I don't like this. Some time ago, we discussed the ideal section for a yard, and I said then that if the section is very deep and narrow, it will just try to rotate about its axis to seek the easiest way to bend. Also, if you put two tubes together, the material near where the tubes touch is doing nothing to add strength and stiffness, but is just adding weight. I stick to my view that the best section for both yard and battens is circular.

The sizes of your mast and battens are about right, but I think you'll need a stronger and stiffer yard. If the length is about 3 metres, the diameter will need to be at least 60 mm, but the use of a span, attached to the 1/3 and 2/3 of length points, reduces the demands on the tube.

Sorry to hear that. The cloth seems good and was quite cheap. 

Two panels done!

Oops! My sail turned out to be an experimental one.

I'm building my own (well, I at least I haven't seen one done this way) hybrid. The sail shape is dowscaled version of Arne's Johanna type sail, AR 2.15.

However, I'm not sewing batten panels, but using a kind of hinge system - but unlike Roger Taylor, I have cut the panels using Arne's camber system (Roger Taylor used straight panels and made the camber using hinges of different lenths). In my sail the hinges are different in many ways.

More on this later, if the sail turns out to look like a working one...

One panel done, six to go!

The cloth, 92g/m2 ripstop polyester recommended by David Tyler, is very easy to work with and seems like a good compromise between strentgth and lightness.

The work on the mast should also start soon. A question regarding hybrid mast: if the top is to be made by glueing two 2x4" planks, what does one glue them with? Epoxy or something else?