The New Atlantic 47 Catamaran by Chris White Designs

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The new Atlantic 47 offers exciting improvements over her earlier, smaller sisters, including a powerful and easy to handle rig, an expanded pilot house, and an innovative galley up/galley down configuration. The A47 is certain to be a great performer, combining the sparkling sailing, exceptional cruising livability and ease of handling that the Atlantic Cats are known for. All in an affordable under 50' length!

5/10/2011

Designs begin in the imagination.
First, a fuzzy concept enters the back of the brain; wouldn't it be great if we could get a large and really livable pilothouse into a smaller cat. And how can we provide the hot performance and features of a fantastic boat like the A57 in a smaller and more affordable package?

After a couple sleepless nights trying unsuccessfully to visualize that concept, the left brain takes over and struggles to turn the fuzzy ideas into a something useable. Part of the left brain's function for a yacht designer is to suffer the tyranny of scale drawings. One of the laws of physics (at least in the pre-quark era when I was in school) is that two objects cannot occupy the same space at the same time. This turns out to be a real problem in boats - and many warm and fuzzy design concepts have foundered on those rocks! But after many iterations of drawing/erasing/moving/jiggling, a balanced cruising yacht begins to emerge. The overriding goal being not too much, not too little and everything in its place. Or as the great landscape architect Frederick Olmstead once said, "never too much, hardly enough."

26 years ago, in 1985, the first Atlantic Cat was launched. Since then, almost 50 more Atlantic Cats of various sizes have been designed and built, along with many other CWD catamarans and trimarans. As you might imagine, that background is incredibly useful in developing a new design. Knowing what works and what doesn't, having drawings, photos and specs to refer to, and of course having had the pleasure of sailing many tens of thousands of miles in the whole spectrum of Atlantic Cats, is the foundation upon which this new design was created. While any boat is a collection of individual features, it must viewed as a whole because every part has some influence on all the other parts - even if it is something as invisible as its weight. As a whole, the A47 is a winner. The design incorporates some new features and in many ways is quite different from some of her older sisters.

Why 47 feet?

47 feet is long enough to incorporate two key features that so many Atlantic Cat owners love - an aft deck behind the pilothouse, and a large pilothouse with very easy access into the hulls.

I have long felt that the mid 40 foot size range is where the dynamics of the cruising cat start to work really well. To be reasonably self sufficient and live a comfortable life on board there is a baseline of equipment and stores that a boat needs to carry. This "payload" for lack of a better word, is largely composed of the same items and weighs the same whether the cat is 40', 50' or 60' long. With hulls of only 40' to carry the load you either have to be very critical of what you carry or else you have to settle for a considerable loss of the performance sparkle that makes a good cruising cat so much fun to sail. By extending the hull length, a considerable gain in displacement is achieved while still having a slender enough hull to perform well.

Pilothouse:

The new Atlantic Cat is 47' long by 24' wide overall, yet the pilothouse (the main living space) is larger than the Atlantic 57! This is achieved by extending the pilothouse outboard closer to the edge of the deck AND by raising the floor level in the aft part of the hulls (galley and workroom) so that it is only one step down from the floor in the pilothouse. This permits a beautiful low profile pilothouse that is quite large for a 47' cat.

Galley:

All the Atlantic cat galleys are large, easy and very practical but the galley in the A47 might be the best one yet. I recently spent several days at Alwoplast inside a full size mock up of the A47 pilothouse and galley, pushing and pulling the location of counters and appliances, adjusting windows and hatches for optimum sight lines and ventilation. Boat interiors succeed and fail on very minor dimensional changes. An inch here and inch there, it adds up and makes the difference between an interior that works and one that doesn't. The A47 pilothouse/galley combination is very spacious and has the interior feel of a much larger cat.

Galley up or galley down? This cat has both. The galley is only one step down, with great big windows all around. Since the pilothouse, galley and cockpit are where you spend most of the waking hours it is nice to have it all closer to the same level.

By raising the galley floor up close to the level of the pilothouse, the width of the floor increases due to the flare in the hull, so the working area in the galley is enlarged and stowage space under the counter tops is increased.

The fridge/freezer is almost the same size as the A57's and uses all the same cooling components. However the position of the fridge/freezer is lower which makes access easier, especially when you're trying to fish something out from deep in the back of the box. A47 cooks will enjoy the large opening window above the sink that faces out onto the aft deck. The window also makes passing food or drinks aft an easy task.

plan

Port Hull:

The port hull adjacent to the pilothouse incorporates a workbench like most of the other Atlantic Cats but the aft part of the hull can be configured in different ways. Several customers have expressed a preference for a 3rd double cabin, so that is shown on the layout drawing. Alternatives could be a single berth cabin or more workroom or home office space, or something else entirely...

Aft Deck:

There is a sizable aft deck which is protected by a much higher bulwark aft than her Atlantic Cat sisters. This bulwark/crossbeam was added so that the pilothouse could be built more simply and with larger windows than the other Atlantic Cats. On the starboard side there is a 'walk thru" to the stern deck making access to the dinghy very easy and with minimal up and down. To port is a built in seat that can be used in conjunction with the moveable pilothouse table for outside dining that so many people enjoy on the larger Atlantic 57.

Passage from the aft deck forward can be made either through the pilothouse or on the secure side decks along the pilothouse. The side decks are narrower than the bigger Atlantic Cats, but with a rail outboard instead of lifelines and a hand rail on the cabin top, walking along the side deck will be secure.

Sailplan:

Because of her slender hulls and relatively light weight the A47 can utilize a sailplan that fits under the 65' fixed bridges that are scattered up and down the US East and Gulf coasts. That feature opens up the option of ducking inside many harbors that are otherwise inaccessible to a boat with a taller mast.

After sailing 24,000 miles with the Atlantic55's self tacking jib, I'm certain this is one feature that everyone will appreciate. Need to tack? Just turn the wheel, or push the autopilot "tack" button and it's done. Tack back? Done, no effort at all. When the wind pipes up, the jib reefs deeply while still holding its shape because the sheet lead automatically adjusts itself to the correct position. Sailing deep off the wind the jib boom holds the sail out to a very efficient shape. It is a powerful sail that is easy to handle.

The mainsail is handled in standard Atlantic Cat fashion. All sheets, vangs and reef lines lead to the center cockpit. There is no need to leave the cockpit to hoist, douse or reef. The vang/preventers led to the end of the boom allow perfect control of gybes in any wind conditions and excellent shape control when sailing off the wind.

There are several options available for light air down wind sails. Spinnakers can be simply carried without a pole and easily doused by using a sock. A bowsprit can also be used to carry more genoa-like reaching sails that roll up on the typical endless line furlers. Each type has its pros and cons and are the subject of much debate as to which is best. I'll leave it to the owners to decide which downwind sails they want to carry.

The mast can be aluminum or carbon. For general cruising use there is nothing wrong with an aluminum stick. It is far less expensive than carbon and much less likely to be damaged if struck by lightning. Carbon fiber masts are lighter, which is good, the weight difference being approximately 150 lbs. Yes, having one probably makes the boat a little faster (maybe by 1% at best) although I don't at all subscribe to the notion that it is a must-have item.

Beneath the waterline:

Forget the daggerboards! I know, I know, this is heresy. Burn me at the stake!

It's clear from the performance of the Atlantic 55 and A57, which have fixed fins and retractable boards, that upwind performance with the boards retracted is still quite good. Basically, if a cat is reasonably light, has an efficient sail plan and some type of fin under the hull, it will sail well. Daggerboards are vulnerable to breaking if you hit something. Both daggerboards and pivot centerboards are heavy, expensive to build and get in the way either on deck or inside the accommodation spaces. Everything has its price.

So the question becomes, what can be done to improve the efficiency of the hull fins to daggerboard level without making them excessively deep?

The answer: put a flap on the trailing edge of the fin. This makes so much sense. It is simpler to construct and maintain, weighs very little and is not vulnerable to damage. Yet a flap has the ability to dramatically improve the performance of the fin.

Let me explain: The typical symmetrical daggerboard creates zero lift unless the hull is sailing a little bit sideways in the water. In order for anything beneficial to result from the increased draft of the daggerboard it must go through the water at some "angle of attack" to the water flow. Normally a good sailboat going to windward will be "making leeway" of 3 to 5 degrees. This means that the boat is turned 3 to 5 degrees to the rush of water coming along the hulls, which is highly inefficient. Unless the hulls are operating at this inefficient angle to the water flow the boards have no angle of attack and cannot provide any lift to combat the sideways push from the sails. So in order to get "lift" from the board you need to accept an offsetting "drag" penalty from the hull.

What makes the most sense is to have an underwater foil that is adjustable so that it can provide lots of lift while the hull tracks nearly straight thru the water. By far the simplest way to do this is to install a flap on the trailing edge of a fixed fin.

I can see all sorts of beneficial uses for fin flaps beyond just sailing to windward. They can be used to balance the boat under different sail trim. They can be used to combat crosswinds in a docking situation. They can be very effective sailing down wind too. Flaps set at negative angles will reduce drag and help "push" the boat to leeward which is just what you want when deep reaching.

There is even the possibility for using the fin flaps as a built in drogue. By setting them in opposite directions at high deflection angles they will be very effective "brakes" and could be handy in conditions where you need to slow down. Each flap will have an independent control and will be adjustable from the helm station.

Steering:

I have used mechanical, rather than hydraulic steering systems, on the Atlantic Cats since 2002. The A47 will also use a simple, reliable, low friction mechanical steering system. Some of the details have yet to be finalized so I will leave further discussion to a later date.
Other than to say that people will be surprised by the simple elegance of the system!

Propulsion:

The engines are located under the raised sole in the galley and the opposite workroom. This position is somewhat further forward than the other Atlantic Cats and allows for the use of either a saildrive or a standard shaft drive. Having experienced both engine types in the same design I prefer the saildrive because they transmit considerably less vibration to the hull structure and also seem to be quieter in operation than shafts. However, some owners have strong preferences on this subject and this design is versatile enough to do either.

Electric:

The wide pilothouse offers lots of space for solar panels. By using LED lighting and efficient refrigeration, the solar output and standard engine alternators will typically keep up with the normal electrical demand. Additional output can be added with a windgen or additional alternator output.

Safety:

Last but certainly not least is the overriding concern for safety. The record shows that the Atlantic Cats are some of the safest cruising boats afloat. Construction scantlings, while lightweight, are very robust. Extra material is placed where it is needed to absorb impact and provide a fail safe structure. The risk of falling overboard is greatly diminished by the center cockpit sail handling. Crew fatigue and the errors in judgment that can go with it is minimized both by the enclosed pilothouse, which provides for comfortable, dry watch keeping and also by the ample bridge deck height and soft riding hull shapes that virtually eliminate the tiresome and hull and underwing pounding that plagues many other cats. Critical parts of the boat such as props and rudders are protected from impact with flotsam and grounding by the hull fins. Watertight collision bulkheads are standard in each hull, and will prevent extensive flooding in event the hull is holed. As ultimate crew protection, a capsize habitation area is provided where the crew can stay dry and protected in the highly unlikely event the boat is capsized. The ocean can be a hostile environment, with an Atlantic 47 you will be prepared for it.

Contact Chris White for further information on delivery schedule and cost.