Lumbar support radius for bench back?

[Tom Hyde]

I'm designing built in benches (two matching at 6'6"). I want to make them as comfortable as possible. I've got general dimensions down but want to build a curved back with lumbar support. The benches will be combined with a table so this is for upright seating as opposed to lean back lounging. I'm planning on using bending plywood built up and then laminating shop cut VG Doug Fir onto the ply. All of this will be new to me (so it's a good thing this is for an addition to my own home).

I've searched for some guidelines on design and am coming up empty. Definitely going to make a 2' mockup but I'm looking for a starting point. Any links, insights, suggestions would be greaty appreciated!

[Wayne Lomman]

Does your car have adjustable lumbar support in the driver's seat? Set it to suit yourself then make a pattern of the shape. If you don't have such new fangled luxuries, ask around to see who has. Cheers

[Yonak Hawkins]

Here are some interesting solutions on google you might scale from : https://www.google.com/search?q=wood...HQH-DkkQsAQIPA

[Phil Mueller]

You'll find lumbar support to be a pretty individual thing. Couple things to keep in mind. Lumbar support should start just above the belt line; C1 vertebrae. Pressure on the upper pelvic bone can quickly cause fatigue. Depending on the height/shape of the individual, this is typically 7-8" above the seat. The depth of the seat is important as well. If the knees hit before the person's back can reach the back of the bench, lumbar support is nil (it will either cause them to slouch, or if they scoot to the back of the bench, the front of the bench will pinch off blood flow to the lower legs). The front of the seat should be about 1" from the knee when sitting against the back of the bench. Too little seat depth and the lower leg towards the knee won't be supported...again fatigue.

This is what causes automotive seat folks to design to average, with some adjustability. Even then, folks way outside the norm are often never really comfortable.

If you're looking for ultimate comfort, you might want to consider an upholstered bolster attached along the back (the foam has some ability to conform to different shapes/needs), or individual lumbar cushions.

[Stew Hagerty]

Here's a great quick reference for how it should fit the body. Just follow the spine:

spinal_guy.jpg

[Jamie Buxton]

Here's a great quick reference for how it should fit the body. Just follow the spine:

That illustration is some idealized slender person. But many people are more rotund, and they don't have that inward curve at the waist.

[Warren Wilson]

Jamie: I believe the profile of the spine will remain essentially the same independent of the profile of the abdomen.

An approach I have used is to cut strips of foam and use hotglue to incrementally laminate up a lumbar curve until it felt right then use that as a model for the final fair curve. Mind you, I had a lot of time and some foam lying around.

Here is an interesting article about normal and less normal back curvature:

http://www.hermanmiller.com/research...en-seated.html

[Jim Andrew]

Honda seats are more comfortable than other small cars. Copy their seat back. Even the Civic has great seats.