I'm in contact with Michelle Thomas at the Aluminium Lighting Company, tel. 01639 852502, and it looks as though I can get a bare conical pole 9.2m long, 165mm diameter parallel for the lower 4m and then tapering to 76mm diameter at the top, with a wall thickness of 3mm. The alloy is 6063T6. I'll be able to adapt the sailplan to fit onto this length of mast. I'm waiting for a quotation.

I've uploaded my first sketch for Weaverbird's conversion from pointy-top to junk.

The sail is of high AR, 18.95 sq m/204 sq ft, and I'm thinking of Tyvek 1443R material. This is 1524mm wide, and it seems to make sense to have a vertical seam in the middle of each panel, as the sail chord is 2.9m and I can make use of some broadseaming at the mid point.

The mast is about the same height above deck as the bermudan mast, with a total length of 9.5m. I'm thinking of a diameter at partners of 145mm.

The battens are 3m long, which turns out to be very convenient, as RBJ Plastics make some high spec carbon tubes of that length, and I feel that if I use very light weight Tyvek for the sail, I should match it with very light weight battens. Might I get away with a one-part halyard, I wonder?

With this kind of tall narrow sail, I'd be using upper and lower sheets to keep control of the twist.