Multihull Structure Thoughts

[oldmulti]

This is about the cats capability, not so much about the structure as we have covered the construction before. The cat we are talking about is the Tiki 21. This specific cat crossed the Tasman sea (between NZ and Australia, about 1500 miles) in 2017. The crew was a father and his 6 year old daughter.

The reason for the trip is a not unusual problem. The girl's mother, New Zealand-based went to Social Services, where she was divorced from the 6 year olds father and had to resort to professional help to find her ex-husband and daughter. The first time it happened was on the eve of a divorce hearing to decide which parent would have the daughter stay with.

The father and daughter went on a sailing trip which was meant to be between 2 NZ ports. The NZ authorities searched for the cat and crew when it did not arrive in the NZ port the next day. When the cat finally turned up in NSW in Australia, the father said he was surprised people interested.

The yachtsman gave an interview to the local media in which he was genuinely puzzled by the «mass hysteria» surrounding their disappearance: “the daughter made a 56-day cruise before she turned one year old, so a 27-day voyage would not be long for her”.
When asked how a catamaran heading for New Zealand Cove ended up in Australia, He explained that he had been caught in a storm on the high seas. The rudder of the catamaran broke and the wind started to blow the boat towards Australia. He had a repair kit to fix the rudder, but the weather kept him from doing so. Asked why he had not reported to authorities in Australia he said he was busy with other things. The boat had ample supplies for 30 days at sea “just in case of a delay in his one day trip in NZ.”

Back to the TIKI 21 capability. The Tasman sea can be a nasty place to sail in and you need to be a good seaman to make the trip unless the weather gods are very kind. But Tiki 21’s have not only crossed the Atlantic but also circumnavigated. Cooking Fat owned by Rory McDougall went global years ago. A Tiki 21 only has minimal bunk room and storage space so you will not travel in luxury but the cat will get you there.

The Tiki 21 is 21 x 12 foot with a weight of 800 lbs and a displacement of 1800 lbs. The 20 foot 104 x 3 mm aluminium tube mast carries a 207 square foot rig. The draft is 1.15 foot.

The jpegs below give an idea of construction. Mainly 6 mm ply and a lot of epoxy and timber.

And to give an idea of the performance of his near standard Tiki 21. “On this day, Little Cat was tacking through from a best of 96 degrees to a worst of 116 degrees, and maintaining an average 3 - 4 knots progress directly to windward. Working in our favour was a breeze in the golden range of 10-15 knots true, and Little Cat had a freshly painted (smooth) bottom.” His Tiki 21 has peaked at over 15 knots on reaches and can average 7 to 8 knots under favourable conditions without pushing too hard. He found good sails help enormously.

 

[SolGato]

Sundreamer is the iconic performance cruising cat designed by New Zealand artist David Barker, and built by David and Fiona Kay in 3 years 7 days a week on a New Zealand farm and launched in 1983. David is an artist first, boat designer second and after building a 40 foot light bridge deck cat, Sundancer, he then designed a 62 foot cat, Stratosphere, for Gordon Miller which was built under David’s supervision. The basic principles of Stratosphere were replicated in Sundreamer but in a slightly smaller and lighter package. David is a lateral logical thinker and could not afford an “expensive” cat built by others and reused the mould (yes, 1 mold generated 14 parts to build the boat) used to build Stratosphere.

Sundreamer is 57 x 28 foot with a weight of 10,700 lbs. The 60 foot mast carries 1070 square foot of sail in its basic rig. The length to beam of the hulls is 18.5 to 1. The draft ranges from 1.3 foot to 5.6 foot over the daggerboards. The tiller steered rudders are kickup. The power was in one hull is a 9.9 HP outboard. This is a sailing machine, the engine is rarely used.

And to the question of performance 26 knots peak, 22 knots averages for an hour and 10 plus knot averages for 24 hours. Yes, it can really sail and has raced successfully under its 3 owner who tend to keep Sundreamer for 10 years plus.

The accommodation is effectively 2 separate hulls, each hull has 3 single berths with 2 additional berths in the forward crossbeam tubes. There is a minimalist galley and toilet facility. There's no plumbing, but a chemical holding tank toilet is used when cruising with more delicate friends. There are only seven electrical switches, for dual logs, VHF transmitter, navigation lights, cabin Iights (concealed neon tubes). None of the owners have upgraded the accommodation finding this minimalist approach a benefit as maintenance is significantly reduced.

Now we get to the fun part. This cats hulls and decks are solid glass averaging 3.2 mm thick. This cat has been sailing for 41 years. Yes, this lightweight structure works very well. The fiberglass was a 6 oz CSM, 3 x 15 oz unidirectional fabrics (effectively a triaxle fabric before triaxle was available) with 18 oz kevlar on the flat and high stress area average thickness is 3.2 mm with 230 x 51 mm klegcell top hat stringers under bulkheads. The bulkheads are foam cored with unidirectionals at 45 degrees on both faces. The cross beam tubes are 2 foot in diameter with foam, unidirectional fabrics and kevlar. There is strengthening under the mast step. The hulls are angled in at the top to reduce the length of the crossbeams. The weight of the 57 foot Sundreamer was 20% less than the 62 foot Stratosphere.

The genius of this build is the majority of the components came from a simple half circle mold. The majority of Sundreamer was lifted from that mold, as were the underbodies, the side decks, and the blisters on either flank. There are 14 different applications of the same shape in Sundreamer, the pieces were simply assembled at the end of the construction process through the magic of fiberglass and kevlar.

If you read the attached PDF you will get the majority of the story but there will be another item tomorrow which will give greater detail. The jpegs give the idea of a spectacular sailing catamaran.

Posted on SA forum today:

 

[BlueBell]

Multihull or Stabilized Monohull?

A Fully Autonomous Ship's Perilous Journey at Sea https://www.popularmechanics.com/technology/infrastructure/a44936536/autonomous-mayflower/

 

[tane]

@Tiki 21:
maybe worth mentioning, that the name of the circumnavigating "Cooking Fat" was a little wordplay with interchanged first letters...
(& that sailing offshore in anything above maybe 12kn windspeed would be living in the waterjet of a fireengine ...we had a 34' Wharram - palatial by comparison - & that could be absolutely miserable. Arriving in the Marquesas we had grownwebs between fingers & toes...what with the aquatic existence...

 

[oldmulti]

Patrick Balta designed a large 78.7 foot motor trimaran "Etoile Express", made of plywood which is easy to build, very light, very thin and particularly economical on diesel. It can reach high speeds with relatively little motive power.

The Express is 78.7 x 29.5 foot with a displacement between 33,500 lbs and 38,000 lbs depending options chosen. The length to beam on the main hull looks about 10 to 1. The draft over the skeg and propeller is 6.8 foot. The single chine hull with a slight V aft but has a steeper V forward. The floats are short and have a flat bottom.

The single 600 HP diesel with shaft drive can power the tri to 24 knots peak speed and average 15 knots using 20 litres/hour. Slowing down to 8 knots consumes 7 litres/hour or at 10 knots 11 litres/hour. Cruising at 15 knots will provide a 3000 mile range with the 4000 litre fuel tank. This is an impressive fuel economy for a simple to build cruising power tri.

The accommodation is not specified but the central hull is long and wide enough to have several double berth cabins and toilet areas. The main saloon upstairs is large enough to have a large galley, seating, dining and inside and outside helming positions. The Express looks like a charter vessel and is used as a chase boat for photography and filming. The Express could also be used as a fishing vessel.

The construction is plywood, timber and ply framing with timber stringers and can be supplied as a kit if required. The hull panels are slightly compounded to add a bit of shape and strength. The structure can be made with light softwoods such as Spruce or Hemlock. The plywood should be of a light species which has a good strength/weight ratio EG Okoumé is satisfactory. The adhesive will be epoxy. A good polyurethane paint will provide good UV protection. The deck frames in one jpeg should give an idea of how much work is required to build a vessel this size in timber. There would be glass cloth and epoxy used to seal the structure. This concept of power tri could be very easily adapted to aluminium or foam glass.

The jpegs give the idea of a very interesting economical power trimaran.

 

[oldmulti]

This item is an indication of the extremes some designers are prepared to go to EG reduce windage on their monohull cruiser racers. Jay Paris has been a naval architect, oceanographer, winch designer for ocean racers and AC 12-Meters, author, and technical editor. His personal boat is a 32 foot sloop Petrel.

Jay has many long-contemplated and refined design concepts he wanted to try, among them them was minimal-windage lifeline Nitronic stanchions made from the high-strength, corrosion-resistant 22-13-5 alloy (also sold as Nitronic 50). Yes rod rigging for large boats.

Petrel’s distinctive lifeline stanchions were fabricated from 0.59“-diameter (15mm) Nitronic 50-60 rod rigging. The choice of material was informed by an earlier event when Ken King was the head of rod-rigging supplier Navtec, he made Nitronic stanchions for his boat. On one occasion they tangled with those of another boat. The stanchions on both boats bent back until they disengaged; reportedly, King’s sprang upright, and the other boat’s remained bent.

The Nitronic stanchion fabricated from rod illustrates has approximately 40% reduction in windage, compared to a 1″-diameter stainless-steel tube for a conventional stanchion. The taper of the upper portion of the rod is just visible where it is not shown on the original drawing above.

Jays plans included a 3⁄16“-thick (5mm) base plate and a 1⁄16“ (2mm) addition to compensate for deck camber so that Petrel’s upper lifeline is 24“ (610mm) above the deck.The first task in fabricating these Nitronic stanchions was to straighten the Nitronic rod rigging, which is shipped in coils. Before use, the stainless alloy must be fed through a straightening device, which any rigging shop that fabricates rod rigging would have. Once it was straightened,

The upper lifelines are 3⁄16“-diameter 1×19, and the middle ones 1⁄8“-diameter (3mm) 1×19. For both, I used antimagnetic Nitronic 50 1×19 wire that had been produced for the U.S. Navy for use on minesweepers but is no longer available. Its advantage for lifelines was that there is no worry about corrosion inside their end fittings. Each Nitronic stanchion weighs 1.74 lbs (0.79 kg), which is 94% of a 3⁄32“/2mm-wall 1“-diameter stainless-steel tube of the same length.

So if you want to have the latest low windage deck gear you know what you have to do. Forget your carbon fibre lifelines go Nitronic. The jpegs give the idea.

 

[oldmulti]

We have had some of the jpegs of this tri before but not much description so we add to the story now. The Patrick Balta 14 mtr tri is a fast cruising trimaran designed for serious offshore work. Patrick Balta. gained a lot of flat panel experience when he worked for Geoff Schoining in Australia. Patrick used this experience and his liking for plywood and timber in a lot of his designs since as we have seen.

The Balta 14 mtr tri is 46 x 29.5 foot weighing 11,900 lbs and a displacement of 14,000 lbs at half load. The 60 foot fixed aluminium mast carries 1100 sq foot of sail area upwind.. The length to beam on the mainhull is 7 to 1. The float length to beam is about 15 to 1 when heeled in a breeze. Draft over the daggerboard is 8 foot. With the board up and the rudder kicked up the draft is 2 foot over the skeg and propeller. There is a 40 HP diesel inboard with shaft drive.

The accommodation has a double berth cabin aft, a cockpit then a main saloon with a galley and a toilet area opposite. A saloon with table and seating (able to convert into single berths) and forward another double berth cabin. There is storage forward and in the floats.

The construction is plywood with plywood and timber edged frames. There are multiple stringers with what appears to be fiberglass tapped chines in the multi chine hulls. The decks have extensive deck beams and plywood roof structures. The cross beams are box beams with timber flanges top and bottom. The cross beams appear to be bolted to the floats.

There are no performance numbers but I would suggest up to 20 knot peaks and 10 knot averages possible in good conditions. The Jpeg aaa and jpeg aaaa below illustrate a 17 degree heel where the main hull is just about to lift. The bow of the leeward float is just submerged but there is still sufficient righting moment to continue to drive on but reefing would be very advised.

The jpegs (spread over 2 items) give you a very good idea of the tri.

 

[oldmulti]

Balta 14 mtr trimaran construction jpegs.

 

[oldmulti]

This item is about a monohull power boat built by a Reid Bandy who runs a one-man design and build shop of 4,500 square foot in Edgewater, Maryland. Reid thinks an efficient boat is more fun than a high speed image machine. There is a lot to learn about light structures in this story.

Reid Bandy, new monohull 32 foot power boat which is a foam-cored carbon fiber sport fisherman he launched in 2023. The custom boat weighs 4,100 lbs fully loaded and weighed only 1,900 lbs, before installing the engine, tanks, and batteries, and can run at 35 knots powered by a single 300 hp Mercury outboard. The hull shape is a deep V of 13.7 degrees at the stern.

Being a sports fisherman, it has an open cockpit with a shelter over the helming station.

The design of the 32 footer evolved over a series of power boat designs he did with a few friends that worked with EG Bruce Farr (Mick Price a designer and CAD expert) and guys who build big sport fishing power boats in South Carolina. Result Reid designed and built a 26 foot Carolina style skiff in 1998 out of CNC-cut jig frames. Reid tried a combination of new materials like Durakore, WEST System epoxy, fiberglass and balsa. A 225 HP outboard pushed the boat over 30 knots.

Next came an experimental 24 x 6 foot Carolina style skiff that was built from a roll of 20-oz 12K, 2×2 carbon twill, some 5-lb Corecell and an old 2-stroke Yamaha 90. The boat weighed 385 lbs without the engine or fuel. It ran at 32 knots very smoothly in small waves.

Reid was inspired to build a better version but was sidelined by restoring 2 large sports fishing boats for over 2 years. But an old customer of one of his other businesses (he owns and runs a many employee successful car body repair shop on the side) came in and wanted a custom sports fishing boat of a similar concept that Reid wanted to design. The owner wanted a light weight sports fishing boat that could get to a fishing ground quickly with needing big engines and a lot of fuel.

Reid then finalised a design and with a friend calculated scantlings required and commenced to build. The hull had a carbon fiber inside skin over 1“, 5-lb Gurit Corecell foam panels and a carbon/E-glass outer skin. Reid chose Gurit’s heat-tempered M80 foam to accommodate the expected heat of an all-black hull, with 12-lb foam in the engine/Porta Bracket-mounting area. The inside skin would be a layer of 11.5-oz 2×2 carbon fiber twill underneath a layer of 5.5-oz carbon 2×2 fabric. The bottom panels would be the same 5-lb M80 core material and carbon fiber inner skin but with a tough outside layer of 17-oz #1700 (no mat), 45×45 E-glass backed up with two layers of 18-oz, 0-90 E-glass fabric. The topside outer skin would be 17-oz, 45×45 E-glass with a layer of 11.5-oz carbon fiber fabric on top for strength and to show under a clear-coat finish. Reid built the decks with 11.5-oz carbon fabric on 5-lb foam. The transom would have as much as 10 layers of E-glass and carbon fiber to tie the engine loads to the transom braces and stringers. (Bandy ended up using nearly 40 linear yds of 17-oz Fabmat tape to make those connections.)

Carbon fiber reinforced composites (CFRC) are twice as strong as the strongest steel. That’s the primary benefit. CFRC also features low crack growth from impact or fatigue and can be cost-effectively and strategically laid up to address strength and loads. However, carbon is highly conductive and electrochemically noble, which means a metal that is electrically connected to carbon fiber will be highly susceptible to galvanic corrosion. All that’s needed to start trouble is carbon fiber, metal, an electrical connection between the two (contact), an electrolyte (salt water), and oxygen (from the water). The situation becomes worse when carbon fiber (i.e., a boat hull) connects to metal (fastenings, through-hull fittings, engine mounts, etc.).

Furthermore, galvanic corrosion around a fastener can produce localised blisters similar to the rampant pox we’ve experienced in legacy polyester/fiberglass boats that spent most of their time in the water. The good news is epoxy resin is substantially resistant to this issue, and an epoxy/fiberglass outer laminate is helpful in that regard while also protecting the carbon fiber from minor impact damage. Carbon and epoxy are fine together, so the answer to the corrosion concern is to insulate metal fasteners from the carbon with epoxy.

The owner wanted to clear-finish the carbon fiber topsides, which put pressure on the builder to achieve a cosmetically perfect layup. Bandy accomplished that with care and 11 coats of clear Awlgrip G3005, with the first seven coats rolled and tipped and the final four coats sprayed to achieve a 20-mil thickness. Then he moved her out into the sun to bake, essentially effecting a C-stage epoxy cure with daytime surface temperatures upward of 120°F (49°C) for a few days.

To quote a test on performance “She quickly lifted onto a plane at 10 knots with essentially no bow rise, only the sensations of acceleration, torque, and power you might expect in a Tesla. She topped out at 40 knots. Fuel consumption gauges indicated 4 mpg at 20 knots and 2.5 mpg at 35 knots.”

Haley (the owner) reports that the boat will run like that in most any sea condition all day long. “The harmonics are good, and there’s no sense of stress on the boat or passengers at that speed. It’s all we would want for our usual transits.” Haley also said “It’s actually “Reid's boat” in his mind. I just get to use it and pay for it, and I’m fine with that. You see, Reid and I share an addiction, but instead of a 12-step program, we just build another boat.”

The jpegs give the idea of an interesting well thought out build.

 

[oldmulti]

We again will feature a power boat but the material and propulsion are different. The Amsterdam canals (Holland) are are over 60 miles long and have 1500 low bridges over them. The city needs the usual Police patrols etc. So Amsterdam order several new tough environmental friendly Patrol boats from Tideman boats. Tideman boats are tough there is a video of them deliberately running a boat up onto rocks at 5 knots plus and pull away with no damage. The canal walls in Amsterdam are rough stone plus many older boats are moored in some canals so coming along side can knock a boat around.

The patrol boats are 30.2 x 8.8 foot with a displacement of 11,000 lbs. The draft is 5 foot. The boat is all electric powered by twin Siemens 30-kW electric motors married to MerCruiser Alpha sterndrives and has 90 kWh of LiPO4 batteries by New Electric Marine. The vessel has a 10 hour range at 5 MPH (8 kmh).

The accommodation is to suit the task, an all weather deck house that has has seating for 5 with an internal and external helming position. There is also a small toilet area and galley forward,

The construction of this vessel is standard Tideman. That is HDPE plastic. The hull skin and decks are 15 mm (0.59”) thick HDPE with the scantlings made of 20mm (0.79“) HDPE. The frame spacings are 500 mm apart. All of the HDPE is electronically “welded” together to form a strong continuous structure.

HDPE is more flexible than EG plywood and requires more support framing but HDPE can be cut with hand tools but the electronic welding requires specialist knowledge. There is a NZ designer who has designed a 43 foot sailing cat for building in HDPE and Craig Schoinning has a 28 foot motor sailer cat designed in HDPE.

The limited jpegs give the idea.

 

[oldmulti]

The Elcat electric power boat is a pure fun device thjat is a lotmore practical than it appears. The Elcat is 14.7 x 8.2 foot and weighs 264 lbs. The carry capacity is 1330 lbs (about 6 people motor and battery package. The engine is a 1.3kW electric outboard motor (Epropulsion Spirit 1) with a 1.3kWH battery (the motor and battery weigh 40 lbs total). Included as standard is a 200 watt solar power to extend range. This combination provides a top speed of 6 knots. Elcat will run many hours at trolling speeds and go even further with an optional larger roof top solar package. The charge time for grid power for the battery is 8.5 hours.

The overall boat is 6.5 foot tall. And the Elcat is transportable as it folds down to 4 x 2 x 2 foot package. Yes, it is a strong inflatable boat.

The internal layout is set up for 6 people to sit or there is enough floor space for 2 people to sleep and do minimal camp cruising. If you have canvas or clear screens all around you can have a nice self contained mini cabin for the occasional overnight.

The Elcat is made with drop-stitched, double-walled, structurally laminated PVC. Think of a whitewater raft or a Navy tender boat, made of the same materials, as a result this craft is made to last.

This is an interesting concept that is more versatile than first appears. The jpegs give the idea.

 

[oldmulti]

Waveflyer is an electric powered hydrofoil flying fun boat for 2 people to have a fun day out on the water. Joshua Portlock, the company’s co-founder and CEO. “We are proud to showcase our Australian innovation to the world”.

The Waveflyer is 9.5 x 4.1 foot with a weight of 440 lbs. The Waveflyer can carry 440 lbs of crew (2 people). The draft is 0.8 foot over the hull with the foils retracted but draws 3.1 foot with foils down at rest. When flying the hull is 2.3 foot above the water. The dual electric engines and battery sizes are not mentioned but the Waveflyer base model can travel for 1.5 hours for up to 22 miles. The optional battery model can travel 3 hours and 40 miles and the final option can travel 4.5 hours and go 60 miles. The battery recharge time is 45 minutes.

Volare’s electric propulsion units are fitted at the back of its retractable foils. When at rest or in shallow waters, these foils lift up level with the hull. In this position, the craft looks like a traditional jet ski, but as it glides through the water and reaches speed, its body rises up with the twin hydrofoil propulsion system slicing through the waves.

The patented W-Foil benefits include higher foiling height, larger wave operation and more dynamic maneuvering with tighter turn capability. Also a tolerance to crew moving whilst underway and a tolerance to payload imbalances.

The Waveflyer takes off at 8 knots and can peak at 22 knots. Parts of the Waveflyer technology is patent pending including the foiling shape and positioning, The foiling control system is an auto-stabilising, semi-autonomous that is controlled by a Flight control Unit (FCU), which is the brains behind the performance, safety and reliability that the WaveDrive system. The fly-by-wire control system also supports remote control, enabling the boat to be guided remotely using a phone app. This feature is aimed mainly at rental operators, who can guide the boat to safety if the pilot falls off. It also comes with a built-in geofencing feature that can keep the boat away from certain areas and restrict it to others. If the boat gets stolen, it can be shut down remotely.

The construction of the hull is fiberglass with some foam. The foil system is aluminum with some stainless steel.

The Waveflyer web site is https://enautic.co/volare and has more detail and video’s of the boat in action. The jpegs give part of the idea

 

[oldmulti]

Hi. A little busy today, will be back tomorrow.

 

[oldmulti]

Hi. Problem with partner's health (minor) will be back Saturday (Australian time).

 

[oldmulti]

After a previous entry of the Elcat electric catamaran fun boat. This 6 meter boat is also manufactured by Hungary's DDD Manufaktúra and is known by the Portless Catamaran name. Again it is an electric powered cat that is more a moveable “island” for a days fun.

The Portless Deluxe is a 19.5 x 10 foot catamaran that weighs 775 lbs in its basic form. The Deluxe has standing headroom and a top deck that can support 770 lbs. The Deluxe is designed to carry up to 8 people. Basic propulsion is provided by an Epropulsion 1 Kw electric outboard but the cat can have two 1 Kw motors or up to two 3 Kw motors but this is not a speed machine. The speed tange is 4 knots with 1 Kw to 8 knots with two 3 Kw motors. The battery capacity can range from 1.4 Kw to 2.8 Kw hours with a 4 hour range depending the engine power. The roof top solar array can extend the range and reduce the recharge time. Realistic range is about 30 miles.

As the Portless Deluxe is an inflatable boat it is very transportable and can be disassembled into components but the total package weighs 770 lbs which will require a good SUV with a strong battery to power the air pump to inflate the boat.

The Deluxe has much more space and comfort than the Elcat 14.7 foot model and as a result is more of a party boat allowing an inflatable lounge, other seating and a proper steering/helming station. With a portable fridge and the optional PVC screens or curtains you can create a weekend camp cruiser in sheltered waters.

The construction again is sturdy drop-stitch double-walled, structurally laminated PVC hull construction used for inflatable paddleboards etc. This is a similar technology used for white water rafts, high speed tenders, rescue craft etc.

Portless also have produced a later model, the Deluse 2 which is 23 x 10 foot, 770 lbs and can carry up to 10 people and is classified as a “trimaran” hull. Interesting. (Image in the last jpeg)

The jpegs give the idea.