The design of soft wing sails for cruising

I still can't understand why you'd bother with a pocket luff unless you were looking for very high performance, and even then they are not always an advantage. Many high performance windsurfers discard the pocket luff in favour of simpler styles, and the new Wasp Moth, designed by the leading Moth designer, is discarding the pocket luff as well.

There's an enormous testbed out there called the real world, which has been showing for decades that leading-edge devices don't come close to providing as much increase in performance in practice as they do in some theories. They are fun in their way (which is why I own three wing masts and about 20 sails for wings or with pocket luffs and camber inducers) but they can also be a massive hassle. There are also some experts who say that pocket luffs only work in extremely high performance craft with very flat sails, such as windsurfers and Moths. That seems to be well borne out in reality.

As an indication of the issues, after 30 years of development, the latest windsurfer sails are often twice as heavy as the very first Windsurfer sails of similar size, and that's all because of the pocket luff, camber inducers and full battens. It's a major price to pay for the supposed advantage of a cleaner leading edge.

 

Production wing sail

I haven't posted in this thread for a while. However, I have been busy none the less. In the past year we have commissioned the K8 Sports boat, fitted with our Semi Rigid Wing (SRW). K8 #1 was first launched on August 29 and has more than met our expectations.

Within weeks of the K8 Sports hitting the water for the very first time, we sold K8 #2. This new boat will be gong to the USA and we are confident that there will be more to follow it.

The K8 Sports is the world's first production boat to feature our SRW technology. The SRW, or semi rigid wing, uses a patented technology that creates a semi rigid aerofoil structure but is still capable of being easily hoisted, reefed and stowed. The SRW is a breakthrough in practicality, usability and reliability of wing sails. It’s simple, lightweight design means that the SRW can be applied to a wide range of sailing yachts. The SRW is the simplest and most practical soft wing sail system on the market.

Nicolas Goldenberg of G Yacht Design has worked with Advanced Wing Systems to design a light, fast, user friendly and enjoyable, 8m sports boat. "The K8 is unlike any other sports boat on the market, simply because all other boats have been designed for conventional rigs. The initial design brief from Advanced Wing Systems was to create an exciting sports boat that is easy to sail with a small crew. The K8 has modern, powerful lines to take advantage of the extra power of the wing. The wide chines provide narrow heeled waterlines and high stability allows the boat to be sailed with 3-5 crew. The trend is away from sports boats which require a crew of 6 or more super athletic members, and the SRW makes this easier to achieve."

The K8 has been nominated for the pretigious Yachts and Yachting Sports Boat of The Year award (http://www.yachtsandyachting.co.uk/2016-sportsboat-of-the-year-k8/)

There is also a good write up in Seahorse magazine which gives a bit more information about the SRW. You can find a copy of that article here: https://www.facebook.com/AdvancedWingSystems/posts/923207771095623

See it in action here: https://www.facebook.com/AdvancedWingSystems/videos/910411365708597/?theater

 

I thought about the tacking for the Bamboo Snake foil. And it won't automatically flip its snake head around after cross the eye of the wind. The sailor must go the mast and flip the joints around, or have some other mechanism to invert that section of the foil. Might be difficult with a big sail.

 

"I still can't understand why you'd bother with a pocket luff unless you were looking for very high performance," -CT249

true, for what I'm doing, i place simplicity and ease of use over performance.

 

Just found this subject thread, and doing a quick read thru this morning,...found this quote and just had to make reference to it over on another subject thread 'Aftmast Rig"

Thank you David

 

Interesting posting Groper. Had to repeat it for a reference later.

 

Tackable Square Rig?

I had given some thoughts of this basic idea to possible making a 'reversible cambered square sail' like that utilized on Maltese Falcon, rather than a fully rotation mast to 'tack over' the square sail.
http://www.runningtideyachts.com/dynarig/

Had an older interesting patent reference, but I will have to find it.

 

Standoff batten rig for flexible airfoil conformation on both tacks

http://www.google.com/patents/US4924793

 

only got to page 8 and ran out of time to review,...interesting subject thread
Brian

 

Just curious if you can run into problems reefing if the battens are too light? I was considering making foam core composite battens for a small 65ft2 wing sail, but concerned they may be too light to come down smoothly if pressed against the mast.