bending and laminating ply

[Tor]

I've recently bent some 4mm ply - not an amazing feat I know. I'm going to bend a few and laminate them to make some furniture.

It's 4mm marine ply cut into 25mm strips, I'm using a heat gun to bend a 75mm radius curve. I'm using epoxy to glue 3 of them together and I'm thinking about reinforcing with glass tape between the laminations and on the outside too.

The final shape will be a flattened "C" shape and will be load bearing I'd like to be able to support around 60-75kg (with a bit of flex :roll:).

Do I need the tape if so what weight?
Will 25mm be wide enough?
If I increase the width will 50mm bend in the same way?
Is 50mm twice as strong as 25mm?
Will 3 laminations be enough?

I'd rather use your collective knowledge than have to attempt this and break many pieces but if the second approach is my only choice then I'll be posting on owthathurts.com :q

Thanks,

Tor

[HammaHed]

I think that without a full set of engineering drawings....

and

Without a testing of the timbers......

Etc., etc., etc.

Also while I don't know the exact purpose, location and fitting to other bits....

SOME flexing may be good.....

But are you also including the "trip over the cat in the dark" loads? Which can easily be 3 or 4 times as high as a static and gently placed load.

And they can be "peculiarly applied" through the unit...

What may be a reasonably stable unit, with some side loading and a doubling of the force = instant collapse.

I'd design ONE unit to what you think "seems to be about right" and then apply rigorous tests to it - in combination with the other things that it has to mate with....

And if it passes the test; great, if not examine the points of failure and redesign to reinforce or redistribute the loads and how they FLOW through the chain of parts.

I think it's worth doing these things properly - because people can get disfigured, maimed, and seriously injured through poorly designed furniture.....

You know like folding chairs that cut off fingers, or seat bases that don't - resulting in "rectal impalement" on the seat post; or getting skewered through the guts when one side breaks leaving a sharp pointy broken stick to fall on, or they break their necks, or their arms in the fall etc......

I mean there are a lot of people who die just slipping up in the bath....

There are some things like chess pieces - and it doesn't really matter what they are made from or how they are made - be it plastic, pine or platinum; but there are things where it does matter, and furniture is one of them.

Furniture is like bicycles - best built properly.