Multihull Structure Thoughts

Berret Racoupeau Designs team put up a design proposal for a luxury sailing catamaran. The Wind 130 design from this group will sail well if the design groups previous designs are any indication. The 20 foot draft, with boards down, indicate it will go upwind well and is intended to sail. But the size will allow a lot of very comfortable accommodation as well on this semi custom build. The first Wind 130 is supposed to be available in 2025.

The Wind 130 is 131.2 x 52 foot with an estimated displacement of 230 tons (515,200 lbs). Think this is a bit high, but EG this cat carries when the fuel and water tanks are full, 30,000 lbs of liquids on board. The sail area is unknown. The length to beam on the hulls is about 11 to 1. The draft is 20.5 foot with boards fully down. Power unknown, but think about two 200 HP inboard diesels as the minimum.

The accommodation is anything you want, but the game “hide and seek” is a real possibility on this cat. As the jpegs show, 5 very spacious double guest cabins with full ensuites and at least 3 crew cabins in one bow area. The galley in the port hull is massive and is restaurant quality. The main saloon has seating and entertainment everywhere as do the lower cockpit. The Jacuzzi is a nice touch. The 21 foot power boat in the floor of the wing deck is also an interesting approach to tender storage. The rear fold out swim platforms allow one to either get away or go swimming diving etc. If you cannot afford an island just buy this floating island.

The build is mainly aluminium but the interior will be luxury in lightweight foam glass with veneer timbers and fabrics that we mere mortals could only dream of affording. The electronics, plumbing, engines, deck gear (mostly electronic or hydraulic powered), sound insulation even the sound system acoustics are a design nightmare that will require a full time engineer handyman onboard to keep running to peak operational stands.

There is a reason why boats this large cost in the 10’s of millions. The jpegs give an idea.

 

This is about a monohull but equally applies to a multihull. Some multihulls have “wet” cores where moisture gets under the glass in a foam glass build and soaks the core. In a balsa sandwich this can be a real issue that requires replacement of the core to get back to the strength nof the original structure. In the case of a good quality foam core it is less of an issue for the core but the strength of the area is still compromised.

The amount of wet core also effects what repair is required. If the damaged area is just where the boat has hit a pier or sat on a small rock when sitting on beach the repair of the core and surface is a minor job. But if there is a major crack in the skin and water is able get between the skin and a large area of core you could be up for major repairs. Here is where the experience of the monohull boat builder comes in.

Morris yachts engineer Peter Smith noted that as cored hulls age, the chances of wet core increase. “These issues are becoming more prevalent in this vintage of boat,” he said.

Glendon Stanley, a composites and paint specialist at Morris, explained that the structural core of the yawl in the shop had suffered from water intrusion most likely as the result of multiple groundings. Whatever the cause, water ran freely through open kerfs in the core, traveling the length of the hull and contributing to portions of the outer skin delaminating from the core. Stanley said that, initially, a marine surveyor with a thermal-imaging camera revealed water in the hull and in areas where core kerfs were open. The yard crew drilled into the hull and found blackening in the kerfs where water had flowed. Morris’s crew has repaired other wet-core projects by flushing and drying the affected core, and then infusing the kerfs with low-viscosity resin.

In the yawl, tests indicated that all the core below the waterline should be replaced. Working in sections, the crew had stripped the outer skin, removed damaged core, and cleaned up the inner skin before laying a ply of 1708 fiberglass cloth impregnated with epoxy resin over the exposed Kevlar inner skin. The crew then vacuum-bagged new Divinycell H-130 closed-cell foam core (H-200 in way of the keel) into a layer of epoxy adhesive. Next, they infused the core panels to fill the kerfs with 170-centipoise resin, followed by six plies of fiberglass outer skin. Once all sections of the bottom are completed to that stage, two final plies of fiberglass will be applied over the entire hull before fairing and painting.

There is a point where you have to make an assessment of the value for money. In the case of EG a trimaran it may be easier and cheaper to build a new float than strip back an old float and then virtually rebuild it. In a cat a single hull bottom could be cut off at the waterline and replaced with a new foam glass bottom etc. In the case of the 57 foot monohull yawl, it required 600 manhours of work and thousands of dollars of materials to do the job. The owner loved that yawl.

If you are buying a second hand multihull get a good marine surveyor to do a real inspection of the boat for any issues under water, EG delamination, core separation etc. As the repair cost of delamination especially from a core could be substaintial. The jpegs give some idea.

 

Russell Brown designed and built a 20 foot power proa for his own use many years ago which was admired by many. (first 2 jpegs)

Gavin Brackett, had a chance encounter with Russell’s design was particularly inspired, sparking the question: “How do I build one?” When it came to Gavin constructing his own boat, he wanted to pursue a wooden vessel, much like the craft his family built, but also something unique, efficient and most importantly, fast. Fortunately, Paul Bieker and Russel Brown would come to develop plans for a 25-foot outboard-powered outrigger that checked all of those boxes.

Gavin named his power proa” Surf Scoter”. The power proa is 25.5 x 10.8 foot and weighed 564 lbs at launch. The draft at max load is 1.6 foot. The engine is a 25 HP 4 stroke outboard that provides 25 knots at peak speed with a half load and a cruising speed of 15 knots. At 16 knots in a seaway over an 8 hour run the proa used about 5.5 litres/hour or about 3 miles to the litre. Impressive.

The outrigger’s is to have water ballast system for exceptionally heavy winds and sea states. Using a gear pump so the ama can be emptied and filled from the comfort of the main hull, the outrigger will hold about 200 pounds of sea water ballast for added stability.

Construction Details Primarily 6 and 9mm Okoume BS1088 plywood, CNC-cut, with West System Epoxy sheathed with 200 gsm E-glass. Beams are bent layers of 5mm laminated fir wrapped with E-glass. Gavin glued the ama to its beams, and then bolted the outrigger assembly to the main hull using four stainless bolts, secured with G10 backing plates. This configuration essentially means the outrigger can be quickly retracted against the main hull, making the boat a perfect candidate for trailering.

As you will see in the jpegs Surf Scoter was a well designed and built craft that performs very well suiting Gavin's original intentions. The jpegs give an idea of an excellent craft.

 

A million views OM, must be a book in this surely.
All the best,
RR

 

redreuben thanks for the comments but Taylor Swift would probably get a million views in a day.. This is fun for me, not a profession, and the current designers and full time builders are doing a lot more interesting things than I have been involved in. I will continue here for a while, as books are not as popular as they used to be

 

Taylor Swift is of no substance, flattery was purely selfish so you carry on. But I would buy the book.

 

My suggestions on a book would be to set aside a fair amount of time for fact checks/proofreading. Depending on the source material it is natural for small discrepancies to arise in a almost daily column. Then there is collating the material, do chapters make more sense or is there enough for volumes? " Large cats, the discussions" etc....

 

you SHOULD compile it into a book! (& of course divulge your idendity...[you are not Shawn Arber, btw, are you?])

 

A little insite into Nigel Irens yacht designer and known as an “analog man”. Swedish multihull expert Torbjörn Linderson says: “There is something about working with a person who is “pre digital” and whose performance ideas come from a deep understanding of the yacht as a whole, rather than just numerically driven.” Irens is definitely an analog man who is self-taught and, like Dick Newick, a bit of a seat-of-the-pants designer, his skills are intuitive. “I’m just not a numbers man! I failed miserably at maths as a student. Design courses didn’t exist in those days, and even if they had, I’m not sure I’d have qualified.” Irens sketches his designs on paper and he can cut out the hull design with scissors and balance the template on the edge of a rule to confirm his ideas. He still makes models. How about Irens the eccentric? “I sometimes wonder if I am,” he admits.

In 1973 in a British pub a group wanted to win the £500 offered for the speed sailing event over 500 meters so 10 people paid £50 each (plus unofficial sponsorship from the BBC—most of the materials came from a set designer). The result was a proa with five solid wing sails arranged like a vertical Venetian blind with trailing edge flaps.” Christened The Clifton Flasher, she could only sail on one tack. Nigel helmed her over the 500-meter course at a fastest speed of 22.14 knots.

After this experience Nigel started designing larger boats with his first serious 60 foot cruising in 1977 followed by in 1980 Gordano Goose the 40-foot racing trimaran he built and raced. A list of other significant boats is below.

When Ellen MacArthur sailed into Falmouth after 71 days around the world record, Nigel hugged her in relief and exclaimed like a concerned uncle: “Don’t you dare do anything like that again!” Ellen’s verdict on Irens’s B&Q: “She’s in better shape than I am!” “Nigel is a purist,” adds MacArthur. “If he’s designing a boat to be fast it is fast, and if he’s designing a cruising boat it really does cruise. His boats all have identity, but what sets Nigel apart in my opinion is that all his boats have stunning lines as Nigel is also an artist. To top that he is one of the nicest people I have ever had the pleasure of working with, and I didn’t hesitate one second to put my life in his hands.” A very well respected man.

Nigel is 74 now and formed a design partnership with Benoît Cabaret a decade ago to create the later range of high performance racing and cruising multihulls with the occasional very good monohull.

Nigel liked the idea of lifting a sailing boat on to hydrofoils and only now real progress is being made in translating theoretical gains into tangible ones. The performances demonstrated by Oracle Team USA and Team New Zealand as they battled for the 34th America’s Cup was truly astonishing. It’s only a matter of time before future development work will allow a similar quantum leap in performance in ocean racing and eventually in cruising multihulls.

Nigel also commented “Interestingly, Michel Kermarec, a senior aerodynamicist for Oracle, showed us that a solid wing hardly pays. The lift-drag factor is spectacular, but it’s only on a very narrow band and not useful going upwind. A soft sail can still be pretty darn good. I’d love to do a foil-assisted, rather than foil-borne, freestanding rig.”

A history of Nigels designs between 1977 and 2008. There is more but I ran out of space.

1977 60-foot cruising trimaran Promenade built for Caribbean charter; still sailing in the BVIs today
1980 40-foot racing trimaran Gordano Goose built
1982 40-foot racing trimaran IT82 wins its class in Round Britain race
1982 50-foot racing catamaran Vital takes third overall in the Route du Rhum
1983 80-foot racing catamaran Formule Tag is built; in 1984 she sets new 24 hour record of 512.5 NM
1985 60-foot racing trimaran Apricot wins 1985 Round Britain Race with Irens and Tony Bullimore as crew
1986 75-foot racing trimaran Fleury Michon VIII takes first overall in Route du Rhum
1987 60-foot racing trimarans Fujicolor and Laiterie Mont St Michel launched
1987 40-foot Formula 40 catamaran Data General takes second overall in the Formula 40 Championship
1988 70-foot power trimaran Ilan Voyager wins Round Britain Powerboat record in 72 hours at an average speed of 21 knots with no fuel stops. 60-foot trimarans Fleury Michon IX and Laiterie Mont St Michel are first and second in the Carlsberg singlehanded transatlantic race
1990 60-foot racing tri Fujicolour II launched
1992Fujicolor II wins Europe 1 solo Transatlantic Race
1994ENZA New Zealand (ex-Formule Tag) wins Jules Verne Trophy as fastest boat to sail non-stop round the world, following a 74-day circumnav
1996 Three Irens designs—Fujicolor II, Region Haute Normandie and Biscuits La Trinitaine—win all three places in the Europe 1 Single-Handed Race
1998 115-foot power trimaran Cable & Wireless launched and sets a new round-the-world record, motoring 22,600 miles in 74 days
2002Bayer Crop Science built; it’s one of the first mutihulls built in Nomex sandwich carbon prepreg resin for lightness and rigidity
2004 75-foot trimaran B&Q Castorama built for Ellen MacArthur; a year later MacArthur sets a new solo round-the-world record of 71 days 14 hours
2007 105-foot trimaran Sodebo, designed for Thomas Coville to beat Ellen MacArthur’s solo record, is launched in Sydney; 97-foot trimaran IDEC 2 is launched for Francis Joyon and sets a new 24-hour solo record of 616 miles
2008IDEC 2 sets a new round-the-world solo record of 57 days, 13 hours, smashing the previous record set by MacArthur; Irens is appointed consultant to the Alinghi design team as they prepare to defend the America’s Cup. Sodebo breaks a new 24-hour record of 620.8 miles and establishes a new solo west-east transatlantic record of 5 days 19 hours.

The jpegs are examples of the range of designs that Nigel has done. He is a very versatile and skilled designer.

 

This is the K53 mk 2 =Three Legs III

Nick Keig also built ThreeLegs iv (VSD) and Legs of Man V -both catamarans

 

I like these pictures of the two 53 foot Keig trimarans from the Observer Magazine

 

A couple had a dream to live a life on the water in sunnier climes than Ontario Canada. So Ducan and Annie Muirhead decided to design and build a trimaran. A 105 foot trimaran. The build started in 1987 on the shores of Lake Eerie. In 1980 Cuan Law sailed as a shell with minimal interior to Gananoque where the interior etc was finished. Cuan Law then left for the British Virgin Islands via the St. Lawrence Sea Way, Nova Scotia, Bermuda. The tri then went into charter and 44 years later still be chartered. After sailing about two hundred thousand miles in the Seventies and Eighties, Annie and Duncan now spend most of their life ashore in Tortola, BVI, running the company.

Cuan Law is 105 x 44 foot with a 168,000 lbs (75 tons) with fuel and water. The103 foot masts of the stay sail schooner rig has a working sail area of 5,200 square feet. The main hull length to beam is about 8 to 1. The two 210 hp Caterpillar diesels drive two feathering propellers. There are 4 generators. The speed under power is 8-10 knots, the speed under sail is between 6-14 knots.

The accommodation is vast with 10 guest double berth cabins with ensuites on the main deck around the main saloon area which has a large amount of seating and tables. There is a bar on the main deck. The restaurant quality galley is downstairs in the main hull. On the aft deck is enough external cockpit seating and tables to seat the guests for meals. The toys include 2 sailing cats and 2 x 21-foot 115-hp tenders for diving and shore work. This tri is famed for its diving charter trips as the crew and diving equipment are all first class.

The build is mainly aluminum with ply etc being used for internals. House furniture is used for lounges etc in the main saloon. The strength of the structure was tested in the early build period with one of the coldest times of winter that had 5 tons of ice on her decks, not to mention the icicles hanging off her wing surfaces.

Cuan Law has been very successful in her roll as a charter tri over 40 years. The jpegs gives the idea.

 

Canada eh? It is a bit reminiscent of a Nicol Voyager on steroids. They didn't get help from Bruce Goodson/ Bruce Roberts did they?

Quite a platform with a long track record.

 

Cuan Law also had a sister ship called Lammer Law who was operating in the Galapagos Islands - my parents went on a cruise with her around the islands about 25 years ago, and they had a wonderful time.
When I tried googling her, the first three sites that came up about her were infected by viruses, but I think my AVG apprehended them ok.

This site is ok though -
Galapagos Islands - multicolouredplanet https://multicolouredplanet.com/Grundlefly/Galapagos_Islands

And there was a discussion about her on this Forum in 2013 - scroll down to post #217 :
Trimaran with accomodation in the amas https://www.boatdesign.net/threads/trimaran-with-accomodation-in-the-amas.45437/page-15

 

A story about 2 sister ocean racing trimarans designed by Nigel Irens in 1992. 'Bagages Superior’ was raced by Mike Birch successfully. Mike then sold it to another person in 1994 who entered the Transat double and capsized the tri, the crew and boat were recovered by a Russian ship. Crew returned but the tri “disappeared”. The Star La Trinite had a long and very successful racing career under a few owners and many names. Its longest known name was the ‘EDGE’. It is still racing in 2024 and giving a reasonable account of herself.

Star La Trinite (Edge) was originally a “Formula 40 class” design and is 40 x 38 foot with a weight of about 5,000 lbs. The tri is demountable for transport in a container. The 67.6 foot mast carries a 737 square foot mainsail, a 382 square foot jib and a 925 square foot Gennaker. The length to beam on the main hull is about 14 to 1, the float length to beam is about 16 to 1. The draft ranges from 3.7 foot over the central rudder to 8 foot over the central hull daggerboard. There are float rudders as well.

The accommodation is minimal at best, a couple of single bunks, seats, a minimal galley and navigation area and not much else. This tri was designed as a racer first anything else second. To emphasis the point there are 3 cockpits on this tri, one in the main hull and 2 “flying cockpits” at the intersect of the end of the mainsail traveller track and rear crossbeams.

Both the tris were full carbon fibre foam epoxy builds. They were vacuum bagged or autoclaved depending on the size of the component. The two tri’s were built in Dartington, Devon. Construction had made the jump to all carbon, female moulded, vacuum bagged composites. Campaign budgets were huge. Both the tris were “mini” versions of OMRA 60 tris and were very advanced for their time.

Both tris had structural problems with there cross beams (main cause of 'Bagages Superior' capsize) and Edges crossbeam problems in 2008. These were well built but light boats that had rig upgrades and new sails of EG carbon fibre construction that loaded up the Edge more. I am not surprised a few issues developed.

As for racing Star La Trinite was first in the 199 Around the Isle of Wight race in 5 hours 18 minutes, then went on to a series of local and transocean racing events like the Twostar etc. In the Rolex Fastnet Race in 2015 on The Edge and won the MOCRA Munster Trophy for first multihull under 50′ on elapsed time. It is June 2024, in the Tour of the Island of Sein it placed 7th/13 in Multihulls in a time of 7 hours and 2 minutes.

If you need an indicator of this tri’s capability in 2018 the then owner of the Edge did 306 nm between waypoints in 23 hours. He described as a “Pretty pointless exercise really”. I know many owners who would be thrilled to have a tri with such capabilites. Translation, peaks of 24 plus knots and daily averages of 320 miles plus are possible.

An interesting design that after 32 years is still delivering reasonable racing results. The jpegs give the idea.