I guess I am looking for a logical science-based reason for the line of thought that says an upsized diameter wire is a bad idea, because I have yet to see one. Other than the answer that I provided within the question itself - that it is the elasticity or “springiness” that is the principle advantage.
That is not to say that another explanation doesn’t exist, and maybe we will come across some evidence in the future?
In the physical world, 200 lbs of tension is, by definition, 200 lbs of tension, no matter what, a piece of fishing line, or a ½” diameter steel rod, is applying that tension. The old Italian proverb “Arithmetic is not an opinion” is appropriate to apply to this point.
If a given side-wise thrust at the mid-point were applied to the above two materials under tension, and, if “stiffness” were the qualitative difference under examination, then it would, in fact, favour, and not hinder, the heavier of the two – the steel rod. Like DaveB has witnessed in his forestay.
So, a pertinent question to ask now would be- how would these target tension numbers have been arrived at in the first place?
I think it would be fair to say that Macgregor has built the boat to specifically designed pre-loads on each of the rigging points, ones that meet all its structural requirements. For example, as I mentioned before, aft-swept spreaders require a complex calculation of trigonometric force coupling that opposes the forestay tension.
We know what the owner’s manual “loosely” (sorry, bad pun
) suggests for tension, (for those of us who have read it) and it seems to indicate a preference for a somewhat lower tension than would be a standard operating procedure elsewhere in the industry. Presumably, for a reason, whatever it might be.We also know the diameter of the wire that the designers chose, it arrives from the factory with the boat, and so from that can calculate the design tension in pounds (approximately, from the percentage of breaking strength, as previously discussed).
The reason that the rigging tension happens to be specified in percentage of breaking load is that it allows the wire to be tensioned with an easily-defined safety margin for absorption of shock loading without failure. And wire is sold with this specified breaking strength.
And now that we have arrived at the design target tension range in pound units, we should be able to be easily attain it by a larger diameter wire tensioned to that same tension, measured in pounds, but at what would be a lower percentage of its breaking strength. And it would provide a larger margin of safety before failure from snatch loads. How can that be a handicap?
Unless, of course, elasticity is a prime consideration.
- Brian.
– Good test- cranking up the jib halyard tension (temporarily) would also increase the tension on the top shrouds – and I don’t think there would be any danger of over-tensioning them either. And of course jib shape would go south. But it would be the equivalent of adding more forestay tension and maybe removing some sag. 
, don't think that is going to happen 
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