SP Digital Strain Gauge for measuring Finn Leach Tension

Essential Finn tuning equipment for setting mast position and achieving desired leach tension.

This digital gauge comes with length of cable for attaching to halyard, a hook for connecting to outhall and integrated tape measure for ensuring accurate leach length.

Supplied with 9v battery.

Method. of use.

1. Position your mast ring at deck level to suit the conditions. Normally further forward in windy conditions and set back in lighter breeze.
2. Switch the gauge on, connect your outhall to the hook and hoist the cable to the top of the mast, locking it into position with the halyard lock.
3. Adjust the length of the outhall to achieve the desired leach length - this is normally 3020mm for a new sail, but bear in mind that sails shrink over time. You will need to use a tape to confirm the length from the halyard fixing shackle to the marker band on the end of the boom. Once you have done this you can use the built in tape to reference the distance between the gauge and the marker, making it quicker and easier in future.
4. Sheet the boom to the deck with the end of the boom set out to one side with the end touching the edge of the gunnel. You should aim to be consistent with your system for setting leach tension, always do this setup on the same side of the boat and sheet to the same position.
5. Once the boom is sheeted into the required position you can read the tension on the gauge. This can be done in kilograms or pounds. Your sail manufacturer will have a guide for what you should be setting. Often for NS it is ~72lb and WB is ~35kg. But this is something you will come to play with and find a setting that works best for you and the conditions.
6. In order to adjust the tension, you need to wind the mast step forwards to reduce the figure, and backward to increase it. Make a note of the change a single turn on the bottle screw makes, this will help to calculate the position needed for your desired tension.
7. You can also add or remove chocks of various sizes, from behind the mast at deck level, to adjust the tension. However, as stated above you would normally set this for the conditions and make adjustments at step.
8. Once you have your desired position you can experiment with the effect of x amount of turns on the bottle screw and various chock adjustments to enable you to make adjustments on the water with confidence that you aren't affecting your leach tension too much.