Multihull Structure Thoughts

The University of Western Australia owned a custom built 33' Shark Cat with twin V6 OMC Seadrives which were rated at 220hp each from memory. T\hey carted this boat all over WA on a semi trailer behind leased prime movers. I had it in my yard for a couple of days in Port Hedland on their way to Lake Argyle in about 1987.

 

This is about a $1.3 million New Zealand dollar ($US790,000) boat of which the engines will cost about $NZ300,000 and at maximum speed use 400 litres/hour. You will be travelling between 47 to 52 knots depending on your option. You will be comfortable in your 3 double berth cabins and spacious main saloon as long as your running in smooth water.

The Profab 1200 is a Roger Hill designed outboard powered fast cruising cat. The Profab is manufactured in NZ by Profab who do mainly aluminium monohull and multihull power boats up to 110 foot. The Profab 1200 is 42.6 x 15.4 foot with a displacement of 26,200 lbs. The hulls are asymmetric with the flatter sides in the tunnel area. The draft is 2 foot. The 2 outboards are Mercury Verado 600 HP, 7.6 litre, quad-cam V12 engines.

Fuel economy becomes an interesting discussion. Your 1600 litres of fuel will be consumed at 400 litres/hour at 47 knots, at 32 knots (fast cruise) you will use 180 litres/hour and at 25 knots cruise 120 litres/hour. At minimum planning speed of 14 knots you will use 68 litres/hour. Multiply the fuel use number by $NZ2.30 to get the running cost. So, at 25 knots, you are spending $NZ278/hour ($US167/hour). At 47 knots (or 52 knots if you order the optional foil kit) you spend $NZ920/hour ($US552/hour) to get places. If you can afford the upfront price, I guess the fuel bills don’t matter.

Accommodation is 3 separate double berth cabins and toilet showers in the hulls. The main saloon has seating, a table, large galley and internal helming position. The aft cockpit is large and the outboards are quiet allowing you to enjoy the sunshine at a reasonable speed.

The construction is aluminium with 6mm running surfaces, 5mm topsides and a 4mm superstructure. The roof, however, is all composite, reducing the weight by about 50% and allowing for a slightly lower and softer looking profile. The Profab company specialises in alloy and the build is to a high standard. The Profab 1200 is a semi-custom build, so the interior layout can be changed to suit the owner’s needs.

An interesting very fast catamaran cruiser. I hope you can afford its running costs. The jpegs give the idea.

 

INCAT HULL CPV2099 / Electric WPC is a long name for the Incat 148E, roll-on roff-off passenger (RoPax) catamaran ferry for operating in hybrid modes, as well as a potential full battery operation at a later stage. The ferry is for transporting cars, trucks and passengers on up to 100 miles on regular ferry runs. The design was done by Revolution Design Pty Ltd (sub company of the builder Incat Tasmania Pty Ltd) and was initially done in collaboration with ABB.

The 148E as it is now known is 485 x 100 foot, weighs 2400 tonnes and has a draft of 13.4 foot. The hull length to beam is 22 to 1. It can carry 1200 passengers and has 5100 x 10 foot of vehicle traffic lanes to carry cars and/or trucks. Main machinery installations are for propulsion 2 x Podded drives of 5.0 - 9.6 MW. ESS (Zero emission configuration) Interim range extender 36 MW – 75 MWh which are 2 x CAT XQC Gensets + 10MW ESS Range (Zero emissions configuration). Maximum range is 100 nautical miles with 2 hour recharges at 10 MW – 20 MW. Speed is between 20 and 25 knots depending on powering options.

It would feature ABB’s Onboard DC Grid power distribution, ABB Ability Power and Energy Management System (PEMS), 800xA distributed control systems, a remote diagnostic system, and two Azipod® propulsion units enabling highly precise control and manoeuvrability maximizing efficiencies. In the first instance, the hybrid-electric propulsion solution envisioned for the Incat 148E will involve the vessel’s diesel engine charging a shipboard battery, whose output provides the flexibility in power management to improve fuel efficiency and cut emissions. When shore charging facilities are available, Incat-built electric ferries would make greater use of batteries, with project goals envisaging installed battery power of up to 30 MWh.

These high speed electric cat vessels can for a given number of passengers and cars can reduce emissions by 40% over conventionally powered ships for a given speed. As the cruise industry is finding, they produce twice as much pollution for a given holiday as a person who flies and uses land transport is only. In short electric ships/ferries are a real saving to the environment.

The jpegs give the idea.

 

This is about a large sailing cat with not much detail which will be built by Echo Yachts in Australia. Echo Yachts have also built a similar sized power catamaran which will be the main feature. First we will deal with the proposed sailing catamaran.

Dykstra Naval Architects are the designers of a full-custom 187 foot, twin masted catamaran sailing yacht with a 17,200 square foot Dyna rig (think Maltese Falcon) that will be built by the Australian Superyacht builders Echo Yachts. The yacht is commissioned by an experienced private client and is likely to be the world's largest sailing cat.

Dykstra Naval Architects is providing the yacht's exterior styling, layout and naval architecture. Detailed naval architecture and structural design of the aluminum cat will be done by the Australian firm One2Three Naval Architects. Echo Yachts has signed the build. The only jpeg available is below.

Echo Yachts and One2Three Naval Architects also designed and built a 184 foot power catamaran for an owner who wanted an improved version of his 180 foot power catamaran (will feature tomorrow). The cat will be used for charter, research work and private cruising. Charley 2 was delivered in 2023.

Charley 2 is 183.6 x 48.5 foot of unknown displacement. The draft is 10.7 foot. The 2 engines are 1,600 HP Caterpillars. The cat can peak at 17 knots but has a range of 3,380 miles at 12 knots. Accommodation is for 18 guests and 19 crew. The layout is not available but the few interior jpegs show a lot of space.

Echo Yachts builds mainly in aluminum but is capable of very high quality interiors and composites.

To give a feel of how big this cat is it has a few RIBs are aboard as well as a custom composite 39-foot (12-meter) power catamaran tender. This tender comes outfitted with sonar equipment to support wreck-finding and -diving missions. The cat tender further launches and retrieves via a platform aft. Plus, the platform lends an extra benefit for the crew. It makes it easier to access more of her aluminum surface for cleaning and maintenance.

The remaining jpegs are of Charley 2. I hope we get more detail of the sailing cat as it is built.

 

Charley is a 150 foot power catamaran that acts as a support vessel (yes, a support vessel) to carry toys etc for the White Rabbit fleet of 3 power monohulls from 182 to 278 foot and 2 power trimarans of 202 foot and 276 foot that are available for charter. Charley carries such items as tenders and water toys like a 40 foot custom built carbon fibre power catamaran, a 23 foot Castoldi jet tender, a 20 foot Pioner multi, 4 X Yamaha wave runners etc and a Decompression Chamber for the divers. It also has a helipad for those who want a high view of areas of interest.

Charley is 150 x 46 foot with a length overall of 169 foot if you include the aft tender and loading ramp. The displacement is unknown. The length to beam on the hulls is 15 to 1. The draft is 10.5 foot. The 2 engines are Cummins QSK60 rated at 2013kW @ 1900rpm (about 2550 HP). The maximum speed is 20 knots, the cruise speed is16 knots with a range of 2,500 Nautical Miles. The Naval Architecture is by LoMocean and the builder is Australian superyacht builders Echo Yachts.

The accommodation layout can be seen in the jpegs and Charley can accommodate 18 guests and 13 crew. Yes, Charley can be chartered independently if you cannot afford both the 276 foot power tri and Charley for a few weeks (think $1 million plus charter fee).

Charley is the largest resin infused catamaran ever built in Australia. The design and construction of Charley took two and a half years from inception to handover and resulted in a very high standard of finish thanks to the latest 3D design and 5 axis mould cutting and vacuum resin infusion techniques employed by the shipyard. Echo in-house design and manufacturing have over 240 skilled staff plus they use outsourced suppliers etc. These boats take time and big money to build.

To give an idea of the vessels Charley supports/shadows the last jpeg is of the 276 x 64.3 foot “White Rabbit” which is the largest superyacht built in Australia and the largest aluminum tri-hull superyacht in the world.

The jpegs give the idea.

 

The final 2 parts of the Echo Yacht builds of the luxury charter trimarans that the Charley series of cats support. The first one will be the 84 mtr White Rabbit Golf. The design was done by One 2 Three Naval Architects and the construction and part of the naval architecture was done by Echo Yachts. Golf was delivered in 2018 and refurbished in 2021.

White Rabbit Golf is 276 x 66 foot with a loaded displacement of 1340 tons (3,001,600 lbs). The length to beam on the mainhull is 10 to 1. The draft is 14.3 foot. Main Electric Propulsion Plant 4 x Caterpillar C32 Gensets, V-12, 4-Stroke-Cycle-Diesel, 940ekW, 1800RPM, 690V, 60Hz. 2 x Caterpillar C18 Gensets 690V 60Hz, I-6, 4-Stroke-Cycle-Diesel, 550ekW, 1800RPM, 690V, 60Hz. Electric Motor 2 x Kongsberg / Stadt 690 volts 2100kW electric drive motors Gear Boxes ZF 7661. Tail Shaft 2 x 47 foot x 185mm diameter. Propellers 2 x 6.5 foot diameter 5 bladed Rolls Royce Controllable pitch propellers. Think about the cost of the stainless steel propeller shafts and propellers alone. There are several fore and aft water jets for control and 4 “control” fins to minimise the tri’s motion.

The accommodation is in the jpegs but basically Golf has 11 cabins and two master staterooms can comfortably accommodate up to 22 guests. In addition, she has a crew of 34. There is an internal lift for clients who don’t want to climb the 4 set of stairs to reach the top deck. The saloon, galley etc is just pure luxury. There are “toys” on board but the serious toys are on the support vessels.

The construction is mainly Aluminum with composite materials as required. The internal fittings are a combination of composites and high quality finishes.

The peak speed 18 - 19 knots at 1,190 tonnes displacement. The cruise speed is13 knots. The range at 12 knots is 4,658 nautical miles (no reserve), 4,235 nautical miles (10% reserve). The fuel tanks hold 166,000 litres of fuel oil. Translation this tri only uses 35 litres of fuel per nautical mile at cruise speed.

This is a very successful charter vessel that only a few will enjoy but it give a guide as to what is required to get a very effective power multihull for long distance travel. The jpegs give an idea. The first jpeg is what the owner wanted and the remainder is what was built.

 

The power charter trimaran White Rabbit Echo preceded the White Rabbit Golf. The owner, Goh Cheng Liang (Singapore), had the idea of a power trimaran after several monohull power boats. The owner went to Australia’s North West Bay Ships Pty Ltd for the design (with Sam Sorgiovanni) and construction of the trimaran Echo in 2005.

The White Rabbit Echo is 202 x 51.5 foot with a weight of 382 tons (855,680 lbs) and a loaded displacement of 520 tons. The length to beam on the main hull is 11.5 to 1. The draft is 10.8 foot. Main Electric Propulsion Plant are 2 Caterpillar 3512BTA, 1566kW @ 1880 rpm Gear Boxes 2 off, ZF 4660 reverse reduction gearboxes driving h7 duplex stainless steel propeller shafts 31 foot x 164.6mm diameter and 5-blade Bruntons custom propellers. There are bow and stern thrusters. Echo’s peak speed is 19 knots and cruises at 12 knots. Echo has 117,000 litres of fuel with a range of 5000 miles at 12 knots cruise using 23 liters/nautical mile.

Echo’s accommodation has 5 guest cabins and a master cabin she can accommodate 16 guests. She also has a crew of 16. On her upper deck is a karaoke and piano lounge while the dining room is situated on the main deck and seats 14. On the sun deck you will find a Sky Lounge with a glazed panel sweeping overhead. A passenger lift connects several decks. Echo also features an aft dive room with a swim platform and is fully equipped with dive compressors and dive equipment. She also has a 27ft Yamaha fishing tender as well as two 19ft jet tenders, two jet-skis and an assortment of water toys.

Echo’s basic hull and deck structure is aluminum. The interior fitout ranges from composites to EG teak and marble where required.

A few points. The 202 foot Echo is less than half the displacement of the 278 foot Golf. Echo has 3,132 Kwin engine power, Golf has a total of 3,760 KW of engine power. The main hull of Echo has a 11.5 to 1 length to beam, Golf has a length to beam of 10 to 1 on the main hull. Both tri’s can achieve the same top speed and cruise speed. Translation, the 278 foot Golf, is a later more efficient design requiring less power relative to its size that the 202 foot Echo.

The jpegs give the idea.

 

The Trifly day sailing trimaran was developed and built around 1990. The aim was to have a reasonable performance cruising tri for a few people just to get on the water. The tri can be disassembled for trailering.

The Trifly is 14.75 x 9 foot with a weight of 164 lbs with the main hull weight of 74 lbs. The 23 foot 2 part 52 mm aluminium mast carries a 104 square foot of sail area. The float is 8.1 foot long. The mainhull length to beam is about 6 to 1. The draft is about 2 foot over the mainhull centreboard.

The tri is designed to be crewed by 2 people but is easy to single hand due to the simple wishbone boom rig.

The construction is solid fiberglass with ribs and some supporting frames. The cross beam tramp support structure is aluminium tubes.

The performance was described as a fun machine thast could sail to windward well when the crew sat out on the floats.

The jpegs give the idea.

 

I hand one. Problems..ok but problems

 

A short one about a cute little power cat that most can afford. The 11.3 foot Ripwave is the design and initial build of one man who wanted to have some fun on a minimal budget. Ripwave Boats are now manufactured by Clearwater Hydrofoils LLC.

The Ripwave is 11.25 x 4.5 foot with a weight of 170 lbs and a displacement of 800 lbs. The draft is 75 mm empty and 130 mm when at full displacement. The hulls are shallow V planning aft rising to a sharper V at the bow. The hull length to beam is about 7.2 to 1. The power is a 5-10hp short shaft outboard. Initial testing had an 8 HP outboard doing 22 MPH but the 10 HP fully loaded rigs cat do about 20 MPH.

Now we come to the qualifications. This is not an open ocean boat. Smooth to rippled water only in EG bays, lakes and rivers. You can carry a reasonable load but you need to load the cat sensibly to maintain a balanced craft, not 3 people at the bow try to go fast.

This cat is an excellent platform for fun, fishing etc and has some storage area for stuff if you want to take some camping gear etc.

The build is listed as moulded fiberglass. I suspect the majority is solid glass with some core material.

The jpegs give the idea.

 

If you are capable of TIG welding and want a strong dingy that will service you as your tender, then this is a possible option. It is strong but will be a little heavy but it can be sailed, rowed or motored to get you around. The first one was a tender on a yacht that went global and as you will see in the jpegs it went to a few interesting places.

The Aludink is 11.25 x 4.65 foot and carries a used mirror dingy rig of 55 square foot. The Aludink can have a 4 to 15 HP outboard. There are buoyancy tanks that can support the dingy and outboard motor if you were to capsize. The toughness of the aluminum construction was a major asset. There was no need to worry about landing on any beach, or coming alongside strange docks etc.

The carry capacity is 2 crew and some stores but the dingy has carried 6 people and still had enough freeboard to cross a lagoon. No mention of sailing qualities but the jpegs indicate reasonable abilities.

The construction is aluminum. The sides and bottom are 2.5 mm 5052 H-34 marine grade aluminum. The transom is 4.5mm aluminum with some additional framing for the outboard and and kickup rudder. There is a forward bulkhead, buoyancy tanks which strengthen the gunnels and hull bottom. The keel line adds to structure. A daggerboard case is welded to the keel line.

If you have rocky shorelines or need to deal with wharves with mussels growing on them this may be the dingy for you.

The jpegs give the idea of the dingy and its construction.

 

The DUO 480 Adventure is an open bridgedeck variation of the DUO 480 C cruising catamaran designed by Bernd Kohler. Bernd’s DUO 480 C (Jigsaw is another name) is one of his more popular designs and has been featured in this thread. The DUO 480 Adventure should be even faster and simpler to build but not have as much internal room.

The DUO 480 Adventure is 15.75 x 7.9 foot with a weight of 314 lbs and a maximum displacement 1,010 lbs. The 2 windsurfer carbon fibre masts (slightly modified) can be rotated to furl the biplane rig mainsails. Each mainsail is 86 square foot for a total sail area of 192 square foot. The length to beam on the hulls is 13.5 to 1. The hulls are asymmetric and do not have any boards. The hull provides the lateral resistance. The DUO is fully trailable being able to be launched the same as beach cats.

The build is plywood and timber and has been simplified to allow a rapid build. All you need is EG a flat garage floor and you will be able to build the boat. The material list for the cat is:

The cat basic structure is 6 mm ply for planking and bulkheads, 8 mm ply for underwing and keels, 4 mm ply for rudders and 12 mm ply for rudder cheeks. The rudders have a small amount of carbon fibre in them. All exterior surfaces are covered by 220 gsm glass and epoxy. The timber is 25 x 25 mm for stringers and other reinforcing. The cross beams are 90 mm OD with 5 mm walls. The mast support tubes are 60 mm OD with 5 mm walls. The build time is claimed to be 300 hours if you know what you are doing, but this design would be a good starter boat as a first run at boat building.

The accommodation is minimal as the hulls are 1.15 foot at the waterline resulting in a storage or a very slim berth is all that is possible. This is basically a fast fun day boat that you can store your camping gear in the hulls then set up a tent on the bridge deck for overnight stops.

The performance will be surprising good if the Duo 480 Adventure emulates or exceeds the performance of the 88 lbs heavier Duo 480 Jigsaw cruiser.

The jpegs give the idea.

 

This is about a guy who builds in Brisbane, Philippines or Cambodia depending on which “source” you buy the boat from. Tim Mumby is a real person who designs and builds real cats and I have seen his work. He does a good job and can deliver a 48 foot aluminum cat in under 2 years if required. Tim employs local workers and craftsman who are well trained and supervised to produce a good quality of finish to this cats.

The Mumby 48 is 48 x 24.6 foot with a weight of 13,700 lbs and a loaded displacement of 19,500 lbs. The 61 foot aluminum fixed mast carries a 850 square foot main of 10 oz dacron, a 516 square foot genoa, a staysail 107 square foot, a Screecher of 970 square foot and a spinnaker of 1560 square foot. The length to beam is 12.2 to 1. The draft ranges from 1.8 foot to 5.9 foot with the daggerboards down. Underwing clearance is 2.95 foot. Engine power required is 2 x 30hp shaft drive with folding propeller. Hull Wetted surface area including rudders 413 square foot. LCB 25.35 foot aft from waterline. Total drag at 9kts 622 lbs.

The Mumby 48 is a semi custom design that can have a variety of layouts to suit the owner. So, there is 3 of 4 double bert cabins with toilets in the hulls. The main saloon has a dinette, a large galley and entertainment area. The large cockpit allows easy sail handling.

The construction is mainly aluminum. The structural hulls, bulkheads, main deck, superstructure constructed using certified (DNV or similar class) marine grade 5083 aluminum. Designed by Tim Mumby. Hulls are 4mm 5083 aluminum. cabin top, decks are 3mm 5083 aluminum. There is a lot of stringers and frames in this cat to support the light skin. As with all aluminum builds these cats have a lot of small easily formed parts that can be quickly assembled into a total structure.

The Mumby 48 is a fast cruising cat that has no problems averaging 10 knots. I will quote the Tim. *Our average day run on "Trim" after the last 32,000 n miles {circumnavigation via south Africa} was 238 miles / 24 hours. top speed reached a few times was 22kts.”

A very solid fast cruising cat that is well proven. The jpegs give the idea.

 

Hi OM, I had lunch and a couple of beers with Gary last week. While getting on a bit he is still sharp as a tack. I'll PM you his email.

 

This was going to be a simple expose of a 42 foot proposed cat but it took a detour. Uwe Jaspersen conceived and designed the Moxie Yachts’ M37 and built it at his company, Jaz Marine, in Cape Town, South Africa. In his career, Jaspersen has worked on high-tech custom Gunboat cats, and as a specialist in composite structures and at other companies. Uwe passed in about 2020 and only the 3D renders of the 42 foot cat exist and are the final 3 jpegs.

The Moxie M37 also known as the Island Hopper 37 is 39.5 x 22 foot with a displacement of 6065 lbs. The 54.5 foot rotating wing mast carries a sail area of 555 square foot in the main and foretriangle. The forward jib can be self tacking. The initial jibs were hanked on but a roller furling system was optional. The draft ranges from 2.25 foot to 7 foot over the asymmetric daggerboards. The engine power is two Lombardini 20 HP saildrives.

This cat is a performance cruiser (remember he worked for Gunboat as a composite specialist) and as a result the hulls are thin, the boat is light and the layout is orientated to sailing first with the accommodation fitting around the performance requirement. There are 2 double berth cabins with associated toilet/showers another single berth and a galley in the hulls. The bridge deck has a forward cockpit with all sail controls around the mast and 2 excellent “helming” seats. Aft of bulkhead is an optional open or closed seating area with a table and a small aft cockpit. The layout is different but practical for a fast coastal cruiser. There are canvas/vinyl forward and roof coverings.

The construction is mainly foam glass in vinylester resin.

The performance in testing when the boat was not overloaded showed the cat was capable of wind speed or exceeding it up to about 15 knots. The asymmetric slight C curve daggerboards help going upwind and provide a small amount of additional stability. This cat was never designed to have EG airconditioning or toys etc on board. It only has 200 litres of water tankage etc. Weight really is the enemy of this cat if you wish to have the high performance on offer.

The jpegs give the idea. The final 3 jpegs are of a design that I suspect may have gone into production if Uwe had been with us longer.