Short answer

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.

Tuning has an order, and skipping steps produces a rig that looks tuned at the dock and bends under sail. Centre the mast first: run a main halyard to the same point on each toerail and compare — equal measurements mean the masthead is centred.

Set rake before tension. Rake affects helm balance, and changing it later forces you to redo shroud tension anyway. Work from the designer’s or manufacturer’s specification where one exists, because it is written for that hull.

Tension the cap shrouds evenly, counting turns so both sides stay matched, then bring intermediates and lowers up to keep the spar in column. Sight up the mast track frequently — the track is the straightest reference the spar has.

A dock tune is a starting point, never the finish. Sail on both tacks in working breeze, check that the leeward shrouds are not excessively slack and that the mast stays in column, then adjust, and re-tension again after the rig settles. The rig tuning guide covers fractional and multi-spreader rigs.

Step by step

  1. Slacken and start clean

    Back off turnbuckles so you are tuning from a known state rather than an unknown one.

  2. Centre the mast

    Run a halyard to the same point on each toerail; adjust cap shrouds until measurements match.

  3. Set the rake

    Use the designer or manufacturer specification. Adjust with the forestay and backstay.

  4. Tension cap shrouds

    Even turns each side, keeping the masthead centred as tension rises.

  5. Straighten with lowers

    Bring intermediates and lowers up to remove sideways bend. Sight the mast track.

  6. Sea trial both tacks

    Sail in working breeze, check column and leeward slack, then adjust.

  7. Lock and pin

    Lock turnbuckles and fit new split pins. Record the final settings.

Key facts

Correct order
Centre, then rake, then caps, then lowers, then sea trial
Centring method
Main halyard to the same point each side
Straightness reference
Sight up the mast track
Always finish with
Locked turnbuckles, new split pins, written settings
Never final
A dock tune without a sea trial

Full background: read the guide