Soft Wing Sail

Do you find it difficult to get enough luff tension to maintain the leading edge shape?

 

thanks for the answers. i was thinking why you mentioned less heel
for a straight up wing, and figger the answer is the lack of twist
that again made me think twice on sketch (attached) i'm playing with,
as a bipod counters heel but adds drag to lift to some amount

 

It took some time and some more battens to have a nice tensioned leading edge. It is now much nicer than what you see in the web site (don't have new photos yet). It is not a problem any more.
Ilan

 

Yipster:

Mentioning less heeling for cruisers was for two reasons.
1. It shows less waisted wind forces and better water line,
2. most cruisers are sailing with their wifes. Ask my wife how important it is.

There is a leech twist in Omer wing sail. Please have a look in the gallery. It is clearly shown at the first three pictures.

 

If you want to discuss twin rigs like this, it's probably best to start a new thread . But when you do, this might be a place to start.

It really takes a multihull to make use of the concept because you need lateral separation between an inclined sail and the center of buoyancy to make the inclination worthwhile. As long as you trim the two sails the same, there's not a big difference compared to a single sail. The real gain is when you sheet them differentially. Easing the windward sail and driving with the leeward one does not reduce heeling moment about the lee hull, but it does produce an upward force. Easing the leeward sail and driving with the windward one substantially reduces the heeling moment about the leeward hull, but at the expense of a downward load. So I believe the rig is really best suited for landyachts and iceboats that can benefit from the reduction in heeling moments, but don't pick up a lot of drag with an increase in down force. And it's best suited for rigid wings because of the need to feather one sail or the other.

 

Ilan;

Have you raced the wingsail yet? How did it perform? Can you please provide us with a link to results?

Thanks

 

No. Not yet. Just finished all phases of development. The polar diagram shows the official standard Elan 37 performance in blue and the performance of the same boat with wing sail in red. Sorry, it is not completed yet. Will be done in the near futur.

 

Can only ask a quick question at this time as I'm on a trip to Seattle.

How do your 'sliding spreaders' rotate with the rotating mast??

 

Ilan,
I am curious as to how this sail differs from previous versions like the Flip-Flop rig (now the SwingWing) by Sunbird Yachts in the late 70's (UK) and the soft wing on Yves-Marie Tanton's "Magie Noire" (http://www.tantonyachts.com/834picsthumbnail.htm)
Can you explain? I am not trying to be negative (although I usualy succeed in the end ) but to understand the differences and how yours is better.
Steve

 

Omer wing sail

How do your 'sliding spreaders' rotate with the rotating mast??[/QUOTE]

Brian,
The sliding spreaders slide up and down along tracks attached to the mast. They can not rotate relative to the mast. They rotate together with the mast.

 

Steve

I don't know were to start answering your question, however:

The #834 66' Frp. "Magie-Noire", is a free standing wing mast. It is not a wing sail.

There are also some Old Chinese junk / wingsails, some of them are very good.

Talking about wing sails only, I can say that Omer wing sail is the only one I know, that has relatively very good aerodynamic performnce, up wind as well as boat speed in all wind directions (see performance/polar diagram), it can be hoisted and reefed, has variable geometry and the camber is easily changed and trimmed, very easy to handle, good for short hand etc.

I think it would be better if you looked at www.omerwingsail.com to see all of these differences.

Hope you keep on being positive after visiting the web site

Ilan

 

Sorry, I did not notice the tracks at first glance. I was in a hurry out the door for a trip at the time I first looked.

 

Not wanting to disrupt this thread, but to get this question out of the way, you need to compare sail to weight ratios of other designs similar to yours. Use the Bruce Number which is formulated thus:
Bruce number = square root of working sail area in square feet divided by the cube root of the displacement in pounds. Racing designs will yield 2 or more. Less than 1 will be quite sluggish.
Now, back to the wingsail action!

 

So how can you tell if one type of sail is more efficient than other.?

So how can you tell if one type of sail is more efficient than other?
For a given square foot, how would sail wing compare to regular sail? How would you do numbers?

 

The scientific method is the double blind test. However, one boat, using the two rigs in turn and sailed by the same crew, should come up with some good numbers. The nominal square footage of both rigs should be the same.

That is how to compare the efficiencies. It was by testing various rigs, Gaff, Marconi, Sloop, Cutter, Schooner, Ketch, Yawl etc., that conclusions were drawn and sailplans evolved. Ilan has taken his fighter pilot knowledge and created his Soft Wing sail. It works! His boat originally had some kind of rig, which he replaced with his Soft Wing. Let's wait until he confirms whether he kept the same area of sail, or whether he downsized, but kept the same speeds.

That should help.

Pericles