Anonymous wrote:

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The correct angle is easily found by making a circle whose center is where the slingpoint should be and whose diameter is the width of the head of your sail. A chord that passes through the centre of the circle at any point will give you the required balance for that particular angle.

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Paul,

Could you perhaps provide a simple graphic example of this procedure? My rusty old brain is failing to visualize it from the text.

Thanks,

Curtis

Arne, what I would call a low stress rig, is one that, as nearly as possible, takes up it's required position, before putting on additional lines. This means minimal loads on the lines required to pull it into position and to get the sail to set well.

As you have said (and I've also said) one of the keys is the relationship between sail balance and yard angle. More balance, lower the yard needs to be. Less balance, higher the angle it needs to be. The correct angle is easily found by making a circle whose center is where the slingpoint should be and whose diameter is the width of the head of your sail. A chord that passes through the centre of the circle at any point will give you the required balance for that particular angle. I've also found that in practise, the slingpoint likes to be closer to the mast than applying Hassler's rules would give you.

The other major thing that I've found that helps to keep stress low is to attach the standing part of a three or five part halyard roughly 5% of the yard length aft of the slingpoint. The effect is not as great for a five part halyard so for that I generally allow more drift. I've found that doing this alleviates the need for a THP.

To date, I've not found that I need Hong Kong parrels. I normally just use two running parrels and sometimes a standing parrel connecting the second and third battens from the bottom. That plus a YHP is all I use. I also now use Dyneema for my batten parrels as it does not stretch. I put batten parrels on all the battens and the yard. The batten parrel on the yard helps to keep it under control when hoisting in a seaway and it also makes sure that the forward end of the batten can never slip around the mast.

With due respect to David, I entirely fail to see any need for jointed battens today. Sewn in camber is always going to be more reliable than joints nor do I find that jointed battens can be relied upon to flip as intended. As for joints plus camber, to me that is putting every possible complication one can into a sail and I don't see the point. What I've seen with Annie's sail, just strengthens my belief that it's not the way to go.

Slieve, I get that you're being deliberately obtuse in order to score a debating point.

The question is why? You know full well that a lower yard angle results in more balance area, lower stresses in the sailcloth, particularly alternating stretching on the bias at the throat , and lower loads on any hauling parrels; all of which makes for a better rig for relaxed cruising.

Arne knows it too, as he has just reported on how these desirable characteristics are evident in Ketil's new sail; and knowing Ketil's need for speed, I don't imagine that any tradeoff in terms of poorer performance would have been acceptable. 

It really isn't more difficult to grasp than that. There is a possible range of yard angles, just as there is for batten angles and all other aspects of the geometry of the JR. I postulate that the range of yard angles that is easiest to live with is 45˚ - 60˚. Angles of 70˚ - 80˚ result in higher stresses, and having tried such angles, I am no longer prepared to accept those stresses. Lower angles carry with them the possibility of overbalance (except in the special case of SJR), which is unpleasant and potentially dangerous. There isn't any calculation to be made. There is simply the choice of where on the range of angles you want to settle, and determining whether you have a very good reason for settling very far from the middle of the range.

You seem to be asking why Weaverbird's rig does not exhibit much balance area. The answer is simple. The internal layout of the boat meant that the mast had to be right at the forward end of a workable range. I still achieve low stress in the cloth; and I achieve zero stress in the hauling parrels due to not having any, just as with the SJR. The latter is simply because the battens butt against the after face of the mast, not because of the geometry of the sail. Having no hauling parrels has resulted in less stress on an ageing, weakening sailor.

With more freedom over mast placement, she might well have been wearing a SJR, believe it or not. Made according to my own ways of doing things, of course, and having cast a seaman's eye over existing examples, particularly Amiina, and noted some areas where I believe that there is room for improvement. And that raises the question: why the need to be so prickly and unpleasant when someone tries to improve the breed? No single one of us has a monopoly on all the right answers.

Wherever I post the question David, we need an explanation of how to use simple geometry and trigonometry to calculate the lower stresses you are achieving in your rigs, so that we can improve our rigs. Simply quoting the notes I printed of my experience is not enough, particularly as you do not use the key points they recommend.

We need help to understand the basis of your statements as alone they do not add up.

Cheers, Slieve.

I know that some of you folks have made junksail models from string and battens only (no canvas) and hung them up. It appears that this exercise favours sail planforms with slightly convex luff to balance out the curve in the leech.

However, there is a big noise factor in that equation  -  the sheet.
I soon learned that the sheets wanted to have a saying, both in Malena’s blue sail, and in Johanna’s and later sails. If I set up the HKP for calm conditions while hoisting the sail, first time, it could happen that those diagonal creases re-appeared in one or two panels, once close-hauled in a breeze. Opposite, when running before, it could happen that a crease appeared in the opposite direction.

Nowadays, when the THP-YHP-combination removes most of the loads on the HKPs, these will be easy to set up so that the sail stands without creases, both when close-hauled and when running before. The HK parrels should still be of a stiff halyard type, but 6mm will do fine  on sails below 50sqm.

With Slieve’s über-clever combination of batten parrels and downhauls in his SJR sails, one can of course forget about the HKP, but that is another story...

Arne