Atlantic 46 and A46/LR Catamarans by Chris White Designs

a46

The ATLANTIC 46 combines the ingredients for high performance, livaboard comfort and rugged durability into a seaworthy, attractive, package. She was designed to sail, not sit at the dock. Her hulls are long and lean, the bridge deck is well aft and high off the water to minimize slamming when sailing in rough conditions. The mast is within easy reach of the secure cockpit for easy single handing, and the enclosed wheel house will make you wonder why you ever went cruising without a protected watch keeping station.

The A-46 has a modern maximum waterline length hull and a powerful sailplan, insuring excellent performance and easy motion at sea. Her (light cruising) displacement to length ratio is 62, which indicates a very efficient hull form. In comparison, an all out racing catamaran class like the Formula 40s will have a D/L ratio of about 30 and the heavier production cruising catamarans are in the range of 80-120.

An evolution of the A46 is the A46/LR, which is much the same design as the original but slightly longer. Many owners wanted to incorporate more fuel and water capacity, larger and more diverse electrical systems, desalinators etc... In order to carry this additional weight the hulls were lengthened about 2' and other minor changes were made to increase the payload capacity. For the long range cruiser or livaboard sailor the new version will carry heavier loads better.

There are other cats of similar length with more "room" and that may be just the thing to function as a dockside condominium or "charter barge" but you'll seldom find a cat with a better balance of features for serious cruising than the A-46. Briefly, here are the highlights:

Accommodation and Deck Plan

The most striking feature of the A-46 is the central cockpit/aft pilot house layout. All sheets, halyards, daggerboard controls and reefing lines are within easy reach of the helmsman. No matter what the weather there is no reason to leave the security of the cockpit - except to retreat to the shelter of the pilot house when it gets too nasty outside. In ordinary sailing weather, cockpit steering provides full visibility of sail trim and allows the sailor to get in the groove with wind and waves as well as see where he is going! At anchor an unobstructed breeze in the cockpit will keep you cool.

There is excellent 360 degree visibility from inside the pilot house, enabling it to be used as a watch keeping station while on passages. Special heat-strengthened glass is preferable to Plexiglas or Lexan for these windows; glass is very scratch resistant, it doesnít expand or shrink as much as Plexiglas or Lexan with temperature changes (which often leak because of this), and tinted glass can provide excellent visibility while limiting heat gain in the pilot house.

All navigation functions are performed in the pilot house. There is a large chart table (two drawers can store the largest charts with only one fold) and plenty of room for electronics. The navigator faces forward and has full visibility, allowing for less confusing navigation and piloting since bearings can be taken without moving away from the chart. A fast sailing boat requires more frequent position updates than a slow one, the A-46 nav station is in the right place to make sure that navigating is not ignored.

pilot house

An inside steering station can be incorporated to starboard opposite the nav station. This can be accomplished either by installing another wheel or more simply by using the autopilot remote control. All commercial vessels have enclosed steering stations- could it be that the people who go to sea on a daily basis know something that sailors don't?

The insulated roof of the pilot house is an ideal location for solar panels. There is room to mount six 50 watt panels. These will provide most, if not all of a boat's electrical needs day in and day out with minimal weight and complication, and without any noise. In conjunction with some of the new desalinators like the Power Survivor 35 and 80 gal. per day models and high efficiency electrical refrigerators, it is possible to have a constant supply of fresh water and a cold ice box without having suffer the weight and noise of a gen-set.

One of the beauties of catamarans is that they can easily carry a great cruising dinghy. Whether your preference lies with an outboard powered hard bottom inflatable or a 14' traditional pulling boat there is room to hoist it up behind the pilot house where it is relatively safe from theft while anchored and out of harms way when sailing.

Getting on and off the boat from the dinghy is easy via the wide steps built into the transom. The steps also make swimming from the boat a pleasure and provide a perfect place for a outside shower.

The galley is arguably the most important aspect of a cruising interior. The A-46 has space for a 3 burner stove with oven and broiler, a large sink with fresh and salt water pumps, capability to carry up to a 10 cu/ft refrigerator/freezer, 14' of open counter top and plenty of storage space for utensils and food. Fresh water tanks are built into the bilges, low and amidships where they belong. Standard capacity is 100 gallons in two tanks.

The A-46 has two large double bunks located amidships where the motion of the boat is least. There is sitting headroom over the bunks for comfortable reading in bed and excellent cross ventilation from nearby deck hatches and opening ports.

The port hull is arranged as the owner's cabin. A large double berth is positioned across from a double size dresser. The spacious head and adjoining shower are forward of the double cabin. The forepeak has room for storage and hanging lockers. The aft portion of the port hull contains a workbench with drawers for tool stowage and a place to clamp a vise.

A guest double berth is located in the starboard hull. This can be configured identically to the owner's cabin to port or have a table associated with the galley. A single berth is located forward. These two cabins share a head and shower.

Performance:

The A-46 is one cat that will not sail like a dog! Coupled with an efficient underbody that utilizes retractable daggerboards for excellent upwind performance, her easy to handle but powerful sails will yield consistent speeds of 8 to 12 knots. Reaching in stronger breezes will generate 16 to occasionally 20-plus knots of boat speed. She will tack smartly through a 90 degree angle. While no cruising multihull (and few racing multi's) will ever out point a racing monohull, the A-46 will get to the windward mark first by sailing a few degrees lower but going much faster.

With roller furling headsails and slab reefing gear on the mainsail, short handed sailing is as easy as it gets. The mast can be a rotating airfoil section or a standard fixed aluminum spar.

Cruising sailors with little experience often put performance near the bottom of their list of priorities. They claim that they're in no hurry and would much rather be comfortable than go fast. Well, I'll have to agree up to a point but I draw the line when a cat can't sail appreciably better than a fast cruising monohull of the same size (and this includes light air and sailing to windward). Some "cruising" cats have really miserable performance. You can now spend heaps of money to buy various factory-built cats that can't do better than 120 degrees between tacks! Or that couldn't sail a sustained 13 knots unless it sailed over Niagara Falls. Ridiculous! At least for a cruising multihull. Unless you can gain the light and effortless feeling of a magic carpet ride over the waves from a catamaran there really seems to be little point in having one.

Shallow draft:

A cruising boat that draws only 2'8" is versatile. Beaching on the tide for bottom inspection or maintenance is simple, cruising areas are practically unlimited and a well protected hurricane anchorage is easier to find.

But shallow draft is not good thing when it comes to clawing upwind. So the trick is to have the fin area and depth when itís needed and be able to retract the fins when they are not needed- like when trying to get into a pristine anchorage that no one else can get to, or motoring, or sailing in light breeze. From many perspectives, dagger boards are the most efficient means of achieving excellent performance with shoal draft. While there is always the risk of breaking a board if it hits a rock, the daggerboard trunks of the A-46 are designed with impact absorption in mind, so damage will be confined to the daggerboard and not occur within the hull. The daggerboard section is carefully shaped to conform to a high performance NACA shape, this minimizes drag and vibration at high speed. The design of the form fitting dagger trunks eliminates the common problem of daggerboard noise in the cabin. Because the top of the daggerboard is always visible from the cockpit there is never be any uncertainty as to the depth the board is lowered- an important safety consideration. The dagger boards are light enough to be buoyant so they are easy to hoist to full up position.

drawing

The ATLANTIC series of cats are very maneuverable and tack smartly. This is in part due to the semi-balanced spade rudders which are carefully profiled to a high performance section through the use of full sized construction patterns. Rudder posts are built from laminated composite materials to increase strength, reduce weight and eliminate corrosion.

The rudders and props need to be protected from grounding damage and this is done through the use of the small belly fin on the underside of the hulls. The belly fin is the deepest part of the hull so the boat will sit on that when grounded or hauled out. Given the sometimes careless way of boatyard employees when it comes to chocking up a hauled-out boat a sturdy "bumper" on the bottom of the hull is a nice thing to have.

Engines:

The twin engines of the A-46 are located aft in separate engine compartments. This has proven to be a very good arrangement because it isolates most of the engine noise, vibration, and smell from the primary living space. The twin engines permit the boat to be turned without any forward motion and "walked" sideways in close quarters. Now that yacht harbors are so crowded with expensive boats it's essential that maneuverability under power be absolutely sure in all conditions. In these days of expensive AwlGrip paint jobs, accidents can be very costly. A twin screw cat is probably the most maneuverable vessel afloat; with one engine ahead and the other in reverse the wide separation of the propellers produce enormous leverage that will turn the boat without the need for forward motion, no matter what the conditions. Anyone who has tried to maneuver a large boat in close quarters on a windy day will understand that attraction.

While nothing compares to twin engines, maneuverability under one inboard engine is acceptable and as an economy or weight saving measure this is a viable alternative.

Twin Yanmar 2GM30F (27 HP.) engines will yield a range under power of 500 miles at a cruising speed of 9 knots with the standard fuel capacity of 90 gal. in the A46/LR. The range can be extended 50% by slowing down to 6 knots.

A pair of Volvo 2003 engines will push the A-46 to 10.5 knots maximum, 9.2 knots at 2300 RPM. Addition of a turbo charger to the Volvo 2003 will bring the maximum speed up to 11.5 knots.

Construction Plans:

An ATLANTIC 46 can be built for you by a custom boatshop or you can build it yourself. In either case the construction drawings need to be detailed, accurate and complete. All of the exterior surfaces of the A-46 have been computer faired to .5mm accuracy and the resulting "lines" have been ported over to a CAD program to create all of the working drawings. This allows a great degree of accuracy and consistency to be carried through all of the design drawings which means the boat is faster and easier to build in the boatshop!

Buying a Custom Built Boat:

Several excellent builders have experience constructing the ATLANTIC catamaran and will be happy to quote price and delivery date. Please call Chris White Designs for additional information.