Multihull Structure Thoughts

This is a design study that Andy Waugh Yacht Design has done hopefully for a very rich client. We are talking several hundred million for the client. The craft name is “Decadence” and the vessel is a Swath, a small water area vessel with its main buoyancy support under water. The advantage of a swath is it can be smoother riding through a rough seaway. Important for rich people who expect the world to adapt to them, where the rest of us have to adapt to the world.

Decadence is 262 x 100 foot with an estimated displacement of about 1640 tons or 3.6 million lbs. The hull width of a pod at the waterline is 8.5 foot. The underwater tube width is 17.8 foot which gives a length to beam of 14.7 to 1. The draft is a worrying 25 foot. The underwing clearance is 5.8 foot. Renderings also show Decadence with retractable or inflatable sails, which the firm says provide additional wind power. Motive power is unknown but will be “30%” more efficient than conventional power.

The design is based on a catamaran with submerged cylindrical hulls attached to a central body by "stilts" with a minimal cross-section. It offers the advantage of several technical developments, including an estimated 70 percent reduction in pitch and roll movements compared to a traditional yacht for greater comfort and safety. All while offering "unique and exciting aesthetic possibilities yet to be fully realized in the luxury superyacht sector," according to the design firm.

The draft of 25 foot leads to an interesting statement by the designers “The stability of the SWATH hull "negates the necessity to shelter from adverse weather conditions”. Translation you may not be able to get into many harbours or marinas so park offshore and use the two 45 foot power boat tenders or helicopter to get to shore.

Accommodation is vast and can be any layout you specify. But the crew will be living in the 17 foot tubes below the waterline along with the engines, fuel and water tankage. I hope the tube hulls are painted yellow so the crew can feel they are living in a Yellow submarine (sorry to Beatles fans).

An interesting concept, good luck to the designers, builders and owner as they bring this craft to reality. The jpegs give an idea.

 

That’s just wrong on so many levels.

 

Hello Oldmulti,

many many thanks for your answers. With your permission I post your information in the SA Forum Thread about SIB.

Have Fun, Michel

 

I don't agree. It's not even wrong.

BTW, according to Perplexity searcher, not a single boat designed by Andy Waugh Yacht Design was ever built.

regards

krzys

 

Went over your head. Sorry, shrug.

 

Luckystrike. its OK to post the SIB item on the SA forum.

 

Sadly this is another one of those, swath in name only, but very little reference to the actual hydrodynamic characteristics of a real swath.
Since the 'design', is rather overshadowed, as expected, by fancy colour renderings and not much else....

 

Maybe AI will let the "artists" legitimize the doodles by doing the engineering and actual plans. Of course you don't actually need to be able to draw to create the concepts these days so artist may be the wrong term.

 

Infiniti Yachts from Spain have over 20 years of expertise in designing and building foil-assisted yachts up to 142 feet, Infiniti Catamarans has consistently enhanced the performance and comfort of these vessels using advanced retractable foils. These foils have been demonstrated to reduce pitching by up to 42% and on superyachts decrease heeling by 30%. The Infiniti 62 catamaran features twin helical DSS foils, which improve performance by reducing drag, increasing speed, and enhancing stability. These foils can retract seamlessly for added versatility.

The Infiniti 62 is 62 x 31.3 foot over the hull but with the DSS foils fully extended the overall beam is 45.3 foot. The rudders have T foils on them to aid with stability and provide lift. The “displacement” is 47,000 lbs. The carbon fibre wing mast carries an unknown amount of sail. The length to beam on the hulls is about 12 to 1. The draft is between 2 foot over the hull and 8.9 foot over the daggerboards and rudders. The engines are Volvo Penta 300 HP diesels Model D6-IPS800 (listed, but I doubt this much power).

DSS foils cannot have their angle of attack cannot be adjusted resulting in a catamaran that is very sensitive to fore and aft trim. Do not overload the EG bow storage or you may find you have a no foil lift. The DSS foil is designed to provide a boost to performance at times, while being simple and easy to use (you pull the foil out and that’s more or less it) thus allowing it to be used by regular sailors without physics degrees. The lack of trim ability makes the DSS foil ‘dumb’, but it takes some wisdom to appreciate the subtlety of its shape, curvature, and section, as well as how it relates to the water plane, the centre of buoyancy, and the boat’s centre of effort.to make really effective use of the foils.

The accommodation is 3 double berth cabins (including I master cabin in 1 hull) and ensuites in the hulls and a main saloon that has seating, a table and galley connected to a large cockpit by large opening doors.

The company’s “performance” claims are theoretical, but are peak speed of 26 Knots and the cruising speed is 18 knots.

Construction is claimed to be all foam carbon fibre epoxy which explains its lighter than average weight. This company has produced many high performance monohull, multihull sailing yachts and power boats. They have the experience to build a good boat. The designer is unknown but the company outsources the design work on other vessels.

The jpegs give the idea of a cat that hopefully will be built soon to confirm its capability.

 

Infiniti 60 powercat is meant to be a tender for super yachts but can be used for daytrips or short cruises as required. The Infiniti 60 Powercat has retractable foil technology, developed by Infiniti Yachts and designer Hugh Welbourn. This offers the benefit of speed, reduced fuel consumption by up to 35%, and provides a more stable ride with much dampened pitching. With retracted foils the Infiniti 60 Powercat fully beach able.

The Inifiniti 60 powercat was designed by INFINITI YACHTS & DESIGN UNLIMITED and is 60 x 21.3 foot with a weight of 29,800 lbs. The draft is 2.4 foot. The engines are 2 Mercury 600 HP Verado’s. The fuel tanks total 2000 litres and the top speed is between 35 to 40 knots with a cruise speed of 28 knots. The numbers are from 2 conflicting sources so I cannot be sure what the real situation is.

In one report they state that the Mercury 600 HP engines are diesel fuelled and can kickup for beaching (wrong on both points). Mercury 600 HP Verado’s.have a fixed upper body and a turnable propeller foot and run on unleaded fuel. This is the reason that the power heads on the aft deck of the Infiniti cat has such a tight fit.

The accommodation is either 3 or 4 hull based cabins with doubles or 2 single berths per cabin. There is a least 2 head shower compartments. Now the interesting part. Then main cabin can be an open area with a minimal to a full galley arrangement depending on the purpose of the boat.. If the Infiniti 60 is used as a tender a minimal galley can be done, but if the boat is used as a cruiser a full galley can be done. The helming position is in the main saloon. There can also be a flybridge helming position.

The construction is listed as “state-of-the-art materials like epoxy infused carbon/foam and e-glass/foam”. To achieve such a low weight for a 60 foot cat would require some very good design and building especially with EG induction cookers, 2 fridges, Corian bench tops and soles in showers along with electric TECMA Carbon toilets etc. I wonder why this vessel is in the millions of dollars.

The foil system is a variation of the DSS foils developed by Infinti and Hugh Welbourn. The foils provide lift to increase speed and help minimise pitching providing a more comfortable ride.

The jpegs give the idea.

 

This is about a couple who enjoy boating and like to build their own. They started with a couple of trailable monohulls then refurbished a Piver type tri. The easy stuff. Then built a Farrier 9A, got an aluminum fishing ski boat then spent 5 years building a Farrier F32 extended to 36 foot. These were all practice runs for their 2019 project commencement, a 50 foot Chamberlin designed power catamaran which they are now building. The couple who are building this cat, pretty much alone, have had the usual slow downs, covid, cancer etc but are now building at a reasonable pace. (Why have I not done more in my life!).

You start with a plan, speak to a very competent design team, buy the plans, you have the land, you buy a very large shed, do a proper concrete foundation, build the shed, obtain the tools (you have probably spent over $50,000 by now) Then you start to buy your materials for the hull moulds. I feel tired even writing this. So, what did they choose to build?

A Chamberlin 50 foot cruising power cat. The cat is 50 x 20.9 foot with a estimated displacement of 26,000 lbs. The length to beam on the hulls is 16 to 1 with a Tennant canoe stern displacement hull shape. The draft is 2.7 foot over the keels, rudders and props. No engines are specified but similar sized Tennant displacement hull power cats are powered by two 200 to 230 HP Yanmars, that use only 2.7 Litres per NM at 18-19 knots.

The accommodation is aimed at serious cruising. 2 double berth cabins forward with 3 single berths in the hulls if required for grandkids etc. A proper bathroom with shower toilet basin etc and space to dry yourself etc. The main cabin has seating, table, galley, entertainment, navigation and inside helming plus 2 armchairs for really comfortable seating. This cat is setup for 2 to travel in real comfort.

The general summary of the structure of this cat is it is foam e-glass all in epoxy. The 20 mm foam is initially covered in 415 gsm uni and epoxy then the flat sheets are placed on the chipboard hull mould. The bottoms are strip planked foam glass strips where required. The entire outside of the hull is then covered with 1150 gsm triaxial with strengthening as required. The hull is then faired and put into its cradles. The second hull is produced. Then both hulls have an internal layer of glass done with a minimum of 2 layers of 600 gsm double bias, Strengthening is done as required. Bulkheads and the underwing is done next followed by the cabin roof which are all done as separate parts until the cat is ready for assembly.

Reading the website will give more insite. The build of this cat is at 50ft Chamberlin Catamaran Build https://50ftcat.com.au/

The couple building this cat are skilled and appear to work well together. Home builders can achieve great things if there is mutual support. Sorry about the limited jpegs but the website gives a clearer idea.

 

OldMulti, you exhaust me with your persistence

I have a question: I would like to build ( because this is not a production concept ) a vessel. Ive spent some time considering it, and talked to NAs, so this isnt out of the blue. Ive looked at the numbers. This vessel:

1. Is seakindly. Does not heel or roll much, and is stable in most conditions
2. Takes unstayed masts
3. Is not fast, is not slow, but can be slower if required to meet the other criterion
4. Is large, for a couple.
5. Can be single handed
6. Can stay at sea for as long as the food holds out
7. Initial estimate for main hull is 65x16. Overall beam 40, which gets right into the L/B sweet spot for a trimaran. Low angle of incidence, but flare above the WL behind the first 1/3

I have tailored the idea both mathematically and conceptually, and my conclusion is that a fat hulled trimaran, with minimal dihedral, and no structures extended onto the cross beams constructed of alloy main and wood/epoxy amas fits the bill. Especially if I put tackled, pocketed leeboards on the main hull. The amas would be habitable, and at about 200%, as well as perhaps 20% shorter than the main, and incident with the aft end of the main hull. They would have foam filled crash bulkheads and at least several inches of foam against the hull. The main could be Al, but I'm leaning towards steel w Al deck structures, and wood/epoxy decks.

I am not concerned about speed, I only care about seakeeping, seakindliness, simplicity of rig, and range. If she performs as well or better than a deep keel mono of her displacement, I'll be happy.

What say you, sir? Am I missing something?

EDIT: I'm familiar with Brent Swains work, and I follow SV Seeker, a 74 foot origami ship built in ..no kidding.. Oklahoma. I think his method would be a great candidate for main construction.

 

T. B. You will get many ideas on this forum about your needs but I will suggest you look up a 62 foot tri called "That". The story of the build is at: How THAT Came About - Part 1 https://www.mayaparaiso.com/stories/that/that1.php
The tri has a fixed rig but could be converted to freestanding masts by EG Chris White or Mr Marples. "That" has sailed far and is seakindly, reasonably fast and has a cargo hold/work shop that is 16 foot long to do timberwork. The hull is cold molded timber built on a constant camber mold. A very simple way to make a monocoque shells for the hulls. Bret Swains approach to building is very good but constant camber building is just as simple for hull shells.

The jpegs will give the idea.

 

Thanks so much. I was familiar with this story...I think I must have read it about 10 years ago.

In my case, "That" isn't what I'm looking for. She's lovely, but I need the amas to be habitable, and for the main hull to have more volume. Ive helped repair a constant camber built hull, so I'm familiar with that as well. The reason I'm leaning towards alloy or steel for the main isnt cost, its ease of repair and abrasion and puncture resistance.

I suppose I need to scan concept drawings

 

Portuguese Thomas Costa Lima designed a tourist cat for 150 passengers for day tripping. The visual aspect of this cat has been designed to attract attention for customers. The underlying catamaran is a sensible power cat that could be converted to a cruising cat if you wanted accommodation and reasonable range.

The Seagull is 60.6 x 26.3 foot with a weight of 54,000 lbs, the displacement is likely to be about 100,000 lbs with 30,000 lbs of people and over 20,000 lbs of liquids. The length to beam is about 9 to 1. The draft is 4.6 foot. The engine power is two 225 HP engines with shaft drive. The fuel tankage is 2000 litres.

The Portuguese-built power catamaran designed to accommodate events on board. She has two independent exterior decks (allows you to create two different environments, each with a unique atmosphere), two bars, a large glass-enclosed living room and bathrooms. Equipped with Bose audio system, Video/TV and Wi-fi. It can fit 150 passengers between the main deck and large fly deck, complemented by a net at the bow.

No indication of performance or fuel usage but being a charter cat I would expect a cruise of 9 to 12 knots. This is designed for a task and appears to be very successful as a charter cat.

The jpegs give the idea.