cantilevered bookshelves

I'm trying to design some curved-front bookshelves that will appear to float unsupported from a wall in a contemporary living room. Any pointers to places where I can get ideas for how to make this work?
I'm imagining shelves 66 inches long, that curve from no depth at both ends to 18 inches deep in the center. In the center, they will be cut to fit around a 17-inch wide column that protrudes 7 inches from the wall. Wall is gyp-board over steel studs, and the column is probably gyp-board on furring strips.
I'm thinking of sandwiching two thicknesses of 3/4-inch plywood together with a U-shaped steel channel (the type usually mounted on a wall to support bookcases, ironically) in the middle of the sandwich to resist longitudinal sagging. But the support from the wall has me stymied.
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On May 26, 1:59 pm, Dennis McClendon <"dmcclendon AT rcn DOT com"> wrote:

The type of U-channel you describe essentially provides a cantilever depending upon the style you choose. I use the double standards around my place and fasten directly to the studs. If you wanted to hide them then you could do so any number of ways. Here is an example of the standards I mean.
http://www.rockler.com/product.cfm?page 6
They stock a similar product at HD though I don't find it on their website.
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I thought the proper term was a stress skin panel. I did not get any Googles on that term for a shelf.
The idea would be to make a lattice work shape of the shelf you want, a bit like a hollow core door. This lattice would be thin slats that would easily lend themselves to your curved shape, the slats can be half lapped. Leave a void on the side that will attach to the wall. Glue a skin, such as 1/4" ply to both faces of the lattice. Attach a block that is a tight fit in the void pocket(s) that you created to the wall surface. Slide the finished shelf onto the ledger blocks and pin/screw/through bolt if you want it removable; glue and clamp for permanent installation.
I hope I described it well enough to get you started or that someone else will come up with the proper term to find an internet reference with pictures. You can carry tremendous amounts of weight on these things.
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Agreed, they work well. I leant on mine after installing it, it showed no signs of moving.
This system has been described in at least 2 magazines over the past few years. FWW was one, and I can't recall the other. Somebody with a FWW index may be able to narrow it down, then maybe you can find it in the local library.
Barry
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This is a bit hard to explain without a picture but I'll try.
Make a strip the same thickness and material as the shelf and lets say 1 1/2" deep. Counter bore some holes so you can have a 6" bolt stick out every 12". Attach this strip to the wall with typical anchors so you end up with a 1 1/2" deep shelf with bolts sticking straight out into the room.
Now make your shelf so it has 6" deep holes bored in the correct locations and an opening on the underside, big enough to attach a nut and tighten it up.
Because you want the shelf to die into the wall at the ends either build the strip and shelf and then shape them together or just shape the shelf first and then rip the strip off the back side of the shelf and mill the counterbores, etc. You'll lose the thickness of the blade but the curve should still be smooth enough at the joint.
On May 26, 11:59 am, Dennis McClendon <"dmcclendon AT rcn DOT com"> wrote:

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Dennis McClendon <"dmcclendon AT rcn DOT com"> wrote in

Ikea sells a "beech" shelf called Lack, which is supported by concealed fasteners. Shelf is ~ 2" thick, a small torsion box-like structure.
Other possibility is a torsion box fastened to the wall via a French cleat- type fastener. Split the cleat to allow for your column.
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Thanks for the several useful responses. I'm concerned that with such a deep shelf increasing the leverage from the weight of the books, my biggest problem is going to be mounting into the wall. I think I probably have four studs along the run, but it seems like there will be a LOT of force trying to bend or pull those fasteners out of the studs. Unlike the situation with a kitchen wall cabinet or angled shelf bracket, none of the load is being transferred the other way, into the wall or wallboard.
I have a couple of the Lack floating shelves. They're ingenious in design, but IKEA warns purchasers about a maximum load on them.
The protruding column is a concrete pier (this is in a highrise condo) and I'm thinking that may provide some help to me. If I can anchor solidly into that at the cutout points--seven inches in front of the main wall--it seems like the weight of books on the back part of the shelf will partially balance the weight on the front part of the shelf, making these anchors pivot points that are largely supporting the shelves vertically, and relieving stress on the wall mountings.
The torsion box seems a much more complicated project than sandwiching U-channels in between plywood. Would that provide benefits for my support problem, or is it more to avoid longitudinal sagging?
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Dennis McClendon <"dmcclendon AT rcn DOT com"> wrote in

Our Lack is used more decoratively and for little pictures, rather than for bookshelves.

I'd contact the condo board people because if this pier is part of what holds up the high rise, you might not want to drill holes in it ...

U-channels in between plywood is like the start of a torsion box. I think you'd want to have the back "wall" of such a torsion box - be it metal U-channel or solid wood - sturdily fastened to the wall studs. Then, where it leans against the pier, it should do so tightly, so top and bottom portions of the wood or U-channel lean/hang against the pier so as to provide support.
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Han
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OK, plan B.
Anchor a steel angle into the side of the concrete column have it toed up, notch the shelf so the angle is hidden inside the edge and bottom of the shelf.
On May 27, 9:21 am, Dennis McClendon <"dmcclendon AT rcn DOT com"> wrote:

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Dennis McClendon wrote:

do a search on "torsion boxes". FWW had an article some years back.
Good luck, Harvey
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This would make them float...
http://www.leevalley.com/hardware/page.aspx?c=2&pQ933&cat=3,43648,43649
"Dennis McClendon" <"dmcclendon AT rcn DOT com"> wrote in message

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I think this is the basic idea of the Lack shelves of Ikea.
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Han
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Look in the June 2007 issue of Woodworker's Journal. Ian Kirby has an article on "torsion Boxes" and it includes mounting them on a wall if I remember correctly.
Wayne
Dennis McClendon wrote:

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