Multihull Structure Thoughts

A short one about a person who was inspired by some racing catamarans that were designed by Lock Crowther. The Cox 45 “Hurts so Good” appears to be similar to cats like Top Gun etc. The aim of these cats are performance first, cruising capability second. People think cats like this will be cheaper and faster to build but in the real world they end up being about the same cost and build time.

The Cox 45 is 44.3 x 23.3 foot with a estimate displacement of 11,000 lbs. The aluminium mast carries an unknown sail area but has carbon sails and several spinnakers. The length to beam on the hulls look about 14 to 1. The draft is listed as 1.5 to 5 foot over the daggerboards and lifting rudders. The engine is a Yamaha High Trust outboard of 25 HP running unleaded fuel. Fuel tank is 25 Litres. The electrical system has AGM batteries and Solar Panels: 1 x 125W + 1x 80W.

The accommodation is mainly in the central pod cabin. 2 single berths laterally forward, a small dinette with a “small” double berth on 1 side and a small galley in the aft corner of the pod cabin. To give a feel for the galley a stove: Metho 2 burner, Water Tanks: 50L and a Fridge: Waeco 50 Litre. This is a minimalist cruiser. There can be a single berth in each hull but no real cabin space.

The construction is strip plank cedar, e-glass and epoxy. There would also be plywood bulkheads etc.

Its good that different designs are done and built but please be clear about your intentions. If you want a racer build a racer, if you want a performance cruiser design and build that. But when you have a racer that you try and convert it to a “fast cruiser”, the limitations of the accommodations become frustrating over time.

The jpegs give the idea.

 

The KAICYCLES, a Spanish firm in Barcelona, NEO X2 and NEO X4 electric catamaran models are currently in the prototype phase as water sport cats for couples or for rental boats for guided tours for navigation of environmentally sensitive areas.

Both the NEO X2 and X4 are 12.1 x 6.5 foot with a weight of 589 lbs. The draft is 0.5 foot with a propeller depth of 1,6 foot. The motor type is an electric outboard 6 HP (3.5 KW). Spain only allows a maximum of 3.5KW for this size of “commercial” boat. Passenger capacity 4-person maximum.

The preferred motor is a Navy 3.0 Evo Long Shaft direct drive outboard electric motor of 3.5 kW, equivalent to 6 HP, with hydrogeneration function weighs 22Kg (49 lbs). The E80 battery (4,096 Wh) weighs 48Kg (107 lbs). Evo Remote Control. Y Type Communication Cable. 2 Units Communication Cable 5m. E series battery communication cable 1.5m. E Battery Communication Terminator. And Remote Battery Switch. Type E 30 A H Battery Charger.

The build is fiberglass hulls with a foam glass deck panel and a fabric sun roof. At this size of cat the build does not have to be fancy as puncture resistance of a thicker hull skin is more important than ultra light weight.

No performance numbers but expect about 5 to 8 knot speeds depending on passenger load.

This is showing that for inshore or near shore boating these types of cats are very viable. Pity the poor fish that will be quietly approached and protentional caught.

The jpegs give the idea.

 

SIG is a range of luxury cruising catamarans designed to be fast, innovative and easy to handle. The intention was to make 60 foot and 80 foot versions available, but so far only the SIG 45 have made it into production. The design work by VPLP proceeded in 2012 – 14 for the larger cats but no production appears to be done. The SIG 45 (Builder Lebreton Yachts) was an open bridge deck cat that was light, had good sail area and was fast. The 60 and 80 footers where full bridge deck but still light and with good sail area. There was to be an open bridgedeck 60 footer GT version but it was not developed.

The SIG 60 is 60 x 28.25 foot with a displacement of 25,353 lbs. The carbon mast height is 85.3 foot carrying a 1,324 square foot mainsail, a 732 square foot jib, a 1,938 square foot gennaker and a 2,691 square foot spinnaker. The draft varies from 3 foot to 9 foot over the daggerboards and rudders. The engines are two 53 HP inboard diesels.

The accommodation is unknown beyond it has 8 cabins which can be configured to suit the owners requirements from a charter vessel to a very fast cruiser. The main saloon is large.

The build is listed as prepreg carbon on foam with epoxy. This would require post curing in an oven or autoclave. If the quality of the SIG 45 is anything to go by this would have been a well built cat.

The SIG 80 was meant to be the queen of the fleet and in the initial design proposal was 78.7 foot long, but a later design update lengthen the SIG 80 to 83.4 x 36.1 foot with a displacement 63,950 lbs. The carbon mast height was proposed to be 118 foot carrying a 2,260 square foot mainsail, a 1,227 square foot jib and a 3980 square foot spinnaker. The draft ranges from 3 foot to about 11 foot aver the daggerboards and rudders. The 2 engines proposed were 170 HP each.

Company advertising said: “The objective of the luxury yacht SIG80 is to combine outstanding performance with true luxury. The speed potential of a well designed 80ft catamaran is enormous. With one important caveat: it must be light. Every additional kilo creates a speed penalty. By specifying modern composite materials in the hulls, rig and joinery, Le Breton Yachts has created a yacht that will outperform anything currently on the market, while providing a vast saloon, five cabins, four heads and crew quarters for three, including a small mess.” And: “The accommodation layout provides an owner’s hull to starboard, with a private owner’s apartment aft and cabins for children or close friends forward. The design offers an optional cockpit entry to the owner’s aft cabin for additional privacy and practicality. In the port hull, there are two double en-suite guest cabins aft and a galley/crew mess and a twin cabin for the crew forward.”

On performance: “Luxury yacht SIG80 will be one of the fastest cruising vessels in the world, capable of speeds well in excess of 30 knots with effortless performance and superb handling. The deck layout enables sailing by a small crew.”

Again, the construction is prepreg carbon on foam with epoxy mainly in molds. This would require post curing in an oven or autoclave.

The jpegs give the idea of 2 what could have been sensational high performance cats.

 

Neo Yachts & Composites are an Italian firm who employed Naval Architect Marco Veglia (the architect of the Slyder 47 and the Mattia 52 and 60 cats), to design the NEO 560 performance cruising catamaran. Neo have been in business since 2006 building mainly very high performance racing mono hulls. Neo are experts in carbon fibre construction. There previous catamaran experience is the NEO 410 which is featured on page 212 of this thread.

The NEO 560 is 55.9 x 28.1 foot with a weight of 31,970 lbs. The 85 foot carbon fibre fixed or rotating wing mast carries 1202 square foot mainsail, 915 square foot jib and a 1,722 square foot Code 0. The length to beam is about 10.5 to 1. The draft ranges from 4.9 foot over the rudders and 12 foot when the daggerboards are fully down. The underwing clearance is 3.4 foot.

The accommodation is either an owners double berth cabin in one hull with a crew cabin in the bow. There are 2 guest cabins in the other hull wall with ensuite toilet showers or 2 cabins/ hull. The main saloon has a large main seating/table are some secondary seating, a helming navigation position and a large galley between the main saloon and large cockpit.

The construction according to Neo Yachts & Composites philosophy, is fully built in carbon fibre composite in prepreg or infusion with epoxy resin. The materials are prepreg unidirectional and axial fabric carbon laid in molds the components are cooked in an oven at 70 degrees centigrade. This build a light but can be expensive cats.

The performance of this cat will be very good. By my calculations it will be able average 12 knots and peak near 25 knots under really good conditions. Real cruising world this will do EG 230 mile days regularly.

This is a good cat to be built by a good builder, if you want a very fast cruiser this could be the cat for you, that’s if you have a few million in your bank account. The jpegs give the idea.

 

The following is a motor sailing catamaran with an aluminum alloy hull for expedition voyages in high latitudes with a small crew. There is a reinforced hull with the possibility of drying in low tide areas and well protected rudder and propellers. The Naval Architect is Alexander Morozov and the preferred builder is Igor Dudnikiv.

The K55 expedition catamaran is 54.8 x 26.9 foot with a weight of 40,300 lbs. The 61 foot aluminum fixed mast carries 1600 square foot of sail area. The mainsail is a semi junk type mainsail to make it easier for one person to control. The length to be on the hulls is 8 to 8.3 to 1 depending on the load. The draft over the fixed fin keels is 5 foot. As a motor sailor it has 2 Yanmar engines of 150 hp each with shaft drive. Diesel electric hybrid systems can be installed as an option. The electrics include an Ocean Generator 10 kwt and a second Generator of 5 kwt An inverter of 3 kwt connected to 2000 watt of Solar panels with a 50 A charger 50A and 1000 ah of Li-Fe batteries. All connected to PMS epectric power management.

The layout and capacity is designed for a permanent crew of 3 people (married couple + 1 person) with the possibility of receiving additional guests 2-4 people. Workshop room in the hull and office workplace in the cabin. There is a fully enclosed deckhouse with internal control post. External helm stations are only for manoeuvres in port and under sail. The aft and forward cockpits are smaller than average as this cat is designed for higher latitude sailing. The cat has heating, air conditioning and a galley all designed for long term cruising and has the required electrical power infrastructure to support the requirements.

The build is a simple chine shape aluminum hull and deck structure. Alexander has designed other vessels for high latitude sailing and understands the requirements. EG there are n4 watertight bulkheads in each hull.

This is a strong boat built for a purpose. The jpegs will give the idea.

 

Naval Architect is Alexander Morozov also did another motor sailing catamaran with an aluminum alloy hull for expedition voyages in high latitudes to the tropics with a small crew. There is a reinforced aluminum hull with the possibility of drying in low tide areas and well protected rudder and propellers.

The “Liza 60 Expedition” is 59 x 22.6 foot with a weight of 60,480 lbs. The ketch rig carries a 52 foot aluminum foremast and a 44 foot aluminum mizzen mast. The total sail area is about 1900 square foot. The draft over the rudder and propellers is 3 foot. There is no indication of centre boards etc. (This is a motor sailor). The engines are 2 x Volvo-Penta 160 hp with shaft drives. The cat will cruise at 7 knots and has a peak speed of 13 knots. The 5500 litres of fuel allows a range of up to 5000 miles at cruise speed and good conditions. Installed lithium-ion batteries (5000 Ah) in combination with solar panels (2200 W) make it possible not to use the 12 kW / 220V generator at all in everyday sailing or when on anchor.

Now we get to a few unique features of this cat. The high rigidity of the hull, combined with removable wheels (4 pieces of 2 wheels from military aircraft) and mounted on keels, allows the catamaran to be rolled ashore using hand winches or as a trailer to a truck without a crane or lift. Mounting / dismantling of wheels takes 2 hours of work. The second feature is the masts can be lowered for passage by river routes, where the clearance of the bridge is small. The masts are raised/lowered without involving a crane, the masts are raised and lowered to a horizontal position by winches in 1-2 hours of crew work.

The accommodation has 6 cabins with 13 berths and 5 toilets mainly in the hulls and a large main saloon with galley, seating and navigating facilities. There is heating and airconditioning facilities along with entertainment devices.

The construction is aluminum throughout with an easy to clean, simple internal fitout. There is a lot of insulation used in the hull and deck structure. The chine hull shape makes the build simpler but this structure is strong to allow (Yes, these are real statements by the designer) “It possible to run aground and not be afraid of hitting reefs / rocks when moving at full speed” with “Protection of propellers in the form of a steel frame allows you to navigate in ice. Standing rigging is designed for an unlimited service life, steel wires with a diameter of 19 mm are filled with zinc in cones, which is more reliable than conventional modern fittings. The mast will not break even if one of the shrouds is damaged.” And “The main idea in this project was to make a solid and self-sufficient expeditionary platform for living a board, like a "ship for the apocalypse" in our difficult times.”

This cat is designed to sail any ocean you want and according to the designer is capable of handling many difficult situations. A good example of a long term cruiser that puts priority on survival whilst having moderate performance. The jpegs give the idea.

 

Cattywampus is a Kelsall 38 design and was built at Maine Yacht Center. It was started in 2014 and was partially finished by the owner for a launch in 2019. I suspect the shell was professionaly done and the internal fitout was home done but not fully completed.

Cattywampus is 38.3 x 21 foot with a weight of about 11,000 lbs. The Sparcraft aluminium mast carries a basic rig of 800 square foot in the main and foretriangle. There are other sail options. The hull length to beam is about 9 to 1. The draft is 3.1 foot over the mini-keels. Engines are twin Tohatsu 20HP fuel injected outboards. The cat can do 9 knots cruise for 20hrs on 32 gallons of fuel. The electrics include 2 new AGM deep cycle batteries with a 3000W Victron Inverter Charger.

Accommodation has a double berth aft in each hull, 1 single berth forward starboard and 1 head forward in the port hull. The main saloon has a galley, seating and table. A comfortable practical layout for a couple for long term cruising.

The construction is Vacuum resin infused with unidirectional e-glass and H80 Divinycell. Derek has used polyester resin through out his career so I assume that is the resin system. Kelsall cats have a long history and when built to plan and last very well.

Most Kelsall cats sail well as cruisers. Kelsall has done a few racing designs that raced well and when they had the name “3 Legs of Mann” went very fast for there type of cat.

The jpegs give the idea.

 

Never heard that Nick Keig had any Kelsall cats named Three Legs, was this after the tris?

 

The following is an interesting cruising cat with some performance and several interesting features. The cat is well suited to coastal cruising for a couple for an extended period or a family for shorter periods. It can also be used for local racing. This cat’s big advantage is its accommodation for the size of cat. The designer is Adrian Rogers, an Australian designer who specialised in a lot of very practical small to medium sized multihull designs.

“Roger Ramjet” is 31 x 19.6 foot with a weight of 5,600 lbs. The 34 foot fractional rig mast carries an unknown sail area but estimate about 600 square foot in mainsail and jib. The draft varies from 1.5 foot when both daggerboards and rudders are up to 5 foot when boards are down. The power is a Yamaha 4 Stroke 25 HP which does 7 knots at cruise.

This cats accommodation is good. There are double berths in the stern of each hull. A toilet in one bow and a single berth forward in the other bow. There is a reasonable galley in the hull then we come to the main saloon. 6 foot headroom and a full size dinette. Beside it is a L shaped seat. But the real joy is the conversion of a large part of the seating area to a full king size bed. Those who live in tropical areas will appreciate the comfort of this arrangement in a 31 foot cat.

The helming is in the cockpit on a seat that allows a view through the cabin windows when seated and when standing seeing over the cabin roof, Under the helming seat is the outboard engine. But the real joy of this cockpit is the mast halyard control lines which run from the mast under the underwing to halyard locks on either side of the helming seat. The halyards then can be lead to the mainsheet which in the rear of the cockpit for adjustment. 1 winch for all mainsheet and halyard adjustments. There are 2 other winches for headsails, spinnaker movements. This is a well thought out arrangement for a cruising cat which may be single handed a lot. The roller furling jib means not having to go forward the majority of the time.

There are no performance figure beyond the owner claiming it is an easy to sail craft that is close winded and capable good performance against other boats. I have sailed on an Adrian rogers 30 foot tri and a 32 foot cat, those boats sailed well across the wind range so I have no doubts this cat would also do well.

A very interesting and good design with several interesting features. If yo want a 31 foot boat with 40 foot comforts this could be a good option. Unfortunately Adrian Rogers does not have a web site and I do not know if he is still active in boating. The jpegs give the idea.

 

Cavalier MK2 From a "Short history of Kelsall Designs"

Legs of Mann I-II-III-IV Legs of Mann I, Legs of Mann II, Legs of Mann III, VSD and Legs of Mann 1V were all built by Nick Keig. 37, 53, 53 tris followed by 63 foot race cat and 52 foot fast cruiser. Five multihulls within 14 years. Nick got together a great team of builders to assist him. Typical was 9 month build time.

I will do an item on the 52 foot very fast cruiser tomorrow

 

Derek Kelsall and Nick Keig did many design/build together. Derek had a creative design mind and Nick had a very practical approach to building, as his 35 x 15 foot shed provided the space to build many simple components for assembly in outside “greenhouse shelter”. Nick’s trimarans were well built and successful on the race circuit. Nick then produced a 63 foot racing cat that had a short fast life under the VSD sponsorship. Finally Nick decided fast cruising would be good and asked for a 52 foot fast cat from Derek. The result was Legs of Man V.

Legs of Mann V is 52 x 24.5 foot with a weight of 9,000 lbs and a displacement of 15,700 lbs. The 60 foot long, 97 square foot, rotating Gougeon wooden wing mast carries a 682 square foot mainsail and a 420 square foot genoa. The length to beam on the hulls is 10.5 to 1. The minimum draft is 1.5 foot to over 5 foot (if it has fixed keels, more if it had daggerboards). The power is a 9.9 HP outboard (yes 9.9 HP, Nick is a sailor). The underwing clearance is 2.4 foot.

The accommodation has a double berth cabin aft and a double berth cabin forward with a toilet in each hull. There is a galley in the port hull and a formal toilet shower bathroom in the central part of the starboard hull. The main saloon has seating and a navigation station, but what the main saloon lacks is headroom with only 5.3 foot available over the majority of the floor area except a small central fore aft slot.

The construction is mainly flat panel foam e-glass polyester resin. The hull bilges are rounded segments integrated into the build. Nick built half length hull panels inside his shed then assembled the cat outside.

Performance was very good. Nick describes Legs of Mann V capable of 13 to 15 knot speed range whenever the wind cooperates. Nick Keig built a very fast cruiser capable of going far. But Nick was a sailor first and a cruiser second. A simple light engine and a low windage bridge deck was more important than a big engine and 6 foot headroom.

The first be 2 pages of jpegs give the story. The other cat jpegs featured is what a “cruising” version of the 52 could turned into and is available for sale on EVACOM. The Caitanya 52 foot cat is 2 foot wider, 4,400 lbs heavier, carries about 100 more square foot of sail and has a full headroom main cabin.

 

The following motorsailor cat was built between 1998 and 2003 by a homebuilder to a Alexander Verheus design. The Lexline 38 was conciebed from the start as a motorsailor and had wide high volume hulls with a central pod to house the motor and Sonic outdrive leg.

The AMD Lexline 38 is 38 x 20.2 foot cat with a weight of 13,440 lbs carries a Sparcraft Aluminium 53 foot mast. The Bermuda cutter rigging is Inox 10mm caps and forestay, 8mm side rigging and 7mm diamonds. The sails are a 360 square foot mainsail (dacron) with 6 full battens and a Profurl roller furling genoa of 344 square foot. The draft ranges from 2.5 foot to 6 foot over the ashwood centreboard. The engine is a 36 HP Vetus diesel driving through a kickup Sonic outdrive leg with a 3 blade fixed solid propeller. The engine drives the cat at between 6 to 9 knots with a fuel consumption of 5 litres per hour. The fuel tank is 250 litres. There are 2 x 110 Ah 12V batteries with a Vicron Phoenix Combi 1 charging control unit.

As you will see in the jpegs this cat has a very large underwing pod that contains the engine and outdrive. This will impact its sailing performance as wave interference will build up in the tunnels. The result is a claimed speed of 6 to 12 knots under sail and motorsailing.

The accommodation includes 2 double cabins in the hulls, a toilet bathroom in one hull and a downstairs galley and dinette in the other hull. The main saloon has full standing headroom, helming position and additional seating, call the main saloon a rest viewing area and a pilot house. The cockpit is practical for helming and sail control with the mast aft Prout type rig allowing easy access to all halyard controls. Also there is easy direct access to the engine under the cockpit floor.

The construction is basically WRC (strip plank western red cedar core) and epoxy glass for the hulls and decks with ply cross beams and cabin superstructure. There is an aluminium forebeam.

This cat was initially owned by a disabled person which helps explain the motorsailing aspect of what is a pure cruising catamaran. A design to suit a function.

The jpegs give the idea.

 

(fun fact about an older generation of Sonic drives (1980): they contained 9 litres of gearbox oil-2 imperial gallons!)

 

Nova Luxe took over Scape, a South African builder of power and sail cats in 2020. They are promoting the Scape 40 sports again which is a performance sailing cat by Simonis-Voogd catamaran design. The initial build Dual Flyer was used in charter and was for sale recently.

Dual Flyer is 39.3 x 21 foot with a weight of11250 lbs and an additional maximum load capacity of 8,800 lbs. The 53 foot aluminium mast (248 x 175 mm) with 10 mm caps, 8 mm forestay, 8 mm aft intermediates and 7 mm diamonds. The boom is a 165 x 101 mm section. The fore beam is 175 x 116 mm mast section with an 8 mm seagull striker wire. The rig carries a 603 square foot mainsail, a 387 square foot fore triangle and a 120 square foot storm jib. The length to beam is about 11 to 1. The draft ranges from 2.6 foot to 6.6 foot draft over the curved daggerboards. The two Yanmar 29.00hp diesels have a sail drive leg with 3-blade folding propellers. There are 6 x 100w flush mount solar panels.

The accommodation is good for an open bridgedeck cat. In each hull there is an aft cabin with queen size double berths. Forward in one hull is a galley area over a raised floor which has a centrally mounted diesel engine under it. The galley has for EG . Corian finish, 1 x Vitrifigo fridge, 1 x Custom Vitrifigo freezer, 2-Plate induction stove, 1 x Oven, 1 x Double sink with hot and cold faucet. Forward is a head and shower. In the other hull is a seating, navigation, entertainment area over a raised floor with engine under with a single berth forward or head forward. The open bridge deck can have a large seating and a very effective cockpit.

The construction is foam glass with vacuum bagged epoxy resin hulls, deck and bulkheads including the main crossbeams. All furniture is foam glass and is structural with all panels tabbed into the overall structure. (some production cats just have bulkheads “glued into hull slots”).

Performance. The centrally mounted engines should give an indication of the performance intention of this cat Best described as a very fast cruiser. The advertising includes this line: “Dual Flyer can be sailed short handed with all lines and winches controlled from one central location. She includes asymmetrical dagger boards to create lift for a faster pace overwater, easily reaching 25 knots.” I suggest under very good sailing conditions it may peak at 25 knots. I would suggest 300 mile days are possible with 10 to 15 knot averages more realistic.

An interesting fast cruiser that should be a good local racer. The jpegs give the idea.

 

Eric Lerouge designed the KSENIA 152 / VIK152 to be a very fast cruiser. Three have been built by amateur/professional combinations. The cat is big, light, has big sail area and reasonable accommodation. This is a classic Eric Lerouge design. He knows what makes a good fast cruising cat.

The VIK 152 we will talk about is 50 x 27.5 foot with a weight of 15,800 lbs and a displacement of 21,300 lbs. The 67.9 foot carbon fibre Axxon rotating mast (weight 515 lbs) and carbon fibre boom carries a 1000 square foot mainsail (6 battens), 670 square foot genoa, 968 square foot code 0 and a 2150 square foot screecher. The draft ranges from 1.8 foot to 8.8 foot over the carbon daggerboards. The 2 engines are Craftsman 40.4, 40 hp diesels. Batteries are a bank of 12V/200Ah with 400W solar panels and a Victron mppt charge controller.

From the numbers you get the hint the owner wanted a high performance cat. The accommodation layout reflects this. The owner only wanted 6 berths with an owners cabin in one hull and 2 double berth cabins in the other. There is a bathroom in each hull. The main saloon varies according to the build. This specific cat has a large galley an multiple seating area’s. The cockpit is large and focussed on sailing.

The build is Vinylester-Sandwich hulls with the deck being Polyester-Sandwich and the cat has Kevlar infused bulkheads. Wise use of materials to suit the structural components.

This a 300 mile day plus cat that would have peaks of over 20 knots. On a fun day sail you could average 10 to 15 knots or run faster than windspeed in lower winds. Yes, we have a fast cruiser that a couple has already done a tour of Europe and the Med.

The jpegs give the idea of an excellent design.