Multihull Structure Thoughts

Monohull sea sleds that do EG the Transpac are an interesting breed of boat. They are very light for their length and are designed to carry the largest spinnaker possible to break race records. The sleds are generally narrow with deep keels and can sail upwind but reaching and running are what they do very well. The construction of these boats is always interesting as light weight is the goal. The sled we will discuss is the 80-ft Global Voyager, being built for Dave Raney, the current owner of the Wylie 70 foot Rage.

Let’s look at a new build, the boat is 80 x 13.75 foot with a displacement of 29,500 lbs and ballast of 12,750 lbs in a bulb at the end of a keel. The 95 foot carbon fibre mast carries in a fractional rig 2,100 square foot upwind in a mainsail and jib. Spinnakers, Code 0’s etc are used and will add to the area. The draft is 12.5 foot over the fixed keel. This boat will need a very good depth sounder. The engine is a 110-hp Yanmar auxiliary diesel

Global Voyager is Dave Raney version of a cruiser racer. The deck has a 2 step cabin top for greater crew protection, there is more room inside for the family and the boat is easier to handle with better deck gear and some power assistance when cruising. The fact the design could also win a Transpac is just a side line.

Back to the build. When Tom Whylie ran the numbers, he found that a wood foam build was only slightly heavier and as the owner liked wood the design is a wood foam carbon composite. Steve Randler, the builder, for the inner skin used 1⁄4″ x 3″ (6.35mm x 76.2mm) Sitka spruce strips in the 0° direction (i.e., longitudinally), which will be visible in the interior and Western red cedar for the concealed surfaces. That will be followed by 3 layers of unidirectional carbon at 90° to centerline, and by ±12-oz/sq-yd (407-g/m2) carbon over 1 1⁄4″ (31.75mm) M80 Corecell 5-lb (2.3-kg) foam and M100 Corecell 6-lb (2.7-kg) foam above and below the waterline. The outer skin is all carbon, first ±12 oz/sq-yd, then four layers of 11-oz/sq-yd (373-g/m2) cloth. The bulkheads are tabbed in with 3 layers of 17 oz on each side, to the skin, except where it was going to show in the areas where spruce partial frames take up and form the corner.

The maststep, is laminated Honduras mahogany glued with epoxy and reversed grain. It is part of a strong “eggshell,” designed and engineered to bear loads exceeding 40,000 lbs (18,143.7 kg), with a 2:1 safety factor. For support, Rander added three plywood floor timbers underneath the mast that spread fore and aft to about 30“ (0.76m). The hull skins underneath the floor timbers were reinforced to be about 2“ (50mm) thick, by Wylie’s estimate. “The basic call is 1¾“ [44mm] thickness, but there’s so much extra carbon tapered out locally,” he said. “And the same is true on the outside. Steve made the foam a little thinner in that area, and there’s a nice large patch of multi-directional carbon.” Tapered foam helped the reinforced area match the rest of the fair hull surface.

The deck inner layer is 1⁄8“ (3mm) sapele plywood which is the visible part of the cabin ceiling, then the deck’s plywood inner skin has to be built up with composite layers. Then added a 1“ (25mm) Divinycell M80 core and the outer skin consisting of a combination of 0-90° and ±45° carbon. There are doublers for, EG jibsheet tracks, that go on the inside, and they have to be let into frames and stations before the deck can go on.

The 7‘ 4“ (2.24m) carbon-composite spade rudder and the 12‘ 6“-deep (3.8m) keel was fabricated. The keel’s 12‘ (3.65m) steel fin was fabricated to a NACA profile and will hold nearly 100 gal (378.4 l) of diesel. The lead ballast bulb is cast directly onto it and won’t be removable.

The jpegs give the idea of a very well built high speed vessel that is supposed to be a cruiser racer. Even your cruising crew could get this boat to peak at 30 knots. A 300 mile/day cruiser.

 

The following power cat design was done in 2011 by Sterling Design international (SDI). A nice cruising charter catamaran that in the original form was 58 foot but when it hit the water was 65 foot. Big by our standards but SDI has done a few other designs EG Ponant Explorers 8600 ton 420 foot cruise ships. SDI among other projects also is doing Ponant 590 foot Swap 2 Zero sailing vessel with 10670 square foot of aerofoil shaped solar wing sails etc. To SDI this cat is small and done as a special one off.

The power cat is described as a Trawler. The 58 foot trawler is 57.75 x 19.33 foot. Displacement about 70,000 lbs. The hulls are 6.4 foot wide at the waterline which means a length to beam on hulls is 8.9 to 1. The draft is 3.75 foot. Engines 2 x Yanmar 6LY3 380 hp/3300 rpm. Bow thrusters are Vetus 140 kg of thrust 24 V – 5,7 kW. Performance is at cruise speed 17 knots with a peak speed of 19 knots. The range is about 1000 miles at slower speeds EG 8 knots.

The accommodation is a total of 4 double berth cabins plus 1 crew cabin. The master or VIP double berth cabin occupies the forward end of the wingdeck area followed by the helmsman position and then the galley, seating and entertainment area. The aft cockpit is connected to the main saloon. Each hull has 2 sleeping cabin with toilet. There is a crane on deck with room for toys etc. The flying bridge provides an additional helming position.

Alu Marine shipyard builds the 65 foot version in aluminum on demand. These cats are used in charter work mainly.

The jpegs are of the trawler as designed and the last 2 jpegs give an idea of SDI other work.

 

Michael W. Schacht is an artist and designer living in Port Townsend, WA. Micheal has a very creative mind and has a very good eye for shape and proportion. The fact he also has design capability is a real bonus. When he applies his talents to multihulls he produces some very interesting results.

The following sailing proa design is evolutionary. The basic shape started as a Pacific Proa then went to a folding Pacific Proa and I have seen a Harryproa type version.

Black Swan is a 40’ center cockpit cruising proa. The proa is 40 x about 21 foot and can fold to about 10 foot with its swing arms. The displacement is about 10,000 lbs. The float is 32 foot long. The two 34.7 foot carbon fibre masts carry lug sails of 280 square foot for a total sail area of 560 square foot. The length to beam on the main hull is 8 to 1. The draft is 3.5 foot over the rudders at each end and 5.85 foot over the float based daggerboard.

Why an 8 to 1 length to beam? It was based on the work of Edmond Bruce who tested various length to beam ratio’s and found 8 to 1, neither too fat for speed, or too thin for load carrying. Edmond also found length to beams of 12 to 1 for higher performance and 16 to 1 for racers were good. The “fatter” 8 to 1 hull might be a compromise, but Micheal used the hull to explore hull sections and accommodations potential. While the extremely narrow hulls seem very slippery when considered on their own, the fact is, a cruiser has a certain amount of volume required, and if you squeeze the hulls so thin that they become virtually uninhabitable, then the accommodations spill out into pods, blisters and bridge deck cabins, all of which take their own toll on weight, simplicity, efficiency and speed. The wider hull permits comfortable (though not lavish) accommodations with no additional wings, pods, or deck cabins required.

There was a study of the hull shapes (first jpeg) and Micheal decided on a flat bottom with angled sides (number 2) as it provides reasonable accommodation and is simple to build. Construction is all stitch and glue marine plywood/epoxy, though the free-standing masts are carbon fiber simply because the benefits justify the price.

As I said the design evolved and I do not know if anyone built the design. The jpegs give the idea of a very interesting design.

 

The following cruising pacific proa has been designed by Othmar Karschulin and initially named P 12. The first was built by Manfred Meier in Germany. This proa is named “Mareinoa” and is 39.2 x 23 foot with a weight of 4,900 lbs and a displacement of 6,250 lbs. An additional 300 to 450 lbs of water ballast can be carried in the float for additional righting moment. The dual A frame 44 foot mast bases are mounted on the crossbeams and joined at the mast head to carry a roller furling main on a wire of 295 square foot and a roller furling jib of 295 square foot to either bow. The draft over the rudder daggerboards is 5 foot when down with a draft of 1.4 foot when the boards are up. The length to beam on the main hull looks about 12.2 to 1. The outboard power is 15 HP. The pod on the main hull serves 2 purposes which is increased accommodation and an assistance to righting if the proa is overpowered. This proa can be disassembled for transport on an 40 x 8 foot trailer.

The accommodation is 2 double berths, a galley with storage and limited internal seating. The use of the pod area allows the double berths to be 6.5 x 6 foot wide. The cockpit is spacious without the interruption of a single mast.

The build materials are Airex sandwich panels and epoxy resin/biaxial triaxial glass cloths which have an excellent stiffness/weight ratio with outstanding insulation properties. The cross beams used are composite with flanges to hold the beams in are steel.

Othmar did an investigation into what hull cross sections and shapes would have the least resistance across a speed range. The first jpeg gives the results. It interesting that Othmar then choose a hull shape of a shallow v which he didn’t show the results for. The next jpeg shows the drawings for the P 12. Othmar choose a simple multichine section for following reasons
* easy to build in composite (or plywood)
* safety when grounding
* stiffness in longitudinal direction.

An interesting design and good information on hull shapes. Be warned, these numbers are a guide not definitive. Each design sometimes use higher resistance hulls to improve seakeeping or EG load carrying. The jpegs give the idea.

 

The following is a few additions to the P 12 and hull resistance items. The proa P 12 “Mareinoa” was test sailed by the builder and Othmar in 2014 with the following results. The proa’a shunting works very well in under 10 knot winds conditions. It needs less than a minute for 2 people to roll in the foresail, change the rudders, move the main to the other side, and unfurl the new foresail.

“Wind conditions were 2-3 Bft, and some little gusts. Main surprise the yacht sails always barely slower than the measured apparent wind on board. That means at last we sail faster as the true wind. Some measurements:
Apparent wind ~ 5-6 knots - boat speed ~ 5 knots
Apparent wind ~ 8-9 knots - boat speed ~ 7,5 knots
During maximum speed the ama was barely lifted. The boat was always perfectly balanced, and need no rudder action. Although we sailed without daggerboard, the leeway was low as we saw at the lane behind the boat.”

The first jpeg is of the rig of “Mareinoa” which had a weakness in gusts. The top of the masts flexed too much. Additional stiffening was done.

Next on hull resistance. Malcom Smith is a Naval Architect with an interest in proa’s who calculated some resistance of hulls at various length to beams for comparison. To quote Malcom “In my opinion there aren’t many general rules for hull design. Each design needs to be considered individually based on the specific requirements of the intended purpose.”

As an example he compared a 16.3 foot hull with 265 lbs displacement. The first hull had a length to beam of 16 to 1 with a round bottom (gray line, lowest resistance). Next was an 8 to 1 hull with an elliptical bottom and an 11.6 foot waterline length (blue line, second highest resistance). Next was an 8 to 1 with semi circular section and a waterline length of 10.3 foot (red line, with highest resistance). Finally, was an 8 to 1 hull with a modified draft and a full 16.3 foot waterline (purple line second lowest resistance).

Translation of the above. The displacement was fixed so the waterline length varied according to hull shape. The result was waterline length is very important, the hull shape was of less importance. The shortest waterline 8 to 1 hull with the “best” semicircular cross section had twice the resistance of the 16 to 1 hull. The longest waterline 8 to 1 with a simple hull shape only had a 25% increase in resistance compared to a 16 to 1 hull.

In short, length to beam has less effect than waterline length in this comparison. If you can have a good hull cross section shape with a reasonable waterline length and displacement you should get a low resistance. The second jpeg give the idea.

 

To show the range of Michael Schacht work, I will show another conceptual design he has done. This design is a 24’ row/sail, long-range adventure cruiser. It’s suitable for one or two crew. The basic idea is a muscle/sail power craft that would do well in the generally calm conditions. Optimizing the boat for human and/or wind power raises some issues but this design should be able to go to windward well and handle some moderate weather. I would best describe the design as a bay/coastal cruiser.

The Intrepid is 24 x 12 foot overall with the main hull 3 foot wide and has a 2 foot waterline beam. The length to beam on the mainhull is 12 to 1. The float is 16 foot long. The displacement is (guess) 800 lbs with 2 crew. The mainhull has 2 windsurfer carbon masts which stand 15.4 foot above the deck and 2 specially made sails of 65 square foot a piece for a total sail area of 130 square foot. The draft ranges from 150 mm to 3.2 foot over the daggerboards. There are multiple boards for drift and rig balance control. The motive power is oars.

The reason for the proa configuration is to allow for the narrow waterline for ease of rowing.

The build is strip-plank with glass and epoxy for the hull and ama, plywood decks. The “accommodation” is a self-draining cockpit, and room to sleep two, end to end. The cockpit has 2 very comfortable rowing seats.

Intrepid is the sort of boat that could do a Race to Alaska providing its crew with a bit of comfort and a lot of fun. Sorry but only one jpeg but it gives some of the detail.

 

Oldmulti, do you have information about the privately built catamaran Selway Fisher 254?

 

Norma1234. All I know is:

Multihull Structure Thoughts https://www.boatdesign.net/threads/multihull-structure-thoughts.62361/page-24
Large Catamarans https://www.selway-fisher.com/YachtCats.htm
Large cats

 

The largest model in Nautitech’s range is the Nautitech 48 Open. The 48 was launched for initial sea trials in late 2023, and is the last design of naval architect Marc Lombard before his premature death in September 2023. This is a serious ocean going cruising catamaran built by the French company, Nautitech.

The Nautitech 48 Open is 47.75 x 26.2 foot with a weight 29,760 lbs. The 66 foot mast carries a 915 square foot mainsail and a 455 square foot self tacking furling jib. There are many other sail options. The length to beam is about 10 to 1. The draft over the deep fixed fin keels is 5.1 foot. The engines are two 60HP D2-60 Volvo’s. Digital tank testing was carried out to find the right balance between the desire to minimise hull width to optimise performance and a coherent interior layout. The hull shape was then honed to give comfortable motion at sea, with reduced pitching, easy tacking across a wide range of conditions and a responsive feel to the helm.

The accommodation is very good with a 2, 3 and 4 sleeping cabin options. I have chosen the 3 cabin option. One hull has a double berth cabin aft, a large toilet and shower then a forward single or double cabin. The other hull has an owner’s cabin with ensuite toilet shower. Forward is a multipurpose cabin called a “Smart room” that is a laundry and a workshop for repairs etc. This area could also be converted into an office. The main saloon has a large galley and seating/table area with a large sliding door to a external cockpit with additional seating. The helm positions are on either aft corners of the cockpit to provide a clear view of the rig for good sailing. Exposed helm positions are not fun in rough conditions.

The structure is designed to minimising weight with including vacuum infused hull construction and infused sandwich bulkheads. Assume foam cores and vinylester resins. The keels are separate structures that can breakaway if you seriously run aground.

The performance of this cat “In gusty winds of 18 to 22 knots, we sailed 12.3 knots of boatspeed at 60 degrees AWA. She kicked up her heels, never feeling overpowered or squirrely. Off the wind, she tracked well despite the lumpy seas, and we still held onto 8 knots at 120 degrees AWA.” “Instead, we surfed, speeding ahead and touching 14.4 knots. We had just hoisted the gennaker on the new Nautitech 48 Open in 20 knots of breeze.” Other tests have reached 17 knots in semi surfing conditions and upwind in a short chop there was some underwing slapping. In short a cat that can sail well and could average 10 knots in the right conditions.

An interesting cat that has a good balance of accommodation versus performance in a true cruising cat. The jpegs give the idea.

 

The Formula 40s multihulls were an interesting time in multihulls. They started as mainly catamarans and had to conform with a few simple rules like 40 foot long maximum, a minimum weight of 4000 lbs and a maximum sail area of 900 square foot (?).

In 1986 the majority of the fleet were catamarans, VPLP started to design a trimaran with a blank sheet of paper. The challenge was a minimum weight trimaran which sailed like a catamaran, flying a hull. That was something new at the time as most trimarans sailed on the main hull, with floats to balance the boat for transverse stability. VPLP had the crew on the windward float, three rudders, and aimed to sail flying a hull. Biscuits Cantreau 2 was faster and beat the catamaran fleet.

Biscuits Cantreau 2 started as 40 x 34 foot over the hulls with sliding hiking racks for an overall beam of 40 foot. the weight was aimed at 4,000 lbs (1.8 tons) but the tri ended up weighing 5,150 lbs. The original aluminium wing mast was 67.8 foot high but was replaced by a 67 foot carbon wing mast of 500 mm chord. The length to beam on the main hull is 12 to 1, the length to beam on the floats is 15 to 1. The draft is 9 foot over the central hull daggerboard. Later angled boards were added to the floats. The tri had 3 rudders on the sterns of the hulls for 1987. When the tri needed power it used a 25 HP outboard.

This started as a race boat without accommodation. Later 3 berths were installed and camp gear for the rest. This tri is still a racer.

The build was built by Jean LeCam in carbon for his own use at JMV in 1987. The materials were carbon fibre either side of klegecell in epoxy with some uni-s glass in the structure. This would not have been a cheap build in 1987. The early 2000’s upgraded Nigel Irens designed mast, boom and bow spirit were autoclaved prepreg carbon. The boom has internal hydraulic ram for adjustment.

This tri was the forerunner of most of the developments in things like OMRA 60 tris which provided the groundwork for the modern Ultims. PS Biscuits Cantreau 2 was a very successful racing tri that is still racing today in both the US and Thailand. Its peak speed according to the designer was 28 knots, according to the last owner 38 knots. Lets just call it fast.

The jpegs give the idea.

 

Today we will talk about the F 40 cats that Biscuits Cantreau 2 was able to defeat. Initially F 40’s were mainly cats but Jeanneau decided to do a “production” F 40 cat. Nigel Irens did the design and Jeanneau did 3 “generations” of the design. Each generation was slightly lighter, had a better structure and often had a taller mast but the same sail area.

Fleury Michon was number 1 in the series in 1985 and was 38.7 x 25.2 foot with a weight of about 4,500 lbs. The mainsail 680 square foot and the jib was 300 square foot. The length to beam is about 14 to 1 on the hulls. The draft ranged from 1.5 to 5 foot over the hull based daggerboards. The build of this cat is unknown but some of the initial boats were polyester, e glass and foam. The crossbeams were carbon fibre.

The “generation 3” Jeanneau F 40’s were 39.6 x 25.2 foot with weights as low as 4,100 lbs with 62 foot carbon fibre rotating masts that carried a 775 square foot mainsail and a 130 square foot jib. The draft of the daggerboards had increased to 8 foot. The structure of the hulls by this stage were Kevlar / epoxy / carbon, foam with Kevlar or carbon daggerboards with Carbon beams and prodder.

The foil, mast and sail shapes had improved over a couple years as well as the structures. The result was the early F 40 cats could peak at 20 to 22 knots but the later F 40 cats could peak at 20 to 26 knots. The tris started to come into the F 40 class and had an advantage in lighter winds due to less wetted surface and in stronger winds due to being wider and having more stability and could peak at 28 knots.

There were about 10 Jeanneau (not sure) produced and some are still sailing in their original form. But some F 40 cats have been “converted” into cruisers or in the extreme “Data General” was converted into a sailing cat that trapeze artists could perform on. (Look at the last 3 jpegs if you doubt me).

This was an interesting period of multihull development and helped advance multihull sailing and structures very rapidly. The jpegs give the idea.

 

Pierre Jacques Kubris Designs did a couple of interesting designs. After deigning a 24 foot tri there was an evolution into a 26.1 foot design which was aimed at being a high performance cruiser racer. This design was done in 2009. The tri called “Blue One 26” if shown in the first 2 jpegs. The Blue One 26 is 26.1 x 22.5 foot with a weight of 1680 lbs and a displacement of 2580 lbs. The sail area ranges from 590 square foot upwind to 1,076 square foot downwind.

The structure is foam glass with the crossarms foldable as in swing wings (like Dragonfly tri’s). I do not know if ant were built but this is an impressively light structure for a 22 foot wide trailable tri.

In 2013/14 Pierre did a further tri along the same lines, the K.libre 7.50 which is in the final jpeg. 24.6 x 19.35 foot with a weight of 1970 lbs and a displacement of 3000 lbs. The carbon mast is 37.5 foot tall and carries a mainsail sail area is of 300 square foot, the Solent is 152 square foot and a spinnaker of 505 square foot. Draft ranges from 1.4 foot to 5 foot. There is a central hull centreboard and 2 float based lifting daggerboards. This design has less cockpit and a small functional cabin. The crossarms again were a swing wing to allow it to be trailable.

It is interesting as to how these designs developed. There was slightly less beam and more displacement which shows that either a more realistic assessment of the true weight ofb these tris were done or for a production machine cheaper heavier construction was done. Carbon fibre and epoxy is more expensive than vinylester and e-glass (in most locations).

Sorry about the lack of jpegs.

 

I am confused by this monohull or cat or hydrofoil powerboat. This is a convertible 3 person speed boat that can become a floating island, a catamaran speed boat or a hydrofoil depending on the positioning of the hydraulic cross arms.

The Kormaran is an Austrian build and design by a company who thinks about boats in a different way. The Kormaran is 23 x 5 to 11.5 foot wide depending if it is configured as a monohull or has it hulls spread apart by hydraulics to form a catamaran hull shape. When you want speed you can lower the hydrofoils and raise the entire boat over the seas. The power is a 493 HP engine that powers 3 water jets. Top speed is 45 miles per hour with a range of up to 200 nautical miles at slower speeds.

This is a day boat with 3 seats for impressing the local folk at speed and acting as an island when the hulls are spread apart to form a trimaran and the decks are folded out for sun baking. To quote Kormaran “The kormaran ‘K7’ is a 23 foot speedboat that can change shape + pilot settings at the push of a button. its electronically activated hydraulic-arms are central to its adaptability: when drawn inward, the outrigger hulls fold into a monohull watercraft; when deployed partially, the body stands above the water surface, acting as dual hulls of a catamaran watercraft; when deployed completely, the body is submerged effectively becoming the third hull of a trimaran watercraft. the luxury watercraft also features a set of fold-out hydrofoils, enabling it to lift the body further above the water in monohull mode, creating a smooth experience that reduces water resistance by up to 80 and consumes less fuel.”

The K7 innovative design is crafted from foam, epoxy and carbon fiber, the hydraulic arms are a blend of titanium and stainless steel, while the interior is trimmed in soft leather. the hull and deck surfaces are covered in veneers of black-jointed teak wood.

This is a design for fun and as a toy for a superyacht. As you will see from the jpegs this is a very flexible design that will need to treated carefully as there are many parts to its design.

 

The final Pierre Jacques Kubris Design trimaran we will do is the VOD.K 7 metre. This is a transportable cruiser occasional racer trimaran. This design was done in 2017 and is an update on his earlier work with a relatively more powerful hull form and rig.

The tri is 23.5 foot long and about 19 foot wide folding by swing arms to about 8 foot wide. The weight is about 1700 lbs and a displacement of about 2600 lbs. The mast is 32 foot high and carries about a 290 square foot mainsail and a 125 square foot jib. Other sail options are available. The draft is over the rudder and float based daggerboards is 4 foot. The advantage of float based daggerboards are that as the tri heels addition draft is provided for the boards. The disadvantage is depending on the angle to the wind you are sailing at your board centre of lateral resistance and centre of sail effort can get unbalanced requiring more rudder angle to maintain a course. The float design is modern with full ends to allow more power when reaching.

The accommodation in this tri is good for its size. It has 6 foot headroom over the main saloon area due to its high freeboard. The downside is windage upwind. There is a berth forward and a berth under the cockpit. There is seating in the mainsaloon with a small functional galley. The toilet is under the head of the forward berth.

The construction will be a foam glass structure and I am sure will have carbon fibre reinforcing in the cross beams.

If my numbers are correct this tri will sail well and be an all round performer. The jpegs give the idea of a design that I hope has been built.

 

The following is about a charter trimaran that is advertised as a “world cruising Trimaran”. The tri was built in 1988 by Technicoque in France to a Michel Joubert design. The tri has been refitted 3 times to bring it up to specification.

The tri is 79 x 27.5 foot with a displacement (suspect weight) of 100,800 lbs. The 67 foot mast carries a 1070 square foot mainsail, a Solent of 590 square foot, a Genoa of 860 square foot and a Gennaker of 1180 square foot. All the headsails are on roller furling gear. There are also 3 spinnakers. The draft is 6 foot over minimal fixed keels. There are 3 engines, in the main hull a 305 Hp Volvo and in each float 60 Hp Perkins. The 5000 litre fuel tank will give a 4500 mile range at 8 knots using 30 litres/hour when running on the main engine.

The accommodation is vast. There are 6 double cabins for guests and 3 crew cabins. The main saloon has much seating and a very large galley bar area for the guests. There are 7 toilets/shower areas. There are 3 engine rooms. The flybridges can accommodate guest lounges as well as crew.

This tri is not push button but the gear is aimed at short handed sailing. The sppeds of thios tri would probably average 9 knots and peak at 14-15 knots on a very good day. The wave interference between the hulls would be significant as this is a very narrow trimaran for its length.

The construction is listed as fiberglass but I suspect it is foam glass as it is not to heavy for its length, As with all these charter machines comfort over5ides performance. As a global cruiser it will be a very comfortable tri but for 4 people you would be better of getting a modern 50 foot multihull that will be comfortable for fewer people, probably perform better and be cheaper to maintain.

A reasonable boat for a limited audience. The jpegs give an idea.