Thread: supporting mdf table top

Check with the sagulator....

The Sagulator - Shelf Sag Calculator

EDIT:

Ah, now I see what you mean...400mm overhang is going to be a little springy, but the bigger problem as I see it is tipping of the desk when someone uses it to help them stand up. If the whole depth of the top is 900, 400 overhang is pretty nearly half that so there's a pretty good moment arm there!

Do a test version of the top with plain MDF and see if you can live with the deflection and how likely it will be to tip - it's not like you can't reuse the MDF on something else!

Thanks splinter, what a handy calculator, will have to put in my favorite list. From what I could work out with a 30kg load the mdf will sag will be around 0.6mm over 300mm. I would imagine when in use there would be very little load.
My main concern is the top sagging over time. I think because because the table will be attached to the cupboard and the slight curved return will give it a wider stance. Sorry the drawing was done some time ago, the top is around 1000 and the base is around 600.

My concern with any desk/table etc design is that there is always a small chance that people end up sitting on them and then ????

It's a bit hard to see from the shots how exactly to fit it but if it were me..... Steel!

I'd cut a 5mm deep rebated channel into the underside of the desktop and run a 25mm square steel tube across the span. (1.6mm wall thickness)
So long as each end of the tube is 'keyed' into the side supports you'll be fine.
This could be attached using a multi-surface glue (expoy or suchlike, hell even Sellys quick-grip would do) and some screws from beneath.

This should create the long term 'sag resistance' required, have enough strength for someon to sit on it, and if the rebate was set say 10cm in from the front you'd never even see or feel it!

For greater strength you could even use a 50x25mm tube, laid flat, but probably not necessary.....

Seal it with whatever, could be paint to match the timber if you want, to prevent surface rusting and you're all set!
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Years ago I made a desk with a 2.2m open span underneath and a 16mm MDF top. The frame is basically 50x25mm steel tube and I can stand on this desk with minimal (a couple of mm) flex.

Here's a picture of it in my office, the black line above the draws is the front steel bar laid flat. The MDF top basically just sits on the frame with a couple of screws to stop it sliding around......

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