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Is it possible to make the storage bench below using only wood glue, screws, and 3/4-inch plywood or MDF?

The only requirement is that it must support a 80lb kid sitting on it. 4.5" floor clearance is a must. I don't think it would be strong enough (diagram is to scale). Any ideas to make it stronger are much appreciated. I'm in a remote area with limited tools (saw, drill, screws, glue, and 1 trip to home center)

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  • I would put a back on the bench as well as maybe a center divider to help with the weight. – Jeff Cates Feb 10 '17 at 5:07
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    Consider adding a 2x2 or 1x4 as a beam under the main bench. That will help to reinforce the parallelogram (easiest mode for lateral collapse) as well as the bending of the top MDF board (flexural failure mode). – Hari Ganti Feb 10 '17 at 19:41
  • Thanks guys, very helpful. Flexural failure was fun reading up on. I know there's a right way to do this with thicker wood but I'm intentionally taking shortcuts for time's sake. – AnthumChris Feb 15 '17 at 3:56
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ideas to make it stronger

Resisting vertical forces

Add a rail front and rear, inset from front and rear edges. The rail would be 31" wide x 2" high. Make it taller for greater strength.

Resisting lateral forces

The greatest weakness is lateral collapse by lozenging. Adding metal corner brackets or adding a back panel would prevent that. With an inset back panel you wouldn't need a rear rail.

Minimum would be an unobtrusive triangular wooden brace centrally at each end of the underside of the top, glued with tenons or plenty of dowels.

  • Out of technical curiosity, how could this design be achieved without back panel or rails? Thicker wood and stronger joins? eg goo.gl/KfLVBk – AnthumChris Feb 10 '17 at 12:37
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    @Chris: Thicker wood, stronger wood species, wood with fewer knots, steel corner braces, smaller span, lighter children, planet with lower mass, ... – RedGrittyBrick Feb 10 '17 at 14:46

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