Chair Design

Chair Design

One of the most difficult tasks the furniture draughtsman has is to design and lay out for the shop the drawing of a chair that will be satisfactory. No drawing is more deceptive than the full size for a chair, and it is by experience only that a draughtsman can judge what will result from the working drawing. Most draughtsmen of considerable experience when working out a detail endeavor to have before them a chair somewhat similar to the one they are drawing.

A good chair should first of all be comfortable to sit in. If intended for general service it ought not to be too heavy to move about easily, and it should be well proportioned.

Seat Height

In planning the seat determine its height above the floor, its width at the front, its width at the back, and the depth from front to back. These vary as desired, and what will make a satisfactory chair for one person, may be quite unsuited to another; consequently there are all sorts and sizes of chairs. It is, however, desirable to have a starting point from which to reckon, and experience has fixed a chair seat eighteen inches above the floor as proper, no conditions being given. If it is less than this it is considered low, and if more it is high. The purpose for which a chair is to be used also serves as a guide for dimensions. If intended for use at a writing table eighteen inches will be 'satisfactory; if for a dining chair eighteen and a half, or nineteen inches is not too high. Occasionally as high as twenty inches may be used. When the chair is not to be used at a table seventeen and a half, or seventeen inches high is satisfactory for most purposes.

Castors

In making the drawing from which a chair is to be constructed care must be taken to determine whether it is to have castors or not. If it is to have them the leg must be shortened accordingly, for the average castor is one and five eighths inches high from the floor to the top of the plate screwed to the under side of the chair leg.

Seat Depth/Size

The depth of the seat, that is, the distance from the front to the back, is varied with the height. It is not entirely a matter of appearance, though within limits it may be made to please the eye. Generally, the lower the seat, the deeper it should be. If the chair seat is high, and too deep, the feet of the occupant will not rest on the floor, if he sits back in the chair. Such a chair is uncomfortable, and any one using it either sits on the front edge, perhaps tilting the chair forward on the front legs, or uses a foot stool. Either there is no support for the back or none for the feet when such a chair is used.

A chair that is too low, and shallow in the seat, obliges the occupant to stretch his legs out in front or he becomes cramped against the back of the chair so that almost unconsciously he tips it backwards. Many have tried to devise a rule by which the correct proportion between height and depth of seat can be determined, but thus far none seems to suit all conditions. Approximately, the sum of the depth of the seat plus its height is equal to thirty-five inches.

Chairs for use at a table may be from fifteen to eighteen inches deep; comfortable, upholstered chairs twenty inches deep; large, low, upholstered chairs may be twenty-four inches deep inside measurement. The width of the seat, from side to side, may be any size called for by the character of the design, except in the case of an arm chair, when it must not be too narrow.

Arm Chair Size

Arm chairs are necessarily wider than others, in order that there may be room between the arms for a person to sit easily without feeling crowded. The space between the arms should not be less than twenty inches at the front edge of the seat, nor less than eighteen at the back. The arm ought also to be of such a height, slope, and length that it will form a convenient rest for the hand and forearm, as well as a side support for the body. Here again arises the conditions of the use of the chair; for, if it is to be used at a table the arm ought not to project forward in a way to prevent placing the chair as close to the table as is desirable for comfort. For such chairs the arm post, that is the upright from the seat supporting the arm, if a continuation of the front leg, is curved backward sufficiently to keep the 'Scroll of the arm back of, or on a line with, the front edge of the chair seat.

Armposts

The arm post may, however, not be a part of the front post, but entirely independent. Then, it also receeds that the scroll of the arm may be kept well away from the front of the chair, as in the picture below. This arrangement has the advantage of leaving the front of the seat free from obstructions that too closely confine the sitter.

Arm posts on the front edge of the seat interfere with ladies dresses, and in many of the French chairs the arm posts not only recede but curve outward at the same time, thus giving considerable more freedom for the person and the clothing.

Backs

It is customary to make the width of the seat at the back a trifle less than at the front, in order to avoid the optical illusion of its appearing wider at the back than at the front, as is sometimes the case when the sides are parallel. This difference in width is about two or three inches.

Slope and Reclining

The amount of slope given the back depends on the use to which the chair is put. An easy chair reclines the most, and just as a low chair is deeper in the seat than a high chair, so, too, may the back slope more on a low seat chair than on a high one. A chair with arms may also have a back more inclined than one without.

The appearance of stability is largely influenced by the inclination of the back. So much so, that it is found desirable in most chairs to slope the back legs outwards a little to counteract the apparent tendency of the chair to upset. An arbitrary rule is: the slope of the back for a chair without arms should not be more than one fourth the depth of the seat and chairs with arms not more than one half.

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