If you wish to trim your rig accurately it is best to have some thought of the strain within the shrouds and stays, both by guidelines of thumb or a extra actual methodology, akin to this. Right here, you measure the stretch of the wire as a proportion after which set up the strain as a proportion of the wire or rod’s breaking load.
You’ll be able to both measure the stretch of all of the wire or part of it, e.g. 2m. Accuracy will enhance with the pattern size. Start with a minimal rigidity within the wire.
Mark off a 2m size of the shroud on one aspect of the boat utilizing the shroud terminal for reference. Measure the elastic extension (f) of the measured size because the rigging screws are alternately tightened, little by little. Cease when f = 3mm. (4mm on fractional rigs with aft swept spreaders).
Observe that stretch of f = 1mm over a pattern of 2m of the wire corresponds to five% of breaking load impartial of the wire diameter. For rod, an f = 1mm stretch over 2m corresponds to 7.5% of breaking load. Use the same methodology to determine backstay rigidity. Do not forget that a unique pattern size may have a unique stretch for a similar load. Additionally do not forget that the stretch is all the time measured from hand tight wire/rod (minimal rigidity).
Mark up the shroud Mark up 2m of shroud utilizing the terminal for reference…
Rod rigging is made from a straight, single strand. Wire rigging is made from many twisted strands. Usually rod rigging is 20% stronger than wire of the identical diameter.
Wire has the benefit of an early warning of fatigue when a strand breaks. Fatigue in rod occurs with none warning in any respect. It may be sudden and typically catastrophic.
Tensioning cap shrouds
When you may have straightened the mast sideways and adjusted the rake, it’s time to have a look at the cap shrouds. Tighten the cap shrouds to roughly 15% of breaking load. This corresponds to a stretch (f) of 3mm over a size of 200cm. On a fractional rig with aft swept spreaders the cap shrouds needs to be tensioned to twenty% of the breaking load. This corresponds to a stretch of f = 4mm.
Measure the stretch…then measure the elastic extension when the rigging has been tightened.
To keep away from extreme forestay sag upwind, the cap shrouds needs to be comparatively extremely tensioned. If 20% cap shroud rigidity just isn’t enough to maintain sag at an appropriate degree, enhance the strain to 25% of breaking load. Don’t exceed this rigidity.
Slack rigging will produce shock hundreds that may trigger rig failure and will even deliver the mast down. Observe that you just won’t be able to overtighten a wire of 40-50cm size with hand instruments. The decrease shrouds and intermediate shrouds needs to be fairly free at this stage.
If the mast has distinct bends it is best to attempt to straighten them by sight and hand tensioning.
Many yachtsmen intuitively rigidity their standing rigging and modify it later when crusing has begun. This may increasingly result in acceptable outcomes however the strategies described above, whereas taking a while, are extra sure and dependable.
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