Well at least by taking the top surface of the roof off to expose the balsawood core we understand why it rotted.
Balsa wood is not very strong and so when you build boats in this way you’re supposed to put strengthening pieces where ever you have fittings going through the balsa wood sandwich. That way you can bolt or screw fittings tightly and they don’t move.
In Anne Marie‘s case there are no such strengthening pieces and so the balsa wood core moves slightly with the stresses and strains of a boat.
As soon as this happens the water starts to sleep in around the bolts or screws into the interior. Water and time take their opportunity and the fibres breakdown and rot.
For Anne Marie’s saloon roof this means the main entrance, the central hatch, two circular vents, two sets of handrails and one mainsheet traveller are all vulnerable All of these provide opportunities for movement and water ingress.
Strangely the only one that appears in good condition is the hatch surround in the centre of the roof.
Needless to say I shall be fitting plywood strengtheners where ever there might be an opportunity for fixings to go through the roof to provide the strength necessary in those areas.