I'd like to make a shelf from 17mm (2/3") thick plywood, whose back will be affixed to a brick wall and its front will be suspended by metal cables from a concrete ceiling (e.g. something with the same principle of the construction in this image).
I'm aiming for a shelf about 2m (6ft 6.7in) wide and 80cm (2ft 7.5in) deep.
Naturally, I'd like the shelf to be as stable and robust as possible. I tried consulting the Sagulator, but I think my case requires 2D load analysis, whereas the Sagulator is apparently only 1D. So my questions are:
For affixing the back of the shelf to the wall, are 3-4 metal "L" brackets (distributed along the shelf's length) preferable to having a wooden support beam (as in the previously linked image)? What length of brackets should I get?
Will 3-4 metal cables in the front be enough? Will adding a metal support strip in the front of the shelf (through which the cables will pass) provide a significant improvement of the shelf's robustness?
What mass could I safely load on such a shelf?
Many thanks in advance for any help.