Concept 63 Catamaran by Chris White Designs
Longer is Better
Catamarans sail best when the hulls are very narrow for a given length. The slender hulls create less wave making resistance at higher speeds allowing better acceleration through the 10 to 12 knot "resistance hump" that many fuller bodied cats experience. Also a significant gain in seakeeping, comfort in waves, is experienced due to the narrow area of water plane. In simpler terms, slender hulls more easily slice through waves and do it with less pitching and rolling.
The disadvantage to narrow hulls is that the volume below decks is reduced and this generally makes it impractical to design a cruising cat less than 60' in length with hulls as fine as desired. However, if the length of the boat is allowed to stretch out to 60' or more while at the same time keeping the overall weight of the vessel down to the lower end of cruising displacement spectrum an extremely efficient hull form results that, due to its sheer size, has plenty of internal volume to provide excellent accommodations.
The Case for Limiting Size
The size of a boat is a product of many dimensions, length, width, height, surface area, and weight. While increasing the length of the hulls is very desirable it is not always as beneficial to increase all other dimensions. While longer is better, bigger boats cost significantly more to construct and require a great deal more effort to sail. The typical 60+' catamaran is often a VERY large boat. With overall beam of 30' or more, a loaded displacement of 50,000 lbs. and a mainsail of 1,000+ sq/ft which weighs upwards of 300 lbs. Cats of this magnitude are usually too large to be handled without experienced full time help. And the sheer size and weight of sails necessitates electric or hydraulic powered winches for halyards and sheets; adding further to the weight, complexity and cost of the vessel. Also, the mast height of a sloop rigged cat is well over 65' which prohibits access to much of the Intracoastal waterway and other harbors that could provide shelter in a blow.
Therefore, in the design of the Concept 63, the primary goal was to incorporate the benefits of long slender hulls without making the vessel so large and unwieldy that it no longer can be handled safely by a cruising couple or family.
The C-63 accommodation plan is somewhat different than ordinary. Because of the boat's long overall length she can carry a large deck house without looking ungainly or top-heavy. Living spaces within the deck house are very pleasing because they have nice exterior views and great ventilation. The large deck house also offers a degree of "elbow room" usually not found in a sailboat less than 100' long.
Aft Deck House
While variations in the accommodation plan are possible, and encouraged, to suit different owner's requirements the standard configuration boasts a spectacular cabin aft. A king size bed with access from both sides is a feature rarely, if ever, seen in a cruising cat even though it is almost the standard plan in large cruising monohulls. Sleeping in the aft cabin while under way will be a treat since it is well away from any water or engine noise.
The aft cabin head and shower is located in the adjacent port hull, 3 steps down from the cabin level.
The starboard hull adjacent to the master cabin can be configured to suit. Anything from a dressing room to a child's cabin can be used in conjunction with the master cabin . Alternatively, a fourth private double cabin can be installed in this space with access forward through the engine room and as well as deck access.
Forward Deck House
A spacious cabin that measures 13' long by nearly 20' wide is the "living room" of the boat and incorporates the galley, eating and lounging space and the navigation station. Large windows on all sides provide a panoramic view and numerous ventilation hatches keep the "house" cool in the hottest weather.
This galley is a cook's dream come true. Meal preparation, even in rough weather, will be a pleasant experience due to the visibility of the horizon and excellent ventilation in all working areas of the galley. Lots of counter space, plenty of easily accessible stowage lockers, a huge refrigerator/freezer, full size polished SS sink are some of the prominent features that will help to make the tough job of galley slave an enjoyable one.
The navigation station is immediately inside the deck house to starboard, convenient to the cockpit helm. The chart table permits the largest NOAA charts to be spread out unfolded, and has plenty of chart storage space in the full size chart drawer beneath. Radar is installed on a pivoting bracket that allows it to be viewed from the cockpit through the large window in the aft wall of the deck house.
Two Forward Double Cabins
The forward half of each hull is devoted to a private double cabin. Both cabins are identical and contain a hanging locker, dresser, seat and storage spaces. Upper and lower bunks seem to offer the best use of space and the most versatility of accommodation. However, the upper bunk is wide enough to be used as a reasonably comfortable double berth. Each double cabin has its own private head and shower located just aft of the cabin door.
The diesel engines are located in dedicated engine rooms, completely separate from the accommodation areas. The engines are accessible from all sides for maintenance. There is standing headroom in the engine room and a small work bench and tool stowage built in for extra convenience. Auxiliary machinery, such as a gen-set, desalinator, air conditioning, is located at counter top height on the underwing within the engine room for great access and quiet operation.
Engine size can vary from 45HP to 100 HP. Twin 45's will yield 10 knots. The larger engines have the capacity to push this cat to 14 knots. Standard shaft drives to geared folding propellers are used for maximum reliability and efficiency. Engine vibration is minimized through the use of Aquadrive CV joints and soft mounting the engine.
Propellers are protected by the draft of the hull which is grater than the shaft, strut and folded propeller. Beaching this cat poses no problem for the props.
A modern ketch rig with fully battened main and mizzen and roller furling jib is appropriate for this design. A ketch splits the sails to more easily managed size and keeps the center of effort low which is more in keeping with the design concept of moderate overall beam. It also offers substantial advantages for offshore sailing; a reefed mizzen makes a great riding sail while waiting out a gale either hove to or hanging on a parachute anchor. Ketch rigged boats are also extremely fast. While they typically give up a slight bit (approximately 3%) of windward ability in light air compared to sloops this is usually of little concern in a cruising context because usually once boat speed drops to 6 knots or less the engines are started.
Masthead height is under 65' from LWL. As previously mentioned, this offers increased flexibility in cruising the East and Gulf coast since the Intracoastal Waterway is always an option in foul weather as well as other harbors that are obstructed by highway bridges or power lines. To take full advantage of the super shoal draft possible in a cruising cat it is also necessary to keep the overhead clearance below 65'.
Spinnaker and mizzen staysail can be flown in light winds for incredible off wind speed. Using both of these sails should enable reaching speeds nearly 1.5 times wind speed in light wind conditions. There is nothing as fast a ketch on a reach. Just look at the favored big boat rig among the round the world racers of the Whitbread Race, they are nearly all ketches.
While many schemes have been tried for hoisting and carrying the dinghy on large cats none are as useful as a rigid platform with a powerful crane hoist. The slatted after deck area becomes one of the most functional places on the boat. It is a perfect spot for fishing underway (great for cleaning fish too) or organizing watersports while at anchor. The dinghy(s) can be securely carried on board when sailing offshore and are safe from theft at anchor, an important issue in some locations.
Modern epoxy composite construction is used throughout the Concept 63. Hulls, decks and cabins are built from epoxy and uni-directional glass fiber skins cored with thicker than normal PVC foam. The additional foam thickness provides better thermal insulation in hot and cold climates as well as additional sound deadening and structural rigidity.
Crossbeams, the heart of a catamaran structure, are laminated carbon fiber/epoxy. This ensures a strong, stiff structure that will withstand the rigors of long use in the wild ocean. It also contributes to maintaining a taught headstay which dramatically improves windward performance over catamarans with more flexible structures.
As with all proper multihull designs, the Concept 63 is unsinkable. In event of collision or other calamity no matter the size and number of holes she will not ever sink, an important safety feature for ocean cruising!
Each hull incorporates two collision bulkheads forward and a third watertight bulkhead aft. Violation of any of the watertight subdivisions means only a very slight amount of trim or heel, typically less than 1 or 2 degrees. While not recommended, it would be possible to safely sail long distances with both bows flooded back to the collision bulkheads.
The CONCEPT 63 is a thoroughbred cruising catamaran that has been conceived from scratch to address the needs and problems of fast long distance cruising by a small crew. Neither a reworked racing cat design nor a scaled up smaller cruiser she delivers exceptional performance under both sail and power combined with extremely comfortable accommodations and very high degree of safety.