Catamaran Sailing and Handling

Prerequisites

Before starting you should:

• Hold, or be working at, Day Skipper level: be able to sail, anchor, berth and plan a coastal passage in a monohull.
• Have read the docking and close-quarters handling lesson.

Learning Objectives

By the end of this lesson you should be able to:

• Explain how a catamaran's stability differs from a monohull's, and why that changes when you reef.
• Manoeuvre a twin-engine catamaran in a marina using the engines to steer.
• Sail a catamaran efficiently, including tacking, and avoid the common handling faults.
• Anchor with a bridle, and know the catamaran's specific safety features and risks.

Stability: Why a Catamaran Is Different

A monohull is stabilised by its ballast keel. As it heels, the righting force grows, peaks at around 60 to 90 degrees, and the boat warns you it is overpowered by heeling and rounding up.

A catamaran is stabilised by its beam: the leeward hull supports the weight. Its righting force is very large at small angles and peaks at only around 10 to 15 degrees of heel, when the windward hull lifts. After that it falls away quickly, and beyond about 90 degrees it is stable upside down.

What this means for the skipper:

• The boat sails flat, so it does not warn you by heeling. A gust that would lay a monohull over just makes a catamaran accelerate and loads the rig.
• Reef by the wind speed, using the manufacturer's reefing table and the true wind on the instruments, not by feel. Reef early, especially downwind where the apparent wind feels light.
• Keep the mainsheet ready to release, and never cleat it and walk away in gusty weather.

Engine Handling

Most cruising catamarans have two engines, one in each hull, about 6 to 8 metres apart. This gives a lever arm that makes them very manoeuvrable under power, more so than with the rudders, which have little effect at low speed.

• Centre the rudders and steer with the throttles in tight spaces.
• To move sideways, combine opposed engines with the rudders: for example port ahead and starboard astern with the helm to port moves the boat to port. Practise this "walk" in open water first.
• The high topsides and flat underside give a lot of windage and little grip: in a crosswind the whole boat slides. Approach upwind where you can.

Sailing

• Upwind: catamarans point less high than a performance monohull, typically 50 to 55 degrees to the true wind. Do not pinch: keep the boat moving.
• Tacking: a light catamaran loses speed quickly in the turn. Build speed, turn steadily, and hold the jib aback briefly if it stalls. If it stops head to wind, reverse out with the rudders or use an engine.
• Downwind: fast and comfortable, but the apparent wind is low and hides the real wind strength. Reef before you turn back upwind.
• Speed: a catamaran can surf and exceed hull speed; watch for the leeward bows burying in big following seas.

Anchoring and Mooring

Anchor with a bridle: two lines from each bow to a hook on the chain, which spreads the load and stops the boat sailing round its anchor. Let out the bridle once the anchor is set so the chain hangs below the bridle. Catamarans draw little water, so you can anchor closer in, but their windage means they swing differently from monohulls nearby.

For mooring buoys, pass a line from each bow through the buoy's eye and back, rather than a single line, to stop chafe and sailing about.

Safety

• Capsize: a capsized catamaran usually floats. Stay with the boat. Most cruising catamarans have escape hatches in the hulls; know where they are and how to open them, and keep a grab bag and knife reachable.
• Bridgedeck slamming: waves hitting the underside of the deck between the hulls. Slow down or change course.
• Crew safety: the big flat deck feels secure, but the boat accelerates sharply in gusts. Clip on in the same conditions you would on a monohull.

Worked Example

You are chartering a 12 metre catamaran. The forecast is 15 knots of true wind, gusting 22, and the reefing table says first reef at 18 knots true and second at 24. The crew are enjoying a broad reach with 12 knots of apparent wind.

• On a broad reach, apparent wind is far less than true wind. Check the true wind on the instruments: in the gusts it is 22, above the first reef point.
• Head up to reef before it gets worse, with the mainsheet ready to ease. Reefed, the boat is easier to handle and safer for the beat home, where the apparent wind will increase.

Common Mistakes

• Reefing by feel instead of by the wind speed.
• Steering with the wheel at low speed instead of the engines.
• Coming into a berth across a strong wind without a plan for the windage.
• Cleating the mainsheet in gusty weather.

Summary

• A catamaran is stable at small angles but gives no heeling warning: reef by the numbers.
• Two widely spaced engines make it highly manoeuvrable: steer with the throttles at low speed.
• Use a bridle at anchor and a double line on buoys.
• If it capsizes it usually floats: stay with the boat and know where the escape hatches are.

Check Your Understanding

1. Why should you reef a catamaran by wind speed rather than by feel?

Answer: It sails flat and gives no heeling warning when overpowered, so you must use the instruments and the reefing table.

1. How do you spin a twin-engine catamaran to starboard on the spot?

Answer: Port engine ahead, starboard engine astern, rudders centred.

1. What is an anchor bridle for?

Answer: It spreads the anchor load across both bows and stops the boat sailing around its anchor.

1. Why is downwind sailing deceptive?

Answer: The apparent wind is much lower than the true wind, so the wind feels lighter than it is.

1. What should you do if a catamaran capsizes?

Answer: Stay with the boat, which will usually float, and use the escape hatches if you are trapped inside.