Sailors frequently talk about the fact that sailing and sail trim on a multihull remain worlds apart from what is experienced on a monohull. It's not so much the nature of the sailors themselves but the performance of their craft that is the distinguishing factor. There are many subtle differences between monohull and multihull vessels, but one of the greatest differences between them can be found in the relative motion of each kind of boat.
Multihull Motion While multihulls sail faster, the sensation of speed can be less than on a monohull due to the wide decks and virtually no heeling. Multihulls don't plunge and rise through the waves like a heavy displacement boat.They stay on the surface of the water, so their motion is lighter, quicker, less sustained in one direction. Some long-time monohull sailors miss the steadiness and responsiveness of a keelboat, but most ultimately have an easier time with the multihull motion. Personally, I found it just as easy to be seasick on a multihull as a monohull.
Light Displacement Sailing Multihulls have no use for heavy ballast, since their comfort and safety depends on their ability to remain perched on top of the waves. Good performance is linked to the designer's recommended payload, which is usually relatively light compared to the boat's displacement. This is one reason many liveaboard and charter multihulls lack sparkling performance, because they've been loaded in excess of the designer's recommendations. You'll need to get used to the handling of a light displacement boat. We've mentioned how multihulls can accelerate rapidly, and similarly they lose their way rapidly upon heading into the wind, much to the chagrin of neophyte sailors as they attempt to anchor, shoot moorings, close with docks, and come about. In general you'll need to head up closer to your desired stopping point than you would in a ballasted boat (a little unnerving in the beginning), and maintain boat momentum to make good gains to windward and to bring the boat smoothly through a tack.
Shallow Draft Most cruising catamarans have either low profile fixed keels (draft typically ranges between two feet four inches to three feet six inches) or daggerboards where the draft can vary from less than two feet with boards up to over six feet with boards down (trimarans typically have one centerboard or daggerboard in the main hull). It's often a major adjustment for monohull sailors to cruise on a shallow draft multihull. I thought my mother-in-law would faint her first time aboard our cat as we nonchalantly sailed at seven knots in five to six foot deep, crystal-clear Bahamian water.
Room With A View Multihulls have lots of room topside for sail handling and crew maneuvering. Catamarans usually have full-width travelers for the mainsail, and those designs with bridgedeck cabins have the added advantage of a saloon area almost on level with the cockpit providing good visibility of the surrounding water. This allows crew members to stay in touch with the those in the cockpit and with the course being steered. It's not unusual for one crew member to help navigate while tending to some domestic chore below in the main cabin.
I found it difficult initially to steer a straight course over the wide foredeck of a catamaran. As shown in Figure 1, the secret is to sight over some point up forward that keeps your line of sight parallel with the boat's centerline, and make sure you always steer with that point as a reference.
Upwind Sailing Years ago multihulls were considered to have poor windward ability, but modern cruising multihull designs exhibit very respectable upwind performance. Those boats with sleek topside profiles, efficient hull shapes, and daggerboards or centerboards will point the best, but even on a cat with bridgedeck accommodations and integral keels you can make better way to windward than equivalent monohulls if you know what you're doing.
One trick is to not pinch a multihull as close to the luff line as you would a heavy-displacement monohull. By falling off just a bit and keeping your sails full, you'll maintain momentum and higher average speeds, and you'll avoid making excessive leeway. Maintaining speed is especially important when getting ready to come about, since good momentum helps take your boat through a tack smoothly. All tris and most high-performance cruising cats with daggerboards tack with little effort. The balance of the cruising cats now on the market come about less quickly (especially if they have excessive windage), but usually without a problem. The two vintage cruising cats we owned would come about in what I'd call a stately fashion.Light winds with choppy seas were always a bit of a challenge since it's hard to gather the momentum needed to overcome the seas in those conditions. You might occasionally have to backwind the jib to avoid being caught in irons, but the technique should only be employed as a last resort since it tends to slow your progress.
A Case for Multis by Kevin Jeffrey
Cruising Multihull Sail Trim by Kevin Jeffrey
Keeping It Simple by Doreen Gounard
Buying Guide: Wind Generators