Multihull Structure Thoughts

Bon Pelley Enterprises built this 70-foot aluminum displacement catamaran in 2004 as a Canadian vessel designed to navigate safely in the rough seas of Newfoundland doing Pink Shrimp fishing. In 2015 a university purchased the cat, lengthened it to 90 foot and converted the cat into an exploration vessel. In 2020 she was sold again to a private owner and upgraded for remote marine exploration and diving. The yacht has also been designed to be self-contained, with easy access to all the mechanical functions of the vessel and the duplication of all key machinery. The initially cost $3 million (2004 money), the conversion cost over $1 million and the cat is now available for sale at $2 million.

The cat “Rogue” is 90 x 29.9 foot displacing 140 tons (313,600 lbs). There are trim tanks (15 tons of salt water) to ensure a balanced vessel under various loads or weather conditions. The length to beam on the hulls is 10 to 1. The draft is 8 foot. The engines are 2 x 400 HP inboard diesels, NTA855, Cummins. Fuel tanks total 45425 liters (12,000 gallons). At cruising speed, the cat can sail 6000 miles. Peak speed is 14 knots. Aft of the bridge is solar panels that produce about 2.5 kw of energy.

The layout is in the jpegs below, but the cat has 3 gest cabins, 4 toilets, a large galley and lounging area internally. The deck house and deck space is very large as are the storage areas (previously fish storage tanks).

Why the interest in this design? Comments like this “On her maiden voyage the owners took her through 18' to 22' seas on the bow and on the stern. Speeds reported while in these seas, on the bow 8 to 10 knots and when on the stern 12 to 14 knots. They report that she was comfortable in all conditions.” Rogue was built as a 70' to Canadian offshore fishing aluminum cat built to standards and has double framing in the bow sections. She was operated as a fishing vessel until she was sold to the University and converted to a research vessel and recertified for research uses by Transport Canada. The bulb bow shape and forward deep V bridge deck shape forward would significantly help going into 20 foot plus seas.

The jpegs give the idea of an interesting design.

 

I'm sure someone is composing a furious missive about windage and inadequate bridgedeck clearance.

There's also something else I can't quite put my finger on ...

 

Reminds me of a cat that featured in several Inside Multihulls and Multihull World magazines - probably late last century. I recall she was German, built of strip planking, and may have had a name beginning with P?

She was built keelless with rockered dory hulls that provided enough lateral resistance to make way to windward, but the idea was that if hit by a wave she would skid sideways rather than tripping over her keels... There was the story of her rounding Cape Horne, and (I think in the same story) she proved the theory and avoiding capsize.

I had a quick look under the house, but the pile of magazines was too daunting to start flicking through.

Does this ring bells for anyone?

 

All At Sea was this the cat from Page 16 Multihull Structure Thoughts> Fallado is an interesting cat designed by Harm Venema and built 1990. LOA 44 ft BOA 24 ft Bridge deck clearance 0.8 metre Draft 0.7metre Main 48m2 Genoa 45m2 Gennaker 80m2. The design and build contracts said the boat had to be capable of sailing around Cape Horn. The boat has sailed around the globe via the four Southern Capes. This is the toughest boat for its size I know. Fallado's has flat bottoms and is constructed as follows:
- a superstructure built with West System. One inch duraKore (a sandwich of cross grain balsa and 1.5 mm hardwood on either side) sheathed in fiberglass and epoxy, 2000 gsm glass on both sides with Kevlar on the bottom and in stress areas.
-a solid base to the hulls built up from 5 layers of 8mm strip planked cedar for a thickness of 40 mm with 2000 gsm glass and Kevlar layer. This is reinforced -five bulkheads, the three main ones are 82 mm thick, 8 mm plywood either side with internally framed 50 x 66 mm timber and foam. The main bulkhead is reinforced to allow for 40 tons of load.
-the bridgedeck is built in the same way, 82 mm thick, 8 mm plywood either side with internally framed 50 x 66 mm timber and foam.

 

This item is about a home designed and built power catamaran. Simon and Anna Ganley wanted a power cat for exploring parts of New Zealand. “It had to be reasonably fuel-efficient, comfortably fit our family of four and fit within a 12m marina berth,” said Simon. Simon’s a civil engineer with a solid background in GRP composites. So, 5 years later after working on average 15 hours per week (about 4000 plus hours) Simon and Anna produced the GHB power cat Makédo. It took another 6 months to have the cat professionally sanded filled and painted (part time by the painter).

Makédo is 35 x 15.7 foot with a weight of 7,650 lbs (including engines) and a displacement of 9,400 lbs when loaded for Xmas cruising. The hulls a semi displacement with a length to beam of 14 to 1. The draft is 1.3 foot. The underwing clearance is 2.8 foot. The engines are 2 x Yamha F60 outboards. The cruising speeds are between 12 to 15 knots. The fuel capacity is 380 litres. Makédo’s equally happy at displacement speeds of around 7 knots and tops out at 20 knots. Fuel consumption at 14 knots is 17.8 litres per hour, both engines, dropping to 15lph at 12 knots. The range at 12 knots is over 300 miles.

The accommodation is an open plan layout. The hulls are narrow so only have tanks in them. The bridge deck has a central helming position forward with a double berth either side forward with about 4 foot headroom. Aft of the helming position is a galley on the port side and a dinette on the starboard side. Beside the dinette is a separate toilet that is entered from the cockpit. The cockpit is an integral part of the living space connected by a large glass door.

The build is composite. Makédo’s construction is a foam-cored, epoxy sandwich: Corecell foam for the hulls and Divinycell for the bulkheads. The hulls are laminated using triaxial glass, with biaxial for the bulkheads. Carbon fibre was used strategically, such as where bulkheads joined the hulls, the chamfer panels, the cabin-top and window mullions. The hulls were laid up in a single set of half-hull-shaped female MDF moulds battened with pine stringers. Only one set of half-hull moulds is required; they’re reversed 180 degrees for the second set of half-hulls. Most of the interior can be installed before lifting the half-hulls from their moulds, which helps keep the designed shape. Joins are located on the centrelines rather than the gunwales. Most of the laminating is done horizontally and therefore assisted by gravity.

The boat was assembled in the backyard from essentially a giant kitset. The four half-hulls (two inners and two outers) were glued and glass-taped together in pairs to create the twin hulls. These were then glass-taped to the bridge-deck, followed by the cabin sides, cabin-top and window mullions. The hulls were canted inwards by five degrees at gunwale level, which shortened the width of the bridge-deck by 180mm.

This cat is a very impressive home design and build that has fulfilled its design intentions of its owners very well. Well done Simon and Anna Ganley. The limited jpegs give part of the idea.

 

The F 22 was a personal project for Ian before his death in 2017. The project had built 20 plus F 22 before the moulds etc were sold after Ian’s untimely death. The plan rights went to a USA person and company that now has legal issues to contend with, so any plan sales are very uncertain. The Farrier plan portfolio is a very small part of the disputes, and I do not expect any resolution in the near future. Result there are builders with partially built F 22 that cannot complete the projects because plans for cross beams were not included and the cross beams were to be purchased from a third party company. The F 22 was a brilliant design which had all of Ian Farriers acquired knowledge applied to it.

The F 22 was 22.9 x 18.1 foot (can fold to 8.2 foot) with a weight of 1,300 to 1,500 lbs depending on the materials (there is a full carbon F 22 that weighs 1075 lbs). The displacement is 3080 lbs. The 31 to 35 foot mast (depending on sail area and mast materials) carries between 328 square foot to 389 square foot of sail area in main and jib depending on mast chosen. The draft ranges from 1 to 4.9 foot over the slightly offset daggerboard in the main hull. The outboard can be a 6 to 8 HP.

The main advantage of the F 22 was it had more room than a F 24, was lighter, had more beam and larger floats. In short, a more powerful tri than the F 24 that was optimised for sailing and trailering. The problem was it ended up being expensive for a “22 foot” boat. This was mainly due to the structural and build costs. The foam core sandwich construction throughout had double bias or bi-axial glass fabrics. Carbon fiber is used selectively in highly stressed areas, while main hull keel is reinforced with Kevlar, both sides of core. This helps stiffen the hull for rig loads, plus is an excellent barrier against hull penetration should boat go on rocks. Beams are a carbon/glass composite, with multiple layers of carbon fiber unidirectional, top and bottom. Fully resin infused with a vinylester/epoxy resin to optimize structural properties. There is an F-22 weighing just 480 kg, built completely in carbon epoxy by Melvest Marine.

The sailing qualities are excellent. The peak speeds achieved are 20 knots with averages sometimes as high as 10 knots. In winds below 5 knots it performs well but once winds exceed 5 knots the F 22 starts to sail very well on all points of sail. As Sail magazine said in 2019, "Under sail, in near perfect conditions, we easily hit 7.5 knots and occasionally just over 8 sailing hard on the wind in just 10 knots of breeze. Bearing away and unrolling the screecher our speed shot up to 10 then 11.5 knots, eventually touching 14 knots”. It is a very high performance cruiser racer.

The jpegs below give an idea of the F 22. The PDF’s will give an idea of the shape.

 

Offshore NZ 1100 HTC is a New Zealand design (Dan Leech) and built (Offshore Boats) power catamaran dive and fishing cruiser. It is an excellent performer with enhanced fuel efficiency thanks to hydrofoil between the hulls and has a spacious cockpit with good shelter and good accommodation for weekend stays.

The 1100 HTC is 36.1 x 12.6 foot and weighs 16,800 lbs and can carry up to 16 people which means with full tanks and engines a displacement of around 24,000 lbs. The draft is 1.5 foot. The engines are 2 x 350hp Yamaha V6 outboards with 2 x 400L fuel tanks (can take 4 x 500L). Cruise speeds can be from 18 knots to 32 knots. The range at 32 knots cruise is 350 nautical miles. The maximum speed is 44 knots. The foil between the hulls helps the fuel efficiency. If you use the optional 4 x 500L fuel tanks you can get an 800 nautical mile range.

Th accommodation is a double berth cabin forward on one side and a utility room aft. In the other hull is a toilet shower area forward and a single berth aft under the saloon dinette. In the main saloon is a forward helm position then a galley to port with a dinette to starboard. The aft cockpit is connected to the main saloon by large glass doors.

The structure is aluminium built to survey standards. This means it is strong and capable of being driven hard in rough conditions.

To give an example on 1 boat test to a 70 mile away offshore location “There was still a good metre and a half (5 foot) of swell running and quite confused water between the Heads. With a long way to go, we pushed through the slop at around 25 knots, experiencing a dry and mostly comfortable ride, even with the seas on the nose – a catamaran’s least favourite angle of attack. Dialling back the speed a little avoided the odd hard landing we experienced coming off the back of a particularly large or steep wave. Fairly soon the islands were behind us, and the sea state became more regular, allowing Outahere to cruise at 25-plus knots again in comfort.”

Dan Leech has designed many other power catamarans with mainly planning hulls from about 6 to 12 metres built in either aluminium or composite. All his cats work well in rough water around NZ and elsewhere.

The jpegs give the idea of an impressive power catamaran.

 

This will be a 2 part item on a group who wants to advance yachting as they have done for 150 years. The group wanted to build an ocean racing sailing trimaran that could peak at 55 knots and maintain 40 knot averages. A dream you say, they have only spent 3 years and 200,000 work hours on the project so far. Gitana’s team (backed by the Rothschilds) are producing this tri at La Base, a former U-boat submarine base at Morbihan, France.

Gitana 18 is 105 X 75.5 foot with a displacement of 43,600 lbs. Mast is a carbon fibre wing of 121 foot that carries a Sail area downwind 6,780 square foot and an upwind 4,844 square foot. The rig can be deflected up to 35 degrees if required. The draft is 13.7 foot over various foils, rudders etc.

Now I will talk about the concept, hulls, build and rig. The foils supporting this tri and the reason they hope tri will hit 55 knots will be discussed tomorrow.

Gitana 17, the previous Ultim launched in 2017 was the first giant tri to take flight, and already has won most things. “What we’re doing here is really on another level, but it’s also going to be a risk,” explains project manager Sébastien Saison. “If we had wanted to be 100% sure that we’re going to win the next Route du Rhum in 2026 we would have gone safer. It would have just been a bit of an evolution. But we know that’s not the future.” It was the opportunity to do something extraordinary that drove the project.” “Ariane de Rothschild was quite clear about it: if they invest, and if we are to do a new boat, it has to be disruptive. It has to be another level up,” recalls Saison. Ariane de Rothschild was less interested in media exposure and race wins.

Gitana 18 is conforms to the Ultim rules and is built from composite, high strength carbon, specialised foam and Nomex, high strength epoxy with the 80% done in autoclave at CDK Technoloiges in Lorient. The structure was designed in cad/cam and FEA technologies with very little prototype testing. If there was any doubt about the possible success of the structure specialised software was developed new structural analysis of the overall structure. FEA is identifying load paths that were not expected and would not have been easily found by conventional build and test approaches. This became very important in the foils developed for the Gitana 18.

The hull shape is based around a foiling tri. The hope is the tri will off in winds over 10 knots (with a boat speed of 20 knots), so Gitana 18 will be sailing on its hulls in light airs. The main hull is length to beam is 26 to 1 with a round bottom and floats length to beam is 22 to 1 with a near flat bottom. This configuration with a light displacement and 4,844 square foot of sail upwind will sail faster than the wind (over 2 times) without foiling.

The rig is a 121 foot carbon fibre wing, shipped over from Southern Spars New Zealand, which has an impressive amount of flex. When you are building speed and power to take off, particularly in lighter airs, you need camber in your rig. But when in flight mode you need it flattened off to depower. The solution is a mast which can be bent, with the spreader angles flexing by up to 35° to create camber in the middle of the section. Rams control the power – one on each spreader – in a system which can be handled by a solo sailor, rather like cranking on the Cunningham on a dinghy or windsurfer rig. Sheet loads in this rig can be up to 14 tons (31,500 lbs) which requires very powerful winches and very strong gear.

More tomorrow. The jpeg give the idea of the hulls and rig of the tri. Foils tomorrow.

 

Part 2 of Gitana 18 sail racing trimaran Ultim. Today we will focus on the foils which will be the reason the tri will hopefully peak at 55 knots and average up to 40 knots when racing.

Gitana 18 is 105 X 75.5 foot with a displacement of 43,600 lbs. Mast is a carbon fibre wing of 121 foot that carries a Sail area downwind 6,780 square foot and an upwind 4,844 square foot. The rig can be deflected up to 35 degrees if required. The draft is 13.7 foot over various foils, rudders etc.

On previous Ultims the foils are generally C foils on the floats with T rudders on all 3 hulls. Gitana 18 will have AC monohull type T foils that can fold up on the floats, a central hull daggerboard with a T foil at its base and Y shape rudders on all 3 hulls. Each foil structures can be adjusted with either flaps on the trailing edges, height adjustable and angle adjusted as required.

Why the development? “When I reached 37 knots on Gitana 17, all the appendages started to cavitate. That means lots of drag and damage on the foils. They degrade very quickly. It’s a nightmare,” Caudrelier explained. “We pushed the limit with a second generation of foils up to 40-42 knots. But in surfing conditions sometimes you can’t stop the boat. You have a big wave, plus a gust, and you go to 45, 47 knots – and then all the boat vibrates, and you know you’re damaging them. You know that at the end of the race, you’ll have lost 10%, 20%, even 30% of the performance of the boat because of degradation. It starts to impact the paint. Then it goes through to the carbon. In the end, you can break the foil because you’ve lost skin on skin. At the end of the race around the planet, I was sailing at 70% of my performance in perfect conditions because the foil was completely destroyed.”

OK. All you need to do is develop new foil shapes to handle 55 knots, change the structure to handle the loads, develop new software to model the foiling characteristic, strength of structure and load paths etc. Simple. First contact the designers of F50 foilers with peak speed is 104 KPH (55 knots), next speak to the AC mono foilers designers who use folding T foils then do more research. Starting to understand the 3 year design build cycle?

The main foils are in the first jpeg. The concept is a high speed T foil that can be fold completely out of the water as required. The control rod can be adjusted to alter the foil angle of attack and the flaps for lift adjustment. The central hull daggerboard has a T foil on the bottom for lift. But the real change is the height adjustable inverted Y shaped rudders.

The Y-foils alone can be canted, raked, and each wing has independently adjustable flaps on the trailing edges. “You have to change the trim of the [foil] depending on sea state, because the sea state makes a big difference in speed,” explains Caudrelier. “So, if the sea state is flat, the wing is horizontal. If the sea state is larger, we have to put it more vertical because it helps when the boat accelerates. The boat starts to fly higher because the foils lift more. Then part of the wing goes in the air, so the foils lift less.” This is a very complicated foil structure to suit a complex sailing environment.

This is like FI motor racing where an incorrectly placed decal can alter the aerodynamics of winning race car. In Gitana case either the sailor or a computer is going to have to adjust the foils to suit the conditions frequently to optimise the performance of the tri.

There is more to this story but I think we need to see if Gitana 18 is capable of getting near the performance level promised. The information learned so far has been very interesting.

 

You're a phenomenal wealth of information and intuition. Yeah, I don't know why I had a "P" name in my mind. Do you know if she's still doing what she was designed to do?

 

The Gougeon 32 and Farrier 22 are probably my favorite trailable multihull designs - but I must point out that the first photo in your post is (I think) F32sr "Jailbreak"....

 

All at sea. Fallado was still sailing in about 2022. She was put up for sale recently as the owners wanted to try living on the land after sailing the globe for a couple of decades. One very good cruising catamaran. A web site about Fallado is:
Catamaran design for heavy weather

 

This is an amateur design that needed to meet a basic set of criteria. The requirements included a max length of 34 foot. Has at least 2.7 foot bridge deck clearance with the bridge deck well back from the bow and stern. It will have an easy to handle well balanced sail plan and accommodation for 4 with 2 large double berths, a small galley and drop down table and an enclosed head. The aim is to cruise offshore to Chile, Hawaii and the Pacific NW of the USA.

The design is 34 x 21 foot of unknown displacement. The 38 foot mast carries about 325 square foot foresail and a mainsail of about 335 square foot main sail giving an upwind sail area of 660 square foot of sail area. The draft over the centre boards is 5.7 foot and over the rudders 3.3 foot. the underwing clearance is 2.7 foot.

The build is intended to be an epoxy-cedar strip hull bottom/ply on frame above (as in Woods Sagita/Eclipse). The amateur designer knows his limitations and intended to take the detailed conceptual design to a professional designer for verification of the design and the final build specifications.

There are a few variations in the rig design, it started as a ketch then went to a wishbone boom sloop and finally a fat head fully battened mainsail sloop.

An interesting concept but I do not know if it was finalised. The jpegs give the idea

 

Don't think i would be a fan of that 'half wishbone' boom,...just very tough to maintain a good shape.

 

Today is about a set of plans for those who need to understand how to build a plywood trimaran. The original designs were done in 1978 (680) and 1980 to 86 (720) by Ian Farrier who updated and combined te plans in the late 80’s into effectively a single plan set that you choose the option.

The 1980 720 is 23.62 x 16.34 foot (folds to 8 foot) with a displacement 2,710 lbs. The 30.5 foot aluminium mast carries 274 square foot of sail. The draft varies between 1.4 foot and 4.3 foot when the centre board is down. The length to beam on the main hull is 6.4 to 1. The structure is plywood timber with 4 mm plywood hull side panels, 6 mm plywood bottoms and 9 mm plywood decks and cabin top on the main hull. The plywood bulkheads have timber backing. The chines are epoxy glass. The stringers and keel line are timber as are the deck beams.

The 1978 680 is 22.3 x 16.4 foot (folds to 8 foot) with a displacement of 2,513 lbs. The 26.5 foot aluminium mast carries 236 square foot of sail. The draft varies between 1.4 foot and 4.3 foot with the centreboard down. The length to beam on the main hull is 6 to 1. The structure is plywood timber with 4 mm plywood hull side panels, 6 mm plywood bottoms and 9 mm plywood decks and cabin top on the main hull. The plywood bulkheads have timber backing. The chines are epoxy glass. The stringers and keel line are timber as are the deck beams.

The accommodation is generally good compared to the tri’s of the time due to the fuller main hulls.

The performance of these tris may surprise you. A well rigged Trailer Tri 720 can match a Buccaneer 24 and a Newick Tremolino 23 in bay racing. A hotted up (with rotating wing mast) Trailer Tri 680 can just about match this group. But please remember these are bay, river, close to shore tri’s not ocean crossers. They perform better in moderate winds when their main hulls can plane.

The only weakness in the designs is the fine ended 100% buoyancy (of total displacement) floats. In later designs, EG F25, The floats had fuller ends and higher buoyancy (EG 150%) which allowed the F25 to sail faster in stronger winds.

To access plans you need to sign up to the following web site using your e-mail address or google, facebook setup, get your access authorized, then look on the left side of the main web page for an item called “files”, click on files and then click on a folder called “plans”. Plans contains 4 items. The plan items require you, to use a ZIP extract program to get PDF plans and build instructions for the 720 and 680. The start web site is: TrailerTris groups.io Group https://fct.groups.io/g/TrailerTris

This 680/720 Zip extract file is 86 meg large as a ZIP, you are getting the full real plans. The jpegs below give some idea of the tri’s.