I think I have solved the problem of the hard turn on the roof. Because the hoop pine veneer is not as strong as the glass on duflex I have been cutting the kerfs down to only about 3/4 of the way through the panel to leave a bit of strength in the board, but this is not allowing the kerfs to work properly and it is only showing at that spot because it is the biggest drop in height between frames. The rest of the roof can deal with it because the curve is gentler. I will cut these kerfs closest to the frame a little deeper to fix the problem. This is probably a good time to remind readers that I am very much an amateur boat builder and these issues are not obvious to me immediately because of my lack of experience.
I spent today doing salvaging offcuts of duflex to make long strips for planking the roof. The warm weather returned which slowed me down a little but I got a lot of strips glued and I think I have close to enough to now do most of the roof, if not all of it. I have found some quite big pieces (including the 2 pieces that were the foredeck that I used duracore on) so I glued them into one big panel about 1 meter wide and 4.7 meters long (the length of the roof). I am thinking I might kerf the front of this panel in 1 piece (Hans idea, thanks Hans) as this section is almost flat across the middle. The 2 pieces that would have been the foredeck were about a meter short for the roof so I had to cobble together a few other pieces. These will end up over the cockpit and at the front where the kerfs will be is one piece with no joins. Joins tend to be weak points but more importantly hard points in the curves. So I should get the curve right even thought I will have one panel a meter wide across the middle.
Then I will use the existing duracore planks either side of the centre duflex panel, then finally all of the thin duflex I have been extending. These are the long tab panels that made up the edge of sheets. I will strip these down into 40mm strips to go around the tighter side curves.
So with any luck, tomorrow I might have some progress on the roof to show. I really thought I would have had the roof finished by the end of the month. I still have a good couple of weeks to go on it. Once I have the roof fully planked I still have to sand back the glue then glass the outside, turn it over, sand the inside before glassing the inside. Then before I fit the roof to the boat I have an idea that I might make a glass panel using the inside of the roof as a mold while I have it upside down. This panel will become a roof liner. My idea is to put a sheet of plastic down inside the glassed roof pr some other kind of mold release, then lay a couple of layers of wet glass down to set, then when removed it will be an exact fit to the saloon roof. I will then cut it into say 3 more manageable pieces and then upholster them. My thinking is that these will be quite lightweight panels and can be attached to the roof using automotive Velcro.