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420 Tuning Guide

The Super Spar M7 mast has a superb record of racing success. You will find this mast used by the fastest sailors around the World and the tuning information is a guide to the best performance that you can achieve.


Measure the spreader length from the side wall to the centre of the shroud. This should be 470mm. To measure the deflection, place a batten across the shrouds at spreader height and measure from the centre of the batten to the back wall of the mast. This should be 175mm.


Measure from the inside of the transom (on the centreline) to the back wall of the mast. This should be 2830mm.


You will need to control the amount of bend in the rig, which affects sail shape and power. Using two x 15mm thick chocks adjust as follows:- Nil chock for wind 0-6 knots 1 chock for wind 6-10 knots 2 chocks for wind 10-20 knots 1 chock for wind 20+ knots.


Using a Super Spar Tension meter measure the shroud tension at approx. shoulder height. This should read: 28 for 0-15 knots 30 for 15+ knots.


Secure a long tape at the lower edge of the upper black band at the top of the mast. This can be done by securing the tape to the halyard but you must be sure that the tape is in the right position. Measure to the top of the transom when there are no chocks in front of the mast, and you have full tension. It should be:- 6051mm (for winds up to 15 knots) 6026mm (for winds above 15 knots).


Make sure that the rudder s in the maximum down position at all times to give you a finely balanced helm. If in any doubt contact your fleet captain or builder for advice.


Angle this forward in light winds. Position it approx. vertical in medium conditions and as the wind increases it needs to be raked slightly aft.