Hi everyone,
Very impressed & grateful for all your replies, esp. in such a short space of time.
Derek: that would be the simplest solution; but (I probably didn't make it clear in my original post) but this would foul up the nearest pulley. With full lock, the springs are almost drawn into the pulley, so there isn't any space for any 'dead line.'
Roo/Larry: what I have done thus far is basically a 'scrapheap challenge' esque rummage around the boat house for suitable materials to do this with, settling on a spare throw line. I think I had previously noticed & puzzled at what appeared to be electrical wire in the boat, but figured at the time (when I was less experienced) that the installer knew what he/she was doing, but once it had snapped (and the strands been retied with a granny knot to get back into the landing stages!) showing itself to be plan copper wire, I realised that anything would be better (copper is far from stretch free). But basically, I doubt that there will be much funding available to get anything else in - the wire must originally have been improvised, it has been there for the last 5 years at least and I'm yet to hear anything from the committee on the subject. But I'll take a look at the link.
Dan: as I've mentioned, I seriously doubt that the electrical wire was the original material. I suspect that the springs are there to maintain tension in the event that the line slips/stretches. However, there is very little space to complete the round turn within the loops in the springs, and between the friction that this would generate and the give in the springs when I'm tightening, I can't develop enough tension in the line. Your suggestion with the shorter lines is basically what I've already suggested, only with he working end of the main line providing the 'short length.' As I've said, I'm using a throw line for this, so I can't really cut off the end(s). While this would work, it would inevitably eat into the steering range. That's the problem here; the slightly unusual circumstances mean that many of the traditional approaches are either ruled out or less than optimal. As for the material, funds permitting, elasticity isn't too much of a problem - this would just add to the elasticity in the springs, making the steering a bit sloppy, but at least stable. The problem in this case appears to be that the rope stretches permanently (probably the fibres compacting over time). However, with the right tensioning system, this should be rendered mute.
Square rigger: I had to feel around for the front pulleys; I recall that they seemed to have semi-circular groves of approximately 5mm diameter; I'm not so sure about the rear ones, but they are definitely different. Either way, the wire definitely wasn't better: it was straight forward multi-strand copper wire, which is very ductile. The bow string tensioner may work, but again, cost is an issue and the extra spring would add more compliance to the system which isn't ideal. A turn buckle would work, except the free runs of the line are far to short compared to the range of motion.
Basically, at least for the time being, I am limited to solutions which use this rope and tension it purely from the end(s), without interfering with with any other parts of the line.
