Plywood question

[throbscottle]

I want to make a plinth/box thing to replace the hearth, to hide the wires from the TV etc which has replaced the fireplace, where there is now a large curved cutout in the carpet.
I was thinking to bend a piece of plywood to fit the curve. I'm guessing the radius is somewhere over a metre.
So I think if it's thin it will bend enough without needing cuts in the back,, but which way is best for the outer layer grain to go: longways or crossways? Also, how thin would it need to be? 3mm? 4mm?
Thank in advance!

 

[Spectric]

Why not make a former and then use several layers of ply to build it up which will give you the curve and strength. You could also make a jig and then make the piece from sections on the router table or spindle moulder using trim cutters with a bearing.

 

[Dee J]

Thin ply with vertical grain on the outer faces is your best bet. 3mm should be fine, but it varies with wood type and ply quality. Laminate 2 or 3 layers with some shaped gluing blocks or framing behind and it'll work.

 

[Bingy man]

I personally think that 3.5. Or 5.5 will work . The thinner the easier but you f do not say how high the hearth is .. I don’t think the grain direction will matter as it’s alternated when manufactured . A meter long will curve without too much force so depending on how deep the curve is you will need to cut it longer than 1 meter .,

 

[Terry - Somerset]

Plywood typically has an odd number of plies - top and bottom plies run in the same direction. It would probably be better if using plywood for the external grain direction to run vertically - on 3mm ply there will likely be two vertical sheets and one in the middle.

Personally I would probably do the job with by making a frame to which the ply/MDF can be glued using the thinnest possible. MDF I recall it is available with slots to make it easy to bend.

 

[Sachakins]

Bending 3mm ply over that radius will be fine, but I would add a couple,e of blocks behind it, Brad nailed or glued to the plinth, then Brad nail the ply to the blocks. That will give you a stable hearth base.

 

[throbscottle]

Wow, so many replies!

I hadn't even thought of layering it up. I'll do that. How well would it work if I attach a single piece to the top first and then layer "in place"? It will have a curved section at the bottom as well to match the outer edge of the top, so it's not like it will be wobbling about much.

It's going to be about 6" high, trapdoor in the top so those cables can still be accessed.