Independent guide: Tuning figures are boat-specific. The designer's or spar maker's tuning guide takes priority; this page explains the method and the reasons behind it.
Quick answer
Rig tuning sets the mast straight side to side, at the right fore-and-aft rake and bend, with enough tension that the rig does not go slack to leeward under load. It is done in two stages: static tuning at the dock, then dynamic tuning under sail. Good tuning improves pointing and sail shape, and it also protects the rig, because a slack rig lets fittings shock-load and bend.
Why tuning matters
- Safety and fatigue. A slack leeward shroud snaps tight with every wave, shock-loading terminals and chainplates. A well-tensioned rig moves less and fatigues more slowly.
- Mast column. A mast that is not held straight can buckle at far lower loads than its design strength.
- Sail shape. Forestay sag and mast bend control headsail and mainsail depth.
- Balance. Rake moves the sail plan fore and aft, changing weather helm.
Static tuning at the dock
- Start slack. Ease all shrouds so the mast can be positioned freely; keep the forestay and backstay attached.
- Set rake. Adjust forestay and backstay length to the designer's rake, measured with a weight on the main halyard.
- Centre the mast. Take a halyard to each chainplate and adjust cap shrouds until the lengths match.
- Tension the caps evenly, counting turns on each side.
- Set the intermediates and lowers so the mast is straight sideways when sighted up the track, with any designed pre-bend fore and aft.
- Set forestay tension with the backstay or headstay adjuster.
- Lock everything — split pins, rings or locking nuts — and tape to protect sails.
See static rig tuning and how to set rig tension.
Dynamic tuning under sail
In 10 to 15 knots, close-hauled:
- the leeward cap shroud should not flop loosely
- sight up the mast: it should stay straight sideways, with no sag to leeward in the middle
- tack and compare; adjust only the leeward (unloaded) side, then tack and match
- check forestay sag against the headsail's intended shape
See dynamic rig tuning.
Tuning by rig type
| Rig | Tuning emphasis |
|---|---|
| Masthead sloop | Forestay tension via backstay; mast in column with modest pre-bend |
| Fractional rig | Pre-bend and mast bend controlled by backstay; swept spreaders — see fractional rigs |
| Swept spreaders, no backstay | Cap shroud tension controls forestay sag |
| Runners and checkstays | Set for conditions; ease and trim through tacks — see racing rigging |
| Catamaran | High shroud tension, forestay via bridle, often diamonds — see catamarans |
Tuning mistakes that damage rigs
- over-tensioning beyond the spar maker's figures, overloading chainplates and hull
- tensioning one side only, pulling the mast off centre
- using the backstay to fix a problem that is really slack shrouds
- leaving turnbuckles unlocked
- not re-checking after a new rig settles
When to call a rigger
A rigger with a tension gauge and experience of your boat type can set a baseline quickly and record it. That record lets you recover the tune after mast stepping or a re-rig.
Related guides
Frequently asked questions
How tight should yacht rigging be?
Tight enough that the leeward shrouds do not go visibly slack in moderate breeze and the forestay sag suits the headsail, but no tighter than the designer or spar maker recommends. Many riggers express target tension as a percentage of the wire's breaking strength and measure it with a tension gauge.
How do I know if my mast is straight?
Sight up the mast track from the gooseneck: it should be straight side to side, with any fore-and-aft bend being the intended pre-bend. Check the mast is centred by taking a halyard to each chainplate and comparing the lengths. Then check again under sail on each tack.
Should I re-tune after a re-rig?
Yes. New wire and terminals settle and stretch slightly in the first sails. Tune at the dock, sail in a moderate breeze, then re-check and adjust. Many riggers include this follow-up in a re-rig.
Common questions
- How do I tune a masthead rig?
Tune a masthead rig by first centring the mast athwartships using a halyard as a measuring tape, then setting mast rake, then tensioning cap shrouds evenly, then intermediates and lowers to keep the spar straight, then sea trialling on both tacks and re-checking. Always finish by locking turnbuckles and fitting split pins.
- How do I set rig tension without a tension gauge?
Without a gauge, set rig tension by counting turnbuckle turns equally on each side and judging the result under sail: in working breeze the leeward cap shroud should go slack-but-not-flopping, and the mast should stay in column. Record turn counts so the setting is repeatable — but a gauge remains the only way to hit a specified figure.
- How do I check my mast is straight?
Check mast straightness by sighting up the mast track from directly beneath it at the gooseneck: the track should run straight with no sideways bend. Athwartships centring is confirmed by running a halyard to the same point on each toerail. Check both at the dock and again under sail on each tack.
- How do I tune a rig after new rigging is fitted?
After new rigging is fitted, tune at the dock, sail the yacht in working breeze, then re-tension once the rig has settled — new wire and terminals bed in during the first sails and tension drops measurably. Plan a follow-up tuning session a few sails after handover and confirm whether it is included in the quote.