How Strong Is This Box?

[hankgillette]

I saw boxes like this at an Apple Store. People were sitting on them while waiting to talk to an employee.

The box looks as though it would be pretty easy to make, but I am wondering how strong it would be. If it is not obvious from the picture, the box is constructed of ¾ inch boards glued up, alternating shorter boards with longer ones to make large box joints.

Other than four ~¾X ¾ inch squares on each on each corner that is side grain to side grain, all the other glue joints at the corners are side grain to end grain. The boxes are open ended, so there is nothing else stabilizing the corners.

Hank Gillette

[jteneyck]

I think they would be very, very strong.  There is long grain to long grain where the sides of the box joints meet.  And as a stool the load is vertical and doesn't stress the joints at all.  It would only be stressed if someone tried to tilt the box up on edge while sitting on it.  Even then, I think it would very durable as long as the joints fit well.  

John

[toolmiser]

I also think they would be very strong. Also agree that racking would be a weak point, but it would take a lot of abuse.

[lincmercguy]

It's essentially a box joint with wider fingers.  If the glue-ups are done properly, it would be strong.  Since it's a box, that will help resist racking.  If it was just the two "legs" and the "seat", I think it would lose half of its resistance to racking.

In today's litigious environment, I might be a bit concerned about using it in a retail setting.  But some places replace that kind of stuff every couple of years anyway.

[AHill]

Looks like 3/4" oak stock. Assuming it's solid oak and 24" wide, I took a trip to the sagulator. Northern red oak with a 250 lb load in the center of the box would cause the top to sag 0.02 inches. So, I think it's plenty strong.

If you think about it, wood ladders have about the same thickness of stock for the steps, and they seem to hold up pretty fine.

[Handplanesandmore]

Strong enough for the intended vertical load IF the joints are built properly and square. As we all know, what appears straight or square may not be so when you put a straight or square to the surface. Racking could be a real thing for an angled joint.

Another concern to me is that if the builder covered any deficiency (gap) with sawdust or sanding to fool the eyes, the joint could be structurally weaker than what a finger joint should be.

Simon

[KC]

I'd think they're incredibly strong if Apple is willing to let people sit on them.  Some kind of mechanica help inside, mabe?

[Cooler]

I sat on them at the Apple store.  I was impressed.  It is not a standard box joint (finger joint). 

I thought about making one.  They did not cut the joints.  They started with boards of exactly uniform widths and assembled them to look like box joints by staggering the pieces.  After the boards were assembled, they assembled them into the boxes using glue only.  My guess is that they had a large belt sander to trim the faces. 

If I were to make one, I would make it three-sided with a single board near the bottom as a crosspiece.  It would be lighter (and perhaps not required).  I would use through-dowels for that.

I did note at the time I saw them, that it was a particularly appealing design.  It could fit in a modern home or, because of the natural wood tones, a more traditional one.  I don't think it would be strong enough for a long bench unless skirts were applied.

The key will be getting the boards all exactly the same width.  Probably by stacking the boards and running them through the planer.