Beneteau wing sail and unstayed mast. option for us

[VeloFellow]

I was just watching beneteau's new wing sail rig prototype. Unstayed mast. This good be a great replacment for Freedom sailors.
It might move CE a little foreward which might reduce weather helm on some models.

https://www.youtube.com/watch?v=H1cEFP_H4Rk[/video]

https://www.youtube.com/watch?v=H1cEFP_H4Rk

There is a similar wing sail design previously in Yachting in 2013. It how ever had specific mast and other proprietary additions.
Omer wing sail
https://www.youtube.com/watch?v=1Qu_ZgQcr8k

[unfetteredalexandria]

When I bought my round-mast F25 in 2007, I to wanted to try to build one of these. A couple years ago while stuck at home during the Government shutdown I did some panel-method simulations on a NACA0012 section that would enclose the mast. I've attached a diagram of the idea. The red rectangle in the left diagram is the foil; it doesn't go all the way up the mast because I would want to keep the lazy jack attachments.

Panel methods don't know how to do drag, but the sims did confirm better lift than a round section trailed by a cambered thin foil (ie a mainsail trailing behind a round mast). Drag should be less overall since the round mast section is very draggy compared to a foil. Better L/D implies better pointing. Extending the foil all the way to the trailing edge like a full wing doesn't seem to help much; the main benefit is to hide the round mast inside a foil; something like a scaled up version of what our wing-mast brethren have.

I've actually built a few NACA0012 battens by bending plywood strips on a jig and enclosing them with fiberglass tape and epoxy. The foil itself would just be a big rectangle of sailcloth with some batten pockets to accept the foil-battens. It could be slipped around the mast and attached to an existing mainsail with say, velcro or zippers. Hoist could be via pennants attached to the mainsail headboard. It could also have an additional sheet attached to the bottom of the leading edge in front of the mast to control camber.

This would obviously be less efficient than most of the professional concepts which have the big end plate boom shelf, but is is something anyone with a round mast Freedom can easily try.

[Castaway]

For those of us who already have wrap-around sails, perhaps we could improve performance by using a shaped (?closed cell foam) filler and U-shaped battens to make the leading edge of the sail more aerodynamic? Probably be a nightmare to reef or hand, however. It would also mean a lot of extra weight aloft, as would any of the suggested batten systems; OK in a 40' Beneteau, less easy in a Freedom 25.

A promising line of development, however, and it really would be interesting to see more discussion about sail shapes on the board.

[unfetteredalexandria]

It is a good point about adding weight aloft, as the F25 is fairly tender. The battens I've built are quite light though, just a few ounces each. Most of the weight would come from the sailcloth. If it's 25 yards of 6.5oz Dacron, that would be 8 lbs or so; call it 10 lbs with the battens. The center of this added mass would be about 15' above the deck. No doubt the metacenter would go up, but maybe not too much to tolerate.

Reefing system would not change from the current system as the standard single-ply main is still there, inside in the foil section.

[Castaway]

No doubt the metacenter would go up, but maybe not too much to tolerate.

I think you're right about that; I was influenced by the comments about the Beneteau and the difficulty of raising the sail on the linked video.

Would you be able to keep a straight leading edge between the battens, or would it be 'scalloped'? The Beneteau looked straight, but I couldn't see how the tension could be maintained, especially since there was a curve in it.

Gerald

[unfetteredalexandria]

There should be tension along the leading edge created by the downward pull of the leading edge sheet attached at the bottom, and the pennants attaching the top of the foil section to the headboard. Still, the leading edge would not be ruler-straight.