Help Bending 5m length of plywood

[djejmz]

Hey guys, new to this forum, and woodwork in general! I was hoping someone would be able to help me with something.

I'm currently carrying out a dissertation on fabric formed concrete, and I need to build a formwork out of wood from which I will suspend a fabric and cast the concrete.

http://www.umanitoba.ca/cast_building/assets/downloads/PDFS/Fabric_Formwork/Thin-Shell_Concrete_From_Fabric_Forms_SCREEN.pdf

If you do a search on that pdf for "FABRIC-FORMED RIGID MOLD FOR THIN-SHELL VAULTS" it should take you to a photo of exactly what I am going to try and build.

My question is, what is the easiest way to "bend" the plywood into that curve, and to keep it from springing back into shape?

Thanks

James

[ian]

Welcome James

I've had a quick squiz of that PDF you linked to.
Interesting stuff -- in my day the cutting edge was 2.5cm thick concrete origami

First question -- does the mold for your disertation need to be 5m long?
5m means 3 sheets of ply and the complications joining those sheets entails.
Could you achieve the outcome using a mold 2.4m or less long?

2nd question -- what shape are you trying to form?
From the example you provide, curve springback is a minor issue. Having a frame strong and rigid enough to support the desired final shape is almost certainly the defining factor.
Do you have a design for the shape?
Have you (or can you) calculate the forces trying to pull the frame and moild cloth out of shape?