How to make a curved corner

[TimB100]

Hi people.

I'm working on a project (bed). It will have 50mm side panels made of 2 sheets of 25mm ply glued and screwed together. That bit is doable but I also need to make curved corners. They have an internal radius of 100mm and external of 200mm.

It would be possible to make a former and laminate round the bend using loads of bit of thin sheet but not at all easy especially over the 1mrt section.

So I was thinking of using a solid section. Say getting some one to stick 4 blocks together and turning it. That would work for the out side but no idea how to do the inside.

Does anyone have any recommendations on how to produce the corners.

 

[transatlantic]

Could you do something like this?

You'd then need to either strengthen it, or design the bed in such a way that it's not a supporting piece (probably the best option)

 

[TimB100]

Hi,

Thanks that's a great idea. Its not a structural part and I could just fill it with and adhesive to fill the voids before bending it. I like it also because I can do it with just a skill saw. Work shop space is very limited.

The other thing I did not say is its not going to be seen. It will be upholstered.

Thanks again

Tim

 

[John15]

Could you cut the curve with a coping saw?

John

 

[LancsRick]

Right angle template with a router with a wide guide bush fitted would be simple and quick.

 

[transatlantic]

Hi,

Thanks that's a great idea. Its not a structural part and I could just fill it with and adhesive to fill the voids before bending it. I like it also because I can do it with just a skill saw. Work shop space is very limited.

The other thing I did not say is its not going to be seen. It will be upholstered.

Thanks again

Tim

Adhesive won't work well as a filler, if at all (unless it specifically mentions it has gap filling properties)

 

[Brentingby]

If you cut the saw kerfs as transatlantic shows, use epoxy thickened with some sanding dust as the filler.

 

[TimB100]

Hi,

The way I see it, you would apply into the cuts a polyurethane glue like Gorilla glue, then fold it over. The glue will be thin enough to not restrict the bend but will expand to fill a lot of the voids and hold it in place over a reasonable percentage of the kerfs.

The issue with a glue sawdust mix is that it will fill the void and prevent it bending. If you try and apply it later it will only fill small voids on the outside.

Cheers

Tim

 

[thetyreman]

I'd use a very sharp chisel to knock off the corner, a bit a time, to create the curve, then go over with a rasp and sandpaper.

 

[transatlantic]

I'd use a very sharp chisel to knock off the corner, a bit a time, to create the curve, then go over with a rasp and sandpaper.

On plywood?

 

[nev]

Multiple sheets of thin bendy ply glued and formed over a simple former, maybe use some pvc plumbing pipe for the round.
Like this without the fancy stuff.
https://www.youtube.com/watch?v=gRyLsO8pTfg

 

[TimB100]

I have made in the past several doors using a Poss.neg mold and thin solid cardboard, using cascamite glue to hold it all in place. But I made a special form for it. It had a big frame and bottle jack clamps to press it down to hold it in shape while the glue dried.

As I'm making a king sized bed its just too big to make a frame up, also no longer have a workshop space big enough.

Using sheets of say bendy MDF means that the flat parts need to be held flat. I just do not have the space or the inclination to build such a big frame.

Using glued ply (25mm and 18mm or 25mm) . I can create a thick board around 40-50mm thick then kerf the sections where the bend is just using a circular saw and flat edge to create the kerfs. I will probably have to make a simple frame with the bend former. Then form and glue one bend at a time.

I have decided against the PU glue like Gorilla glue as it expands and may force the joints open. A cascamite type glue may do.

Another idea as its all being drawn in cad is to design the part so it can be cut by a CNC router. They can cut the kerfs while they are cutting the shape. By using 2 sheets and having the kerfs on the inside I can glue up, clamp and screw the sides together. Once the 2 halves are screwed together they will hold themselves in place while the glue goes off. This will produce a stronger bend and have a nice inside finish.

Cheers

Tim