Supporting a 60 inch span

[Craig D Peltier]

Hi any ideas or experience here on the SMC on whats the best way to support two shelves that may span 60 inches. This is for a built in. Below it will be a plasma, above plasma two shelves. Wood is Sapele
One way I can think of is building the two shelves as its own box and supporting them with dividers an install the box inside the two walls of case.
Other ideas I question is it enough , like:
Double up plywood and use a 1.5 inch face on it.
Single Ply with 1.5 inch face or maybe 2 inch.

Thanks

[Jamie Buxton]

Your idea of making the two shelves into a box works if you put a back on the box, and the back is glued or stapled or fastened to the shelves in some way. The back stiffens the shelves a great deal.

[David DeCristoforo]

I have used 1" X 1/4" steel bars imbedded in the double thickness shelf. Cut a 1/4" X 1/2" deep dado about an inch back from the front edge of the two layers. (You can also put one at the back of the shelf if you want to get really serious.) Drop in the steel bar(s) and glue the two pieces together. Now elephants can sit on the shelf! I have made shelves up to seven feet long like this.

[Frank Drew]

Sandwiching in the steel on edge is a good idea, David. For places where it wouldn't show I've used angle iron for the same purpose, not let in but screwed to the underside of a shelf or cabinet bottom.

A torsion box shelf would be very stiff but more work to make than David's steel reinforced double thickness shelf.

[jim oakes]

Steel is great for this. I always put a note with a marker on a hidden end or edge saying " STEEL HERE " if at all possible. It's for me or the next woodworker who may recycle/repair or need to cut into the work for any reason.

[Tom Veatch]

...
Other ideas I question is it enough , like:
Double up plywood and use a 1.5 inch face on it.
Single Ply with 1.5 inch face or maybe 2 inch.


You can use the Sagulator (http://www.woodbin.com/calcs/sagulator.htm) to give you an estimate on whether these two would be acceptable. Doubt that either one would be acceptable for anything other than a very light load.

[Dennis Montgomery]

The way I do it is just as you described. Sandwich two 3/4" sheets and face them with 1.5" of your choice. I then cut a 3/4"H x 1"D slot across the back and on both ends. Cut the slots before you face it so the facing covers the side slots. Install 3/4" x 1" strips on both inside cabinet sides and across the back. Use long screws on the rear strip and anchor it to the wall studs. Slide the shelf onto the strips and countersink a couple small screws from the top into the strips.

I have done this many times on very long shelves. It works well. If something as heavy as a TV is going to sit on it, I would build the shelf as a torsion box. If it's just for sitting trinkets, then the sandwich plywood will more than suffice.

[Josiah Bartlett]

Why not use a wall mount bracket for the plasma TV, then its not putting any weight on the shelf? The non-swivel ones are pretty cheap.

[Craig D Peltier]

I think im going to add dividers and build it as its own box with a back on it.


I do like that steel idea. Thanks Dave.

[Paul Simmel]

He said the plasma was going to be under the shelf...

... Good idea with the 1/4" x 1" bar. I've straightened warped interior doors this way. It doesn't make them completely straight, but it helps a lot.

[Cary Swoveland]

Why not use a wall mount bracket for the plasma TV, then its not putting any weight on the shelf? The non-swivel ones are pretty cheap.

Thanks for the clarification, Josiah. When I read Craig's post I was wondering how much a plasma cutter weighed.

Cary

[Craig Summers]

Thanks for the clarification, Josiah. When I read Craig's post I was wondering how much a plasma cutter weighed.

Cary

The cutter head is pretty light in the handheld plasma units, the power source and air source are the heavy parts. :D