Multihull Structure Thoughts

This is about plywood construction not about the monohulls but the boats are interesting. The first is about a 62 footer called “Infidel” built 60 years ago by John Spencer in NZ. Infidel went through many owners but became world famous under the name of “Ragtime” winning the Transpac on several occasions and EG Newport Esanda race etc. What is infidel/Ragtime A 62 x 11.9 foot plywood single chine monohull with a 11 foot deep fin keel. In its latest configuration it has an ex TP52 rig on it which is more than enough power to overload the narrow chine hull that was lengthened to 65 foot and had a modified deep bulb keel with the rudder moved aft. It is now a lot faster than when it was built and launched in 1965.

The interesting part of Ragtime is its over haul in 2020/22. The 2 layers of 9 mm plywood over kauri stringers and frame hull required virtually no repair. John Spencer the designer and virtually single handed builder built the design for Tom Clark, a very successful NZ business man. Spencer was not only a fast builder but was very precise resulting in a watertight structure that lasted for years. The floors that supported the fin keel ran the full width of the boat and were designed to meet the needs of the yacht.

In 1965 Infidel/Ragtime did not meet any know structural classification rules (she displaces 24,000 lbs including its 9000 lbs keel in a period when a “fast” 60 footer weighed 50,000 lbs) and was barred from races like the Sydney to Hobart because it was deemed structural unsafe. The fact its was very fast and could outsail the majority of 1965 Sydney to Hobart yachts had ”no” influence on the SYSC decision to ban it.

So how do NZ people build plywood boats that last 60 years. A hint comes from a guy who is an old hand at building Elliot plywood sailing yachts. He is building his Elliot 1150, a multi chine plywood monohull fast cruiser.

The NZ guy said: “The loaned shed was more than three times the footprint of the boat, but I used all of it. The frames, floors, structure, keel, rudder and decks were built off the boat, the bench saws and other machinery required space to use, and materials needed to stay dry. Neil also had a fork-hoist that came in very handy building a boat short-handed. By mid-March 2021 I was setting up the hull. The cloth was laid over the boat and the rebates for the laps marked and cut in with a power plane. The first real problem presented itself when I started fibre-glassing.

The plywood was gassing badly when the resin went on, forming air bubbles that could not be worked out through the heavy cloth. To stabilise the ply, I rolled on resin and applied Peel Ply to remove the amine blush, a chemical byproduct on the surface of cured epoxy that I had to be mindful of throughout the build.

After laying all the cloth over the boat, marking where the sheets lay and rebating the laps into the plywood, each section of cloth was numbered and rolled onto a pool noodle and stacked away under plastic. I mixed the resin while Neil frantically applied it with a roller and the glass cloth was spread over the wet resin and more resin was applied on top. This would give 99% saturation and air removal, and was further fixed with a rubber squeegee that also distributed any excess resin. Finally, a wide steel roller bedded it down for good. I would then clean up and, as the resin was starting to tack off, a layer of micro balloons filler was generously applied. We did just one strip over the boat per day.

Next, we had to turn the hull over Upright and sitting on a cradle, the boat was starting to take shape. After applying resin to the inside of the hull and removing the blush, it was ready for the keel floors and more structure. After glassing the inside of the hull, it was time for keel floors. These are a series of solid wood beams with an engineered layer of fibreglass covering them. I spent over two months just building this structure. The keel floors and associated structure were built off the boat, glued in place, and then glassed to the hull. This area was painted and then the engine (a 57hp Yanmar) was installed. The foredeck (made in foam glass) frames were lofted on the floor in the same way the hull had been, but in foam. When finished, the foredeck structure was lowered into the boat with the fork-hoist and glued down to the hull.

The message here is in both cases understand the materials and timbers you are using, then appreciate the glues/resins you are using. Experiment and test if the EG plywood reacts to the resins being used. Outgassing can happen in ply and/or foams when layups are being done. If the ply surface is effectively sealed prior to a glass surface layup you will have an excellent chance of having a 60 year yacht. Good tight joints with a minimum of filler also helps a lot.

The jpegs are first of Infidel Ragtime, the second are of the Elliot 1150.

 

Pierpaolo Lazzarini has some very big, really big ideas. His latest effort, the Air Yacht, is designed to travel the sea or the skies in style, buoyed by twin helium-filled airships. By sea this “catamaran” will do 5 knots but take off and fly this airship catamaran will fly at 60 knots. Pity the initial estimates for a build is $550 million Euro or about $600 million US. I don’t think we will see one flying anytime soon.
The Air Yacht is 492 x 262 foot wide with each tubular ballon being 50 foot wide. Those twin carbon-fiber airships also feature a honeycomb of cells, or “hives”, that hold 14.1 million ft3 (400,000 m3) of compressed helium allowing the craft to fly at 60 knots for more than 24 hours.
The engines also rotate to push the airship down and land on the water, with depressurization of the helium and ballast anchoring system keeping it on the water, where an “inflatable basement” keeps it afloat and allows it to travel at a speed of 5 kn (6 mph, 9 km/h). There’s also room for an optional helipad on the top of the central deck to allow travel to locations that can’t accommodate a massive amphibious airship.
There is a central pod between the 2 balloons 33 foot wide that houses the accommodation which has a master cabin with 360-degree views, a large dining area and a living area. There are also windows on the outer edges of the airships, each of which contain five en suite staterooms.
The jpegs give the idea of the ultimate luxury that any worthwhile billionaire should aspire too.

 

Hi. I have a minor medical (no real probs) and will be back in about 10 days. Have fun and stay safe for a while.

 

Are you okay, Oldmulti?

 

Thank you Russell. I am OK, just disconnected for a week or so. Back tomorrow.

 

This is about a custom built by Quentin Pascal and designed by Joubert-Nivelt Design for the Route De Rum in about 1997. The cat was an open wing deck 2 person pure racer. She was soon turned into a high performance day charter machine in the Windward Islands. More recently, she performed in local regattas (Heineken Regatta, Voiles de St. Barthelemy, Caribbean Multihull Challenge, Caribbean 600). She got through the demanding trade wind courses well. Everything on this light (10,000 lbs), sporty cat is optimized for performance, yet she is sturdy and robust. She sails in the mid to high teens easily and tops 20 knots in the right conditions.

The cat is 52 x 28 foot and weighed 10,000 lbs. The 60 foot rotating aluminium mast standing rigging is cap shrouds of16mm Dyneema, lower shrouds of 14mm Dyneema and a forestay of rod rigging. The running rigging is Gleistein ropes with a Dyneema core with polyester jacket. The mast carries a 850 square foot mainsail, a 344 square foot jib and a 1,290 square foot screecher. The draft ranges from 4 foot over the rudders to 6 foot over the daggerboards (cut down from racing days). The underwing clearance is 4 foot. There are 2 Yanmar 3YM 30hp engines driving through SD20 saildrives. Under power the cat cruises at 8 knots and can peak at 10 knots.

The accommodation is minimal. 2 berths and 2 toilets. Storage is for EG lifejackets and portable ice boxes. Charter seating is on the trampolines to get that wet feeling.

The build was GRP foam with Kevlar. No idea of the crossbeams. The cat has had 2 major refits of sail gear but the hull has only had cosmetic upgrades which indicates a well built base structure.

A good use of an ex racer that can still show a good turn of speed for the occasional fun race or day charter. The limited jpegs give the idea.

 

The Antigua 37 is a solid cruising catamaran from the 1990’s. It was designed by Flahault Design & Associates, Joubert-Nivelt and built by Fountaine Pajot. The cats basic design maximizes cruising sailing performance and seaworthiness.

The Antigua 37 is 37.1 x 19.7 foot with a weight of 9,920 lbs. The 50 foot fixed aluminium mast carries 738 square foot upwind with optional additional downwind sails to increase p[performance. The length to beam is about 10 to 1. The draft is 3.5 foot over the fixed low aspect keels. The underwing clearance is 2.4 foot. The engine options are either 2 x 20 HP or 2 x 30 HP inboard diesels.

The accommodation has 2 double berth cabins with one toilet shower cabin in each hull. The main saloon has a galley, small navigation entertainment area and a large table seating area. The cockpit has the helming external seating area.

The performance is reasonably good and test reports talk about 12 to 15 knot peaks and averages of 7 to 9 knots. The cat will go upwind reasonably but this is not a high performance cruiser. It will do a good job if you are a true cruiser.

The structure is solid glass underwater and cored glass above the water line. There are few reported structural problems but 30 year old boats have gear sail issues if they are seriously used.

A reasonable cruising design if you can find a good second hand one. The jpegs give the idea.

 

The "Seawolf X" is a 140.25 foot hybrid-electric catamaran, designed by Fulvio de Simoni Yacht Design and built by the Italian ship yard Rossinavi. Th cat is available for luxury charter, featuring eco-conscious design, AI-powered systems, and accommodation for up to 12 guests. The Seawolf X offers a variety of leisure facilities, including a pool, jacuzzi, home theater, and a range of water toys.

The Seawolf X is 140.25 x 45.1 foot with a Gross Tonnage (GT) of 499 tons. This is not the weight or displacement but a old “space” calculation used in shipping. Larger than 500 GT requires a lot more structural and safety equipment on a “ship”, result everyone tries to get below 500 GT. The draft is 6.1 foot. The hybrid electric system provides a 5400 nautical mile range at 8 knots, a normal cruise speed of 10 knots and a peak speed of 12 knots. The other big benefit of the sub-500GT cat was ample area for solar panels (covering 150 square metres total) and plenty of space for storing batteries. When the yacht is in hibernation mode, the yard proposed “giving back” energy to power shoreside residences, essentially making the yacht the most expensive battery bank money can buy.

The catamaran could undertake a 20-day transatlantic crossing and, in theory, burn just 15,000 litres of fuel, compared to a similar-sized monohull burning 60,000 litres. An actual Atlantic run the cat used just under 20,000 litres of fuel. Seawolf X also features Rossinavi’s newly developed AI system, which is designed to predict future consumption, provide recommendations for fuel-saving initiatives and make helpful tweaks around the yacht. “It detects when guests are not in a cabin, and it switches off the air conditioning and the lights”.

The accommodation is vast. There can be12 guests in 5 fully serviced cabins and they are serviced by 7 crew members who have their own separate accommodation areas. The lounge entertaining areas are large and each guest cabin has more space than your average house. The deck area has a forward pool lounging area as well as various sub decks for launching of various water toys.

The performance has been specified above and this vessel is very fuel efficient but this is still an expensive way to transport 19 people across the Atlantic.

The construction is aluminum in the hulls, decks and superstructure. The interior ranges from lightweight timbers, foam glass and a variety of fabrics from leather to silk and linens etc. Light weight luxury throughout.

The jpegs give the idea of what is possible. Recently BYD EV car company announce a new battery recharging system will be available soon for BYD cars in China with under 10 minute recharges for 400 KM trips. This is a real game changer.

 

This is a personnel watercraft that took 4 years from conception to production and sells for about 120,000 euro’s. What? Oh, it has a payload capacity of 100 kilo’s (220 lbs) and can fly on hydrofoils 2 foot above the water at up to 30 knots. The Finnish designer, developer and builder has developed a sustainable single seat hydrofoil craft that uses very low electric power to achieve all of the above.

The Foil.One is 16 x 3.1 foot “monohull” that weights 286 lbs without batteries and 448 lbs with the 2 48 volt 5 KW Torqeedo batteries on board (1 forward and 1 aft or the skipper). The batteries drive an 18.8 KW (25 HP) motor on the rear foil for 2 hours at a cruise speed of about 18 to 22 knots with a peak speed of 30 knots. The range is about 50 nautical miles. Recharge time is 2 hours.

The T foils for and aft have a draft of 3.3 foot in displacement mode, or about 1 to 1.4 foot in foiling mode. The rear foil is fixed with a motor pod at the T foil intersection. The front foil has a flap on the foil which is controlled by a wand (like Moth sail boats) which provides lift depending on the boat speed. Take off on to foils happens at 10 knots. The actual ride height is automatic but can be set to ride slightly higher or lower by a preset knob on the forward foil. Steering is done by handles in the cockpit that turn the forward foil.

The build is “pure” carbon fibre (presumably with epoxy) according to the builder. The shape of the hull and light weight components would allow a stiff light structure og the Foil.One which results in its good performance with small batteries.

An interesting concept that if it could get into mass production would be a lot cheaper. There is a 2 person boat in development which could be very interesting. The jpegs give the idea.