During the previous seasons we have struggled with the main halyard. As soon as we turned upwind or the wind freshened up, the halyard would glide about 4cm through the clutch on the coachroof.
The Sun Fast comes from the factory mounting Spinlock XAS clutches with cams for ropes between 6 and 12mm. Such clutches are recommended by Spinlock for regatta up to 27 foot boats and for cruising up to 35 foot. The reason for this, is the material used in both sails and halyards for cruisers have relatively higher stretch, which absorbs excessive loads.
Veloce’s halyards have dyneema SK78 core which is extremely stretch resistant; additionally, the new main sail is made of mylar and carbon, again with very low stretch.
Supposing a TWS around 24kn (unlikely without a reef, however I prefer to exagerate for the sake of safety margin), a mainsail around 26 sqm is subject to a wind pressure around 240kg upwind and the tension on the clew just above 400kg. The tension on the halyard amounts to a number around the sum of these figures, about 640Kg.
Here the mathematics https://www.riggingdoctor.com/life-aboard/2015/11/19/calculating-halyard-loads.
The diagram above shows the clutch range from Spinlock based on load and line size. It becomes apparent that the XAS even with the current halyard at 10mm. Veloce will be therefore get upgraded clutches for the main and jib halyards, mounting Spinlock XTS clutches which should have the right performance up to 700kg and be safe up to a 1000kg with a 10mm line.
The job is pretty straightforward.
- remove the existing clutches
- remove silicon remains
- fill with epoxy the old holes
- drill new holes according to template coming with the clutches
- screw back on applying silicon on the threads and base of the clutches
Performance report will follow during the season 2020