Multihull Structure Thoughts

In 2010 when Prout had changed its business model to work from China they started construction of a trimaran. Unusual for Prout considering its catamaran past. The trimaran they built is the PT 138, a 138 x 46 foot that displaces (I suspect weighs) 74,000 lbs. The mast is 141 foot high and carries a 2770 square foot mainsail, a 2790 square foot genoa and a 2920 square foot gennaker. OK if you’re going to do trimarans why not start big. Now we add a little confusion, the float length is 70 foot long. At this size you don’t need really long floats but short fat floats are not optimum. The hint comes when you see the 15,000 litre fuel tank and the Caterpillar C12 (445 HP) main engine in the main hull and a Styer 100 HP hybrid desil in each float hull.

The tri was designed for offshore passages and be fast for her owner. The tri will also be available for charter. The tri under sail can reach 20 knots and cruise under motor at 15 knots. Before the first tri was completed an order came in for the second version of the tri.

Now the fun part. How long do you think it took to glass the mainhull, underwings and float hulls? Yes, it took months to build the moulds, weeks to lay the composite PVC foam and G.R.P. with carbon fiber reinforcements then PT-138 hull 02 took just 3 hours to complete what is believed to be the largest single piece epoxy resin infusion in the world, at the factory in China under the auspices of RINA. Think about that. The jpeg shows the number of vacuum lines, resin reservoirs, vacuum pumps, valves and quality control required to do the resin infusion in one shot. Spectacular. The cost of the backup power in case of a power failure would be a cheap investment, compared to the material that you would lose if the resin infusion did not work. The project manager on this project is in the superstar category. The bulkheads and deck would be easy compared to the hull.

The rest of the vessel appears to be built to super yacht standard in the jpegs. A impressive structure.

 

Have to agree, to infuse that thing in one hit is a remarkable feat of organisation and workmanship, just a shame it was a Prout and not a Shuttleworth.

 

Here they mention starting a second hull the following year, which sounds very ambitious -
Prout International starts construction of a second 138' trimaran https://www.boatinternational.com/yachts/news/prout-international-starts-construction-of-a-second-138-trimaran--6989

But Google does not come up with any links showing a finished boat - were either of them actually completed?
The Prout website domain www.proutinternational.com is now for sale.......

 

The PJOA 600 is a camper cruiser catamaran designed for home building. The cat is 20.7 x 13.1 foot weighing 555 lbs and can carry an additional 890 lbs for a total displacement of 1,445 lbs. The heaviest component is each hull that weighs 187 lbs. The rig is a crab claw sail that is hung from a “A” frame mast, and can carry 3 sail options of 130, 150 and 172 square foot depending on weather conditions. The forward lower end of the crab claw sail is attached to an underwing prodder by rope to allow the forward end of the crab claw to rotate to windward for reaching and upwind work. The cat draws between 450 and 550 mm when sailing.

The deep V hulls are Wharam like without centreboards for simplicity of building and sailing in shallow water. The rudders are fixed to the stern and can be adjusted depending on the depth of water. At each end of the hull are mini fins parallel to the water surface to reduce pitching and act as steps when you’ve taken the ground. I have no problems with the aft fins but forward fins like this have been tried by several designers and in at least 2 cases in smaller cats they helped tripping a cat causing the stern to pitch over the bow. Asymmetry of hull shape fore and aft is a better way to reduce pitching.

Storage space and a berth in each hull is provided with the trampoline able to offer two extra places once the custom-designed tent is set up. With the ability to carry a 890 lbs load, 2 crew and quite a bit of camping gear and supplies could carried for EG a 2 week trip in sheltered bay or coastal barrier reef country. The rig and the hull platform can be easily disassembled for transportation on a trailer, reducing into a 20.6 x 5.2 3.3 foot package for storage and transport.

The PJOA 600 hulls are made in stich and glue plywood sheets reinforced with 3 longitudinal stringers per side, supported by 4 wooden frames. The hull external is covered with glass/epoxy. It is a simple structure that the designer estimates a single hull can be built in 2 weeks. Cross beams and all spars are from wood. The main crossbeams are I beams with a plywood web and a top and bottom timber caps. An option for the trapezoidal mast frame can may be made of aluminum tubes.

No performance is known but the designer has done many Crab Claw proa’s before and really understands the rig and how to build boats this size. This is an interesting design that could be a very good shallow draft camper cruiser.

The jpegs give an idea.

 

Kanda is a one person high performance trailable trimaran. The design is done by the Yacht Design Collective. The Kanda is a 13.1 x 12.1 foot trimaran that displaces 300 lbs. The 22 foot rotating mast carries a 91 square foot mainsail, a 47 square foot jib and a 160 or 215 square foot gennaker. The deep daggerboard that draws 3.3 foot and kickup rudder are on the main hull. The length to beam on the main hull is 6.3 to 1. The float hulls have a length to beam of 9 to 1. The hulls are wider than normal but on such a small tri this will not be a great disadvantage as you will be sailing like a cat on one hull in higher wind speeds and in lighter winds the fatter main hull will reduce the wetted surface area.

The rig has minimal wire holding it up and has high aspect ratio sails which should provide a lot of power for upwind work. The tri was deliberately designed to have a wide beam to minimize any capsizes for inexperienced sailors.

The tris structure is constructed in plywood (4 mm and 6 mm probably), covered with fiberglass and epoxy resin. The frames/bulkheads have minimal stringers and the plywood skin has stich and glue taped fiberglass seams/chines. The internal keel on the main and float hulls are plywood structures. The cross arms are made of glued laminated wood. The cross arms are lashed to the central hull with dynmea ropes. The foils are plywood covered with epoxy glass.

This tri is able to be disassembled for transport. Each component is light enough to be moved by one person. This is a fun design that should be perform very well, a poor mans Weta substitute. The jpegs give the idea.

 

The KOMOREBI 138 is a 138 x 41 foot “sailing” trimaran with a weight of 530,000 lbs and a displacement of 672,000 lbs. The wing mast sails have two 106 foot masts carrying 1615 square foot of reefable wing sail on each mast. The total sail area is 3,230 square foot. The “freeboard” is 40 foot and the draft is 10 foot. The main hull has a length to beam of 7 to 1 and 20 to 1 length to beam on the floats. Now we get to the engines, how about 115 HP per float and two 650 HP engines in the main hull. This tri is a motor sailor that can move at 12 to 15 knots under sail or power.

The rig is entirely automated, self-supporting and rotating 360°, Oceanwings® adapts its angle of incidence to the vessel’s point of sail to ensure optimal propulsion. Power is managed by trimming camber and twist. “Not only does it provide exceptional control, it’s also efficient to the point of halving the surface area required to propel a vessel under conventional sail.” VPLP Design is developed this patented technology with 360° rotating unstayed mast ensures optimum trimming regardless of wind direction and the camber is adjustable and reversible. Twist can be implemented to follow wind gradient and thus ensure optimal angle of attack along span.

Accommodation is not a problem, paying for the accommodation, crew, maintenance, fuel, mooring, insurance etc will be a real problem for the majority of people. KOMOREBI, which stands for « Well Being » in Japanese, cost more than, to way more than, $20 million depending on your luxury of finish.

Marc Pajot, a former multihull ocean racer, Olympic medalist and America’s Cup multi challenger skipper is the concept promoter and marketer. He knows his market. There are already requests for larger versions.

The hull, deck structure is aluminum. The fit out is from aluminum, composites and any luxury materials that are remotely water proof.

The KOMOREBI is described as “the perfect synergy between long range ocean cruising & easy day sailing.” The jpegs will allow you to decide.

 

Hello, I apologize for barging in the thread which I am following for almost a year now but I was wondering would any members reading this thread know what was drawn on sheet 6 of a Buccaneer 33 trimaran plans? The sheet is not there (or I have not found it) and I would like to know what info that sheet contained.
Thank you.
Sasha

 

The mega yachts we have seen recently are for owners who have unlimited wealth and want a statement of their values (hint, “I have a bigger everything than you”). They want a multihull because they are in “fashion” and have the space to be comfortable for their family and a few selected friends. As long it can go faster than their monohull mates great. But why spend $20 plus million for a bit of room?

Let’s look at the next step down, the Privilege Signature 640. The 640 was chosen because it has a master sleeping cabin that would be acceptable on a 138 foot mono or tri. The Privilege Signature 640 is 64 x 30 foot weighing 64,000 lbs and displacing 82,000 lbs. The 89.5 foot carbon fibre mast carries a 1,420 square foot mainsail, a 947 genoa, a 334 square foot staysail and a 2,150 square foot Gennaker. The 3,200 square foot asymmetric spinnaker is optional. Electric winches are almost mandatory. The fixed low aspect ratio keels draw 6.1 foot.

The engines are two 110 HP desils. There is 2000 litres of fuel, 1300 litres of water and 300 litres of black water. This alone will weigh 7000 lbs when the tanks are full. Naval architecture and exterior design is done by Marc Lombard Yacht Design Group in co-operation with Franck Darnet of Darnet Design who creates the interior design for EG superyachts and production boats.

The Privilege 640 is priced at about EUR 2.5 million (about $US2.5 million) which includes onboard instrumentation, carbon mast, park avenue boom, basic sails, full fitout etc and a tender (with outboard).

The accommodation space is large with 3 double berth cabins and the master suite. The master suite is 17 x 10 foot with full headroom and a king size bed. Also, there is a proper ensuite bathroom. This is a house size bedroom. Then we get to the galley which can be in a hull if you have a professional crew or up on the bridge deck for comfort and a view. The saloon has a large glass foldable door that allows the cockpit and main saloon form a large open area of 20 x 20 foot for lounging and day sailing comfort. How large is your house lounge family room? There are three about 10 x 10 foot guest cabins for others with associated bathrooms. PS there is also a crew cabin in a bow. The vast cockpit is on the main cabin roof and Bimini top. This is a serious cruiser capable of taking a family in luxury globally.

So, what does this cat sail like with its 90 foot mast and 84,000 lbs loaded displacement. Reasonably well. A test had a true wind of 12/14 knots and they were sailing under sail and power (just one engine is on) at little more than 9 knots, with a fuel consumption of just 10 litre/hour. When the engine was turned off and a stay sail was raised the cat continued at 9 knots on a reach. The wind increased to 20 -22 knots and with the cat broad reaching with full sail the cat sailed at 11 knots with a predisposition to surfing on the 5 foot building waves. This cat could sail at 15 knots plus if driven by a good crew in the right conditions.

The majority of the structure is vacuum resin infused. The hulls start with Isophthalic gelcoat of Signal White RAL 9607 and then a layer of vinylester resin to prevent osmosis. Then the hulls and bridge deck are infused with polyester resin on top of a closed cells PVC foam core. The structural bulkheads are infused glass with closed cells PVC foam core. The bulkheads are directly laminated to hull and bridge deck. The cabin top structure is one piece foam glass under infusion with areas of plywood and aluminum reinforcements added (secondarily glassed in). There are carbon fibre reinforcements as required. The keels are structural and are molded independently from the hulls. If anyone needs to understand why these production cats with full molds take over 10,000 hours to produce have a look at the jpeg of the guy doing the electronics in the stern of one hull. This is just the tip of the wiring run iceberg.

The jpegs tell the story. What is being said is a 64 foot cat can provide as much comfort as a much larger vessel, for the majority of cruising needs, at 10% of the up front cost of a 138 footer. And in the real world the 64 foot cruising speed would be about the same as the 138 footer when sailing or powering.

 

Additional Privilege Signature 640 jpegs.

 

The final conversation about accommodation versus performance versus cost. Real world for most of us is not $20 plus million or $2.5 million, we live in a world of $250,000 or less. What can you get that satisfies the requirement of space, some performance and lower cost? The examples I have chosen are existing designs or former production boats. The KD 1000 from Kohler is an excellent cat of 32.4 x 20.4 foot that weighs 4,500 lbs and displaces 9,400 lbs featured on page 109 of this thread. The Grainger Raku 32 is a 32 x 17 foot cat that displaces 6,700 lbs. The Heavenly Twins 26.5 x 13.8 foot displacing 6,700 lbs. The Summer Twins 25 x 16.5 foot displacing 6,500 lbs.

Each of these boats can be had for less than $250,000 if home built or brought second hand. The requirement is for space. Each has full or near full headroom through out cat. Each has a least one decent permanent double berth. The Heavenly Twins has an 8 foot wide double berth in the aft cabin if required. All cats can sleep at least 4 people. Each cat has a full headroom galley and a separate toilet area. Each cat has a dinette.

The difference is the amount of “walking around” space. The 32 foot cats have some room to move around. The 26 and 25 foot cats require you to plan how you move past people. When I walked through a Heavenly Twins, the room inside was amazing, which is the reason it sold over 400 boats. At least 2 Heavenly Twins have sailed around the world. So, each of these cats have enough room to live aboard for extended periods for at least 2 people.

Now we come to the real issue. Performance. The Raku 32 will match or exceed a Privilege Signature 640 and the 138 foot tri in sailing performance, and if it has the right power, in motoring performance. The only difference is in winds above 25 knots the Raku 32 will need to back off, the larger boats will still be sailing OK. The KD 1000 will be slightly slower but still probably match the larger boats. The KD 1000 will be a more practical cruiser than the Raku 32 because it has a greater payload capacity.

The Heavenly Twins and Summer Twins have good accommodation but have moderate performance at best. Either cat will peak at 10 to 12 knots and average at best 7 knots over an extended period. Their upwind performance will not match the 32 foot cats. The 32 foot cats will give you reasonably comfortable 150 to 200 mile day performance. The 25 and 25 foot cats will give you at best 130 miles per day and be uncomfortable in the wrong conditions, such as upwind, just choose your weather and course carefully.

Result. In the real world a smaller cat will give you the majority of the capability and comfort of a much larger boat at a price may can afford. But there is a lower size limit where reasonable accommodation and performance is available. That limit appears to be about 30 foot, below that size either accommodation space or performance is compromised.

Finally, what do you really want from a cruiser? In my world it is reasonable accommodation and 7 to 8 knot averages. Sailing at 15 knots is fun, but very wearing over a long period, due to the constant unpredictable movements. So a 30 foot cat achieves what I need, but if your spouse requires space and daily showers start working harder to pay for a larger boat.

The jpegs give the idea of each cat mentioned. Tomorrow fast fun.

 

Those Heavenly Twins things have no forefoot. Pitchy pitchy A over T

 

The Swiss cat 55 was designed by Sebastien Schmidt in 2010 as a high performance cruiser. The cat is 55.7 x 25 foot and weighs 31,350 lbs and displaces 39,200 lbs. The 70 foot carbon fibre mast and boom with a 970 square foot fathead mainsail, 333 square foot staysail, 807 square foot genoa and a 1020 square foot gennaker. All the running rigging is Kevlar. The prodder takes the roller furling fore sails loads instead of independent cross beam structures. The hull based daggerboards draw 10 foot when down and underslung spade rudders draw 3.5 foot. The hull length to beam is about 11 to 1. The numbers indicate a seriously fast performance cruiser capable of touching above 20 knots and sustaining 10 to 12 knot averages.

The accommodation has 3 queen size double berth cabins with toilets in the hulls. The bridgedeck main saloon has the large galley, dinette and chart area. The main cockpit is large for sail control and lounging.

The structure is interesting. Warning, even with full production molds this cat take 8,500 hours to build (twice as long as a large simple production series catamarans). The SwissCat structure is made of Divnycell PVC foam e glass fabric sandwich which is epoxy resin infused and reinforced with carbon fibre unidirectionals. An insulated room in the shed even allows post-cooking of the infused structures. The X ray jpeg shows the bulkheads used in the cat. The dark black lines on the keel, gunnel edges and around some bulkhead edges are the carbon fibre reinforcements built in when the cat hull structure and bulkheads are infused. Also, the prodder has substantial carbon reinforcement. The hull and deck are painted in polyurethane paint to save weight over a “gel coat” finish.

This cat has the usual quality finish and consumer demand has resulted in a 48 foot version being made available. The jpegs give the idea.

 

The KSS 30 is designed by Derek Kelsall to be an economical performance cruising cat for family sailing. The KSS 30 29.5 x 18.2 foot that weighs 5,800 lbs. The fractional rig has a fixed or rotating 39 foot mast that carries a 333 square foot mainsail and a 150 square foot jib. The forestay is attached to a prodder forward of the bridge deck. Most of Derek’s smaller bridge deck cats have about 8 or 9 to 1 length to beam style of hulls. The hulls have low aspect ratio keels that draw 3.3 foot. The rudders are underslung spade rudders. The underwing clearance is 2 foot.

The accommodation has a double berth aft each side of the cockpit. A toilet in the bow of a hull and a single berth or stowage in the other bow. The bridge deck cabin has a dinette and a smaller but practical galley with near full headroom. Most of his smaller cats perform well on all points of sail but this is a cruiser design for practical comfort not outright speed.

As with the majority of Kelsall’s designs the structure is polyester or vinylester e-glass PVC foam resin infusion structure. The hull can be formed using KSS build approach and many of the bulkheads, deck panels etc can be done as flat panels using resin infusion. Nothing hard, but if you are new to resin infusion do a few practice runs and speak to people who have done it previously. To infuse correctly is more about a good set up, reliable vacuum pump and be willing to check continuously to ensure you have no bag leaks etc. It does not require expensive consumables, but the job can be a lot easier with good consumables. Please do not think the KSS build method will simplify the total boat build. It makes the exterior finish easier but the rest of the build is similar to other methods.

Kelsall’s plans are reasonable but you have to have an adaptable approach to building in the KSS method, as things don’t always shape as expected due to differing fabrics, resin types, bending approaches etc. The plans cost $6,000 US. The jpegs give an idea.

 

The TF10 trimaran designed by DNA has been featured before but this is an update. The TF10 is 36 foot length overall with a 32.7 x 22.3 foot basic boat and beam including benches of 25 foot. The tri can be folded to 8.2 foot for trailing. The weight is 3,136 lbs and a displacement of 4,256 lbs. The 53 foot carbon rotating mast carries 484 square foot, a jib of 300 square foot and a 764 square foot gennaker on a furler. The maximum draft with foils down is 8.4 foot. The main daggerboard foils as an example are 11.8 foot long by 400 mm at its widest point and 100 mm at its smallest point. Each foil weighs 100 lbs.

The TF10 foiling trimaran flies with a 4-point foil setup with the TF10’s main foils and T-rudders minimize the pitch and roll movements. The float based main Z-type daggerboard foils provide the necessary lift to be able to foil. The T-rudders with horizontal elevators generate lift and/or downforce. The advantage of the 4-point-foil setup is that the crew does not have to pick up the daggerboards during manoeuvres. This significantly reduces the crew’s actions.

The performance of this tri is what you imagine. 30 knots plus is not unknown. It can go upwind and reaching at faster than wind speed in light to moderate conditions. The tri points very well as most of its sailing is logically “upwind” even when reaching. Testers claim it’s very easy to sail the tri due to its electric actuators that change the position (angle) of the foils and rudders with a single push on the button. DNA has done a lot of work with A class cats, Gunboat G4 foiling cats etc on foil shape and control techniques of foils and are getting nearer useable foil setups for every day sailors.

The TF10 foiling trimaran is completely made of pre-preg carbon with a Nomex honeycomb sandwich structure. Most components are cooked in an Autoclave to ensure quality and consistent finish. The foils are done in a ‘one-shot’ production process, with continuous fibre foils produced under vacuum and cured in an Autoclave. The production method was specially developed to create a hydrofoil that cures in one go, without glue joints and including internal stiffening ribs. The result is a strong light hydrofoil. All foils are finished with high-quality paint finish. The DNA has an automated Zund pre-preg cutting machine that prepares the laminates with high precision. They also have a five-axis milling machine (with a working range of 18 x 8 x 6.5 foot) to prepare tooling moulds automatically. This allows DNA to produce new moulds for eg foils quickly as shapes and sections improve.

The jpegs show the tri and some of the foils and structure. One TF10 (Mad Max) is owned by an Australian, the boss of APC logistics, who has had many interesting high performance multi’s in his life. He flew to Holland with his crew to try out a TF10 before he committed to buying one. He currently is having a lot of fun.

 

The Outcut 29.5 is a folding and transportable motor sailing catamaran. The Outcut is 29.5 x 11.5 foot and can compress to 8.2 foot in 90 seconds by the press of a button. The weight is 3,135 lbs. The approximately 37 foot mast carries a headsail only rig with a jib and gennaker. The rig can increase the cats speed by about 30% under good conditions. The hulls length to beam ratio is 18 to 1. The cat draws 1 foot without its rudders.

The Outcut 29.5 is from the Italian shipyard Outcut. After four years of research, the DHR (Dynamic Hull Range) folding system allows variable width beam for easy transport. The folding system has electronic and hydraulic components. When the floats are folded, the living space does not change, maintaining the same interior layout.

The simple and uncluttered layout has 4 berths. A cabin at the front with a large double bed (5 x 7 foot) and a saloon with table for six guests which converts into a double bed (4.5 x 6 foot). A bathroom with shower completes the set and the saloon can also be fitted with a fitted kitchen with sink and two-burner stove. The headroom is not specified but looks about 5 foot. The hulls house the tanks for fresh water, fuel, batteries and two large storage areas.

The structure is mainly PVC foam e-glass sandwich that is vacuum bagged in moulds. The cross beams are carbon fibre boxes that slide within each other for compression of the hull structure underneath the edge of the main cabin pod. The hulls have several sealed compartments to make the cat unsinkable.

The jpegs give the idea.