Mainsail Trimming on a Catamaran vs. Monohull: Key Differences in Rig Setup
When it comes to mainsail trimming, catamarans and monohulls use different rigging systems to control sail shape and performance. While monohulls rely on a boom vang, catamarans take advantage of their wider beam by using a traveller system to adjust sail tension.
In this guide, we’ll break down how the rig setup differs between catamarans and monohulls, and how to correctly trim a catamaran’s mainsail for optimal performance.
How Monohulls Control the Boom
On a monohull, a boom vang is used to apply downward pressure on the boom.
The boom vang is a rigid or rope-based structure running from the boom to the base of the mast.
Its role is to hold the boom down and control the leech tension, preventing excessive twist in the sail.
When easing the mainsheet, the boom vang helps maintain the sail’s shape by keeping the boom level, reducing power loss.
This setup is essential for monohulls, where the narrower structure doesn’t allow for a wide traveller track like a catamaran.
How Catamarans Control the Boom
Catamarans do not use a boom vang in the same way monohulls do. Instead, they utilise a traveller system that runs across the entire width of the stern.
Why Do Catamarans Use a Traveller Instead of a Boom Vang?
With a wide structure, catamarans have enough space to install a long mainsheet traveller across the back of the boat.
This system allows precise control over the downward tension on the boom, making adjustments smoother and more efficient.
Instead of adjusting boom height with a vang, the traveller controls the boom angle relative to the wind.
Mainsail Trimming on a Catamaran
Since the traveller replaces the boom vang, most sail trimming on a catamaran is done differently compared to a monohull.
How It Works:
Keep the Mainsheet Tight
Unlike a monohull, where easing the mainsheet allows the boom to rise slightly, a catamaran needs to maintain firm sheet tension to keep power in the sail.
Adjust the Traveller, Not the Mainsheet
If you ease the mainsheet, the boom will rise, spilling the top third of the sail and depowering the boat.
Instead of easing the mainsheet, adjust the traveller up or down to change the sail’s angle of attack while keeping even tension across the leech.
Better Control in Strong Winds
In gusty conditions, using the traveller to ease the sail allows the boat to depower smoothly without causing excessive flogging in the mainsail.
Why This Matters for Performance
Using a traveller instead of a boom vang means catamarans can maintain a more balanced sail shape, even in changing wind conditions. This results in:
Better speed and efficiency, as the sail maintains its aerodynamic profile.
More precise depowering, without excessive sail twist or loss of control.
Smoother handling, especially in gusts, since the mainsail adjustments happen with less load on the sheet.
By understanding these key differences, catamaran sailors can fine-tune their trim for maximum performance, making the most of the boat’s wide structure and efficient rig setup.
Final Thoughts: Mastering Mainsail Trim on a Catamaran
Trimming a catamaran’s mainsail is all about traveller control. Unlike monohulls, where the boom vang plays a major role, a catamaran relies on its wide traveller system to maintain proper sail shape. By keeping the mainsheet tight and adjusting the traveller for angle changes, sailors can optimise performance and maintain control in various wind conditions.
If you’re looking to sharpen your catamaran sailing skills, join one of our hands-on sailing courses and learn from experienced skippers.
