Multihull Structure Thoughts

Am I correct, that the French Hydroptere toy in the drawing has aerodynamic ailerons to increase the righting moment? It is a rare solution, do you know any fill-sized boat using it?
BTW, the ailerons in the picture seem to be set in wrong way, to increase the heeling moment.

regards

krzys

 

wich picture ?

 

Myszek. When built there was no ailerons. Please look at the following web site which gives history and jpegs.
Untitled document
https://www.histoiredeshalfs.com/50 multis/G J3 Paul R.htm

 

The Supercat 20 was originally conceived by Bill Roberts as a very high performance day sailing catamaran. The builder was originally Formula Racing Sailboats which was purchased by Boston Whaler. Bill Roberts and Steve Edmunds designed and had production builds of several other Supercats from 15 to 30 foot. These cats ranged from fast to exceptionally fast. The 30 foot models were the fastest cats on the water in their day. The 20 foot Supercats were a revelation when they first appeared on the market in 1980 and even today are competitive with a lot of the modern non foiling designs.

The Supercat 20 was 20 x 12 foot and could be compressed or disassembled to 8.5 foot for trailering. The weight was meant to be 450 lbs. The initial mast was 31 foot and carried 275 square foot of sail in the jib and main. The final optional rig had a 38 foot mast height with 344 square foot in the main and jib. They then provided a prodder with a larger 110 square foot jib and if you were brave enough a screecher option. The draft is 3.5 foot with hull based daggerboards down. The hull sections were fuller in the ends than a lot of designs allowing more power reaching and less prone to pitch poling than EG Tornado’s.

The original Supercat 20’s were solid glass but later versions were foam glass in epoxy. The cross beams were 6061 114 x 3.2 mm wall aluminium tubes for the fixed beam versions. The sliding beam version used 6061 115 x 3.2 mm wall aluminium tube segments attached to the hulls with a 102 mm tube for the centre of the beams which could be slide into the 114 mm tubes attached to the hull. A detachable dolphin striker had to be removed before compressing the cat. Either version of the cat took more than an hour to set up or breakdown if transported.

So, what was the result. Supercat 20’s have been used in Race to Alaska, Worrell 1000, Everglades etc and many local races with success. To quote one owner: “Having raced and long distanced cruised (at 15 - 20 knots) the Supercat 20 on the West Coast, Gulf Coast, East Coast, and Great lakes, the quick performance and stability is excellent in all types of wind conditions and sea states.” Yes, it is fast especially in light to moderate winds with its larger optional rig. You need to be experienced and brave in stronger winds reaching with larger sails as even with it 12 foot beam things can happen very quickly.

If you can find a good second hand version you will have a smile on your face. The jpegs give the idea.

 

This one:


krzys

 

This is about excess, $200 million plus type of excess. An owner wanted a comfortable long distance monohull fast cruiser that has a net zero emissions when travelling. The owner has real money and was willing to pay for an innovative solution. When the idea was pitched to designer Marnix Hoekstra at Vripack, he was instantly enthusiastic. Dykstra Naval Architects was the next to embrace the project, followed by Vitters Shipyard, completing a Dutch trifecta. After more than six years of work, project 3094, aka Zero, is finally nearing launch.

Zero is an aluminum monohull of 226 x 36.5 foot with a displacement of 962,700 lbs (about 450 tons). The 200 foot carbon fibre fore mast and 182 foot aft carbon fibre mast in a ketch rig that carries a sail area 18,858 square foot upwind The draft ranges from 16.4 to 27.5 foot using a raising keel. Power is provided by 28 tons of batteries equal to 5.2 megawatts of power which comes from 100m2 of solar panels that can churn out 23kW while also capturing up to 55kW thermal energy 9more details later). But the real power generation source from hydrogeneration by propellers is a staggering 230-250kW of electricity when the boat is making her optimum 16 knots of boat speed under sail. But even from speeds of 8 knots the boat can cover her own energy needs – both for sailing systems and hotel loads. Maximum range under power is 400 nautical miles which means this boat really needs to sail well.

“The design of the hull was very important in conserving energy while under power and also being able to sail in as light a breeze as possible,” explains Dykstra partner Mark Leslie-Miller. “We really made a very long hull for the amount of interior space.” Dykstra tapped into software and expertise of Emirates Team New Zealand as they sought to find the sweet spot between low drag and high form stability. “For different points on the polars, we could see how much speed it cost or gained if we changed the parameters of the vessel,” explains Leslie-Miller.

“She should reach peak speed in 15-20 knots of true wind,” says Eduard van Benthem, a highly experienced marine engineer and project manager of Zero. “But hydrogeneration could cost up to two knots of boat speed, so it makes sense to find the right sailing conditions.” There is some experimental sail monitoring tech, which might be more familiar from the world of self-driving cars. Lidar scatters invisible light towards the sails and picks up reflections that allow a computer to build a 3D image of the sail shape in real time. This is used to make recommendations to the crew. “One of the things we see on large cruising boats at some point mid-ocean, is that getting the sails trimmed optimally becomes less of a priority,” explains Leslie-Miller. “We want to help the crew with that.” There is more computerisation to balance the wind speed versus yacht stability, wave conditions and optimum routing to achieve a fast passage.

Zero carries 110 guests and requires 12 crew whilst sailing. They live in luxury and comfort due to the on board environmental controls provided by the “hotel” facilities.

Now this is a aluminium build but to achieve zero emissions several unique things have been done. The first part is to extract waste heat from the many onboard devices and from a novel glycol circuit cooling the solar panels. Then molten salt battery stores it for use during the night. As well as using the harvested heat for hot water systems, established heat-fired chiller technology uses the heat energy to cool another water circuit to around 12°C which is circulated through wall and ceiling panels throughout the boat to cool the living spaces.

At the same time, natural ventilation replaces inefficient fans, thanks to a smart redesign of the carbon mast by manufacturer Carbo-Link, the designers realised that they could exploit a natural chimney effect – if the masts could be built hollow and perfectly smooth on the inside. As the mast heats up during the day, the hotter air inside starts to rise, pulling in stale cabin air from below. “By using the mast as a fan, we save 3-4kW in forced ventilation”. Altogether, Zero’s cooling is eight times more efficient than traditional aircon, saving 300kWh of energy every day.

Insulation, Zero has double glazing with a heat-reflective finish, a 2-3cm layer of cork between the Tesumo decking and the aluminum substrate, and a novel melamine foam, called Sorbermel, lines the interior. It’s more efficient than glass wool, giving a 70% weight saving for the same performance. “Normal insulation is held to the aluminum hull with metal pins, but all these pins are potential heat bridges,” says Van Benthem. “So, we took literally thousands of them off and glued on the melamine instead.” Designers designed a camera system to monitor the temperature of the pans on the induction hob. The idea is to warn the chef if they are overheating – a feature they reckon will save 50% or more cooking energy. They also re-engineered the extractor fan to harness the Venturi effect, halving the amount of ‘good’ air drawn out of the galley and slashing energy use by 60-80%. On deck, the custom sheet winches have a rewind mode which actually generates electricity – just like the brakes on a hybrid car. “It’s not a vast amount, but every little helps,” says Peute. It’s the same for the 13 captive winches hidden below the deck, which generate power as they pay out.

The jpegs give an idea of a very innovative boat that has some good ideas that mat be applicable to a smaller boat. But if you want smaller luxury at EG $4 million get a 70 foot carbon cat cruiser which will carry 10 guests at 15 knots.

 

This is a small warning about building multihulls. If you want to build a smaller cruising trimaran you can choose a simple to build design that will sail well but may not be optimised for accommodation and performance. The alternative is to build a really good modern design that can do all things well. Lets look at EG the Seaclipper 28 tri versus the Farrier 22. Each of these designs are not fully available on the market therefore I hope this comparison will not offend too many people.

The Seaclipper 28 was designed by John Marples and is a simple plywood structure with a dory main hull and deep V floats. The trimaran was originally designed with fixed beams but a later version had swing wing beams and a full headroom main cabin. The down side is it had a 5.25 foot wide main cabin and limited accommodation. The Seaclipper 28 could sail well on all points and had a peak speed of about 17 knots.

The Farrier 22 trimaran was designed by Ian Farrier and is a foam glass in vinylester (preferred epoxy) resins using advanced fabrics and vacuum bagging etc in its build. The hull were all round bilge and decks etc had to have forms or moulds for building. The accommodation was brilliantly fitted into the main hull allowing a 7.8 foot wide main cabin. The farrier folding beam system allows trailing and the wide beam provides a lot of stability for high performance with reported peak speeds of 22 knots.

So why not build a Farrier? It will take the average home builder twice as long to build a F-22 compared to a Seaclipper 28. The F-22 would have more accommodation and be faster under sail but the complexity of the F-22 build is interesting.

An F-22 plan set has 46 pages of design material for the metal parts used in the build, it has 90 plus pages of design material for the hull and deck components of which there is often multiple items of each of design pages. There is also taping instructions to join parts etc which if not followed accurately could cause significant problems later. There is another 100 plus pages of information related to setting up the mast, mast building, sails, rigging, trailering, trailer design, outboard installation electrics etc.

A Seaclipper 28 plan set is much simpler (the plans are comprehensive they just do not require the multiple pages as each part is simpler) as cutting a set of plywood bulkheads and eg plywood hull panels is simple then add timber as required results in a fast hull structure. The crossbeams are basic lumber section glued together. John designed strong simple to build boats.

Result F-22’s will provide you with a faster tri with more comfort but will take longer and more money to build. The Seaclipper 28 will be on the water faster, due to a faster build, for an average builder and will perform well, but its resale value will probably be less (although its likely to be cheaper to build).

Please understand what is important to you when you build and understand your capability and patience. Thee first jpgs are of the Seaclipper 28 then the F-22.

 

@zero:
"zero emissions" on an absolute, pure, unadulterated top-of-the-line luxury vessel...hilarious!

 

The Triumph Trimaran was produced in 1973 by the Snark Products which started back in the mid 1960’s. It was a simple design based around the small Piver designed trimarans of the time. Jim McMullen was a cofounder of the original company and created an approach where he sold the boats as part of promotions with other companies like Coke, Vicks, Budweiser etc. 8 and 10 foot monohulls worked better in promotions than the trimaran so the tri had a short life. Snark Products was sold to the DDB (3 rd largest advertise agency in the world at the time) which rationalised the product range and after a time sold the boat business to others.

The Triumph Trimaran is about 9 x 5 foot that weighs 100 lbs bare and can displaces 500 lbs. The freestanding mast has a lateen rig carries 60 square foot of sail. The draft is 1.4 foot.

The trimaran is constructed of the trademarked 'Corelite' which was bonding the ABS skin to a foam core. This was one of the first “production” foam glass structures in production.

The designed sailed OK but was not a racer, this was very much a fun day sailing boat using the rig off other Snark monohulls. An excellent trainer for kids or nervous adults.

The jpegs give the idea.

 

The next part of designs and home builds. There are several generations of multihull designs available for people to build. The first generation are the plywood Piver tri’s and Wharram cats of the 1960 and 70’s. During this time other designers like Jim Brown, Norm Cross etc started to design improved variants of plywood trimarans etc. during this period those who could market well often sold more plans than those that designed better boats.

During the 70’s fiberglass polyester, strip planked cedar epoxy or foam glass polyester multihulls designed for home builders started to appear. Most of the designs ranged from very conservative woven rovings, CSM, foam and polyester resin or the more aggressive unidirectional glass epoxy strip planked cedar. There were exceptions Derek Kelsall designed 40 foot cats and tri’s that did not use CSM and just laid 2 layers of 18 OZ woven rovings onto a 12 mm foam core in polyester resin. The majority are is still sailing today.

In each case as the designers learnt about the structures, they modified their design approaches. The original Farrier F-24 plans had CSM next to foam in the builds with polyester resins. Later Farrier plans for EG F-82 or F-22 Have virtually no CSM in the build and use either double or triple bias fabrics and in some cases uni directional fabrics in either E-glass or S-glass. If you want the ultimate performance in a lot of Farriers plans, he suggested Carbon Fibre alternatives. The preferred resin for Farriers later boats is epoxy although vinyester is acceptable. The same development path occurred with other designers like Crowther, Kurt Hughes, Schionning, Norm Cross etc. The only designer that only partially moved forward was Derek Kellsal. Derek stayed with polyester resin and foam but changed to double or triple bias e-glass cloths. In his racing designs he partially used carbon fibre and epoxy.

The result of this design development was that home builders often ended up with lighter stronger boats which often were easier to build due to the next development which started in the 1990’s. Flat panel construction. Designers, especially catamaran designers realised they did not have to curve every surface. The hull sides and the majority of the decks could be made from flat panels and only the EG hull bottoms need to be built as a curved surface. This allowed a panel to have a good gelcoat finish prior to even being attached to flat panel bulkheads. The hull bottoms then would be attached to an almost complete structure.

In the 2000’s the next step forward came with improve masts, rigging and fitting like chain plates. The ability to home build caron fibre masts or wing masts and the use of Dux fabric stays to reduce weight aloft improved performance. Chainplates are rarely metal in modern designs they are either unidirectional glass or carbon fibre firmly attached to bulkhead by a spread of the glass or carbon over a good area. Again, a home builder could get a high performance rig for similar cost to an aluminium mast and stainless steel rig. Ian Farrier in his later designs said it was preferable to use fabric rigging to stainless steel.

In the 2000’s there was increasing use of vacuum bagging to get better fiberglass to reduced resin ratios which improved the structural strength of a structure whilst reducing weight. Also some home builders were experimenting with resin infusion build techniques. Now many designers are providing advice on how to use resin infusion in their designs.

Translation of all the above. Modern designs often are much better cats or trimarans than 30 plus year old designs. It’s because the boats are often stronger and lighter which combined with better hull shapes and lighter rigs allows the cat or tri to be driven faster across the board.

One comment though, if you want the ultimate in accommodation and space all the above may be of little interest and if you believe in sailing with many naked young ladies because of marketing material a lot of the above is of little value.

A few jpegs for you.

 

Palanad 4 is a Sam Manuard-designed scow-bow monohull IRC racer that won January’s 2026 RORC Transatlantic Race after crossing in just 8 days 5 hours. Palanad 4 averaged 17.68 knots over the 3,500-mile Transatlantic race. Yes monohulls, even non foiling monohulls are getting very fast across oceans.

Palanad 4 is a monohull that is 49.9 x 16.1 foot with a displacement of 14,840 lbs. The fractional sloop carbon fibre fixed mast rig has a 1,076 square foot mainsail, a 592 square foot jib and an A2 screecher/spinnaker of 3,014 square foot. The draft of its canting keel is 11.5 foot and it also has 2 daggerboards. This is a very light powerfully rigged monohull with good form stability due to its scow shape. Result 17.7 knot averages across the Atlantic.

Palanad 4 is a development of the Class 40 monohull scows which were developed from the Mini 6.5 racers. These boats have less than 15 year development history and are still improving. The potential of the scow concept in larger sizes combined with foils will be very interesting and will challenge multihulls.

“Even back in 2020, when we launched the Class 40, we were already thinking about what a bigger boat could look like,” he recalls. “A full-scale scow, no restrictions, where you can really play the game without class rule limitations.” Downwind, the boat is notably dry. “At 20-25 knots of boat speed there is barely any water on deck,” Manuard notes.

“That’s not just performance – it’s comfort… and comfort is performance.” But one of the biggest surprises has been just how effective the boat is to windward thanks to the effects of the chines when heeled. While scow-bows are often associated with reaching and downwind dominance, Palanad 4 has shown impressive upwind ability, delivering speed without the slamming traditionally associated with fuller forward sections, and without water ballast. Manuard noted: “The boat needs to sail above a minimum heel angle of around 18-20° in order to improve its hull drag as well as reducing the slamming impact through the waves.” The scow-bow creates early planning, with the flat bottom generating lift and the wide bow power. The chine assists upwind performance when the boat is heeled.


Designer Manuard also points to the advantage of a smaller crew: “Palanad 4 does not require a huge number of crew onboard since the hull form stability is huge. So compared to a more traditional slender hull, we sail with maybe 30-50% less crew. This is cutting down the sailing weight and the owner’s nightmares!”

The build is mainly carbon fibre foam epoxy by resin infusion done in a very controlled environment.

This is a pure racing monohull but cruising versions will be developed. The accommodation of a cruising version will have the equivalent of a 60 foot mono accommodation in a 50 foot package.

The jpegs give the idea.

 

Have we run out of multi's?

 

Eurosnob. No, we have not run out of multi's but the problem is they are just getting bigger, more expensive and less likely to be able to be afforded by a lot of people who read this blog. I can give 50 items about the latest 50 foot plus multi stateroom charter cats or high performance 50 foot plus tris, proas etc. The majority will be production boats that I cannot get specific structural details for and often are very similar to each other. The days of home built boats are declining and designers of home built boats are available, but designers prefer larger boats that they will get better design fees for. The days of Ray Kendrick's Scarab good trimaran and catamaran boat plans for $150 are nearly finished. Richard Woods, Kurt Hughes, Wharram etc do some reasonably priced plans as did John Marples but they are winding down their businesses with fewer designs being done. Now its Grainger, Schoinning etc with multi thousand dollar plans. I have access to many plans but if the designer is still working, I will not publish details unless it is released elsewhere publicly on the web. So, I am doing multis and other stuff that is interesting (to me) for the time being.

 

Write on.

 

Fair enough. It's your thread, only your opinion matters.

You're certainly not wrong about everything getting bigger & more unaffordable!