Three fibreglass ring moulds...

This photograph shows the three ring moulds. The idea is that the mould halves are bolted together and then the gelcoat and fibreglass are laid up into the small gap on the inner edge of the mould. This will produce a neckrings that are hollow and also have an open inner edge.

Each ring will then be filled with expanding foam, and filler used to finish off the inner surface.

Result: an ultra-lightweight neckcage.