Benchwork dimensions

[electrolove]

I'm looking for a way to fasten benchwork to the wall. What do you guys think of this idea?



Is it necessary to have a l-girder attached to the wall, or will a 1 x 4 be enought?

Can I use smaller dimensions on the wood for the front l-girder?

Maybe there are better ways then this?

I know that I can do it like this:



http://s145079212.onlinehome.us/rr/howto/splines/index.shtml

But the problem is that I must be able to take the benchwork down from the wall in 100 cm pieces so I can't use this idea. That's the reason I'm thinking of l-girders.

[jeffers_mz]

This is a little complex, but...

In your example, the 2 by 2 is attached to the wall, (concrete block?) and the plywood spar is screwed into the side of that. right?

Compare that to a ladder built of plywood rips or one by four. In the ladder, the spars or rungs are screwed through the back of the rail before hanging it on the wall, right? Then the force of gravity tries to pull them out in order to allow the front shelf to sag.

In your example, the force of gravity acts to shear off the screws into the 2 by 2 block. If you were using nails instead, a 16 penny sinker would successfully resist aboout 200 pounds in tension, but would resist between 1000 and 2000 pounds in shear. That's a big difference and that's why your photograph example works. By using the fasteners in shear, you cantilever the shelf out off the 2 by 2 block.

The problem then is that you need removable sections, which leave nothing at the wall side for support once it is loose from the wall. The benefit though, is that while attached to the wall, you don't need any L girders, that whole thing isn't going anywhere till the concrete block wall does. So....how to get the best of all possible worlds?

I'd approach the whole thing differently. I'd build a simple ladder from 1 x 4 or plywood rips, and use at least three inch screws to hold it together. Then I'd deck it and here is the variable. Quarter inch plywood would give you all the side to side stability you'd need when the unit was detached from the wall. Properly fastened, you'd have more lateral stability than any L girder arrangement. However, while attached to the wall, the fasteners through the plywood would be put into shear, helping make up for the ladder rung fasteners which can only hold at tension levels in this arrangement. At that point, quarter inch plywood may not provide enough "meat" to hold the vertical fasteners tighhtly enough to get the "shear benefit" from them. For that reason, you may need to use half inch for the deck.

It's easy to test though. A one foot test section attached to the wall will easily tell you how well the cantilever is working. Lean on it and decide. If the front 1 x 4, blocking, and quarter inch deck try to pull away from the 1 x 4 that's attached to the wall, try it with half inch decking instead. In fact, try it with no deck at all and see how it feels. What have you got to lose?

For final assembly, get some PL 400 and glue the rung blocks and the deck down too. That way all the forces won't be concentrated on the walls of the screw holes holding down the deck, but will be spread out over a much larger area.

[electrolove]

Sonds like you have some great ideas, even if it's hard for a Swede like me to follow your description 100% in a foreign language. Do you think you can draw a little picture for me, if it's not too much work for you? That would be great.