How to buy the right catamaran for you

When it comes to buying a catamaran, it’s very much a case of horses for courses. Some cats are built for performance, others for fast cruising with varying levels of compromise, while many more are intended to carry a big load and pack all the comforts of home. *Joe Goddard offers some catamaran buying basics to help you on your way...

Multihulls are the in-thing. The increase in demand for these craft has surprised many traditional monohull proponents and builders. Some 30 or 40 years ago, catamarans were designed and built for the daring adrenalin junkies or the few early adopters living on the fringe.

Australian designers like Lock Crowther, Jeff Schionning, and Tony Grainger have laid the foundations for today's multihull design, with many projects undertaken by amateur builders.

The French designers and builders Fountaine Pajot and Lagoon now dominate global catamaran production, with the South African Leopard by Robertson and Caine giving them a run for their money.

Overall, the charter market has helped increase the demand and manufacture of heavier, slower and “apartment” style cats. So, too, have buyer's and boater's needs for more comforts aboard.

Of course, the advantages of multihulls over monohulls make practical sense for many boat buyers — they don’t heel over, they are fast, and have plenty of room. And these boats don’t need deep water and can easily be beached.

All very compelling reasons to buy a multihull, right?

THE BASICS OF DESIGN
Boat show buyers often look no further than the creature comforts and reputation of the brand, which makes their choice easy. However, with such a large investment, buyers need to look at the basics of the design so that they understand the true technical character of the boat.

These technical features are based on the length, weight (displacement), sail area, draft and bridgedeck clearance. It is vital that the buyer understands the limitations of their boat to avoid future problems or dissatisfaction.

Production builders in the past 15 years have ironed out potential safety issues like capsize and pitch poling, so buying from a well-respected manufacturer will give the buyer confidence. This combined with proper seamanship and navigation skills will enable the cruising sailor and family to enjoy a lifetime of multihull sailing.

HULL SHAPES
Efficient movement through the water is about how the hull (s) are shaped. Does the hull have fine bows or a blunt “bath tub” designed look? A big mistake made by catamaran owners is to load up their boat with all the comforts of home and expect the boat then to perform like an America’s Cup racer.

Catamarans cannot be loaded more than their design waterline and most are sensitive to weight, unless designed as a heavy displacement cruiser. Bows with a blunt bathtub shape have the advantage of buoyancy when sailing (to avoid a pitch pole in a storm) and to take extra payload.

A light and fast boat has a slimmer hull shape and is a safer boat when you are trying to outrun a storm. Lighter boats also require less power and fuel, and they are easier to manoeuvre in the marina.

Fine shaped bows of something like Mojo, a stunning Schionning 15m catamaran, point to more of a performance-orientated catamaran compared with, say, the fuller bows of the Bali 4.5 or, say, the Lagoon 420 (our review), which are ready to carry a big payload of pleasure boaters.

Having said that, even Lagoon offers more performance-orientated models such as the Lagoon 450 S (news) that recently launched for local multihull buff and accomplished racer Tony Considine.

Another relatively new arrival is the performance orientated family of Ker-designed McConaghy Catamarans (news).

So the first thing a buyer must determine is: what type of sailing will you undertake? Liveaboard, long distance cruising, fast coastal cruising, racing, or just leisure and pleasure on your local waterway?

LENGTH TO WATERLINE RATIO
The design ratio that offers some insight into the performance question is the displacement (weight in salt water – long tons) to length number. This number is very indicative of the likely potential speed of the boat and the ability for the hulls to be loaded up.

Length is the waterline length (in feet), but very similar to overall length on the new catamarans. (For this “D/L” formulae; the length number is cubed to be the same dimension as the displacement).

The D/L number can be used to compare boats of any size…

The Lock Crowther-designed Catana 44, first built in 1992, was one of the initial fast French production boats to hit the market; it has a D/L ratio of 94 yet a large and modern interior.

Fountain Pajot’s Lavezzi 40 designed by Joubert-Nivelt in 2003 has a D/L of 99. This design included a rotating mast for better performance.

The fine bows and exhilarating performance of the South African Tag 60, designed by Kiwi Greg Young, has a D/L of 80. One of these recently sailed from the Gold Coast to Hamilton Island in 44 hours, a distance of 600nm, averaging 14 knots while cruising, eating roasts and enjoying the comforts of the air conditioning, dishwasher, washing machine and dryer!

At the same time, a whole spate of catamarans has become popular for their load carrying and sturdy nature, making them ideal for charter work. As a generalisation, catamarans with a D/L greater than 100 tend to have blunt hull shapes, be designed for big loads, and need more wind to get them going.

SAIL AREA
Similar to the power-to-weight ratios used in the performance of motorcars, the sail-area-to-displacement ratio is the equivalent in sailing performance.

Sail area is measured in square feet, the displacement figure in long tons, to the power of 2/3. The Tag 60 mentioned previously has a SA/D ratio of 39.

French builder Outremer has always built fast boats, its 55ft boat designed in 1991 has a SA/D ratio of 32. A good all round power to weight design is the Berret Racoupeau designed Fountaine Pajot Helia 44.

This modern all-rounder has a very acceptable SA/D ratio of 24, providing a nice sail in under 10 knots of wind while accepting a large payload.

The Australian built Lightwave 48 Grande is also a good performer; it has optional dagger boards and big payload capacity and a SA/D of 28. Cats with a SA/D ratio under 22 won;t have the same sailing performance in light winds.

The stunning performance offered by US boats Gunboat, Tag and Australian Schionning are for those buyers needing a lot of speed! Fast passage making ability is found from Grainger designs, French Outremer and Catana and Australian Lightwave cats.

Normal cruising and payload carrying boats are defined by European Sunreef, Nautitech, Fountaine Pajot and Privilege plus Australian Perry and Seawinds.

The heavier boats are slower in light airs but capable of carrying large payloads. Rather than ghost about with a full crew, it might be time to start the engines.

UPWIND PERFORMANCE
The ability for the catamaran to sail upwind well is determined by the hull shape and keel shape. Catamarans that have daggerboards that lift up and down from each hull will sail up to 10 degrees higher than a cat with sacrificial keels. These daggerboards do take up room inside the boat hence reduce interior space and the added disadvantage of beaching, so daggerboard boats are for the more racy owners.

Lastly, the effect of the bridgedeck clearance needs mentioning. This is the distance from the waterline to the bottom of the cross beams between the hulls. Ideally this measurement is greater than 750mm for most boats.

Designer Tony Grainger believes bridgedeck clearance should be 6-7 per cent of the waterline length; so a 12m boat should be 780mm. A reduced clearance could mean the boat will slap and slam in the ocean and cause an uncomfortable ride. And waves hitting under the deck will slow down the boat.

AND ANOTHER THING
At which point, we should chime in and add that with boat buying it’s very much a case of horses for courses. While some may seek a fast coastal cat, others are perfectly content gadding about their local waterways. Indeed, sailing performance seems to be taking a back seat to comfort in the broader pleasure-boat market these days.

As a rough rule of thumb, experienced cruising sailors will say they sail 25 per cent of the time, motorsail 25 per cent of the time, and motor 50 per cent of the time. So we will add that you should consider performance under power as well. This is essential in all coastal cruising boats, particularly in pitching seas going to windward. How much clean water is that prop getting?

At the end of the day, it all gets back to what you intend to do with your catamaran. Optimal sailing performance is an important aspect of your cat purchase. Hopefully, Joe's article helps you crunch come numbers and enlighten yourself in the burgeoning catamaran market.