Gardner,
The two would definitely need to be independent; otherwise,
instead of a graceful foil generating lift and directing airflow
onto the said, the mast would just be a big slab out there creating
turbulence.
However, as with standard rotating masts, you can find a
relatively happy medium that will work for many wind angles. With a
noticeable part of the wing aft of the center of rotation, and with
the sail itself pulling on the wing's trailing edge, the mast will
automatically want to rotate into a reasonable angle.
If you limit the rotation with a rotation limiter, you'll be set
for just about everything except a tight beat and a run. And even
in those cases, you'll still probably be more efficient than a
standard D-section aluminum stayed mast. If your rotation limiter
were adjustable, you'd have even more chances for optimization. I
pretty much leave mine set on tight-medium and adjust it only if I
refuse to let someone else out-tack me downwind.
Of course, if you did want to race, and eek out every possible
eighth-knot from the boat, you'd need a set of blocks to fine-tune
the mast angle relative to the boom on all points. But that's a lot
of work.
However, now you need to strong sets of bearings: one for the mast
to rotate freely from the boat, one for the vang-less boom to rotate
freely from the mast. That's more complexity, more expense.
---
If you're serious about keeping expenses down, another option is
the swing-wing soft wing sail described by Kim and Rudolph. One
mast, no boom, no rotating bearings anywhere, no sail track. I know
you're plans haven't revolved around this rig, but I thought I'd
mention it again since you've been focused on cost lately. Unless
you're going with a schooner rig (where I'm not sure the swing wing
would work), it would be hard to beat in terms of price.
- Mike
Gardner Pomper wrote:
I am under the impression that with a wingmast, you need to rotate the
boom independently of the mast, so that the wing is at a steeper angle
to the wind than the sail. Am I correct in this?
If so, that seems like you could no longer have the boom fixed to the
mast and use the mainsheet to adjust the angle of attack. Wouldn't you
need extra lines to trim the wing seperately from the sail, especially
in light air? If so, that seems like a major disadvantage for a
cruising boat.
Thanks for any help clearing up my confusion.
- Gardner