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Setting up the mastGraham Williamson gives some fundamental tuning advice - Spring 2002 |
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A common cause of a boat not performing, or performing well in some conditions,
but not in others, is incorrect setting up of the mast. This is of course essential -
without this as a datum, no other settings are going to be right for both tacks. It
may be that 150mm of windward rake is very fast, however unless you have a
very sophisticated rig, this immediately becomes 150mm of leeward rake as soon
as the tiller goes across! The following procedure is pretty basic but needs to be
gone through step by step to get it right - and it is worth getting right. I write as
one who ought to have known better, and still got it wrong last year! Step 1 Set up the boat level athwartships, and roughly level to her fore and aft waterline. You can only guess at this, refinement of rake settings can only be done during sailing by trial and error. Step 2 Sight across the transom to make sure the boat is not twisted, and the shroud points at deck are level. Step 3 Run a line along the centreline of the boat, make sure the mast step and/or gate are on it! Adjust if not. Step 4 Take the shrouds out of the spreader ends. Step 5 Stand the mast, pull on enough tension to tighten the shrouds without bending the mast, make sure the lowers or strut are completely loose. Step 6 Sight up the mast to make sure it is not bent. Step 7 Hoist a tape on the main halyard - neither the measuring tape nor the halyard should stretch! Measure down to the points where each shroud penetrates the deck. Adjust as necessary to get the mast upright. Step 8 Drop a plumb line from the main halyard to double check for vertical and straight. Step 9 Pack the sides of the mast gate as tight as necessary to allow stepping and removal, but no movement during sailing. Step 10 Using a convenient balcony, such as at Shoreham SC, to set the spreaders for deflection fore and aft, and side to side, measuring from the shroud. In the picture below, there is about 40mm outwards, and 15mm forward deflection, which would be for powering up a fairly soft mast section.  Step 11 Re-attach the shrouds to the spreaders. Step 12 Check the mast for straight again, and check the measurements to the deck again. If they are different, check the spreaders again. Step 13 Tighten the lowers or strut, checking carefully that they don't push or pull the mast out of column. Adjust them if they do. Step 14 Check using a tape measure that the mast remains upright side to side throughout the full range of rake, ie, it is not moving diagonally across the boat. Step 15 Calibrate for rake using a plumb line from the main halyard and measuring to the plumb line from the lower band, using just enough rig tension to keep the mast straight. For windward purposes, upright equals about 170mm. Off wind in lighter conditions the mast will want to be further forward than this. Mark off the end of the jib halyard in convenient steps, probably 50mm, and log what the rake is at each of the marks.  See another example (colour) here In the picture, the end of the tape has been set at the extension of the sail track, since this is a 'measurement point' as defined in the 'Equipment Rules of Sailing' for the boom band. This is not crucial, but if you were replacing a mast with an integral track with one that has a bonded track the difference could be 20mm. Step 16 Have a beer and relax in the knowledge that another excuse for poor performance has been consigned to the bin! See also: Calibrating the Rig - Graham Williamson Rig Tuning - Mike Calvert How To Tune |
