Core77

[jammin]

How about a user built chair made from other objects you already throw away?
Maybe from garden waste.. things which would bio-degrade over time, but could be made into a solid object.

[bluegrrrl]

i'm not so sure about stone chairs - finding specific shapes and sizes of stone would be difficult, and you'd probably end up needing stone-cutting machinery to get the exact shape and size that you need. i like the idea of concrete furniture though..especially the ones on http://www.urbisdesign.co.uk/furni.htm

[73lotus]

I've regrouped and refined my idea a bit. I have tried to itemize the problems and possible solutions to make inexpensive outdoor furniture that is not a consumable/disposable:

Why is cheap plastic and metal furniture a problem?

- Invariably ends up in landfills or other places in the environment
- Not biodegradable
- while it is recyclable, I think the size of chairs, etc. cause people not to put it out with their soda bottles, etc.
- also, recycling and remaking more plastic/metal chairs continues to use energy
- plastic itself carries a connotation of being cheap and disposable
- durability of plastic (UV damage causes breakage from becoming brittle and color fading)
- durability of metal (corrosion, physical damage to structure, finish)

Possible materials that could replace plastic and plastic/metal in this application:

- wood - while technically renewable, the few species that are truly durable outdoors are expensive and/or endangered; biodegradable over time, but not easily recycled
- stainless steel - very durable, but expensive and not completely resistant to corrosion (stainless); non-renewable resource, limited recyclability
- aluminum - moderately durable as a material, but not cost effective when a lot of the material is needed to make truly durable; also non-renewable
- wood/plastic composites - durable and eco-friendly as it uses recycled materials, expensive in terms of start-up costs (molds, or dies for extrusions); continued disposable connotation associated with it because of the plastic content?
- concrete - durable, available to both industry and DIY'ers, very dense (good for durability, bad for transporting), less density with composite concrete but drives costs higher and possibly eliminates the DIY element; not quite eco-friendly to produce
- stone - durable (most types), free (found/natural stone), no environmental impact; not available everywhere or in sufficient quantities, random sizes and shapes not conducive to reproducing a standard design
- recycled organic materials - while definately eco-friendly, making any kind of pressed/molded organic material durable for outdoor use, if possible, would push it towards becoming non-biodegrable (addition of plastics?); leaving it biodegrable is not breaking the consuming cycle

While my first solution was to have a DIY 'kit' that helped the end user construct a chair from locally-obtained stone, the problem of non-uniform sizes and rock types, along with limited availability and mobility, has led me to abandon that idea. My next solution is concrete. This leaves several options as to the type of concrete used and the ability to retain the DIY aspect (a good selling point at this time, IMO). Obviously, to overcome the high density and weight of concrete making the seating too heavy to move by the consumer, the form itself should me minimal, both in terms of size and material usage. While concrete composites, such as foamed concrete and fiber reinforced types, are readily available, they often need special equipment or materials not as readily available to the consumer for construction. This is not a large obstacle if the weight can be pared down enough to make transporting the seating easier, as the pieces can be sold in a finished state. I think that the DIY trend is popular enough to persuade consumers to build the chairs on their own, and can be sold as a well-developed mold (also, a mold rented locally is a possibility) with the consumer purchasing the concrete (or other casting material) separately. While I am currently thinking that the mold would be biodegradeable/recyclable, the end product would not be. I believe that this solution would ultimately use less energy - more energy would be needed in transporting the heavy finished seats; having a re-usable or rented mold uses even less energy, but durability of the molds vs. cost is a concern.

Here is a "sketch" of my revised idea for a DIY cast concrete chair. The back doubles as an arm rest or writing surface should one choose to sit 90 degrees from normal.

[yo]

Here is a "sketch" of my revised idea for a DIY cast concrete chair. The back doubles as an arm rest or writing surface should one choose to sit 90 degrees from normal.

That's mickey D's dude, I'm loving it. Well done, well shown. You could even do a 2-mold chair if you wanted to incorporate arms and a back. I could also see a lounge version for poolside. Get nice and toast in the sun.

[bluegrrrl]

That's mickey D's dude, I'm loving it. Well done, well shown. You could even do a 2-mold chair if you wanted to incorporate arms and a back. I could also see a lounge version for poolside. Get nice and toast in the sun.

looks good - but i wonder if you could make interlocking components instead, so that you can have a chair in a variety of styles, made with the same basic parts...

[yo]

Would it come as a kit. Perfforated cardboard sheets that a user assembles and then poors concrete into? Then you could design a variety of products that could be sold inexpensively at Target in the garden section. I'm thinking of the inetlocking CNC'd plywood furniture they had there last year.

[73lotus]

Yes, an simple interlocking cardboard mold is the 'packaged' part of the product that the consumer would theoretically purchase, along with their castable material (concrete, plaster?, DIY composite?). The idea is to have the mold packed flat as sheets of either perforated or pre-cut parts that would be folded and assembled into the mold. There are definately other furniture items that can be made the same way - pretty much anything that could be an extruded shape - tables, lounge chair, chaise, bench, etc. Alternately, several of the chairs could be placed next to each other for the bench feel.

I'll see what I can come up with re: arms, multiple parts/styles, and interlocking peices. That may ultimately take the concept away from the inexpensive aspect and/or deter people to undertake the project because of the complexity or time needed. I'll definately sketch some things out, as I've already thought of a few ideas..

[hitch]

Regarding the posted sketch -- totally gorgeous, and very elegant solution. As a former engineer, though, I gotta point out the structural issue inherent in the design. Casting a flat, thin slab in concrete is generally a bad idea unless it's reinforced. Unless you're expecting the DIYer to purchase, bend and place rebar in the mold before pouring, you'll have cracking and probably failure on the seat slab pretty quickly.

It might help to arch the bottom?

[73lotus]

hitch, thanks for the input. The last 'sketch' I posted has the thickness at 1.5" but I will do a bit more research on the cement itself to see what should be done. The image really does not show the scale of the chair, which is 18" wide/deep with an 18" seat height.

I have seen other pieces of furniture (tables, countertops) that appeared to be of similar thickness, but they very well could have been reinforced in some way. I would prefer to keep the cross section thin, but adding ribbing may bring the mold into a more complex form than can be made with cardboard, and asking the end user to add rebar is too much.

Perhaps I can find a better (i.e. DIY-type) of reinforcement that is both inexpensive and requires minimal to no tools. One Idea that comes to mind is adding some steel pipe and elbow joints using off the shelf parts from the hardware store, but ultimately, I may need to re-think either the thickness or overall shape to keep the chair as simple as possible.

[bluegrrrl]

Perhaps I can find a better (i.e. DIY-type) of reinforcement that is both inexpensive and requires minimal to no tools. One Idea that comes to mind is adding some steel pipe and elbow joints using off the shelf parts from the hardware store, but ultimately, I may need to re-think either the thickness or overall shape to keep the chair as simple as possible.

if the span of the seat is going to be a problem, could you not do a slatted seat, made just with steel rods or flats, rather than using the steel to reinforce the concrete? (you will have to worry about joints, tho) embedded reinforcement needs to be a minimum of 50mm away from the outer atmosphere which means that the seat slab would have to be at least 100mm thick (reinforcement in the middle, and 50mm of concrete on either side) this is for buildings tho, i dont know whether different rules would apply for simple garden furniture. the concrete uprights on your chair wouldnt be a problem as concrete is good in compression

[hitch]

Well, the thing with concrete is, making it thicker won't necessarily help -- its strength to weight ratio in tension is abysmal, which is why almost all large concrete structures have steel reinforcement (and why very few of them are slab shaped). It does have two great advantages though: it's very strong in compression (as bluegrrl pointed out) and it can be molded in any shape.

I think if you had an angled or arched connection between the legs and the seat, that would avoid a lot of tension cracking problems in the seat slab -- check out Gaudi's columns on the Sagrada Familia, or even Gothic cathedral arches and buttresses. Great examples of turning a structural necessity into something beautiful. Just my own prejudice...

[hitch]

How about something like this?



Not quite the minimalist masterpiece of the previous sketch, but I think it might hold up a bit better. You could probably pull it off with a 5 part mold. Or even 3, if you don't mind them being big and weird.

[bluegrrrl]

well here's my sketch - not particularly attractive, but made of flat interlocking pieces. the seat is supported by a *cross* underneath it - don't know if it will work or not - but if it does, you wouldnt have to use arches like in hitch's previous sketch

[abby]

I like the fact that that can be disassembled. I also like the idea of building your own chair from several parts--it would also allow you to "design" many different chairs from just a few different pieces. As a consumer I know I would personally love to see a kit that lets me build a chaise longe, upright chairs or a bench from a standard set of pieces. The more jobs something can do, the greater percieved value.

Would concrete be light enough to move around? Would it be comfortable to sit on?

[73lotus]

I've been thinking about the problems with my last posted sketch - mostly, that the flat plane would need reinforcement of some type. Fiber-reinforced concrete is widely available and costs no more than plain 'just add water' mixes; probably not enough reinforcement to prevent failure of the chair, however. I've wondered if some type of reinforcement could be included with the flat-packed mold - possibly wire mesh or molded plastic. Unfortunately, the more complex the chair gets, the higher the cost will be; exactly what I'm trying to minimize to make this more appealing than the plastic/metal chairs on the market.

The estimated cost right now is:

- $5.00 for the cardboard mold 'kit'
- $10.00 for two 60 lb bags of concrete

- aprox. $15.00 total, plus taxes

And yes, the thing would weight around 120 lbs as shown in the last posted sketch. Moveable - yes - but it would require 2 people. Think of the chairs more as a semi-permanent installation, which adds to the idea that this chair is a non-disposable alternative.

Multiple parts is definately do-able, as are styles, although i think it will be difficult to get very many styles with simple shapes and forms, but I'll try to post my solution tomorrow.