A high-level backrest is virtually essential to the proper role of an easy chair in providing support for the trunk. Its shaping is something of a challenge. It is possible to design a gentle lumbar curve that will suit most users, but an equivalent pad for the neck and occiput is more problematic. Ideally, this should give you similar support to the natural action of clasping your hands behind your head. A sensible way of achieving this is to incline the upper part of the backrest forwards from the main rake by around 10° and to provide a movable cushion. (This solution has been adopted on certain British Rail seats but, unfortunately, the range of adjustment of the cushion is not quite adequate for the shorter person.)
The fundamental problems of designing an easy chair had essentially been solved by around 1680, as the collection of almost any English country house will testify.
Ergonomic research has merely confirmed the intuitions of the designers of the past.
However, the present-day furniture showroom typically presents a range of styles that, in ergonomic terms, are rarely better than just adequate and not infrequently fall short on numerous criteria. There are, of course, exceptions but these are commonly either reworkings of traditional types (such as the ever popular ‘William and Mary’) or else chairs that are described as ‘orthopaedic’ and sold more as ‘aids’ than as the furnishings of a stylish home.
The most common failings in the contemporary armchair are a seat that is too deep and a backrest that is too low. One may suppose that this is due to an attempt to make the seat and back equal in length in the interests of visual symmetry (like the Mies Van der Rohe ‘Barcelona’ chair of 1929) or to an even more misguided attempt to fit the entire chair into a cubic outline (like Frank Lloyd Wright’s ‘Cube’ chair of 1985 or ‘Le Grand Confort’ by Le Corbusier and Charlotte Perriaud of 1928–1929).
Combined with the weighty stylistic influence of these modern masters is a marketing need to incorporate the armchair into a three-piece suite (or some other combination).
With the exception of a few historical types, such as the William and Mary ‘love seat’, high-backed settees are virtually unknown. In reality, as anthropometric data quite clearly show, the backrest height needs to be around twice the seat depth if an easy chair is to perform its proper function.
Tall people sometimes complain of seats being insufficiently deep (i.e. too short from front to back). Observation suggests that on engaging the backrest and finding that it only reaches mid-shoulder level, they move down into the seat in an attempt to gain head support. As a result their buttocks slide forwards until they are in danger of dropping off the front of the seat. (This also leads to the flexed position which is physiologically least satisfactory.) Hence the problem stems from an inadequate backrest rather than a seat that is not deep enough.
A common misconception, held by designers and consumers alike, is to equate depth and softness of upholstery with comfort. The luxurious sensation of sinking into a deep over-stuffed sofa is indicative of an absence of the support necessary for long-term comfort in the sitting position. In functional terms, we are now dealing with something more amorphous than a seat per se, it is in fact an object for sprawling or reclining on, rather than for conventionally sitting on. Structurally, however, the object retains the form of a seat. A seat supports its user in a sitting position and a bed supports him in recumbent position—but there are a whole variety of intermediate sprawling postures which can be perfectly satisfactory, especially when, supported by mounds of cushions, one has the opportunity for frequent postural changes. Taken to its logical conclusion the concept of ‘amorphous furniture’, which does not dictate any posture in particular, leads to items such as the
‘sag bag’—a sack full of polystyrene beads, which enjoyed a brief vogue among young homemakers a decade or so ago. A whole family of all but extinct furniture types, which generically we could call couches, are essentially designed for sprawling—notable members of this family are the ‘day bed’ mentioned in Shakespeare (Twelfth Night, II.v) and the chaise-longue. A steeply raked easy chair can double as a couch when used in conjunction with a footstool—as in the economically excellent Charles Eames lounge chair and ottoman of 1956 (Figure 4.10). The three-piece suite aims to serve for both sitting and sprawling. It commonly does both tolerably but excels at neither. There is considerable scope for design innovation in changing this state of affairs.
Figure 4.10 The Charles Eames lounge chair and ottoman (1956) give good support in a wide variety of postures.
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