Multihull Structure Thoughts

To finish this detour into dream boats I present Hemisphere, a 145 x 54 catamaran that displaces 660,000 lbs and carries a 174 foot mast with 12,000 square foot of sail. In 2012 it was the largest sailing catamaran in the world. The hulls length to beam at the waterline is 11:1. The two 490 horsepower engines can drive it at 11 knots and under sail has reached 20 knots.

The cat is an aluminium build designed by VLPL with a separate interior designer. Now the fun begins. The US yard Derecktor was initially chosen for the build, and work started in late 2005 with completion scheduled for November 2007. However, with the boat running late, Derecktor experienced financial difficulties in 2008 and the search for another builder began. Pendennis was chosen based on a facility to cope with the beam, engineering ability and favourable exchange rate. And in 2009 the boat arrived in Falmouth, UK, on the deck of a ship, along with 13 containers worth of equipment. Almost two years later, Hemisphere was moored up outside the Pendennis dry dock in which she had been completed.

The interior design brief from the US owners was “Polynesian six star luxury”,’ says Mark Smith of MLD. Although there is a theme of walnut soles and panels in brushed oak and wengé – all of which have a deliberate textured feel – no two cabins are the same in layout or styling. A total of 18 leathers have been used, including crocodile and stingray skin, and there are 15 types of stone. As the jpegs show the interior is spacious and spectacular.

Result of all this luxury and build issues, $50 million in bills and a 6 year build time. No wonder you pay $280,000 per week in charter fees.

Now a general comment about big (above 80 foot) cruising cats. I have helmed many multihulls under 60 foot and if there not to heavy with reasonable sail and boards they generally sail and respond well. Above 80 foot of the 3 big cruising or charter boats I have helmed they all have the same basic issue. Momentum of the boat in waves make them feel unresponsive to rudder inputs etc. What is occurring is the rudders and keels are often reduced in size to keep the draft shallow combined with big propellers in front of the rudders mean the control surfaces often are not working to peak efficiency. Big racing multi’s do not have the same control problems except if they are carrying too much sail.

Hemisphere draft has been kept to 10 feet to allow it to get into smaller ports etc. which leads to the next problem of finding parking spots. The jpegs show some build, interior and toy stores. But one of the really interesting aspects is under the cockpit where there are folding doors so you can lower you 26 foot power boat that is normally stored under the cockpit.

 

Cruising cats with a difference are all around us. The SMG50 is 50 x 26 foot weighing 18000 lbs and carrying a 535 square foot main on a roller furling arrangement, a 500 square foot self tacking jib with a 925 square foot code 0. The A frame carbon fibre mast(s) is 65 foot high. The A frame mast allows the main to be on a roller reefing arrangement allowing easy reefing and control. The first 3 boats were built in 2011-13 then due to difficulties of getting a good builder the original design/marketing person from Bulgaria sold the moulds in 2015.

The SMG50 was designed by Gerhard Schein whose goal was to be able to sail with his wife comfortably. The concept is the easiest to handle ocean cruising catamaran in the world. You can sail the SMG50 single-handedly. The cat has a forward cockpit (more than 270° viewing angle from the helm) allowing easy access to the sail handling controls. The downside is you are exposed to the wind etc going upwind in rougher weather.

The A-frame mast is fitted on the deck and all the force on the rig goes into hulls. This eliminates the stress point in the beam. Furthermore, there is no dangerous boom needed as the main sails is like the jib on an easy to use roller furler. The advantages of more stability, better sailing performance close to the wind and easy sail reefing with roller furler on any course are big advantages.

Fast sailing combined with easy to use handling can mean speeds over 20 knots in good conditions. In flat water and light winds there are claims the cat can sail faster than the wind (depending on payload). Tacking angle including leeway is 90 degrees.

The center cockpit is just 3 steps away from the inside navigation table. Equipment for all sails is reachable from the cockpit and ergonomically designed. Winches can be operated electrically or manually.

The interior is pretty standard with a downstairs galley and double bunks as required. The boat can be fitted with standard house hold equipment on board possible (dish washer, fridge, freezer, microwave, stove, washing machine etc.). Take your choice either buy cheap up front and replace internal equipment or pay money buying equipment designed for the marine environment which will often last a lot longer.

The cat is built in South Africa. The structure is epoxy unidirectional e-glass on Airex PVC foam both resin infused and bagged. The A frame mast is built from carbon fibre. This is a relatively light, simple boat that you can sail effectively when your short of crew. A very good cruiser that hits its intended aim. The jpegs give the idea.

 

The SMG50 seems to have its rig quite well sorted. Anyone on the board experienced anything similar? I see Bernd Kohler offers vertical furling main rigs on some of his designs, on single or A frame mast, with wishbone booms. I assume that it is a cheaper option than an in mast or boom furling system. Now having a furling jib on my boat, the idea of being able to furl the main in the same fashion has some attractions.

 

Some interesting info re the original rig on this design boat here Is it just me, or is every Newick ever built as ugly as sin? http://forums.sailinganarchy.com/index.php?/topic/205080-is-it-just-me-or-is-every-newick-ever-built-as-ugly-as-sin/&page=2

Quotes from 'Bad Ron' "Yes, a White Wings. I took the mizzen off to see how the boat balanced and to see if there was any performance difference. Never put it back on. I also changed out the Ljungstrom sail. There was no way to keep the sail from opening up while gybing. When it’s really windy and you are going very fast downwind and all of the sudden you have twice as much sail area… Not good. The flare in the bow of the main hull saved us from an otherwise certain pitchpole".

and;

"The mizzen was quite small and too close to the main. It wasn’t possible to get any flow over it, upwind anyway. Off the wind it must have added something, but it was tiny. It wasn’t so bad with the original sail but when the big square top went on the problem with flow became even worse. The mizzen mast was handy to hang a shade cloth from while at anchor. …hardly a saving grace. There wasn’t any change in balance without it.
The boat needs a jib. Tacking in windy conditions is a challenge as momentum is lost mid tack in the waves. There is no jib to back to bring the bow over. I’ve played with a little heavy jib of a Wavelength 24 and that works well. The sail has a wire luff but it’s difficult to get any tension on it with the freestanding mast. Sets okay in the lighter winds and adds quite a bit of power to the rig.

My boat is “Drifter” not the original White Wings. Built about the same time though".



There was also a 28' Sparkdesign that had a similar Ljungstrom cat ketch rig to the original White Wings. I wonder how the rig functioned on the smaller boat.

 

Dalliance is a small tri designed by the builder for the Florida 120. The boat is 17.5 x 12 foot weighing 700 lbs and able to carry 400 lbs payload. The sail area is between 165 to 190 square foot depending on the sails. The original floats were 15 foot long and had a 600 lbs buoyancy then new floats were built with1500 lbs buoyancy. The original boat took 18 months to build and included parts from previous boats but the tri was progressively upgraded over another 2 years as required. This meant new floats, cross arms and rig. Total cost of the boat is under $8000 after the modifications.

The basic design was done by the owner builder as he was annoyed at previous professional designs leaving out details of components or lacking in building instructions. He used design software from Greg Carlson’s Hulls freeware to get the basics correct. The choice was initially a hard chine main hull and float design then the floats were upgraded to round bilge design and construction. The new floats design were generated via Carlson’s Hulls, and then faired and smoothed the bulkheads by splining the points of the hard chines when lofting them.

The main hull was a stitch and glue 5 chine plywood structure of 5 and 6 mm ply with a 200 gsm cloth epoxy covering. The final version of the floats were two layers of 3 mm cold moulded plywood covered with 200 gsm cloth. All hulls have frames and stringers. The main hull has 3 full bulkheads (under each crossbeam and cab/cockpit bulkhead). In the main hull there are also 2 half bulkheads.

The original cross beams were 102 (outside diameter) x 3 mm aluminium tubes 12 foot long. The cross beams were later modified to simplify transport. The centre 6 foot of 102 mm tubes were permanently attached to the main hull. The outer ends of the cross arms (which are permanently attached to the floats by 6 mm vertical brackets) were made from 95 x 3 mm aluminium tubes 4.1 foot long which could slide inside the 102mm aluminium tubes. When fully extended the 95 mm float tubes only have 200 mm inserted into the 102 mm centre tube. The tubes are held in position with 12 mm stainless steel bolts. The new cross beam structure is still 12 foot overall. The floats mounting points were moved 300 mm aft during this rebuild to minimise water hitting the cross arms.

To quote the owner on performance of the boat. “I am generally pleased with the performance I have achieved with what I’ve used. Admittedly, at 19′, her mast is very conservative (or short) for a boat with her stance and stability. A taller mast and increased sail plan would improve her speed. However, it’s possible that a taller rig might not actually improve her intended “performance”. Dalliance is a micro-cruiser, not a racer. And she excels at providing a dry comfortable ride, with ready-to-use (i.e., no assembly required) camping like conveniences once you stop for the day. However, I do find myself wishing she would foot a bit better to windward.

Because of the deck/topsides layout and resulting sheeting angles for the head sails, when going to weather she points highest under main and staysail. She will point 45 degrees to the wind, and with leeway factored in, will make an honest 98 degrees between tacks under main and staysail. She tacks smartly with the board down. However, in really shallow waters, with the board way up, you have to plan your tacks, and backing the jib is helpful in getting her bows all the way through the wind.

She is very comfortable to sail from the protection of the cockpit/cabin, there are few boats I’ve sailed with that outpace her beside beach/racing cats. Speeds (so far):
— The best sustained speed I held for 30 minutes or more at a time is 8 knots
— The highest speed I’ve seen on my Garmin GPS is 12.3 knots

Sailing anywhere between a close reach and a broad reach she is a joy and puts a smile on my face. However, I have found, like in 2012 FL 120, in a rough chop or when footing quickly through waves, and she exposes the bottom of her hull to the waves, there can be pounding that both slows and annoys me.”

The tri has a single bunk with a porta loo and a small table. Headroom is 3.2 foot. A boat designed as a micro cruiser that fulfills its function well. Good concept.

 

We are going to talk about speed under sail. The sailing speed record is currently held by Paul Larsen who achieved the average speed of 65.45 knots over the 500m track. The next design is aiming for 80 knots by 2022. A fanciful dream you say? Let’s look at the team who plans to do this work.

SP80 was born from the encounter of three engineering students passionate about sailing, kitesurfing and speed. This project is support by EPFL university which helped developed Hydroptère between 2006 and 2009. Numerous teachers previously involved in either Hydroptère's or Alinghi's adventures also give their support to SP80, gathering all the ingredients needed to create great innovation and to develop new technologies.

Created in 2018, SP80 is a team composed of EPFL students and Alumni who passionately believe that through the combination of sailing, kitesurfing and engineering principles, they can significantly outperform the standing sailing speed record. Gathering members with strong experiences in high speed sailing and engineering, the team has been working since then on the design of a pioneer kite-boat to take up this challenge.

The ”boat” to achieve the 80 knots uses a boat with shaped hulls, propelled by a kite wing while the overall stability is reached thanks to super ventilating hydrofoils. The jpegs give the idea. Normal hydrofoils work up to about 50 knots but after that they tend to cavitate. At speeds above 50 knots a super cavitating or super ventilating foil shape is used. This shape basically an elongated triangle with a thick back edge as shown in a jpegs. Paul Larson, current record holder ,used supercavitating foils to get to 65 knots but he was literally cutting the back edge of the foils down during the record attempts to increase the speed of his boat. There was theory and there was a learning curve as Larson went along. The SP80 project will be in all new territories that will need to be developed over the next few years. When it works, we will all know the recipe of how it works.

The boat is 23 foot long and is intended to weigh 340 lbs. See sp80.ch to get an overall view of the project.

 

There are a few issues with the rig here that are not addressed in the advertising blurb.
First is the inefficiency of the rig. Going with two masts is less efficient than one. A compression member carries load according to its moment of inertia. This goes up by the fourth power as size increases. So to get two columns to carry a compression load, you have to use two masts which are not much smaller than just one single one - so the rig becomes much heavier. That is why bridges can have single compression towers at each end but lots of tension wires. Tension is fine to break up but you combine all the compression you can.

Then there are planform inefficiencies. Genoas are triangles and airfoils don't like triangles. For all their faults mainsails are now getting very square up top. This is more efficient than a genoa's planform. So less efficient again. Plus add in headstay sag too.

Then going downwind you get the boomless main problem. Why do almost all multis have booms when they have such low foot loading? To help keep the main flat when eased and allow sailors to vang the main down by pulling down on the boom about 2/3's of its length. You can't do this with a genoa so you lose efficiency downwind as well. Its will get too full again.

Then there is setting efficiency. A main can be pulled up and down the traveller centimetres at a time. to get the best combination of camber, twist and angle of attack. Most genoas have at most two tracks, or they can have an adjustable barber hauler. But a main can be adjusted very finely to get the best sailing performance whereas a headsail often is too full when eased, and too twisted too, unless barber hauled.

And a dangerous boom? Really. Try going and hanging onto a thrashing genoa in a blow. You can still get knocked heavily by a flogging headsail clew.

So don't buy the selling blurb. This rig will be heavier and less efficient than a typical rig. It may be better for this cruiser but it won't be taking over single mast rigs any time soon.

 

So you have a 2 week holiday coming up and you would like to visit another country by sail. Good idea but he didn’t have a boat. He rang a mate and to see if he wanted to come along and help build the boat a bit. He says OK, lets go. Where will we go? From Australia to Papua New Guinea (PNG) sailing across the 200 miles of the very tide effected Torres Strait.

So they came up with a plan to build a ‘stitch and glue' trimaran that will fit into a Toyota Hiace van, get his van trucked 1300 miles to Cairns, fly up a few weeks later, drive to Cape York (another 600 miles drive over some pretty rough roads), sail across the Torres Strait, give the boat to some kids and fly back.

So they drove up Cape York, spending three days driving to the tip of Australia over a ‘development' road, the road has corrugations from the rain that just never end! There's about 900 back jolts per mile and 5,400,000 for the whole drive.

So on the fourth morning they launched Armadilla for the first time and did the first part of the trip that took five and a-half hours to an island, the top speed was 7.9kts, but at times the tide really held them, as the tides can run up to 7 knots. The longest run was 50 miles between islands being out of sight of land for half a day. They arrived in PNG after 5 days of island hopping, giving the tri Armadilla to the local primary school.

So what was the boat? A 12 x 10 foot open tri he designed (if drawing a box can be called that) that could be pulled apart. Eighteen hours' worth of weeknights and $500 in building materials later, they had a beautiful vessel which was called Armadilla. The hulls are 6 mm ply with strong gunnel strips and minimal bulkheads under the cross beam attachments. They sleep on beaches with a tent etc as there “accommodation”.

The boat featured a rig from an equally race-worthy sailing dinghy found at the Kincumber rubbish dump, a steering oar instead of a rudder to save building time, a pink Cherub symmetrical spinnaker, 100 x 50 mm treated pine crossbeams, and plywood box sections that the four-by-twos sleeved into. These box sections were attached to the boat with uni-directional carbon fibre (as can be seen in the jpeg), purely for the purpose of having something high-tech on the boat.

So, there you have it, an ocean crossing 12 foot tri built for $500 Australian and built in 18 hours. Why do we spend years building these fancy multi’s that cost thousands of dollars? Sorry about that, with a big smile.

 

MTC 40 trimaran designed by Nick Bailey (featured in 506 page 34). WTE is another version, the tri is 40 x 36 foot displacing 9400 lbs and carrying 1000 square foot of sail area. Several versions were built starting in 1993. One in Brazil was built in 1995 and is still sailing. The boat hulls are strip plank Amazon cedar with composite cross beams. The cross beams have foam glass webs with unidirectional carbon fibre in the top and bottom flanges. The reason for showing this design is that the concepts look similar in the main hull, floats and rig but the beams are different. I suspect the strip plank hull structure would be the same. That is 12 mm strip plank Amazon cedar with 2 x 250 gsm UD E glass in epoxy either side. The jpeg gives more detail.

 

Taboo 111 is an interesting cat build by a German guy called Mr Hausner in the 70’s. It is a 60 x 30 foot cat that weighed 19,000 lbs and displaced 25,000 lbs that carried a simple sloop rig of about 1000 square foot. Mr Hausner had an idea went to Cebu found a competent boatbuilder then the 2 of them proceeded to build a 60 foot cat. No plans, just done by feel. The cat is still sailing today after several circumnavigations. The cat was basically a 60 foot wharram type with all accommodation in the hulls.

Taboo 111 structure started with two 50 mm thick keel planks plus a 50 mm external keel cap, 50 x 100 mm frames and stringers at 300 mm centre lines. The hull skin were 7 ply 12 mm plywood covered with epoxy glass. There are 4 main plywood bulkheads of 16 mm ply with 12 mm and 9 mm half bulkheads to add strength. The decks on the hulls were 12 mm ply.

The main box cross beams are 750 x 80 mm. The top and bottom flanges were 50 x 100 mm with 16 mm ply fore and aft faces. There were 50 x 100 mm diagonals between the top and bottom flanges. These cross beams were connected to the 16 mm ply bulkheads. The rudders were transom hung for simplicity. The engine was a 38 horsepower Mercedes desil motor from a taxi that powered a hydraulic driven propeller that could be lowered into the water. It still has its original engine. There are very few electronics on the boat with wool tufts and a mast head windvane is about as good as it gets. Simple and effective boat.

A later copy of the boat was built but did not have the same rigor applied to the construction resulting in a boat that weighed 10,000 lbs more. The second version, Talamanca, decided to copy the original Taboo 111 and got professionals involved. Result great drawings more weight, more electronic, engines etc and not as well built. Taboo 111 had small transoms whereas Talamanca had full canoe sterns with rudders angled in a different direction, the hull on Taboo 111 had straight sides, Talamanca had a slight chine. The overall result is according to one person who has sailed for 4 weeks on both boats is Taboo 111 sails very well whereas Talamanca is not as good. The jpegs give an idea and somewhere I have a full build article some where which I will add later.

 

Referring to the previous post, Wolfgang Hausner built Taboo 3 in 1978/79. He still charters Taboo 3 in the Philippines today. Wolfgang is 80 years old and has lived on his boat for the past 41 years. He has written several books (most in German) about his experiences and his circumnavigations. As you may have worked out Wolfgang is a risk taker and his charters take you to some interesting places. As one guest wrote in a positive review, it was good that they carried a .38 revolver to protect themselves against pirates and crocodiles.

The followings jpegs show a part of the construction and parts of the interior of the boat. The structure of the boat is simple but large and required a lot of physical effort to position eg the 4 x 10 foot 12 mm ply hull panels with just 2 people working on the boat with little additional assistance. The only power tools they used was a ¼ inch power drill with circular saw attachment, a small jigsaw and an small orbital sander. The mast and boom were built from Philippine Mahogany. They used 900 lbs of epoxy to glue and saturate everything for longevity which after 40 years is a very convincing demonstration. Basically 2 years of hard work that resulted in a home for the next 40 years with a simple interior layout that is very comfortable.

Wolfgang doesn’t talk about performance much but Taboo 3 has been in force 10 /11 winds (50 knots plus) and 40 foot seas without a problem on several occasions on its world travels. I would expect 8 to 9 knot averages with 18 knots max speed.

 

For those who have a quite weekend (or week) coming up due to global health issues, then a good read is a complete guide for cruising catamarans in a book format, the following document may be of great interest. It is a 24 meg download and is 300 pages long. Please advise if it will not download there may be another way to access it.

http://fotocontato.com.br/uploads/t...r Cruising Sailors 2008 Tarjan 0071596224.pdf

Also a small PDF about project management of a multihull build.

 

Julius Graupner and Thor Unbescheid have designed “Zero Sail” an 18-meter concept sailing catamaran. It’s about 60 x 32 foot with a 72 foot high 2 part wing mast of 900 square foot. First real problem, no mention of reefing capability but it is “computer controlled”. One of the jpegs with the boat sitting on a calm sea and a thunder head approaching could be very interesting in the real world!

The interesting part of this concept is the construction. An aluminium space frame covered with high-tensile polycarbonate. Both materials are 100% recyclable. The designers are claiming that building with non-recyclable materials like carbon fiber, glass fiber and epoxy is unsustainable ecologically. These guys do not know about some of the new epoxies and fabrics made from recyclable ecological sustainable materials being made for motorsport etc. The basic idea of an aluminium space frame and plywood covering was done in a 42 foot cat “Marara” built in 1958 by a Mr C Walker in California USA.

According to the designers “Unlike other sailing catamarans, the helm stand is placed in the front right beneath the wing sail. Here the skipper is exposed to the elements and has superior oversight. The crossbeam holds the wing sail and has an indicator that shows its angle. The living area with 10 berths and saloon is located in the back. It has a bright living space with huge panorama windows. On the left of the balcony is the connection for charging the batteries and refueling the H².”

 

May I just temper the article linked here with the comment that the author is the same GREGOR TARJAN that oversaw the building and launch of the Alpha
42 ( Be Good Too).
Yes, the 42 foot cat with woefully inadequate 1 1/2 inch rudder stocks , and the anchor chain that run over the top of the forward settee.

Gregors' knowledge or lack there of was certainly bought into question with this design. He did nothing to change the situation with his post incident responses.

 

This is a story of a man who owned a Gunboat 62 cat and decided sailing with 8 friends was annoying as he had to feed and amuse them etc plus his paid crew was working very hard to maintain the boat with a lot of unneeded space. Result he decided to downsize to a better performance boat with only 4 berths but could day sail with 10. What was the boat? “Finn” a 53 x 43 foot tri that weighs 24,000 lbs. The rig is a carbon fibre 72 foot mini wing that can cant 6.5 degrees from vertical depending on the tack. The mainsail is 1130 square foot, self tacking jib of 750 square foot, gennaker of 1600 square foot. The tri was built in China by McConagy an Australian based builder who has done several very high performance tri’s like Ellen MacArthur’s B&Q which held the global single handed speed record at one point.

To quote the owner. “The sensation of sailing a cat is a bit like trying to sail a tennis court. There can also be a false sense of security with a cat. You are stable and upright, until you are not.

Let me say upfront, if you want to race a boat, build a race boat. If you want to cruise, build a damn safe and fast cruising boat. Safety is about speed. Speed means you can outrun weather systems, have less exposure to crew fatigue, and less stress on the boat. When you try to build a race and a cruising boat there are all kinds of compromises that sometimes don’t work out so great.

One of the many outstanding design characteristics of FINN is the X-beam construction. Instead of using less expensive parallel crossbeams, Renaud Banual designed the beams in an X pattern which has the advantage of far greater lateral rigidity and requires less reinforcement and therefore weight on the main hull deck. I am constantly amazed at how stiff the boat is in all condition.”

On the rig the owner said “With a rotating and canting Lorima high modulus carbon spreader-less rig, and an aft ballast tank, the trim and righting moment are greatly enhanced. During a tack, touch a button at either helm pod and the hydraulic ram releases the rig to drop to leeward. Push the tiller over and release the mast rotation and you come out of a tack in less than half a boat length with very little loss of speed.

Spreaders are a failure point. Each turnbuckle is a failure point. They are a pain in the *** to tune. Take a traditional rig off and you will spend days tuning the rig, often with professional help. I can’t thank Bruno and Renaud enough for advising me to do a spreader-less rig.”

Couple the canting rig, rotating rig with the wave piercing bows, FINN is a boat that tacks and behaves. There is no fore and aft pitching that is common on cats, just a smooth piercing of wave crests as the spray is shed to leeward and the main hull and windward hulls stays dry.

Construction is Carbon, E-glass, M foam vacuum bagged resin infused layup. The hulls on FINN are constructed of infused E-Glass/foam, with Carbon-fiber reinforcement where necessary. Her X-Beam Crossbeams are of carbon fiber, as are all appendages and chainplates. E-Glass was chosen to be both a good balance between performance and cost, as well as for being quieter underway and more resilient in the event of grounding.

2 interesting features. How do you keep the matte paint on a boat pristine season after season? Ceramic coating is the answer. Its permanent. Soap water and a good rinse and its is exactly like factory new. Every surface on the boat, inside and out, was coated at the factory. Second ,Whisper Wall: The only way to conquer the hard surface characteristics of modern composite interiors is through a whisper wall system. On FINN, the typical panel system weight was eliminated by using a simple track system which creates very tight surface fabric over 25mm of lightweight adhesive backed foam insulation. A weight study showed that this system was less weight than paint and fairing an interior. The advantage is a soothing very quiet environment under power or while sailing, and a cool temperate atmosphere without the need for AC.

PS its for sale at $US 1.25 million. An interesting machine that has topped 23 knots when “cruising” with 12 knot averages not unknown.