Richard Oates wrote:. Do you have a good supplier for the Weathermax, I rang Contender and they quoted £21 per m plus VAT which seemed quite expensive.

David Tyler wrote:

(Richard:)"One thing I have wondered about with straight battens, a good deal of camber is presumably put into the sail, but around the battens themselves the sail is flat, the camber forming a sort of elongated balloon shape, it seems that the full camber is therefore only experienced of about 2/3s of the sail. I assume the hinged battens alleviate this problem?"

- This is true also. It's one reason for preferring hinges plus a little built-in camber.

 Hm,
I am not so sure about that. Has there been any scientific studies that confirms this assumption?

The only real comparison I know about was on my 23’/1.4ton Viggen, Malena. She was tried, first with a flat sail, then with the same sail fitted with hinged battens (JRA NL 24), and was finally given a new cambered panel sail of almost the same planform (JRA NL 30).

I didn’t have any instruments, except a compass, so my findings are not so accurate, but this was what I felt:

·         With the flat sail (32sqm) the boat was simply not very good when fully close-hauled, and needed to be persuaded to tack. Pointing angle was 5-10° lower than with BR. Even with that big sail, the boat still felt ‘dead’ when heading upwind. Reaching and running was better, and the flat sail also had a strong self-steering effect. It was clear that the centre of pressure, CP, moved a lot aft and forward as the angle of incidence was increased or reduced.

·         When the sail was tried with the hinged battens (in all the horizontal battens, not the boom), the boost in performance was dramatic, almost shocking. Suddenly we could point and tack seriously again: In an unplanned little upwind match-race against a sister boat, Malena went both faster and closer to the wind than the other boat (mainsail and Genoa 1). However, the boat now had a bit more weather helm, and I could not compensate by shifting the sail forward, because that would lead to the fore hinge turning the wrong way. The strong self-steering of the flat sail was now gone. As long as the sail was hauled far enough aft (about were the flat sail sat), handling was generally trouble-free, and reefing and furling was ok.

·         When Malena was tested with the new blue cambered panel sail, I found that the forward-set max-camber point had moved the CP even further forward than in the flat sail, so I had to pull the sail well aft to avoid lee helm. This was just as well, I thought, as this lead to minimum distortion of the sail camber on port tack (with the mast on the leeside). My hunch was that this sail was slightly less powerful than the hinge-batten sail, but my guess was that this had to do with the reduction in overall camber, from 10% in the hinge-batten sail to about 8% in the cambered panels. Still, I felt that Malena now was a straw faster to windward than with hinges, and heeling less. Anyway, with the big sail (32sqm from 1995, with new mast and 7 panels), the SA/disp. was close to 26, so there was never any lack of power.

Conclusion:
My guess, after this not very scientific test with Malena is that there is not very much between the two versions of cambered junkrigs, of same planform and size  -  if both have been given about the same amount of camber.

Since the cambered panel sail of Malena turned out to hold well together, despite the quick and dirty, experimental way it was assembled (amateur method A, later B), I found no reason to go back to hinged battens on later rigging projects.

Arne

David, Arne and Annie

Once again thanks for all the marvellous feedback and information. It’s all really very good indeed. Your photos of making the sail David are great and make everything pretty clear. I would like to come over and look at your sail again soon, maybe when it’s on the boat as I still have quite a few questions. Do you have a good supplier for the Weathermax, I rang Contender and they quoted £21 per m plus VAT which seemed quite expensive. I could ask a local sail maker friend.

I see how the hinge battens work now, quite simple really and something I could make alright. So I guess the way to go may be a combination of hinges and camber. One thing I have often wondered is what happens on the other tack when the wind is coming from the opposite side of the sail to the mast? I guess that the balance of the forward batten (more of it behind than infront of the mast) means the sail will still take up the proper shape. One thing I have wondered about with straight battens, a good deal of camber is presumably put into the sail, but around the battens themselves the sail is flat, the camber forming a sort of elongated balloon shape, it seems that the full camber is therefore only experienced of about 2/3s of the sail. I assume the hinged battens alleviate this problem?

The loan of your sewing machine is a very generous offer. Now that I understand the system of just passing one roll under the arm my machine may well be OK as it’s quite a reasonable make, though it does suffer occasionally from a jamb up which can totally spoil the look of a seam. That’s probably due to poor set up or lack of maintenance and oiling. I must confess I have never really mastered the art of using one properly.

I have a more accurate drawing now and I get the lead of the new arrangement with the mast forward of the hatch to be about 250mm  forward of the existing position. Also it seems to be about a metre higher, will this not contribute quite a bit of extra heel?

I believe the boats are quite light on the helm but as I bought her quite late last season I am not sure about this yet. Have to get out once the weather shapes up. I will look at the rudder as the improvements you suggest Arne should be easy enough. I need a trip to the boat next week to weigh up the mast position possibilities and the next thing for me is to find out exactly  how to make the parners, I guess there will be lots of info on this on the site. I will research before asking about this. Having made a ply and epoxy fitting to allow a wood burner flue through the hull I am not too worried about this aspect.

With regard to the fin keeler Sunbird design, I guess fin is always going to be a better performer with JR rig as well. It would be interesting to find out if the boat still exists. Well, there is at least one potential junkie at Glasson Sailing Club! There may be others at the marina, I’ll have to have a look around. With regard to pubs, there’s only the Dalton left now!

About sailmaking procedures: the big advance we've made in amateur sailmaking is to assemble the sail one panel at a time. Arne prefers never to have to pass a roll of cloth under the arm of the machine, but I find that it's not troublesome to pass just one panel, rolled up and clipped. It used to be a big deal to sew together a whole flat sail and then sew on batten pockets, but we don't do that anymore. Have a look at the way I assembled Weaverbird's sail here . This is the method that I would use for a sail of your size made from Weathermax cloth. It's closer to canvas worker's ways of working than sailmaker's ways, as the cloth is much softer and more tractable than sailcloth, and also the cut edges ought to be turned in.

Richard

Now it dawned to me that I could just as well try a forward-raking mast for the same sail, in the same position.  This allows you to run the mast through the hatch if you prefer that.

Note how all three masts end in the same point in the top. I think the position of the mast top is most important to get the halyard angle right. Here I have also suggested 2 different slingpoints on the yard. In practice I shift the slingpoint on my rigs a bit back and forth until I am happy with it . The two slingpoints shown are on the middle and 5% aft of the middle.

If you go to my page and look up "A white sail for Edmond Dantes" you will see how we work.

Arne