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Pedigree Cats, Inc. Catamaran

Large Catamarans by Lock Crowther

This was written years ago but lots of good info.  Some of the materials and methods of building are now upgraded to the new products and materials available to us today.


We have all seen, if not the real thing, at least pictures of Millionaires Luxury Power Yachts on the Riviera or other jet-setting playgrounds of the world.  This new leader in Catamaran design is, in our opinion, a far superior vessel in every way, to all catamarans ever built.  She is one of the largest fiberglass sandwich structures ever built and incorporates the latest developments in fiber reinforcement technology.  These days nearly all luxury yachts of large size are built of either Aluminum or Steel.  Apart from some new motor YACHTS UNDER CONSTRUCTION IN Japan which incorporate some Carbon Fiber to our knowledge this is the only yacht of her size which uses fiber reinforced plastic sandwich construction.  The benefits of this construction technology are greatly reduced weight and therefore, less fuel consumption, faster speed under sail and a more comfortable motion.  She is nearly 1/3 lighter than equivalent Aluminum yachts and less than1/2 of a steel yacht.

The construction technique used does require more labor in producing the hull shell, but much of the interior lining and fitting out is incorporated directly into the construction of the shell.  Therefore, the total labor content in the completely fitted out vessel is much the same as that for any other construction technique.  The total cost of the yacht is much the same as for Aluminum construction.  Steel construction is totally unsuitable for Catamarans due to excessive weight unless you are into 150’ plus range.

Catamarans are the ideal vessel where large deck areas relatively low payloads, together with high speed, are required.  For the same length a catamaran will provide approximately 85% more deck area and internal cabin space than a monohull.  She will weigh slightly more than a monohull power boat of the same size.  She will, however, be much more efficient and not be so limited by hull wave-making resistance.  A monohull power yacht has either to be a displacement type, which is limited to about 12 knots efficient speed , or planning type, which could travel up to, say 30 knots, but with very expensive engines, a very short range and a very rough ride at sea.  This catamaran will power at 14 knots with fairly small engines and will sail at speeds up to 20 knots fairly easily.  Of course, with the combination of power and sail, she will use a fraction of the fuel of a power and will have an unlimited range.  With larger engines she could be made to go faster, but we feel that the combination of engine size and sails the we have chosen is ideal for her purpose – that is a vessel of unlimited range and luxury which is not restricted by lack of fuelling facilities in way out places and which is more economical to operate that any other yacht.

Slightly smaller catamarans of similar design by Crowther Multihullls have proven that the capital cost of rig and sails can be returned by fuel savings in less than 3 years.  In addition, should the boat be designed purely as a power catamaran then it would be normal to install larger engines.  The additional cost of these engines would compensate for a larger percentage of capital cost of rig and sails.  So it can be seen that the combination of sail and power, which can only be made to work so effectively on a catamaran, is much cheaper to operate and returns the small additional capital cost over that of a pure motor vessel within a maximum of 2 years.

Perhaps the major advantage of the catamaran is the fact it does not roll or heel. All monohull vessels roll.  Whilst they may be stabilized by foils and other means, these are effective only while the vessel is moving and cause increase fuel consumption.  They are not effective at anchor.  All sail power monohull yachts roll down wind; worse still heel and this feature is the one which most limits the acceptance of sail yachts as luxury vessels.  We have found that women love catamarans purely because they don’t roll or heel.  Pot plants and other knick-knacks stay where they are put.

A catamaran can be beached without falling over or damaging the hull or appendages.  This can be purely for the joy of parking in out of the way places or for maintenance such as anti-fouling.  A catamaran such as this has a very shallow draft of just over a meter and so can go safely many places normal vessels cannot.  This feature is particularly useful in the shallow coral reef area of the world.

The interior of the main cabin is more the proportions of a house, not the long and narrow passage of a monohull.  The monohull sail yacht is worse still as the main accommodation is down below sea level with minimal viewing.  The catamaran and the monohull motor vessel both have all round windows but the catamaran, of course, has a cabin twice as wide.  Facilities for passengers, interior furniture arrangements and services can be laid out in a superior manner. 

The engines are not located under the floor of the main saloon as in the conventional yacht but are in separate engine rooms separated from the accommodation areas by sound and fireproofed watertight bulkheads.  The engines are under the deck and cockpit area and so sound transmission into the accommodation is minimized. 

Because of her size she has effectively three decks.  The top deck has a fully enclosed pilot house with protected wing bridges on each side.  All sale controls are on this top deck and lead back to the wing bridges so that interference with people is minimal.  The main deck contains an enormous covered cockpit extending from gunwale to gunwale and to the transom.   Forward of this is the main deckhouse containing all the entertainment facilities with external walkways to the foredeck on either side of the deckhouse.  The foredeck is a great area for lunging and sunning.  The lower deck is in the hulls and contains most of the sleeping accommodations.   

Design Features

1.        The whole of the shell of the boat is constructed from end grain balsa sandwich using triaxial glass fabric on either side. For this size of boat this is the lightest form of construction that can be used without going to the expense of exotic materials such as carbon fiber and Kevlar.   The triaxial fabric considerably stronger than conventional woven roving or chop strand mat and in addition are more uniform in strength in all directions. Woven roving, for example, are only half as strong on the bias as they are parallel to the weave.  The choice of balsa as a core material is dictated by the required properties of the core and cost.  Lighter commonly used PVC foam cores have insufficient shear strength for a vessel of this size.  Higher density PVC foams which are suitable are Justas heavy as the end grain balsa and considerably more expensive.  The end grain balsa has been used for over 20 years in all sizes of boats and is approved by all classification societies.  The balsa absorbs considerable resin protecting it from ingress of water. Any damage to the skin limits the water absorption to that area only as the water cannot travel across the grain of the balsa.  Numerous tests have been carried out to prove that this is the case.


The hulls are constructed in the same female mould. The moulds are constructed from cheap simple materials such as Formica faced chipboard so that the cost of the moulds is recovered in the saving of time in obtaining a smooth finish on the outside of the boat.  A great number of the components of the boat are constructed on flat edges.  This method, whist not new, has been developed over the years to the stage where it is actually quicker than the conventional sandwich construction method of building over a male mould.


The shell of the boat is supported internally by ribs and bulkheads at regular intervals.  The bulkheads are constructed from end grain balsa sandwich and triaxial fabric and the ribs are constructed from foam corded hat sections glassed with triaxial and capped with uni-directional fiberglass.


The whole of the structure of the boat is to the highest available fiberglass technology keeping the weight minimal and the addition reducing the cost of materials and labor over the older technology which uses multiple layers on woven roving and chop strand mat.


Blisters on the skin under the water caused by osmosis have been a problem on many fiberglass boats.  To prevent this problem occurring we have used no gel coats at all as these are susceptible to transmission of water vapor and the beginning of osmosis with the congregation of water vapor around suspended pigment particles.  The outside of the hull is painted with a high density 100% solids epoxy paint which has the lowest permeability to water vapor. Top coats are two part linear polyurethane which are also excellent in this respect.  As a further preventative measure all of the outside skin of the hulls are laid up in Vinyl ester resin which, so far as we know, is impervious to osmosis.  The remainder of the vessel is laid up in normal isopthalic resins which are less expensive.


2.       I have found that twin engines provide the best possible powering for a catamaran.  With two reasonably powerful diesels the wide spaced propellers provide outstanding maneuverability, essential when maneuvering a large catamaran in enclosed waters.  Catamarans are light in weight and have quite a lot of windage; they tend, therefore, to drift quite quickly.  The twin engine set-up makes it look easy.  It is essential to use a large propeller turning relatively slowly so as to produce maximum thrust into strong winds and to obtain the highest possible propeller efficiency.  Such a propeller will, of course, have considerable drag when sailing without the engines.  By using feathering orioellors of the variable pitch type not only can the drag be removed when sailing, but the pitch can be adjusted when motor sailing to give the optimum efficiency and fuel saving.  You can use both motor and sail in an effective manner, the motor providing enough speed to generate a reasonable apparent wind speed across the sails.    As the force is proportional to the square of the speed, the combination of the additional sail force together with the motor will provide amazing high average speeds for almost negligible fuel consumption.  This situation applies to light winds only.  In moderate to heavy winds, the sails are all that is required.  The only time in a strong wind where the sails can be bypassed is if you wish to go directly upwind in the shortest possible time.


There are quite a few proprietary brands of variable pitch propeller and we have used one which will go from forward to reverse via neutral to fully feathering. This means that there is no need for a reverse gear box, just a reduction with a clutch.  The boat can then be maneuvered on the pitch control levers alone at constant engine speed.  This facility is not essential and other catamarans of our design have very successfully used conventional reversing gear boxes connected to variable pitch propellers.


3.       The interior layout has developed from other recent successful designs such as “Tafua”.  We have found it best to keep the galley adjacent to the main salon dining area rather than down in the hull as is done on some other catamaran designs.  This way all of the entertaining can be done in the same area without trafficking downstairs.  The entertaining area extends out of the main cabin onto the huge covered aft deck.  It would be quite possible to cater for 100 guests without being crowded.


Luxury sleeping accommodation for 16 guests is provided in double cabins; five of these cabins are in the hulls and three are on the main deck.  Each is self-contained with a shower, toilet and vanity.  In addition crew quarters are provided in 2 twin cabins sharing a toilet, shower and vanity.  All of the cabins are entirely separate; some of these in the hulls have to be fitted with watertight doors to meet 2-compartment flooding rules specified be Det Norske Veritas for a full ocean-going passenger vessel.  These doors are not obstructive and only require the passengers to step over a low sill.  All of the sleeping cabins can be air-conditioned if desired.


Other facilities include a large laundry with washer/dryer forward in the starboard hull and a large freezer/cool room with 2 chill compartments aft in the starboard hull.  The port hull forward has a storage hold for luggage, bicycles, etc. and a small workshop area aft.  This workshop area also contains the desalination plant and the hot water cylinder.  Access to all of these compartments is direct from the deck as they are sealed off at each end by water tight bulkheads.


Ventilation into the main cabin area is primarily via a built-in baffle system in the leading edge of the wing deck feeding in a high velocity air from the venture effect of the under wing directly to the forward end of the cabin or to air conditioners in the same location.  Ventilation into the sleeping cabins is direct from the deck with separate ventilators for each cabin.


4.       Internal Furnishings

The major advantage of the sandwich construction is the insulation and interior surface finish.  With an Aluminum catamaran it is necessary to line the whole of the interior with insulation such as fiberglass wool or plastic foam covered with Formica faced plywood.  The cost and weight of this lining are considerable.  The insulation of the sandwich is quite sufficient and requires no other insulation material.  Simple supports for ceiling panels are molded into the fiberglass roof beams and the flooring in the hulls and main cabin is either plywood or fiberglass sandwich surfaced in whatever material you desire.  There is plenty of room under the floor and above the ceiling for services such as wiring, piping and so on.


Because of the size of the boat major items of furniture, such as lounges, dining chairs, tables, etc., can be normal domestic size and therefore, cheaper than the custom furniture seen in smaller boats.


5.       Safety

Large catamarans are incredibly safe, probably the safest type of vessel afloat.  This is because stability increases much more rapidly with size than does the power of the wind to overturn the boat.  Doubling the size of a catamaran and changing nothing else requires double the wind pressure to cause a capsize.  This catamaran has been designed to carry full working sail at 50 knots of wind on the side of a 20 degree wave without capsizing.  Long before this point has been reached the sails will blow out.


No matter what happens to this catamaran it will float.  The whole of the shell will float completely waterlogged.  The hulls are divided into 7 separate watertight compartments any 2 of which can be flooded without affecting the safety of the boat.


A bilge pump system in each hull can pump out water from any compartment in any hull.  Similarly a fire pump system in each hull can deliver hydrant water anywhere on the boat.


The engine rooms have remote shut-off of all air vents and a Halon gas system to blanket the engine room in event of fire.


Under power the wide beam of the catamaran makes her virtually impervious to wave-induced capsize.  She is far superior in this respect to the conventional monohull power yacht.  The lead Keel on a sailing yacht, whilst it makes her self-righting, leads to sinking in the matter of one or two minutes should the hull be holed.  This is a far greater risk than the risk of capsize with a catamaran.


6.       Rig and sail

By using two masts the normal working rig is broken up into three approximately equal size sails making the sails easier to handle.  All of the sails are mounted on roller reefing systems, the main and the mizzen reefing inside the masts using the technique developed for the 1980 Single-Handed Trans-Atlantic winner.  The headsail and the staysail reef around their own stays.  The reefing systems are either electrically or hydraulically driven and are remotely operated from the pilot house.  All sails can, therefore, be reefed by push button.  The travelers and other controls which are lightly loaded are operated by conventional hand winches.  The boat can be operated by one person if necessary.


In heavy conditions the mainsail can be furled and the boat sailed under mizzen and headsail.  When the conditions get stronger still the headsail can be furled and the boat sailed under staysail and reefed mizzen.  This will cope with quite extreme conditions beyond which it is not possible to sail, i.e. 60 knots +.  A polar diagram is provided with the design which shows how to operate the sails for various sailing directions and wind strengths.


7.       Services

Fuel, water and sullage are stored in integral tanks under the floor in the hulls.  The fuel tanks are broken into 3 in each hull and the vessel can be trimmed by transferring fuel forward if required.  The fresh water system operates on demand via a pressure pump on each tank.  The tanks can be augmented whenever required by means of osmosis type desalination plant; thus there is plenty of water for showers.  A conventional electric hoot water service is installed operated off the 240 AC systems.  The sullage system collects from the toilets only and is pumped overboard at a suitable location from time to time.  The toilets are of conventional domestic type providing a minimum of maintenance.  Waste water from the sinks and showers, etc. is pumped directly overboard.


The electricity supply is from 2 415 v 3 phase alternator sets diesel powered.  One of these sets is sufficient to supply all demand and the other acts as a standby.  The size of the sets is determined by whether or not you have air-conditioning.  This system supplies both 3 phase and single phase and 24 vdc via a battery charger to the main battery banks.  Each engine also has 24 vdc alternator set which charges the 2 battery banks in each engine room.  1 of these battery banks is used exclusively for the engine starting and the other is normally used for the 24 vdc system.  Navigation lights. Emergency lighting and the electronics are all supplied from 24 vdc system.  Normal lighting and all appliances are supplied at 240 V.


Twin anchors are provided permanently stowed under the forebeam.  The anchors are operated via the electric or hydraulic anchor winch located in the leading edge of the wing deck.  To save weight it is possible to use short amount of chain on each anchor and a wire hawse leading onto a drum on the winch making the anchors and hawse self-stowing.


8.       Performance

It is acceptable that the vessel will cruise at 12 knots under power using the engines specified.  Under sail the vessel will achieve close to wind speed in winds up to 20 knots.  The average speed on a passage under sail and power should be 12-14 knots. (16.1 mph)  Top speed under sail will be 20 knots plus (23 mph). 


We are convinced that the hull shapes we have developed are the most advanced and most seaworthy catamaran hulls to date.  In the past a major problem with very large catamarans has been that their fine hulls allow excessive pitching.  By adapting bulb bows and altering hull shapes at both ends of the hulls we have reduced pitching on our catamaran designs to a lower level than that of other vessels the same length.  The comfort of motion on this catamaran will be superior to that of any other, mono or multi.


9.       Re-Sale Value

Catamarans are showing every sign of becoming the most prestigious vessel.  Luxury vessels always command a high price, particularly if they can be used for chartering.  This vessel is designed to Det Norske Vertas rules and is approved for passenger carrying full ocean0going.  She can, therefore, be sold anywhere in the world and operated as a fully qualified charter boat wherever desired.  For all these reasons we predict that this vessel will be an extremely good investment.

For More Information, email us at  Info@PedigreeCats.Com

Pedigree Cats Catamarans
Pedigree Cats, Inc.
1835 Ocean Avenue  Phone (360) 942-2810 
Raymond, WA  98577         |          Fax (360) 942-2936

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