Multihull Structure Thoughts

Russel, where can you buy his plans ?

 

The Powershuttle 25 was found on the JSYD site, it is a 2003 design that is interesting. The power catamaran is 25 x 13.6 foot and weighs 2000 lbs and displaces 5370 lbs. The cat is transportable as the cat can be broken into 3 components. The hull length to beam ratio of the hulls is 11.1 to 1. The hull shape and flare above the waterline should help reduce any spray or white-water on deck. The outboard power is not specified but I would expect 30 to 70 HP. The fuel supply can be as high as 1100 litres if all optional tanks are installed.

The intent of the boat is mainly a day boat with fishing potential. There are several fish storage areas, one steering cockpit and very limited forward hull accommodation that could handle a loo.

The structure is not specified but it will be PVC foam, vinylester, e-glass fabrics and e-glass unidirectionals. The deck areas may have a light timber overlay for some extra protection. The 3 main components are bolted together with an aft rear beam finally locking together the structure.

Speed is unknown but if appropriately powered 30 knots plus would be possible.

An interesting design, I do not know if this cat was built but it would be fun. Jpegs attached.

 

White Pegasus is a trimaran designed by Dick Newick with Walter Schurtenberger the builder adding to the design. It was launched in Quebec, Canada in 1986. The tri is 55 x 34.5 foot that displaces 13,500 lbs. The 60 foot above deck carbon fibre tube masts carry about 1200 square foot of sail in total between the 2 mains. The draft is 3 foot over the rudder. No mention of a daggerboard but I would suspect it would have one.

If this design looks vaguely familiar, I think it’s a version of Dick Newicks personal tri Pat which was 51 x 28 foot. White Pegasus is longer and wider but has very similar shape in the main hull, floats and cross beams. The structure is PVC foam e glass. The cross arms have carbon fibre in them with water stays to add rigidity. The tri looks as though it could be disassembled for transport judging by the w3ay the crossbeam sit on the main hull.

The major difference between Newicks Pat and White Pegasus is in the accommodation. White Pegasus has a large deck cabin and cockpit aft. The additional space would provide a comfortable tri but was against Newicks KISS principles. I suspect the aft cabin structure was more Walter Schurtenberger concept than Newicks.

No performance information but I suspect with the above numbers it would be reasonably fast.

An interesting design that I would like to know more about. Jpegs attached.

 

I know very little about the following tri but the rig is interesting. The tri is about 29 foot long home built French boat. The boat looks like a foam glass structure. The “mast” is 40 foot of deck and looks like a carbon fibre tube. The double sided sail is 500 square foot. The sail has 4 aerofoil battens that fit around the mast and are reefable as is the top “yard” that can rotate to maintain the top shape. The Balestron boom looks as though a small headsail could be carried if required. Pure wing sails need a well rounded leading edge of the wingsail to get the best performance from the sail or a small headsail that smooths the windflow onto the wingsail. The rig can carry an asymmetric spinnaker which is a real advantage.

The real advantage of this rig is its ability to “twist off” at the top. Even the majority of solid wing sail cats have the ability to “twist off” the top of there wings This is important for 2 reasons. First is you can depower the rig through gusts by allow the top to “feather” but the main reason is wind gradient. Wind close to the sea surface is “slower” due to surface interference. Wind even 30 foot up is less disturbed and is “stronger”. Wing type rigs need to allow adjustment to allow twist. Most yachts that use a conventional soft sail rig have flexible enough sail fabric that partial adjusts to the wind strength differences.

The jpegs give the idea. Interesting concept.

 

A short story about a racing trimaran that has been converted into a cruiser, well more a racer cruiser. Paradox was designed by Nigel Irens/Benoit Cabaret and built by Marsaudon Composites in 2010. The tris is 63 x 48 foot with a displacement of about 19,700 lbs. The 83 foot carbon fibre rotating wing mast carries a 1160 square foot mainsail and a 910 square foot number one with a 1270 square foot gennaker. The draft is 14 foot when its daggerboard is down. These numbers indicate this is a seriously fast boat and according to reports, Paradox is still capable of cruising at well over 20 knots and reaching 30 knots at full tilt.

Compared to a modern ORMA tri, Paradox has an 18 foot shorter mast, 30% less sail, 12 foot less beam and is 8,000 lbs heavier. Paradox is very fast, ORMA tris are spectacularly fast.

Paradox is a cruising trimaran with a simple but comfortable down below with plenty of headroom. The saloon area includes a head, nav station, galley and fold down dining table that seats six comfortably. Two upper tier berths with lee-cloths provide a secure sleeping area in rough conditions. Large double bunks are found in the aft and forward cabin, which also includes a shower and sink. Solar power, a water maker, refrigerator and plenty of storage space for food, Paradox can do trans-oceanic trips.

Paradox construction is from resin infused carbon fibre rather than pre-pregs over a PVC foam core, and is heavier than a racing ORMA but has exceptional torsional stiffness and a much higher load tolerance. Marsaudon Composites know how to build light large fast tri’s having built the 90 foot plus IDEC global racer. To give you a feel for the structure ORMA tris have a single layer of 600 gsm high strength carbon either side of a 18 to 25 mm Nomex core. The real artform of this design is the crossbeam’s structure. Minimal dimensions but maximum stiffness.

The owner is more a cruiser than a racer but to give an example it has done 600 miles around a multidirectional course in 40 hours or a 15 knot average. I think I could accept a simple accommodation layout for that type of average speed.

The jpegs give the idea of real fun boat.

 

The following design has been superseded by later versions but I think this is an excellent large cruising that can sail. The cat is the RB 45 designed by Naval Architect, Albert Nazarov of AMDesign. The design was done in about 2012 and several were produced. The cat is 45 x 24 foot with an approximate displacement of approximately 35,000 lbs. The 60 foot aluminium fixed mast carries a 680 square foot mainsail and a 450 square foot fore triangle. The hull length to beam is approximately 8.8 to 1. The underwing clearance is 2.5 foot. The draft is 3.3 foot over the low aspect ratio keels. The engine power is two 30 HP inboards. The cat can carry 2400 litres of water and 1600 litres of fuel as well which by itself will weigh 9000 lbs. Wonder why these types of cats have 35,000 lbs displacements.

The accommodation is large. 5 separate double cabins and a single “crew” cabin with toilets in the hulls. The main cabin has a large galley, big dinette internal steering position and chart area. The cat has all the usual mod cons such as watermakers, airconditioning, entertainment centre, toys etc.

This design is basically a flat panel structure. It could be built in plywood, aluminium, foam glass or more exotic materials. The production cat is foam e-glass vinylester panels. The luxury version is honeycomb core probably with epoxy glass. Albert Nazarov is an excellent designer with many good multihull design so I would have no doubt about this design. Please research very carefully any company claiming to build this design, as honeycomb cores require very good building skills.

The jpegs give the idea. The designers web site is Albatross Marine Design Thailand - Boat and Catamaran Design by Albert Nazarov http://www.amdesign.co.th

 

Gee those transoms are fat...

 

We have spoken previously of Chris Whites Atlantic 46 performance cruising catamaran. An Atlantic 46 is 46 x 25.5 foot with a weight of 14,800 lbs and maximum displacement of about 20,000 lbs. There is an LR version with 2 foot longer hulls and weighting 16,400 lbs to handle bigger water and fuel tanks. The remainder of the cat is the same. The 61 foot fixed aluminium mast carries an 720 square foot mainsail and 405 square foot jib. The hull length to beam of the hulls is about 12.5 to 1. The draft over the daggerboards is 7.5 foot and the rudders draw 2.66 foot.

The accommodation has 2 double berth cabins with associated toilets, 2 single berth cabins and depending apon the version a galley in the hulls. The main cabin has a seating area, navigation area, internal steering position and access to the forward cockpit which has direct access to the mast and an external steering position.

The production versions were PVC foam e-glass vinylester builds. They were well built and are reliable.

The reason for this item is Atlantic 46 real performance. “Winds were light with no more than 14 kts, but mostly 8-12 kts, but Pegasus is a great light wind boat and we managed to make good time, with a 22.5 day crossing to Cowes, and less than a day’s motoring. I am very glad that we have a large spinnaker, which pulled us some 3000 of the 4145 miles sailed.” Translation 185 miles per day or 7.7 knot average in 8 – 12 knot winds. OK.

Or how about “Pegasus is a fast, safe and steady passage maker. Her maximum speed to date is 28.4kts, but on a trade wind passage we can expect some 1300 - 1500 miles a week sailing conservatively with all the family enjoying the experience.” Translation under moderate conditions 200 miles per day with an 8.1 knots average.

The Atlantic 46 Barn Cat “After 9000 miles of sailing the Atlantic 46, the characteristics that most impress me are how fast and comfortable the boat is at sea. The forward cockpit/aft pilothouse layout, slender hull shape, and powerful rig make a wonderful combination. The pilothouse offers great protection from the elements and excellent visibility. The boat is responsive and a joy to sail between 13 and 20 knots of hull speed. This design helps make sailing fun and safe."

Atlantic 46 Great White “We saw some wild weather after leaving Canada, a ship clocked an official 82 knots of wind one night. Great White rode the storms extremely well, great job on that hull shape. She climbed back up and out of troughs that looked like they would just swallow us. We had waves picking us up by the floor when running with a storm around the Gaspe' peninsula and just burying the front beam into the sea in what should have been a real scary point of sail but those upswept bows just kept coming back up. Dynamic sailing though, 25+ knots at times!"

Under power an Atlantic 46 will do 9 knots with twin 18 horsepower Yanmars and with twin 27 horsepower Yanmars will up this to 11 knots.

The Atlantic series of cats are seriously good performance cruising catamarans. Any cat that thinks 200 mile plus days are normal under many conditions are good vessels. If pushed under good conditions these cats could top 300 miles in 24 hours. But the real advantage is the hull shape allows the crew to sleep and function well at these speeds. Good boats.

 

Palomino (also named Trigger at one point) is a Mike Schacht Design Pacific proa development in about 2013. The proa is 23.5 x 12 foot (including pod) with a 900 lbs all up displacement. Initially a F16 catamaran rig. We will discuss the rig options later. The 16 foot ama is used to windward at all times. The length to beam of the main hull is 12 to 1. The ama is 20 to 1. The rudder boards at either end of the main hull draw 2 foot when down. The daggerboard is in the ama and draws 3.5 foot when down.

The initial design was to be built the main hull in plywood with a dory bottom. 3 sheets of ply length for the main hull, 2 sheets of ply length for the ama. The cross beams are solid laminated timber with water stays for additional support underneath and rig tension for upper support. The cockpit on the main hull is Tremilino trimaran type canvas seats. This would be a simple build with taped seams and minimal timber required for gunnels, stringers etc.

The accommodation is a few protected areas for storage. You could camp sleep on the cockpit floor.

Now the rigs. As stated, the initial design was for a F16 catamaran rig. The only real innovation is that the mast step is mounted over a sliding traveller car which permits shifting the mast step fore and aft by up to three feet, either direction. This allows adjustment of the CLR forward of centre, which helps align the forces of the rig to the hull and foils. It also adjusts the mast angle to cant aft, more like the modern racing cats. It also permits sailing balance to be enjoyed without the jib, since shunting the jib is really the Achilles heel of the entire “beach cat rig for proa” program.

Next for Palomino was a cat ketch, two free-standing masts, 172 sq. ft., sails roller furling around the 25’ masts. The benefits of two, widely spaced sails for a proa are well documented as they permit quick and simple fore and aft adjustment of CE by simply playing the sheets. The problem with the rig is that while it is simple, it is not cheap, the masts are custom carbon fibre.

Final rig development/option was Palomino carrying a WETA mass-produced trimaran rig. It’s only 124 square foot (main+jib) and it should move the canoe along well enough. Considering the relatively low righting moment of this little pacific proa, it seems like a good compromise between manufacturing efficiency, price, and performance.

Interesting design concept. Jpegs give the idea.

 

Thanks for this OldMulti. I am building a small proa of similar size for inland coastal camp-sailing ( Texas 200 and Everglades Challenge type events)and have gained much insight into design from this and other places. I am committed to a schooner rig and it is good to hear that there are advantages to 2 wide-spaced sails for the balance. Im hoping to model my rudder setup off of the harryproa concept of 2 foils more closely mounted without a 3rd center- or dagger- board. I know the answer to the question of centerboard/ no centerboard is "build it and try" which is currently the plan. Whether to have a centerboard and rudders mounted far apart versus 2 bigger rudders mounted more closely to the beams as in HPs is quite an unknown for me.

So my questions - What are the advantages to having a centerboard out in the ama such as your pictures of Trigger above, the CLC Mbuli, Rael Dobkins' proas and others? Many small proas are built that way though Ive seen some with a centerboard attached to the windward side of the mainhull/vaka/canoe. Seems to me the wetted surface is unchanged, but mounting it far out to windward in the ama produces drag there, and an increase in weather helm would result.

Based on your knowledge of the leeway prevention and foils, steering and everything, is it likely I can make the 2 rudders work without a centerboard? Steering from the bow rudder with a centerline-locked stern rudder apparently works quite well on some proas.

 

BCowan You are asking a tricky question because it has a few aspects to it. I have very limited experience of proa's. There are others on this thread occasionally who have thousands of more sailing miles on proa's than I. But think about 3 things. First the weight of a daggerboard and its case is better in the float of a Pacific proa, it helps stability. Second in gusts the daggerboard lifts higher leaving less to stop the proa skidding sideways a bit to ride through the gust. In some designs the lack of daggerboard in the main hull gives more accommodation. Thats the simple stuff. Now the real issues. The CE of a proa's rig depends on the rig type and position of mast/yards. Combine this with a need to keep the relative centre of lateral resistance in a relatively similar position with the CE of the rig you start running into problems.

2 choices. First you fix the lateral resistance and move the rig CE to suit the direction you are sailing in. Or you "fix" the rig and be able to vary the lateral resistance to match its relative position of the CE for the rig depending on the direction you are sailing in. The rudder boards like Cheers allow a "fixed rig" and you adjust the rudderboard depth to get the balance required. You can achieve a similar thing with oversize rudders but they have there own issues.

Excessively large rudders need to be steered well or you are creating unrequired drag. convention says the aft rudder should be the steering rudder which means you have to minimise the steering effect of the lead rudder on each tack and a rudders shape is often different to a boards shape to achieve good steering or lateral resistance. Result of the above HP's have done a lot of work with large steerable rudders closer to the centre of the proa. Rob Denny is an approachable guy, ask a question on his forum for his logic, I am sure he will respond to a general enquiry. Also Russell Brown could be asked as to what approach he preferred on his proa's. My thoughts are Mike Schacht has done a lot of good thinking about the topic and what he has drawn looks good. Hope this helps

 

The Simpson “Liahona” 43 foot cruising trimaran has been discussed before but we have more structural detail today. The tri is 42.6 x 26.6 foot with a weight of 8,750 lbs and a displacement of about 13,000 lbs. The 50 foot fixed aluminium mast carries a mast head rig with 880 square foot of sail area in the main and fore triangle. The length to beam on the mainhull is 8 to 1. The draft over the minikeel and rudder is 2.9 foot and 6.5 foot with the centre board down. The Liahona is an older design done in the early 80’s that is no longer available.

The accommodation is very good for a tri. There are 4 double berths separate head, large galley and dinette. The cockpit is large and has relatively easy access to the rig. There is an inboard engine.

The structure is what was being built in the early 80’s. Hulls are of fiberglass foam sandwich construction. The core material is 15 mm Klegecell PVC foam except for the bow section of the main hull, which is 15 mm Airex PVC foam. The outer skin is 300 gram chopped strand mat, 24 oz. woven roving and 300 gram chopped strand mat. The inner skin is 300 gram chopped strand mat and 800 gsm woven roving. Resin is 1027 waxless slow cure polyester. Total hull thickness is about 19 mm. The stem of the main hull is constructed of 14 layers of 6 mm Douglas Fir, laminated with epoxy.

Main hull decks are of fiberglass foam sandwich construction. The core material is 12 mm Klegecell PVC foam. The outer skin is 300 gram chopped strand mat, 300 gsm woven roving and 300 gram chopped strand mat. The inner skin is 300 gram chopped strand mat and 300 gsm woven roving. Resin is 1027 waxless slow cure polyester. Total thickness is about 15 mm. The deck over the galley and navigation station is constructed of 9 mm Bruynzeel mahogany marine plywood to facilitate deck hardware attachment. Deck beams are Douglas Fir. Deck stringers and hardware backing blocks are Ash timber. Ama decks are constructed of 9 mm Bruynzeel mahogany marine plywood covered with 300 gram chopped strand mat/epoxy.

Crossbeams are Douglas Fir and 9 mm Bruynzeel mahogany marine plywood box beams bonded and coated with cold cure epoxy. Crossbeam fairings are built of cored fiberglass using 12 mm Airex core with reinforcing ribs. Bulkheads are 12 mm and 9 mm Bruynzeel mahogany marine plywood.

Interior furniture is constructed of 6 mm Bruynzeel mahogany marine plywood. Floors and furniture are framed with Douglas Fir and Spruce.

Today structure for the same boat would have EG 2 layers of 600 gsm e-glass biax outside of 15 mm PVC foam with 800 gsm e-glass biax inside in vinylester resin. The result would be lighter, less subject to degradation and tougher. It would also be easier to build.

Interesting boat. Jpegs give the idea.

 

The Warren 32 is a tri that was designed and built in early 2000’s by Ted Warren. Ted Warren was an innovative US designer who specialised in very light weight proa’s and tris. The Warren 32 is 32 x 30 foot that was extended to 33 foot. The beam can be reduced to 8 foot for transport. The racing displacement with crew and rig is 2,200 lbs. The 47 foot rotating carbon fibre wing mast has a 200 mm chord with about 450 square foot mainsail and a 150 square foot jib. The length to beam on the main hull is about 14 to 1. The floats have 6,600 lbs of buoyancy or 300% of racing displacement. The float design suggested the Warren 32 can be sailed on its float in hard conditions. The tri has a deep central daggerboard and a deep central rudder.

The accommodation is minimal with a few single berths, small galley and loo. The headroom is 5 .6 foot. The second version that was built was 36 foot long with a 8.5 foot wide hull with an aft cabin which increased internal room by 53% and gave 6 foot headroom. This tri is a high performance cruiser.

The Warren 32 is a carbon fibre PVC foam through out. The structure is very light. The cross arms are built separately from the main hull and floats. Each cross arm is 11 foot long and weighs under 20 lbs. To give you an idea of how light you can build these tris is a similar 32 racing tri has 193 gsm carbon fibre, 12 mm corecell foam, 193 gsm carbon fibre hull layup.

Be very aware the basic hull layup may be light but in the case of the Warren 32 it has carbon fibre ringframes in the hull. After initial sailing the hulls panted to much and required additional carbon fibre on the caps of the ringframes. The pins attaching the float to the main hull were not a “perfect” fit which allowed some noisy movement. New perfect sized pins were fitted.

How does the tri perform? She ‘ll tack every time without backing the jib and even on the mainsail alone. The ride is smooth in a chop. The fine shape of the hulls forward allows easy entry and dampening is excellent with the flat sterns and large amount of reserve displacement at the bows. When tacking it can go through 80 degrees on the compass, although I think that 90 degrees is more optimum for VMG. The acceleration when footing-off is breathtaking. The numbers indicate very good performance capability.

It’s a pity Ted Warren has retired as he did some innovative and forward thinking designs. The jpegs give the idea.

 

The “Ocean Eagle 43” power trimaran today is very large and not useful to the average person. The construction is of interest and could be applicable to much smaller builds. The trimaran is a series production item mainly for military forces designed by Nigel Irens. The power tri is 143 x 51.5 foot that draws 5.1 foot. The complete composite shell weighs less than 70,000 lbs and can carry 50,000 lbs of engines etc plus another 40,000 lbs of fuel. The total displacement is about 180,000 lbs. The length to beam on the main hull is 12.2 to 1. The performance of the tri is 30 knots maximum speed with 18 knot fast cruise with a 3000 nautical miles range. The slow cruise speed is 12 knots with a 5000 nautical mile range. Translation 4 litres per nautical mile at slow cruise speed. Not bad for 143 foot.

To the structure and build. The laminate design uses mainly glass fiber/epoxy sandwich construction. “Everything … is cored and infused,” says H2X’s head of composites Pierre Lallemand, “except for monolithic areas near the bottom of the hull at the front of the boat.” Carbon fiber was used here as well as in high-load areas like stringer caps and in the arms that connect the amas to the main hull. “The composite structure is well proven,” says Irens, “and essentially uses unidirectional reinforcements along the top and bottom of the ‘shoebox’ formed by the hull and deck.” He adds that off-axis reinforcements (±45°) are used to handle the shear/torsion between the top and bottom. Corecell foam core used in densities from 80 to 200 kg/m3 and in thicknesses from 20 mm to 40 mm, optimized by location to save weight. “The core has a big influence on the infusion,” Denjean contends. H2X used double-cut core, with very thin cuts on the top and bottom that help aid resin flow on both sides. The majority of the structure is resin infused on specific curved molds and flat tables for bulkheads and decks. All epoxy resin infused components are postcured at 60 degrees centigrade. The 143 foot main hull was a one shot, 9000 lbs of epoxy, resin infusion. The 143 foot hull is then post cured as one unit as are the majority of the 106 parts.

Interestingly, despite the main hull’s size, H2X did not do resin flow modelling for the infusion. “We don’t take too much risk when we infuse, we use numerous feed points and short flow distances between them. But we did do a lot of infusion testing on a large glass table to ensure that all of the different cored laminates would infuse completely, without problems.”

Although flat panels could be made on a table, the main hull, the amas, and the arms and other curved structures required shaped molds, nine in total. H2X made its own tooling, having the ability in-house to go from CAD drawings to CNC-machined plugs to infused tools. The molds for this project, however, were built differently, formed directly (without a plug) from CNC-cut wood panels that were sheathed with plywood and composite laminates, and then surfaced with tooling paste and sealant. One issue was to ensure the mold was airtight. The main hull mold surface area totalled 3200 square foot, H2X chose cost-effective wood construction, but had to adapt the surface treatment for the large size and then test it for airtightness. “We do this by putting the bare mold under vacuum and measure how much the vacuum level drops over 30 minutes.” When it was satisfied with the molds’ vacuum integrity, the team prepared for infusion.

Following infusion and cure, assembly begins of the 106 composite parts. Lallemand said “It took several weeks to build all of the structure inside the main hull, including stringers, bulkheads, floors and decks.” Parts were joined by conventional wet layup tabbing, using glass reinforcements similar to the carbon fiber tapes. All of the connections on the outside of the hull were vacuum-bag consolidated after wet layup to optimize impact and environmental resistance and reduce surface preparation for painting.

So you have a simple timber mold, resin infusion using a lot of short runs and relatively low temperature post curing of all components. Don’t be inspired by the size as EG just cutting out the fiberglass to fit all components took 3 weeks for a 10 person team. But there is nothing that could not be done on a smaller scale. Interesting build. Jpegs give the idea.

 

Grainger design produced a TR52 trimaran as a semi custom design. Tony Grainger “The TR52 offers a wide range of options for the arrangement. Configure the TR52 to the type of sailing that suits your style; a comfy world cruiser for family and friends or fully crewed offshore racer with cruising potential.”

The tri is 52 x 40 foot and draws 8.2 foot with the daggerboard down. From here I am estimating the numbers. The tri looks as though it has a 70 foot rotating carbon fibre mast carrying a 990 square foot mainsail, a self tacking jib 470 square foot with a code zero of 850 square foot. The length to beam at the waterline of the main hull about 11 to 1 with the floats length to beam 15 to 1. If these numbers are close to reality this will be a very fast cruiser.

The accommodation of Grainger tris is very good. The 15.5 foot wide main hull at the deck level is possible by the large flare from just above the waterline. Most of the panels in this tri would be flat panels so it is “relatively easy” to build. There are several accommodation options with up to 3 double berth cabins and up to 4 single berths. The toilet can be large or several smaller loo’s. The galley is large with a dinette. The cockpit is large to very large.

The construction will be a choice from flat panel PVC foam e-glass with some carbon fibre to a full PVC foam full carbon fibre structure. This tri is semi custom and Tony will deliver what ever you want at a reasonable design fee. The hull bottoms will probably be round bilge built in separate molds.

The jpegs give the idea. This would be a very fast cruiser that would be a capable world cruiser.