Downhaul and outhaul work together, but the correct settings depend on the sail and mast combination. Start with the rigging guide for your exact sail rather than a universal number of centimetres.
Establish a reliable baseline
Confirm mast compatibility and fully seat the mast joint before applying tension. Set the extension and boom to the recommended starting dimensions. Check that ropes run correctly through the pulleys and that battens and cambers are positioned as the maker describes.
What the controls do
Downhaul tensions the sail along the luff and influences mast bend and leech shape. Outhaul adjusts tension towards the clew and affects the sail’s depth. Their effects vary between constructions; use the sail’s visual trim marks and instructions, not the appearance of a different model.
Tune on the water
After a short test, change one setting within the approved range and compare handling in similar conditions. Record the sail size, mast, extension, boom length and conditions. If the sail cannot achieve the expected shape within its range, check compatibility and rigging before adding more tension.
Avoid forcing the setup
Never exceed the maker’s limits to compensate for an unsuitable mast or excessive sail size. Stop if a component binds or looks damaged. Persistent heavy back-hand pressure may involve trim, harness-line position or sail choice; it is not a reason to keep tightening everything indiscriminately.
Explore the range
Sails · Extensions & Baseplates
Related guides
How to Choose a Windsurf Mast · Windsurf Harness Lines: Fit and Position