# Ideas To Prevent Sagging



## JohnJohnson (Apr 30, 2011)

I have been going through various iteration of a long (72") office desk build and think I have settled on a very minimalist design. My problem is that I would like the table top to be a 3/4" 24" x 72" 3-ply Bamboo with a basic four leg design. 

I know that this will sag if left in this manner, and I was looking for any solution the community might have. I have seen some products that claim to help with sag and was thinking about using a few of them (linked below). Has anyone used them or tried anything similar? What do you all think about a brace like that? Do you have any other ideas that might work?

http://www.closet-masters.net/anti-sagtablestiffener.aspx

Thanks!


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## phinds (Mar 25, 2009)

Depending on how much weight you want it to hold those might work, but I would tend to use a pair of heavy steel L brackets running the length, spaced about 6" apart down the middle of the underside and with a LOT of screws out towards the ends because they're only going it for less than 3/4"

The problem with this is that it complicates putting drawers directly under the top.


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## BigJim (Sep 2, 2008)

Think hollow core door construction, not using the door but build as the door is built.


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## Brink (Nov 22, 2010)

jiju1943 said:


> Think hollow core door construction.


That could be like a torsion box design.

Or, instead of metal stiffeners, why not bamboo aprons? At least they would match.


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## cabinetman (Jul 5, 2007)

If you want just a thin looking top with something like 3/4" and four legs, its gonna sag from its own weight. There has to be some type of support. Depending on how tall an apron you will accept, any framing of sorts can be done within the apron height. 

A simple way would be to use angle iron. HD has a 2"x2"x1/8" that's pretty darn stiff. With that you would only need a 2" cover around the edge. You could get by with one at the front and rear edge, and maybe one up the middle, or two spaced between the ones on the edge.

Or, you could make a hardwood angle, like from Oak or rock Maple, and layout them in the same manner. Those can be just screwed to the underside.












 







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## JohnJohnson (Apr 30, 2011)

Brink said:


> That could be like a torsion box design.
> 
> Or, instead of metal stiffeners, why not bamboo aprons? At least they would match.


I am not a fan of table aprons (just not the style I like), but I am looking into the torsion box design. I could not afford to complete the entire box in bamboo as it runs from $120-$220 for a single 4' x 8' sheet, but I may make the torsion box out of MDF except for the top and possibly the sides. Then use bamboo ply for the top and either use bamboo ply or veneer the sides.

How thin can one go with a torsion box and still get good strength?


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## GeorgeC (Jul 30, 2008)

What is the visual difference between what cabineman suggested and a torsion box of at least the same thickness? The torsion box will need to be at least 2" thick to do what is needed to prevent sagging. It will also be a lot more labor to consruct.

G


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## waterman1971 (May 15, 2011)

I wonder if you could do something similar to the design of the structural insulated panel.


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## woodnthings (Jan 24, 2009)

*Here's a source for bamboo ply*

http://www.mastergardenproducts.com/bambooplywood.htm
You could use two 1/2" pieces glued together with the crown up, a little prestress effect. I think anything 3/4" thick will sag as you said. So...
A perimeter frame/apron.
A single spine down the center under the the whole sheet tapering out to the ends will be barely visible. I would prefer 2 thinner spines myself.
An adjustable truss rod with a bridge like a bass fiddle is sophisticated and minimalist. The anchor points near the ends would have to be fastened securely and/or imbedded in a groove.
I would stick to bamboo for the spines, edge laminated...unless you like a more modern look then you could use metal angle aluminum or steel, but I'd would still want to taper it out at the ends starting from the center. The material, what ever you chose will be in "tension" at the bottom and compression at the top, so less is needed as you go out from the center.  bill
BTW retired Industrial Designer here...Buckminster Fuller used a lot of tension cables in his designs.
http://en.wikipedia.org/wiki/Buckminster_Fuller 
see also: http://en.wikipedia.org/wiki/Eero_Saarinen


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## Brink (Nov 22, 2010)

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

I use this a lot to calculate, figure a desktop is similar to a shelf. Unfortunately, there's no listing for bamboo.


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