Multihull Structure Thoughts

oldmulti · May 1, 2025

The following are some of the possible future designs according to some designers. There was an attempt to get the America's Cup and SailGP groups to merge the design of the yachts used on the two high-profile circuits. This cost-saving measure will ensure that teams only have to purchase one type of boat to compete in both events.

There was a long and torturous path to try and reach a common ground between the F50 catamaran and the AC40 / AC75 monohull yachts, suggesting the ACSGP 51.25 as a design.

The main hull will have a foil arm, while the outrigger will have a T-foil, as has been tested recently in the SailGP F50. The sail configuration was another sticking point, with the double-skinned mainsail favored by the America's Cup contingent, and solid wings by the SailGP representatives. In the end the solution suggested a solid jib, combined with a longer section wing mast, still accommodating the twin main solution.

Now be very careful with this “suggested view of the world of sail racing” as it was released on April 1 (April fools day). Further investigation suggests this would have happened very much in the back ground as the AC is a 3 year negotiation with a week of yacht racing at the end of it. Sail GP is a series of races throughout a year with millions of dollars of prize money. Very different models and very little commonality of approach. Recently NZ AC skipper Peter Burling has quit AC and looks like joining Sail GP. He wants less negotiation and more sailing time.

The jpegs show the ACSGP 51.25 and other concept designs. Study the jpegs for ideas, don’t worry to much about possible circuit mergers etc.

oldmulti · May 2, 2025

Hu'chu 55 is a 55-ft sailing catamaran, designed and engineered to meet the specific needs of actor, producer, and environmental entrepreneur Daniel Roesner. iYacht GmbH managed the Hu'chu 55 project to being one of the most sustainable undertaken so far. iYacht's CEO, Udo A. Hafner stated, 'We have designed and engineered a dozen multihulls in recent years, but the Hu'chu 55 represents a significant leap forward in terms of sustainability and circularity”

The 55 is 55.7 x 28.4 foot with an unknown displacement (estimate 45,000 to 50,000 lbs). The 72 foot fixed aluminum mast carries a fractional cutter rig with a mainsail of about 920 square foot and an 800 square foot fore triangle with an optional Code 0 as an extra. The hull draft is 2 foot with 5.5 over the rudder and fin aft keels. Over the daggerboards is a draft of 9.3 foot. The power is 2 electric motors powered by Solar panels and/or propellers providing generating power whilst under sail. There is ample battery capacity (more than 100 kWh) ensures autonomy.

To minimize the environmental footprint, the Hu'chu 55 extensively incorporates recycled and recyclable materials. Roesner has produced an aluminum specially developed for the Hu'chu 55 in cooperation with a major aluminum manufacturer which consists of over 90 % aluminum scrap and not a single kilogram of primary metal. This scrap, sourced from discarded license plates, road signs, cosmetic cans, automotive and construction, substantially reduces the CO2 footprint of the material to less than 2 kg CO2/kg of aluminum sheet, a mere one-eighth of the market average footprint.

Additionally, the boat incorporates natural fibers, reclaimed wood, and recycled cork. These materials were chosen by Daniel for their environmental contributions and circularity: utilizing reclaimed and recycled products helps close the loop, reduces waste generation, and provides these materials with a second life. The bare metal exterior lends the boat a rugged aesthetic, fitting for an explorer catamaran, while the interior is complemented with various shades of brown and black.

The rig and sail system are designed for easy handling from both the helm position and the aft cockpit. Three forestays with a self-tacking staysail, an overlapping Genoa, and a flying code or gennaker sail offer versatility to adapt to different wind conditions. Optimized daggerboards will improve upwind performance. To make it easier to handle the powerful mainsail, the mast was positioned further aft. This design decision consequently increased the area of the foresail.

The accommodation is set up for 4 people to permanently live aboard with additional facilities to accommodate a film crew to allow production of movies or documentaries for revenue generation.

The construction is mainly recycled aluminum and recycled products for environmental grounds. The rudder axles and the lower part of the hulls have been reinforced to withstand ice conditions and possible collisions with objects. The Hu'chu is also designed for beaching: rudders and propellers are protected by a pair of streamlined keels that can support the weight of the boat when beached.

The cats performance is good with 10 knot averages possible and peaks near 20 knots. The jpegs give the idea.

oldmulti · May 3, 2025

We have already done an item on number 96 an all electric Incat 130 meter (426 foot) ferry contracted by the South American ferry operator Buquebus to run between the Argentinian capital, Buenos Aires, and Uruguay across the River Plate. The vessel was launched on Friday in Hobart Tasmania.

096 is 426 x 106 foot with a dead weight of 1,344,000 lbs (600 tons). The hull length to beam is 19.6 to 1. The draft is 8.2 foot. The 4 X electric motors driving 8 water jets @ 100% MCR and 600 DWT will drive the cat at 37 knots.

The vessel will operate entirely on battery-electric power, carrying up to 2,100 passengers and 225 vehicles across the River Plate. The vessel has 250 tons of batteries and has more than 40 megawatt-hours of installed capacity. Incat said the energy storage system was connected to eight electric-driven water jets and its capacity is four times larger than any previous maritime installation.

The real issue is the recharging at each end of the ferry run. The charging stations are large and required an upgrade to the power grid to support the recharging required.

The build is in aluminum which is half the weight of a steel build to allow for the batteries etc.

The 2 jpegs show the vessel in the water awaiting the finishing work and test runs etc. The PDF is the initial specifications for the 096.

montero · May 4, 2025

That's battery pack ...

oldmulti · May 4, 2025

This item is the disconnected from you and I and a small trip into the seriously wealthy reality.

Bill Gates is selling his personal superyacht fleet and one month after his megayacht was listed, his shadow cat has also hit the market. Bill Gates is an environmentalist. He's also, as of 2021, a superyacht owner, Gates took delivery of the largest vessel to leave the Astilleros Armon shipyard to date, the 224-foot (68.2-meter) shadow catamaran called Wayfinder. The riddle was his choice to buy a shadow vessel when he clearly had no mothership that Wayfinder could shadow.

Then word got out that Gates was preparing to take delivery of a Feadship build that's the world's first hydrogen fuel-cell megayacht. Project 821 is a gargantuan leisure craft with a matching budget of well over $600 million, which we assume comes with matching amenities and features.

Wayfinder was then listed on the charter market, which was followed by reports that this was but a first step towards Gates selling it. Chartering it first would allow word of mouth to spread faster and get potential future owners to check it out in person, at their own leisure.

Then rumours of Gates would also be selling Project 821 and that he'd decided to do it before he'd take delivery of it, allowing its next owner to customize it by further stretching out the construction timeline. The shipyard, acknowledged a potential sale. The reported price is $600+ million.

Wayfinder was listed for sale with Edmiston Yachts, is listing it for the sale for $59 million.

Wayfinder is from the Incat Crowther naval architecture, Oliver Design interiors, and 1,737 GT of interior volume to the 12-guest, 30-crew capacity, lavish amenities, and packed garages. Wayfinder has the added capacity of a toy hauler. This means that it can go anywhere, anytime, with or without its mothership, and with or without the toys the mothership requires. There is a commercial-grade helipad that can double as a massive party venue with a 200-strong guest capacity, or as a pickleball court etc. Wayfinder carries a 17-guest Munson Beach Lander, a 16-guest Compass limo, an Explorer Icebreaker e-Jetboard, and a range of personal watercraft of various sizes.

Amenities range from lavish socializing and dining spaces to single-purpose designer areas, like the waiting lounge by the helipad, an infirmary, a dive center and decompression chamber, a spacious beach club with fold-down terraces, and a well-equipped wellness area and gym (also with fold-down terraces).

Wayfinder is built to the latest IMO Tier III emission guidelines, has an onboard water treatment plan and a dry waste treatment system, in keeping with a zero-discharge policy.

The jpegs give the idea of a cheap 224 foot go anywhere cat. Back to reality tomorrow.

SolGato · May 5, 2025

Some footage that popped up in my YouTube feed of a nice looking Sardine 23.

The design is featured in post #1068 page 72 of this thread.

oldmulti · May 6, 2025

Epoxy versus polyester is an interesting topic. Many production boat builders produce high-quality boats using polyester resins as polyester is well suited for use in a controlled manufacturing environment. The builders can control their shop temperature, have equipment to measure mix ratios with incredible accuracy, and follow a carefully engineered process the same way every time. The slightly lower cost of polyester becomes an important factor in volume boat production.

The conditions for boat repair, wooden boat construction, and other DIY applications are often different. In these cases, controlling the shop environment is not always possible. Repairs and construction projects are often unique and more than just a matter of repeating the same process. For these types of projects, epoxy is a good choice

The difference between epoxy and polyester resin begin with how the molecules react with each other during the curing process. The epoxy resin is often made from a molecule that has a very strong backbone. The resin molecules then react with the hardener molecules in a process that creates a high degree of crosslinking between the resin and hardener molecules. This results in a strong 3-dimensional matrix.

Polyester resins consist of many long molecules with reactive sites at their ends. The catalyst, often MEKP, creates a chain reaction, causing these polyester molecules to begin linking to one another. This chain reaction enables polyester resins to cure quickly, but they will not have a molecular structure crosslinked in the same way as epoxy, and therefore, they are not as strong.

When laminating composites, the chain reaction in polyester requires a specific amount of catalyst, often measured in fractions of a percentage, and good temperature control. Many polyester boat manufacturers have dispensing equipment that precisely controls the amount of catalyst added to the resin to adjust cure speed. Like epoxy, temperature impacts the speed of the curing process. However, polyester has a much narrower temperature range. Builders have to control the shop temperature, particularly in the winter when using polyester.

The stronger backbone of epoxy resin provides high strength and fatigue resistance. This is why aerospace applications, high-performance sports equipment etc use epoxy resin. They can reduce weight by building thinner laminates with higher properties.

Most polyester resins will not cure in the presence of air (air-inhibited), which means the surface appears to be tacky. The underlying layers cure, but the surface layer requires a surface finish to allow curing. Epoxy is not air-inhibited and, provides a solid fully cured surface, even in thin films. This thorough cure also improves the adhesion to wood. Since there are small air pockets in wood, polyester resin does not completely cure at the wood interface, reducing the adhesion.

Polyester resins can have an issue with osmotic blisters. Osmotic blisters can form below the waterline after they sit in the water for long periods. This results from water migrating through the gelcoat into the resin. The moisture will cause the polyester resin to break down in very small voids where the polyester did not completely react when catalyzed. This forms an acidic liquid that can continue to break down the polyester resin. This liquid contains compounds of the dissolved resin and is unable to pass through the semipermeable gelcoat. A blister is formed by pressure created during this osmotic process. Epoxy will not break down from contact with water and has a very high resistance to absorbing water. These properties enable it to be used as a moisture barrier coat to prevent polyester hulls from developing osmotic blisters.

Polyester resin often has a strong odour typically caused by the styrene included in the formulation. Polyester resin normally has up to 30% volatile organic compounds (V.O.C.). This high amount of V.O.C. in polyester resin also results in significant shrinkage when it cures. It is common for polyester resin to shrink over 5% when it cures. Epoxy’s nearly 100% solids content results in extremely low shrink values during curing. Boat manufacturers make substantial efforts to manage the shrinkage of polyester resin when building boats, often by using additional layers of materials on the outside of the hull to mask the cosmetic issues resulting from resin shrinkage.

Translation of all the above is paying for epoxy is often better than trying to compensate for the inferior performance of polyester. Vinylester is a half way house, a lot better than polyester but does not perform as well as epoxy. But one big warning! A really good resin of any type is better than a lower quality resin of a given type. EG a low quality epoxy has 50% of the strength of high quality epoxies.

The above is a lot from WEST and a little from me and my experience.

revintage · May 6, 2025

SolGato said:
Some footage that popped up in my YouTube feed of a nice looking Sardine 23.

The design is featured in post #1068 page 72 of this thread.

Great footage by friend and forum member Christoffer Kedborn aka Sailing Chris.

SolGato · May 6, 2025

revintage said:
Great footage by friend and forum member Christoffer Kedborn aka Sailing Chris.

It’s always a treat to see video footage of the designs discussed and featured in this thread out in the wild doing their thing.

patzefran · May 7, 2025

oldmulti said:
Epoxy versus polyester is an interesting topic. Many production boat builders produce high-quality boats using polyester resins as polyester is well suited for use in a controlled manufacturing environment. The builders can control their shop temperature, have equipment to measure mix ratios with incredible accuracy, and follow a carefully engineered process the same way every time. The slightly lower cost of polyester becomes an important factor in volume boat production.

The conditions for boat repair, wooden boat construction, and other DIY applications are often different. In these cases, controlling the shop environment is not always possible. Repairs and construction projects are often unique and more than just a matter of repeating the same process. For these types of projects, epoxy is a good choice

The difference between epoxy and polyester resin begin with how the molecules react with each other during the curing process. The epoxy resin is often made from a molecule that has a very strong backbone. The resin molecules then react with the hardener molecules in a process that creates a high degree of crosslinking between the resin and hardener molecules. This results in a strong 3-dimensional matrix.

Polyester resins consist of many long molecules with reactive sites at their ends. The catalyst, often MEKP, creates a chain reaction, causing these polyester molecules to begin linking to one another. This chain reaction enables polyester resins to cure quickly, but they will not have a molecular structure crosslinked in the same way as epoxy, and therefore, they are not as strong.

When laminating composites, the chain reaction in polyester requires a specific amount of catalyst, often measured in fractions of a percentage, and good temperature control. Many polyester boat manufacturers have dispensing equipment that precisely controls the amount of catalyst added to the resin to adjust cure speed. Like epoxy, temperature impacts the speed of the curing process. However, polyester has a much narrower temperature range. Builders have to control the shop temperature, particularly in the winter when using polyester.

The stronger backbone of epoxy resin provides high strength and fatigue resistance. This is why aerospace applications, high-performance sports equipment etc use epoxy resin. They can reduce weight by building thinner laminates with higher properties.

Most polyester resins will not cure in the presence of air (air-inhibited), which means the surface appears to be tacky. The underlying layers cure, but the surface layer requires a surface finish to allow curing. Epoxy is not air-inhibited and, provides a solid fully cured surface, even in thin films. This thorough cure also improves the adhesion to wood. Since there are small air pockets in wood, polyester resin does not completely cure at the wood interface, reducing the adhesion.

Polyester resins can have an issue with osmotic blisters. Osmotic blisters can form below the waterline after they sit in the water for long periods. This results from water migrating through the gelcoat into the resin. The moisture will cause the polyester resin to break down in very small voids where the polyester did not completely react when catalyzed. This forms an acidic liquid that can continue to break down the polyester resin. This liquid contains compounds of the dissolved resin and is unable to pass through the semipermeable gelcoat. A blister is formed by pressure created during this osmotic process. Epoxy will not break down from contact with water and has a very high resistance to absorbing water. These properties enable it to be used as a moisture barrier coat to prevent polyester hulls from developing osmotic blisters.

Polyester resin often has a strong odour typically caused by the styrene included in the formulation. Polyester resin normally has up to 30% volatile organic compounds (V.O.C.). This high amount of V.O.C. in polyester resin also results in significant shrinkage when it cures. It is common for polyester resin to shrink over 5% when it cures. Epoxy’s nearly 100% solids content results in extremely low shrink values during curing. Boat manufacturers make substantial efforts to manage the shrinkage of polyester resin when building boats, often by using additional layers of materials on the outside of the hull to mask the cosmetic issues resulting from resin shrinkage.

Translation of all the above is paying for epoxy is often better than trying to compensate for the inferior performance of polyester. Vinylester is a half way house, a lot better than polyester but does not perform as well as epoxy. But one big warning! A really good resin of any type is better than a lower quality resin of a given type. EG a low quality epoxy has 50% of the strength of high quality epoxies.

The above is a lot from WEST and a little from me and my experience.

I strongly agree, I have built several wood/glass/epoxy multihulls since 1981 and never had any problem !
I was told that polyester resin osmosis was salt migrating by diffusion process from resin (high salt content) to water (less salt content, specially fresh water) ?

oldmulti · May 8, 2025

Folks, sorry about being inconsistent about posting items but I am as of next week going to have 2 eye operations spread over the next 5 weeks. Nothing serious but I will have difficulty doing any computer work during that time so I will be leaving it to you guys to keep the thread alive whilst I am away. Have fun and I should return in about 6 weeks, or I may drop a few items along the way if I can.

bajansailor · May 9, 2025

@oldmulti I am sure that everybody on this Forum will join me in hoping that everything will go well re your eye operations in the offing - thank you for this amazing and enduring thread!
Almost 4,500 posts, mostly by you, must be a record on here, and yet you continue to supply us with gems of information and advice from all spheres of the multihull world, both power and sail, trimaran and catamaran.
Good luck re your operations, and we shall look forward to seeing you back here again in due course.
We shall try to keep the thread alive......

tane · May 9, 2025

Best of luck, OM!

Skip Johnson · May 9, 2025

oldmulti said:
Folks, sorry about being inconsistent about posting items but I am as of next week going to have 2 eye operations spread over the next 5 weeks. Nothing serious but I will have difficulty doing any computer work during that time so I will be leaving it to you guys to keep the thread alive whilst I am away. Have fun and I should return in about 6 weeks, or I may drop a few items along the way if I can.

Hope your deal with eyes goes as well as mine did.

oldmulti · May 10, 2025

Thanks for your kind thoughts.

Multihull Structure Thoughts

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