Floating shelves

[pugilato]

I have been asked to install floating shelves in a nook of a friend's house. The walls are cement. I thought I would use metal bars (3/4" square) attached with Tapcons to the walls. Then make corresponding dados along the back and sides of 1 1/2" thick mahogany boards (about 80" long, 14" deep). When ready, the shelves would slide onto the metal bars.

I wanted to get input about the setup... Will the shelves sag much when held along the sides and back with the metal bars? The house is very close to the ocean, so should I make the bars in aluminum or steel? If Al, will the Tapcons react with it?

Here's some drawings to help visualize the project. What it will look like...
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Detail showing attachment system and offset dado on board.
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Detail showing placement of metal bars (each 12 1/2" long)
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I always use these projects to justify getting a new Festool. To make routing the offset dados I would, of course, need one of these bad boys
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Comments are appreciated.

 

[Dane]

Two words.  Torsion. Box.

Use marine grade mahogany ply and edge them with solid mahogany- species isn't important, but since you brought up mahogany...

 

[Jay Knoll]

This might help

http://www.woodbin.com/calcs/sagulator.htm

I don't know if you really need a strip across the entire back of the shelf, a pin - maybe a long tapcon with the head cut off will effectively cut the span in Half.  And if you put some construction adhesive on the back edge before you slide it home I don't think that you'd ever have to worry about sagging.  Of course you'd never be able to get it out without resorting to demo tactics!

 

[sprior]

Another tip that I've seen elsewhere on the FOG (but haven't tried myself yet) is that instead of buying the plexiglass guide get two edge guides and put them on both sides of the router on the guide bars.  This is cheaper and more versatile than the plexiglass guide.

 

[fshanno]

Another tip that I've seen elsewhere on the FOG (but haven't tried myself yet) is that instead of buying the plexiglass guide get two edge guides and put them on both sides of the router on the guide bars.  This is cheaper and more versatile than the plexiglass guide.

I was wondering about the anti-tipping support that the plastic guide provides.  You're aren't going to get as much support with the edge guides.

As far as justification goes, $305?  Ouch.  I'm not so sure.  It sure would be easy to make a little jig that does what the Festool plastic guide does.  The sides wouldn't have to be adjustable, just make if for the material thickness you're dealing with.  How many times are you going to need it?  For pure mortising there are better options I think than the Festool product.  The Mortise Pal for instance blows the Festool template away and it's only $210.

 

[fidelfs]

You can replace the black guides for a wider piece of wood (plywood) to help with the tipping issue.

 

[AdamM]

Hit up Paul Marcel for experience using two edge guides....I know he's done it.  He talks about it in one of his OF1400 videos.

 

[fdengel]

Just curious, why not simply drill pocket holes in the shelves and drive the tapcons in through the pocket holes?

 

[Tinker]

In my limited experience, drilling anything into concrete at any angle other that 90º can be quite a challenge.
i had never used tapcons for anchoring anything.  I don't even know if they were around when i was doing masonry.
I used a lot of anchors that we drilled an oversized hole and then turned a bolt into the anchor that created enough presure from forced expansion to hold a lot of weight.

we also, if we knew from plans, exactly where to put a wood anchor for holding screws or nails, we inserted a thin piece of wood into the mortar joint.  That worked ok with brick as there was wider surface to the brick joint than with block.

for most anchor projects, i had a powder actuated gun that drove the anchor pin with a whole lot of noise and smoke.

Those tapcons seem to be much better than those other methods.  especially now that impact hammers are so light and easy to handle.
Tinker

 

[pugilato]

I did not see that price, but now that I have seen it, it is out of the question. I can see paying good money for good tools, but not for a jig. I can definitely make my own jig to do the same thing, dust be damned. Really, I think Festools are the best and I will continue buying them, I am sold on the system, but this is a bit much.

I really like the idea of using pocket holes and driving the Tapcon through... an elegant and simple solution. I'm pretty sure they sell mahogany plugs.

I saw the mortise pal and I like it. Maybe I will get one if a future project justifies it.

About the torsion box, no go... client wants a slab of solid wood. I tried that approach, but was cut off right quick. Thanks for your replies... I will give the Tapcon thing a test and report back.

 

[rdesigns]

I think your original plan is good, except I don't see any need for using steel for the attachment rails. I would use 3/4" square wood. Much cheaper and much easier to work with. A few Tapcons along with construction adhesive will keep them securely in place, and they will support more weight than the shelving material is capable of bearing.

 

[aptpupil]

I think your original plan is good, except I don't see any need for using steel for the attachment rails. I would use 3/4" square wood. Much cheaper and much easier to work with. A few Tapcons along with construction adhesive will keep them securely in place, and they will support more weight than the shelving material is capable of bearing.

This is the way to go. Metal is overkill and adds the unnecessary step of predrilling. PL premium with tapcons will do the trick. I've done this before and once the PL premium sets up (24 hrs), it's not going anywhere.

 

[pugilato]

Thanks for the replies... one more question. I am thinking of making the dados offset from center. In other words, the dados would be cut 1/4" from the bottom edge, leaving 1/2" on the top to give it strength. Is this necessary?

 

[aptpupil]

Thanks for the replies... one more question. I am thinking of making the dados offset from center. In other words, the dados would be cut 1/4" from the bottom edge, leaving 1/2" on the top to give it strength. Is this necessary?

Good idea.

 

[pugilato]

So the client likes the proposed floating shelves and all, but now she wants LED light strips on the bottom of each shelf. Stipulation... no visible cables, no trim to hide the cables, etc. Just the lights illuminating her books and one switch that will turn on the lights in all five floating shelves. Does anyone make LED light strips that get their electricity through the air?

 

[jonny round boy]

Don't you guys have wireless electricity yet?

Must be NAINA.

[tongue]

 

[Deansocial]

I don't see the problem with the lights

 

[Tinker]

I remember when kerosene lamps did the job

 

[tjbnwi]

POE lighting, easy to hide a CAT 5 cable;

http://lumencache.com

For mounting the shelves; drill 3-1/2" holes into concrete one in the center of the span one 12" off each end 3" deep (plug the drill into your CT and tape the hose to the drill), epoxy 16" length #4 rebar into holes, fab up torsion box (this method also helps with your lighting) shelves leaving a void where the bar will insert, slide shelves over rebar. You can lock the shelves in place with set screws from the bottom if need be.

Tom

 

[sprior]

Maybe this would help: http://www.flatwireready.com/products/lighting.html