As the vacuum former is only curved on one axis, according to anthropometric data the correct angle for lumbar support and reclining is between 16 and 32 degrees, with at least 8-10 inches to fully support the lumbar curve above a compressed seat level.
The anthropommetric data is really useful to get a grap of the average measurements that would fit the widest range of people, to base my seat dimensions on. For example, the seat width – or the cushioned seat part should be 17.5 inches maximum (44.45cm) for prime comfort within seating.
Height from ground to the seat level should be 15.5 inches maximum (39.37cm).
These measurement have to be taken into consideration, especially as the jig made former would be at a 90 degree angle, therefore the 16-32 degree angle and lumbar support curve will be added through foam application, at the beginning of the upholstery process, to create a curve on two axis as opposed to a curve on one, and the level of curve will affect the thickness of foam, which will deduct from the width of the seat .
From some sketches in attempt to discover what angle would produce the best foam curve to seat width ratio. Using one large piece of angled foam, 10 degrees is too small an angle for support based on anthropometric, however 20 degrees takes up too much of the seating room with the foam angled base and would create a too chunky aesthetic. However, building up the foam upholstery in multiple thinner less angular pieces of foam, i could have one piece of concentrated angled foam for proper lumbar support that would provide a 20 degree angle, at only 8-10 inches high, with a piece coming from the top of the chair to the top of the curve to blend the join, this would then be covered in a layer or two of wadding, then covered in textile fabric.