The design of soft wing sails for cruising

I’ve been giving the battens a lot of thought over the last few days. I'd drawn 'batten redesign 3' as an attempt to avoid the problems that arose from having incorporated the secondary axis of articulation. However, recently, I was reminded of an idea I’d had some time ago, where two straight battens were hinged together and then there was a separate non-load-bearing, luff-forming component.

It seems to me that there are several advantages to it:
The load-bearing components are simple straight tubes - easy to make and easy to calculate the strength.
Instead of a nose with two sides, each with only one rather delicate layer of carbon, there is a central tube with a more robust two layers of carbon. One of those layers can be of unidirectional sleeve.
The shape-forming components carry no structural loadings, and can be light.
It is easy to assemble around the mast.

I’ve gone back to the old way of hinging junk rig battens, by making a double wedge that fits within the two tubes. These were known to have disadvantages, in the way that they had been made by simply inserting a double wedge or double cone into the ends of the tubes. They would try to lever themselves apart when the two tubes contacted the wedge/cone or themselves on the concave side. (however, if the geometry is altered so that the points of contact are on the centrelines of the tubes, the situation is much improved). Also, the old design could separate if the sailcloth went slack.

I think I have an answer to these issues. A drawing is attached - batten redesign 5.

I have drawn a double wedge component that is to be cast from one of the strong tooling polyurethanes: http://www.fibertek.ca/smoothon_urethane_casting.htm - Task 2, 3, 4 or 9. These have a tensile strength of about 3 tons/in2. I have put in a figure 8 lashing of Dyneema to prevent separation, without inhibiting rotation. I can re-use my after battens, which have given no trouble, and make new forward battens on the same wooden mandrel. I would have to make a former to mould the “egg” (which would be mounted at mid-height of each panel) and the shorter section of that egg which would be bonded onto the end of the forward batten. These would have a foam core of not greater than 6mm thickness.

When I assembled orders on Soller Composite’s website for ‘batten redesign 3' and 'batten redesign 5’, in order to compare weights of carbon and prices, I found that 'batten redesign 5’ cost a little less, and was considerably lighter.

I think it’s time for a change of direction - the kind of nose I’ve been using is complex to make and assemble, and seems to suffer from an inherently poor strength to weight ratio. Time to go back to something that’s a little closer to junk rig. There would need to be yard hauling and luff hauling parrels, and downhauls that also act as batten parrels, as Slieve uses on his split junk rig.

I have ordered carbon for 'batten redesign 5'.

 

I've written an article for the JRA magazine, going over the whole history of my attempts to make a wing sail, which may be of interest.

 

How does the new design solve the problem of capsized battens?

 

Thanks, this sort of practical info is so helpful, specially the "how it's made" parts.

 

So that we can see the design of David's battens from post 226 without opening them in another application I'm reposting them here:


batten redesign #3


batten redesign #5

 

By eliminating the second axis of articulation, the one which permitted the batten assemblies to bend in an upwards direction. If the batten assembly can only bend one way, that way has to be in the horizontal direction, in line with the forces that the wind is exerting on the sail.

Of course, it may be that the semicircular mast bearings are still needed; in which case, I could bond them onto the starboard sides of the forward battens.

 

If the mast passes through the wishbone battens off-center I could imagine that that would reduce the risk of capsize on one tack, but increase the risk of capsize on the other tack.

 

It could be that the off-centre mast, or any other asymmetry, might introduce unknowns that I can well do without.

Here's a symmetrical layout that retains the single forward batten, and that cannot tilt:

 

Well I am back in the real world and getting caught up on this thread. Have quite a bit of reading to do. Been tearing the interior out of our new boat and thinking about what to do with the rig.

David, there is a chance I could need an excuse for a big motorcycle trip sometime soon. Would you have any interest in showing a visitor around your boat if I where to make it up that way? Unlikely I will have the time to make it that far, but could be possible...and I would love to see your boat to get some ideas for our new one.

 

{answered by private message}

 

David,
sorry to hear that all your recent work has lead down a dead end. Your recent drawing looks admirably simple, so hopefully the final iteration?
One comment, is the straight part rather long? Perhaps build this with cambered panels?
Cheers
Mark

 

Advanced Wing Systems Video

Have a look at http://youtu.be/oNKajpNXb7g

I have been following this thread loosely. There have been a couple of posts commenting on our wing sail. Usually they miss the point by some distance. The real benfits of our system is its simplicity (as redreuben kindly suggested) and its wide range of performance. There are less parts in this wing than just about any other design. It is very stable and does not collapse when at very low AoA. It provides excellent Lift and Drag characteristics. It is light (this one weighs less than 60kg all up, rigging, spreaders, sails, boom, etc, etc). The section is not an N60 and never has been or claimed to be. There IS a high peak in the Cp near the leading edge and this does result in a separation bubble, but flow quickly re-attaches. We can control camber to large extent as well as thickness. The sail twists very nicely and provides very good spanwise section shapes. It does not suffer from the creasing that soft nose wings suffer when twisting (which incidentially introduce big peaks in the Cp near the leading edge). In this video we are pushing the boat to hull speed (plus a bit) in 8 knots of breeze. We have had the same result with the rig on a Classe Mini 6.50 (6.5 knots uphill in about 8 knots). As the wind strength increases we can change the section shape (typically greater thickness and less camber) to give lower lift and drag. It can be retrofitted to just about any yacht. It can be made to be free standing but that is not a good retrofit option for many boats.

In life you have to choose a compromise - the challenge is to choose the best one!

 

SRW System (semi rigid wing) for RG 650 Series Mini

Hello all wing enthusiasts.....
this post follows this mornings post from Greg Johnston from Advanced Wing Systems.
I work very closely with them and have supplied one of my RG 650 series minis to retro fit the all new SRW System.
We have had it on the boat now for over a month and have been extensively testing with some awesome results.
What I am loving about the SRW is that to look at it is a normal rig.....the wing is hoisted, reefed and dropped as a normal sail. It has standard battens designed specifically for the loads required to induce the wing profile. It has no internal framing or mass of structure to deal with when not in use.
We are also currently a few months from launching the K8 sports which is the worlds first production boat to support the SRW System so watch this space as the SRW System hits the global market.
Attached are a couple of photos of the RG 650 with the SRW System and the final rendering of the K8 sports.......
https://www.facebook.com/pages/K8-Sports/311931335651378?ref=hl
https://www.facebook.com/RG650seriesmini?ref=hl
Here are the facebook links for the projects where we have all the latest news.......

 

From Post Number 211

I understand (I think) how deleting the second axis of articulation might mitigate the capsize problem. However I am not quite sure that it might not introduce another... from Post Number 127

Possibly the batten can be designed either with one axis of articulation or with two. Presumably one of these design would be superior to the other when engineering cost/weight and usability are considered - but I am not sure how you can be certain that the single axis of articulation is the superior solution. Am I missing something?

 

mountsbay, welcome to BD.net.