Can you help me build the perfect piece of furniture?

June 26, 2007 12:26 PM

Calling all woodworkers! Can you help a noob build a very unbalanced but sturdy piece of furniture? Googling about joinery has proved fruitless and my woodworking skill is lacking. Feel free to also tell me to give up and recommend custom furniture makers in the Atlanta area!

I'm wanting to build an entertainment center that's... unusual, but seemingly-simple. I'm envisioning three completely open shelves (no back, front, or side panels) of approximately 50"x15"x2" spread evenly over a total 32" height supported by a single, strong "spine". The shelves will not be arranged symmetrically left-to-right - I'd like them to unevenly "hang" off to one side or the other by about 12" or so, and I'd like the support (the "spine") to be tucked all the way toward the back of the piece so that the shelves are unsupported in the front. As a final point, I'd like to use an attractive medium-hardness wood like cedar or maple to build it.

Will a 4" square piece of hardwood (oak?) support the sort of loads that such a big shelf will put on it, given the 12" overhang's torque? Will some simple triangular wedges and beefy wood screws be enough to hold it all together? Should I instead be thinking about some sort of plane-to-post joint that I can't seem to discover? It won't be holding anything much heavier than books but I'd like it to withstand providing infrequent and brief support to drunkards.

I'd considered notching the spine and shelf with some sort of dovetail and using a tight interference fit but I'm afraid that will weaken the spine... and be hard to build with just a circular saw. And how about joining the top and bottom shelves to the spine? Should I notch the shelf around the spine and plane it smooth? Will this require power tools I don't have? (I'm not afraid of a hacksaw!)

Oh hell, should I just give up and stick to building computer programs?

posted by TheNewWazoo to sports, hobbies, & recreation (21 comments total)

Geoff's site for students of woodwork.
posted by popcassady at 12:44 PM on June 26, 2007

also, never forget that your local library can be your friend in all information searches :o)
posted by crepeMyrtle at 12:48 PM on June 26, 2007

There is a reason shelves get supported in multiple places. I don't imagine a wooden shelf of 50"X15"X2 being able to support itself on one spot on one edge.
posted by Megafly at 12:55 PM on June 26, 2007

The force and deflection of cantilever beams is an engineering question, but if you use 4" x 4"s for the planks as well as the beam, you could put solid gold ingots on the shelf (although you'd raise the overall height of unit.
posted by mattbucher at 12:56 PM on June 26, 2007

"force and deflection of cantilever beams" - that's a phrase that could prove useful. I can't remember enough physics to model the forces that would be exerted on the spine, but armed with those words I might be able to ask the right questions if AskMe doesn't come through. I have a gut feeling that the wood will all be strong enough, but the main problem I'm seeing is how to put it all together... clever joins, screws, glue, duct tape...
posted by TheNewWazoo at 1:04 PM on June 26, 2007

if you can't get wood to work, you could have a steel spine built to support steel shelf supports. the steel supports could be hidden in dados cut into the bottom of each wooden shelf. the steel spine could then be boxed-in with wood or left exposed, depending on the look you prefer.
posted by probablysteve at 1:12 PM on June 26, 2007

This should work:

Cut a notch about ¼” deep front and both sides of the beam where the shelves will go.
Notch the shelves to fit the reduced beam.
Countered sink 3/8” lag bolts through the beam in the shelf notch areas into a wall stud.
Insert the shelves. They must fit very very tightly.
posted by mrleec at 1:15 PM on June 26, 2007

How about three of these?

They are roughly the right size and internally have two steel tubes/arms attached to a steel strip that you attach to studs in the wall. Shelf slides over the arms. Rock solid, and no need for a spine at all.
posted by zeoslap at 1:21 PM on June 26, 2007

Also if all you have is a circular saw and a hacksaw forget about it.
posted by zeoslap at 1:24 PM on June 26, 2007

mrleec: Is there a purpose for the wall attachment other than to keep it from tipping over? I had imagined this to be a freestanding piece. With such a long shelf along the floor it should be pretty stable.

zeoslap: I've considered using ikea raw materials (their butcher block planks are cheap!), but am not sure what you've suggested is quite what I'm going for. Also, I more meant to say that I have no fear of manual tools (in fact, I have a bit of a fetish for them), I just don't feel like buying a miter and jig saw for something this simple. (Not yet, anyway)
posted by TheNewWazoo at 1:31 PM on June 26, 2007

This doesn't seem impossible, but it probably isn't worth it to do it yourself, because you will have a very hard time cutting things to match tightly with only a circular saw. If you must, make yourself a little jig to make the cuts into the beam.

If you insist on going ahead, mrleec's method above would probably work, though I'd go 1/2" into the beam, if not more. You would still have to deal with the engineering problem of whether or not your shelves will break or bend unacceptably with the weight you want the shelves to hold. Adding triangular supports forward and sideways underneath the shelf from the beam will help with that (the bigger the better, of course).

Also, unless you are talking about something other than
western red cedar, cedar is considered a very soft wood. Maple would be much better, but not cheap. Fir would be cheaper, if it is available in your area.
posted by ssg at 1:47 PM on June 26, 2007

Afraid you will have to bolt it to the wall. Even a steel reinforced joint at the floor location would be too weak. Try placing the lowest shelf just an inch or two above the floor so it appears to float. You should be able to build this with a circular saw and a drill.
posted by mrleec at 2:03 PM on June 26, 2007

Well, damn. Assuming that I live in an apartment and can't bolt things to walls, any suggestions on how I could modify the basic design to either reinforce the bottom joint or obviate the need for reinforcement altogether?
posted by TheNewWazoo at 2:44 PM on June 26, 2007

Maybe something like a shorter version of this bookcase (on the left)? Can you draw it in sketchup?
posted by mattbucher at 2:53 PM on June 26, 2007

There is a reason shelves get supported in multiple places. I don't imagine a wooden shelf of 50"X15"X2 being able to support itself on one spot on one edge.

Agreed. The joinery isn't the problem -- this thing just isn't going to stand up. Hard woods are heavy woods. And the kinds of things that you'd put on an entertainment center are both heavy and expensive. This sounds like a cool idea, but design is always a balancing act between aesthetics and physical constraints. I've done a fair amount of woodworking, and this just won't work.
posted by svenx at 3:39 PM on June 26, 2007

You might consider making the shelves out of torsion boxes. They'll be light and stiff. But maybe not light and stiff enough.
posted by notyou at 4:29 PM on June 26, 2007

A company I do webdesign work for built this piece, which seems something like what you're looking for. It's maple with a custom green-gold finish, and I'm pretty sure the glass shelves aren't bracketed to the wall. If you want, email me and I can put you in touch with people with more information.
posted by casarkos at 4:31 PM on June 26, 2007

Seconding svenx. Maybe, just maybe you could get it to stand and hold its own weight, but it would basically be sculpture. I doubt you could set anything on it. I certianly wouldn't put fancy electronics on it, nor stand in front of it for too long. And only a circ saw? I don't think it would work.
posted by fantastic at 8:14 PM on June 26, 2007

mattbucher: I've uploaded a quick end-result sketch here with a box of the same dimensions as the TV I'm planning to purchase (32" HDTV at 44 lbs) for scale.

I'm wondering if enlarging the size of the support might help - make it 4"x6" and bring it further towards the front? Or even two supports? Thoughts, if anyone's still listening? :)
posted by TheNewWazoo at 9:15 PM on June 26, 2007

With that shelf on the ground, as in your sketch, yes, you could probably get it to stand up with good tight joints, but you would not want to put anything breakable (like your new TV) on it. It just wouldn't be stable. Think about this: one of the drunkards you mention in our original post comes along and gives the front of the shelf a little nudge towards the back. The whole thing falls backwards. Why? Because all the weight was carried on the back edge of the shelf already, so it only took a little bit of force to tip it over.

If you really want to build this, you could try to figure out a way to securely attach the beam in the dead center (fore and aft) of the shelves, but none come readily to mind for me. Brackets really wouldn't do it, but a really large collar above and below each shelf might work. Then you'd have to reinforce the junction between the bottom shelf and the beam with some sort of brackets. It wouldn't at all have the look you are going for, I don't think.

If you go to two beams (front and back), then you'll be in better shape, but you will still need beefy brackets to keep everything sturdy on the base. But once you have two, why not go all the way and do four?
posted by ssg at 10:55 PM on June 26, 2007

It's a good drawing in sketchup, but I don't think it would work with that small of a support beam--at least made out of wood. Maybe if you had some titanium or steel, but not wood.
posted by mattbucher at 9:22 PM on June 27, 2007