Wing sails for recreational and commercial boats

[boggybrn]

Wing sails for recreational boats

I met an extraordinary Frenchman - Bertrand Fercot last summer. He had built a 30' Wharram catamaran with a mast in each hull and a swing wing sail on each. It seemed to sail really well. Nearly as easy to handle as a junk rig, but much more efficient.

He has since sold that boat as he is near to completing a 46' version, again with a swing wing sail.

Look here for some details: http://wharrambuilders.ning.com/profile/BertrandFERCOT

 

[lw395]

Rigid wing masts

Full wing sails, usually two hinged sections have been raced since 1972 at least.
http://www.team-invictus.co.uk/I4C/History/lac-history.htm

Wing masts with soft sails go back further.

Depends what you want;
Absolute effiency,
effiency per unit sail area
performance vs cost

Controllability is the limitation in dinghy classes.
Blending the efficiency of a wing mast with the automatic depowering of a flexible mast is keeping a lot of people thinking right now.

 

[snowleopard]

This has to be better than a symmetrical aerofoil, not the least because the camber can be changed to suit the relative wind speed.

But have you compared performance with symmetrical and asymmetric settings? I find it wise to test 'obvious' notions, for example I tested the theory that cats should tack downwind and found the best VMG was actually dead downwind.

 

[snowleopard]

Depends what you want;
Absolute effiency,
effiency per unit sail area
performance vs cost

Ease of handling is a key factor, the main reason for choosing my rig.

 

[Garold]

Last summer we were tied up in Dartmouth for a few days next to a Walker Wingsail boat. It was very interesting to see one up close and talk to people who were sailing one (South coast UK up to Scotland was the plan I believe).

I think that one of the guys on board was the son of the inventor and the boat was apparently owned by a very wealthy guy who had sunk hundreds of thousands of pounds into the boat to try to keep it seaworthy and to improve the functioning of it.

The 'son-of-inventor' was a very able, creative and resourceful guy. One minute he had one of the hydraulic drives in pieces, the next he was trying to get the AIS working. However, it looked to me like a boat that needed a full time engineer.

Maybe more damming, I was told by one of the guys onboard who had sailed on the boat from somewhere near the Solent, that it wasn't a particularly good sailing vessel because it was very heavy. He said that they were often sailing at 3 to 4 knots and had to passage plan for these speeds.

If this boat was in any way representative of the benefits to be derived from a wingsail rather than cloth ones, it didn't really work for me.

Maybe a more modern version could overcome some of these deficiencies. If not, I think that it will be very limited in its appeal.

 

[wingsailor]

Can't agree on that. Quite a few symmetrical sections are pretty efficient. Possibly not quite as good as the best of the asymmetric but enough to make the extra weight, complexity and reliability of a variable-camber wing of questionable value. There are other approaches to the variable-camber method. BMW Oracle used two sections with a hinge while mine uses a rigid aerofoil leading edge with a cloth trailing edge.

That's true, I'm an experimenter and I done a few tests with symmetrical sections and assymetric. There is a difference but not, in my opinion enough to warrant the complicated camber-changing strategies employed by some wingsail designers.
Symmetrical sections work very well, especially if they are automatically adjusted by a "tail" (similar to an aircraft) after all, many aerobatic aircraft use these sections and still fly perfectly well.
I've got videos and pictures of some of my tests on my website http://www.sailwings.net

 

[Sequoiah1]

Last summer we were tied up in Dartmouth for a few days next to a Walker Wingsail boat. It was very interesting to see one up close and talk to people who were sailing one (South coast UK up to Scotland was the plan I believe).

I think that one of the guys on board was the son of the inventor and the boat was apparently owned by a very wealthy guy who had sunk hundreds of thousands of pounds into the boat to try to keep it seaworthy and to improve the functioning of it.

The 'son-of-inventor' was a very able, creative and resourceful guy. One minute he had one of the hydraulic drives in pieces, the next he was trying to get the AIS working. However, it looked to me like a boat that needed a full time engineer.

Maybe more damming, I was told by one of the guys onboard who had sailed on the boat from somewhere near the Solent, that it wasn't a particularly good sailing vessel because it was very heavy. He said that they were often sailing at 3 to 4 knots and had to passage plan for these speeds.

If this boat was in any way representative of the benefits to be derived from a wingsail rather than cloth ones, it didn't really work for me.

Maybe a more modern version could overcome some of these deficiencies. If not, I think that it will be very limited in its appeal.

I think the fact that BMWO wing rig worked so well over the conventional rig of Alinghi proves that the wingsail is light and efficient. IMO the only serious problems with Walker Wingsail boats was the boat and that had they just focused on the wing technology as opposed to what was underneath them they might have had a better shot at making something viable. Just like the shambles of the Americas Cup the egos have to have their way.

 

[Ubergeekian]

I think the fact that BMWO wing rig worked so well over the conventional rig of Alinghi proves that the wingsail is light and efficient. IMO the only serious problems with Walker Wingsail boats was the boat and that had they just focused on the wing technology as opposed to what was underneath them they might have had a better shot at making something viable. Just like the shambles of the Americas Cup the egos have to have their way.

To me the really interesting thing about the Walker system was that there was no direct trimming of the wing: no sheets and no rotation of the mast. The whole thing was done by trim tabs - either side ofthe mast, as I recall - which effectively weathercocked the main wing into the desired drive position. It's an incredibly elegant way of doing things, not least because in a gust the wing just overcomes the trim tabs, weathercocks and neatly depowers itself. The downside is that you have a fair bit of windage from the trim system.

John Walker showed me around one of his craft at the Southampton Boatshow. The control system was great: there was just one lever, marked from 100% ahead to 100% astern - you just set the proportion of maximum available thrust you wanted and the wing did the rest. Alas I didn't have time for a test sail, but seeing a ruddy great multihull reverse out of a marina berth then drive out to sea - under "sail" - was really quite impressive.