John,

The main difficulty was to make joints that were strong enough and resistant to cyclical loadings. The bridge pieces behind the mast were rivetted on, and loosened. Welding would soften the alloy. If I made alloy noses again, I would try to bend them around in one piece, rather than rivetting on a plastic piece at the luff. This, I think would be hard to do, as the tube has to be over-bent and then allowed to spring back. It took me a while to develop a former shape just for the nose made from two pieces of tube. It would be as big a development job to develop a former shape for a one piece tubular alloy nose as for a CFRP moulding.

Originally, I intended to go back to a ketch rig. This needed the mainsail to have as much balance area as possible, while the mizzen would have none at all. I got so exhausted making parts for the mainsail, that I couldn't face starting over and making parts for the mizzen, so I adapted my plan and made one single sail. This needed to be in the postion you see it, for helm balance, which has turned out to be very good, and better than the low AR fansail. It's undoubtedly easier to construct a nose with the mast positioned right at its forward end.

I'm still experimenting with the bridge, or batten parrel, behind the mast. There must be something here, but I'm not yet sure what form it should take. At the moment, I favour a Dyneema cord with a nylon tube threaded on, but it could be that the upper battens, which are under compression, should have something more solid. It could also be that these upper battens should have a luff hauling parrel, but I need more sailing time to establish this.

What a great job, nice shape and few wrinkles.  The higher aspect ratio looks very efficient.  Lighter stronger battens are the key to this working well, I'm dying to read the article.

Paul,

Thanks for the kind words. But I must say that I have no sense of being in competition. I'd rather collaborate with others, to work together towards the rig of the future.

I think we've come a long way since the Sunbird Swingwing. We've now got a much better foil section. The fact that Beneteau, with all its design and manufacturing muscle, is also going with a very similar foil section, encourages me to think that I'm heading the right way. The structure of a junk-based soft wing sail is unlikely to change hugely from the shaped nose/hinge/straight batten sort of format in the future,  though it will generally be made in carbon fibre rather than the aluminium tubular design that Sunbird used, and that I made and found to be wanting in my previous wing sails. You may be thinking that the hinges are metal because I painted everything grey, to keep the UV off in the tropics. They are in fact compression-moulded CFRP, and I'll get around to describing the way of making them as soon as I can.

Jerry Barth wrote:

David,

   Is that an ALU light pole that you are using for the mast?  How tall is it?  The wingsail looks good, I'm surprised at how small the stack of wishbones is when it is down.

Thanks,

Jerry Barth

This is a 222mm diameter spun-tapered aluminium alloy tube originally from Nedal in the Netherlands. It was 12m long, 10.5m LAP for my junk rigs, but for this sail, I needed to go for higher aspect ratio. I couldn't figure out a satisfactory way to lengthen it in one operation. I cut it near the top and inserted a length of yellow cedar, sheathed in carbon fibre, thus "hybridising" it. Then I set a 8ft x 10" diameter tube in the boat (with a plug 1m down from the top, craned the mast into it and filled the 1/2" gap with pourable polyurethane. This has turned out well, and the top of the 10" tube is at the foot of the sail. The LAP is now 13m. 

I too, Darren! I surely don't want to discourage you from constructing a wing sail. I just don't think it will be everyone's sail, unless a boat manufacturer decides to produce it.

Good luck!

Arne