Thread: MDF vs PLY for long shelving

I reckon it will sag if you use MDF, why not have a centre support and a front rail?
Ply will do the same unless you go very thick, your bound to put a heavy weight on it one day without thinking... or someone else will!

Particleboard is stiffer than ply, ply is stiffer than MDF. None of them is stiff enough to support their own weight without sagging over 2400.

Mick

I would put at least 2 partitions in that. Otherwise, I'd make the frame up from angle iron and just use MDF for the shelf tops.

Whats wrong with a couple of lengths of pine dowled to span the 600? Be cheaper and a lot stronger. Look better too if you give it some time.

J!

I am assuming by dowled you mean dowel joints?. Would biscuits be suitable as i have a buiscuit joiner?. It looks like pine may in fact be the better option, i will just have to look at the cost.

I wouldn't put any money on pine not sagging over that length either. Unless you are going to laminate up a benchtop from 2x1.

Just out of curiosity, why do you want 2400 between supports?

I never said having no support was required, If it needs to be there I can quite easily put some in, I was more curious about if the stiffness of the various materials availible would be enough for that length...

Well I suppose it seemed from the original question and other comments that this is what you wanted and I was curious as to the reason. If there is none, then I think you are making it hard for yourself. If you put in three partitions for example then you are talking about 600mm by 600mm and sag is not really going to be such an issue - you can use whatever is cheapest for your shelves.

SilentC has come up with the best option, add some doors while your there keep the dust out of your tools.

NS

I think it can be done, not with partitions (which you specify you do not want), but by reinforcing the underside and/or front edge with something VERY STIFF. I do'nt think that a thin bead is nearly enough, and the orientation of the reinforcement will also be important. For something in the order of 2400 I would reinforce the front and rear with a suitable section of angle iron (or a length of steel "strip") which I would face with hardwood. An alternative at the rear would be a dado into the back of the unit into which you could run the shelf. This would support it the entire length (this would not be enough support on its own. You still need to add to the front).

Regards from Perth

Derek

partitions (which you specify you do not want)

Sorry, but I thought we just established that there was no requirement to NOT have partitions :confused:

You guys work it out between yourselves, I've put my 2 cents worth in

I would just run a 2x1 cleat along the back to support the rear of the shelf, I've done it before with success.
Attach the cleat to the rear of the cabinet with screws or glue and brads.

I know I wasn't going to add any more, but really I can't help myself. Don't forget that this thing is 600mm deep (2 feet) and is unsupported for 2.4 metres (8 feet) along the front. Even a 2 x 1 cleat will sag by a couple of inches over that length with any kind of load on it. The back of the shelf wont sag but the front will.

Have a look here: http://www.woodbin.com/calcs/sagulator.htm

You can calculate the sag on MDF or Ply and you can also calculate the sag on a 'beam'. If I sat on a shelf made from MDF that was 2400mm by 600mm it would sag by 203mm. A 2x1 piece of Radiata Pine on edge would sag by 1856mm. In other words it would snap.

A 600mm x 600mm shelf made from MDF will sag 3mm under the same load.

Now thats a handy link! Cheers Silent.

I'd use Silent's suggestion. If you need a 2.4m opening, just put the perps on the bottom shelf, leaving the top one free... You'll need to reinforce the top in a different manner though... A 7"x2" peice of hardwood along the face perhaps, like an apron? That might stiffen it up a bit.

J!

Edit: OR You could put a 15mm thick length of stainless angle/t bar across the underside, like a strongback...