Good rig tuning is not only for racers – it’s essential for the reliability and longevity of the rigging of cruising yachts as well.
It’s easy to assume that carefully tuning a yacht’s standing rigging is solely the preserve of racers that are trying to extract every inch of performance from their vessels. However, proper rig tune is also an important factor in ensuring the strength and reliability of the mast of cruising yachts.
A frequent misunderstanding between owners and boatyards means that on restepping the mast the yard often only tightens up the rig enough to support it at the dock, assuming a rigger will be engaged to complete the job. If, however, the owner has assumed the yard has tuned the rig, the likelihood is that the rigging will be both slack and ill adjusted.
When sailing to windward in a moderate wind there needs to be a little residual tension in the leeward shrouds.
This may partially explain why a huge number of cruising boats have the lee shrouds slack when sailing to windward. The problem with this are two fold: firstly, the movement of the rigging can cause fatigue, increasing the possibility of failure of a key component.
In addition, rigs with swept-back spreaders rely on a degree of tension in the lee shrouds to prevent the rig from rotating around the end of the windward spreader. This explains why boats with in-line spreaders are less sensitive to poor rig adjustment.
How much tension is enough? With the boat fully powered up going to windward in a moderate breeze the lee shrouds should retain a small amount of tension. If not, start by increasing the tension in the cap shrouds on the lee side by a couple of turns of the bottlescrew, then tack and do the same with the opposite side.
Once the cap shrouds are the correct tension, sight up the mainsail track on the aft face of the mast, with one eye as close to the spar as possible – you should see the mast is perfectly straight athwartships. If the centre of the spar sags away to leeward, then the windward lower shrouds or intermediate shrouds (D1s and D2s) are too slack, and vice versa. If in doubt it’s safer to err towards lower and intermediate shrouds being marginally slack than too tight.
Adjust the tension in the lee shrouds, then tack and do the same on the opposite side of the rig.
Having achieved good tune with full sail, check the rig is also okay when reefed in stronger winds.
While the rig should ideally be in column athwartships, it’s important to have some fore and aft bend and the mast must never be allowed to develop a ‘negative’ bend, where the centre of the spar is abaft of the masthead.
If you have any doubt about achieving the correct tuning and tension of the rig on your boat, don’t delay in employing a professional rigger to check that the rig is properly and safely set up.