[HME]

<p>Adrian, I can’t see any replies to your question so, at the risk of rushing in where angels fear … etc., I’ll hazard an answer. I would say that the primary goal of tuning is to get the best performance out of your rig. This to my mind means two things – power and, especially, controllability. Both are involved in each of the two aspects, dimension and tension.</p>
<p>First, getting the dimensions right means that you can ensure that the mast is raked to the point that gives you the right amount of weather helm – just enough to provide ‘feel’ (and a margin of safety if control is lost, so the boat will just round up into the wind and stop), enabling you to sail with minimal rudder when the boat is flat on the water. Second, getting the tension right will enable the mast to hold its position under load – that is, to stand up to the various control inputs that make the sail flatter or, for maximum power, fuller. The values given in the tuning guide will normally achieve all of this.</p>
<p>If this post prompts others to write in with corrections, additions, and (ideally) better answers than the one I’ve given, then great; meanwhile I hope this helps and/or is of interest.</p>