Feet to support a freestanding upright sheet of plywood

[woody1]

I need to support a 4'x3' (HxW) upright sheet of 18mm plywood, capable of withstanding a moderate breeze (hopefully not a gale). Was thinking of using a couple of lengths of 3"x2" (HxW) as feet, with an 18mm slot cut in the middle. Something like the picture below but obviously with longer feet.

Question is, how long to make the feet so it can't topple over in the wind? 2' (1' either side) or longer?

[WTFH]

If it's 120cm high, I'd want the feet to be at least half that in front and behind, that is a fairly large surface area to catch a breeze..
I'd also want it supported by more than 1.8cm, maybe about 10cm would be OK. You might also want to build a frame around it as per your image to give additional strength.

[northernladuk]

Interesting timing. Just this week we've had an incident in our town of a sign outside a shop falling over and paralysing a dog so there is currently an uproar going on on our local FB group. Don't know the details of what happened but very pertinent to this question.

IMO a bit of wood isn't going to cut it. You want to be planning for a very windy blustery day. Having it stand up to a slight breeze and then a gust of wind catches it and it hurts someone then your in a crap load of trouble. 'Hopefully not a gale' is not a way to plan bearing on mind the possible consequences.

It's a normal occurrence to see flimsy home made signs fallen over on the high street. Personally I wouldn't be going with anything less than a proper weighted pavement type sign base. Only you will know where it's going and when but I'd be playing it safe.

[malvolio]

Or build it on a board as a base then put some bricks/sandbags/docile pets to weigh it down?

[courtg9000]

Have a look at retailer supplies outlets, they will have something already done might not be to the design in your pic but they will have something safe and ready to go.

[woody1]

Thanks for all the responses. I didn't say what it was for but probably I should have.

It's a mounting board for our private water system (electrics and plumbing). Currently attached to the back of our garage. The garage is being replaced, and there will be a few days between the old one being dismantled and the new one being installed. I'll use tarps to protect the board from the rain.

The board cannot be moved*, otherwise we'd have no water. And it has to stay upright.

Time to get over-engineering...

* well it will be moved during dismantlement/installation but we'll have no water for several hours on both days

[WTFH]

Thanks for all the responses. I didn't say what it was for but perhaps I should have.

It's a mounting board for our private water system (electrics and plumbing). Currently attached to the back of our garage. The garage is being replaced, and there will be a few days between the old one being dismantled and the new one being installed. I'll use tarps to protect the board from the rain.

The board cannot be moved, otherwise we'd have no water. And it has to stay upright.

Time to get over-engineering...

OK, so you mentioned that the board was going to be 1.2m high by 0.9m wide. It is completely full of stuff, or is most of it at the top?
I would be tempted to build two "walls" of breeze blocks (laid flat), one in front and one behind. You might want to put a board in front of the stuff as well as the one behind that you are fixing them to. With these two walls built then it's easy to throw a tarp over the whole lot, and there's no risk of it blowing over.

1.2m high would be 12 x 100mm, and 0.9m wide would be 2 x 440mm, so you'd need 48 blocks to give you front and back coverage.
The other option would be to build just the one wall (i.e. 24 blocks) and use a ratchet strap (or similar) to clamp the board to the wall.

Don't bother mixing mortar or anything like that. the weight of the blocks will keep them in place.

[woody1]

It is completely full of stuff, or is most of it at the top?

Everything is in the top half.

I like your idea of the breeze block walls. Only I'd have no use for the blocks afterwards.

[WTFH]

Everything is in the top half.

I like your idea of the breeze block walls. Only I'd have no use for the blocks afterwards.

No use for breeze blocks? Inconceivable!

[woody1]

No use for breeze blocks? Inconceivable!

Out of curiosity, any idea how many it would take to keep a body submerged after decomposition gasses build up?