Sounds like a great project
. Keen to hear why you prefer a vertical axis over a horizontal? but anyway for what it's worth I have used plywood
vertical axis vanes. The Fabric
one was a Sayes rig. It had two Tee section posts with a "v" shaped vane made from a heavy fabric sail lashed to the ends of the Tee's.
It worked reasonably well, and certainly seemed to have more power than the standard flat plywood ones I had used before on simple trim tab systems. The sail needed to be very tightly lashed in place.
The best course setting system I have used was a worm drive system much like the Hasler.
This made it easy to adjust while the vane steered. The simpler and more common two disks and a pin in holes clutch
is a right royal nuisance at times, because as soon as you pull the pin out the vane cant steer the boat, and it is hard to get it back in at exactly the right spot, Though I have heard of some cunning ways to deal with this using two pins and elongated holes or somesuch...
I bent a vertical axis vane shaft once in a knockdown. It was 2 inch stainless tube as I recall
. So they either need to be very strong, or have a weak fuse, like the nylon cover, or it's lashings, that can break to reduce the load on the important bits. The same wave ripped the trim tab off the rudder
, we think the trim tab flexed enough to pop out of the bottom bearing.
For my old horizontal axis Flemming I made a light plywood vane with big cutouts and sewed a very light nylon cover for light airs, I could pull it off in over 20 knots and just use the plywood part, maybe something like this could work for you as a reefable sail?
Very keen to hear what you come up with, got to build something for the new boat sometime. All the best with it.