Downwind Sailing for Catamarans That’s Safe and Efficient

Safe and Efficient Downwind Sailing for Catamarans or in a monohull requires a mix of technique, sail setup, and boat handling. Here’s a complete guide to help you maximize speed, comfort, and control for safe and efficient downwind sailing for Catamarans.

What’s Different Downwind?

GENERAL PRINCIPLES FOR DOWNWIND SAILING

1. The Right Course Angle for your Boat
   • Sailing dead downwind on a monohull is slow and unstable but sailing deep on heavier displacement monohulls is still the most efficient. Somewhere above dead downwind will keep the roll to a minimum.
   • To go deep downwind in a modern, light and fast yacht, you could Instead, sail broad reaches and gybe through the wind (“zig-zag” downwind) which improves your Velocity Made Good (VMG).
   • In a catamaran which is much more stable, it is still fast and comfortable sailing deep angles, however the challenges of sailing deep on a catamaran first need to be overcome. 

2. Trim Sails Correctly
   • Ease sails so they’re perpendicular to the wind. This is a problem for Catamarans which have swept back shrouds, so we address this below.
   • Use a preventer on the boom to avoid accidental gybes.
   • Watch for collapse and re-fill of the sails in light winds (especially with swell).

3. Balance the Boat
   • Monohulls: Keep heel minimal; use sail trim.
   • Catamarans: Watch out for pitching or burying bows—reduce sail early in strong wind.

SAIL OPTIONS DOWNWIND

Whilst most modern cruising catamarans are quite quick and easily driven off wind, there is still little benefit in hotting up and sailing tighter angles, ie: doing the bigger distance for a better VMG. Besides, which cruising sailor wants to spend their day plotting gybe angles for best efficiency in a frenzied downwind zig-zag pattern. Most of us want to point the boat towards the destination and forget about it. Well in the trade winds, which is where most cruisers want to be for passage making, the wind is dead behind.

Many suppliers of production catamarans are quick to sell cruising sailors a “Code Zero” and a “Gennaker” that is flown off of a bowsprit or “Prod” and many have a self-tacking Jib. This might do for an island hopper or day-sailor but does not provide the open water cruiser with the ability to sail deep downwind, without causing damage to that sail wardrobe.

Easing the main to 90 degrees on a catamaran is not possible because of the swept back shrouds. The full-length battens of the mainsail will bend around the shrouds when the main is eased to greater than 40-45 degrees. The chafe against the shrouds and the chance of a broken splintered batten tearing through you main becomes a reality.  Sailing in this fashion, a “Code Zero” flown off a bowsprit will be blocked by the mainsail and will become damaged as it collapses and fills repeatedly. The same for a self-tacking jib that can’t be eased out without overtwisting and becoming very unstable. The knock-on effect of an over-sheeted mainsail and unstable headsails is an autohelm that will work very hard to maintain a course, chewing up battery power. Never fear however, we have a solution. It does require a change of mindset however we will walk you through it below.< Main

• If a correctly trimmed mainsail or its battens will touch the shrouds, either reef it till it doesn’t touch the rig, or drop it together.
• If the correctly trimmed main does not touch the rig, then use it either full or partially reefed in combination with the headsails, code zero or Asymmetric, as is appropriate for the wind strength.

Spinnaker /Asymmetric (Gennaker)

• On a broad reach an Asymmetric can be flown from the bow sprit. A symmetric spinnaker will need to be tacked on the weather bow.
• Sailing deep an Asymmetric should be tacked onto the windward bow and sheeted to leeward as normal.
• If using a symmetric Spinnaker, use it as above, however you may need a barber hauler on the sheet, or it may be sheeted to the leeward bow. This will only work if sailing very deep.
• We suggest for cruising passage making, a smaller Asymmetric from a heavier cloth. This will allow the sail to be more versatile.

Screecher (Sometimes incorrectly called a code Zero)

• Screechers are commonly supplied on production catamarans as a permanently rigged sail, on a furler, on the bow sprit. In this configuration it will work from a tight reach to a broad reach. Running with this sail will result in damage due to the instability, especially when flown behind an over-sheeted mainsail.

Genoa/Jib or Staysail 

• Catamarans can sail well with just a genoa downwind, especially in moderate to strong winds, however due to the close inboard sheeting angle of the Genoa/Staysail, especially when self-tacking, when the sail is eased out, it will twist open excessively and cannot be adequately trimmed with the genoa track and not at all with a self-tacking jib.
• The solution to this dilemma is to use the natural beam of a catamaran and fit a pad eye on the gunnel of each hull. The sail can then be sheeted to this pad eye which will be the equivalent of poling out the headsail on a monohull.
• To position the pad eyes, hoist the Genoa/Staysail in light airs and find the outboard sheeting position that presents the best angle for the sail on a run.
• The transfer of the sheet position under sail from standard to the pad eye is easy. You will need a handy billy with a snap shackle each end. With the Genoa sheeted to its usual track, attach one end of the handy billy to the clew and the other to the pad eye. Ease the sheet slowly while taking up the slack on the handy billy till the sail is sheeted to the pad eye. You can reverse this process when removing the handy billy.

The Correct use of your sail wardrobe

• Close hauled
• Light to heavy airs. Your main and Jib will do the work with the appropriate reefing for the conditions.
• Close reach
• Light airs- Use the Screecher and Mainsail
• Heavy conditions- use the Genoa/Staysail and main Furled as appropriate>
• Beam reach
• Light Airs- Use Main and Screecher
• Heavy airs- Use the Genoa/Staysail and main Furled as appropriate
• Broad Reach
• Light Airs- Reef or Drop the main. Fly Asymmetric from the weather bow. Use staysail and or Genoa
• Heavy airs- Use Genoa and or staysail, reefed appropriately.
• Run
• Drop Main
• Light Airs- Fly Asymmetric from the weather bow.
• Heavy airs- Drop Asymmetric and use Genoa and or staysail sheeted to the gunnel pad eyes.
• If you have a genoa and staysail, these can be goose-winged to the pad eyes on the run.

DOWNWIND TIPS: CATAMARANS

1. Don’t overload the bows: Reef earlier than on monohulls to prevent pitchpoling.
2. Fast cats create apparent wind: This moves the effective wind forward, so you may end up sailing a closer angle than it feels.
3. Autopilot Use: In swell, use autopilot with care. Always try to trim correctly and balance the boat so as not to overload the autohelm. The “correct use of your sail wardrobe” above will ensure this.
4. Avoid deep running with sails that do not remain full and drawing: You can get shadowed by your own sails thereby causing chafing and flogging that will cause expensive repairs to your sail wardrobe.