I've noticed this type of c-table in a movie, and wanted to make one of my own. There are lots of this kind readily available from Ikea and the likes, and DIY plans as well. But I wanted really long cantilevered overhang, at least 70 centimeters.

So some physical modelling was due.

I'll only show a path that bore any fruit, quite some time I've spent on the tools badly fitted for the job, and dead-end designs.

Try-and see approach to the design necessitates for a parametric CAD system. Onshape was the one I've used. It interacts well with the simulation tool, is free for public projects and has nice support forum and training center full of videos.

Here's my project It's messy, but It has stored versions, you'll get an idea. Part Studio called "n" is the one that has.

Step 1: The Tabletop

For the tabletop I've bought a board of solid ash wood, it was already level and cut to my size in length, with uneven sides, and I intended to keep it that way.

I've measured the board, and created a model of it in Onshape. (I've made a mistake of cutting the board by hand, so had to include the cutouts in the model.)

Clipboard01.tif
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Step 2: Create the Model in Onshape

1) tabletop

2) left leg

3) shelf

3) inner column

4) right leg

Step 3: Intermediate Step

All the solids are intersecting for a reason - I union them all to feed the model into SimScale

Otherwise I would had to define all the connections in SimScale, and it'd take much more work.

Step 4:

SimScale imports the model from Onshape

Here's this project, you can see a plethora of design and simulation attempts I've tried.

I tweaked and retested my design, so that von Misse stress was below breaking an yield values for both ash wood tabletop and plywood legs. I've used 1.3e7 Pa for yield stress.

I've aimed for 200 kg of evenly distributed load force, with less then 1 cm of sag.