Multihull Structure Thoughts

Discussion in 'Multihulls' started by oldmulti, May 27, 2019.

  1. tane
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    tane Senior Member

    still recall the nice tarry smell wafting down on the breeze as they are anchored upwind of us in Colon, Panama in 83.
    Like us they were on a very tight budget (though we would never have stooped to "lend our books for money" as they did when I wanted a look at their Pilot/Sailing directions...)
     
  2. oldmulti
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    oldmulti Senior Member

    Part 2 of Taulua the 36 foot canvas paper pitch catamaran. This will be about the Tuna rig and what occurred after Taulua reached the Americas. The shell of the cat was basically complete and now the rig had to be created. Wayland wanted an effective powerful rig that had a low centre of effort and was easily handled. He created a cross between a chinese junk rig and a wing sail rig. The mast was a solid timber spruce spar made up from ladder quality logs brought from a ladder factory. The mast was supported at the base and from cap stays only. This allowed a batterned wing sail, with a double sided sail around the mast, to be reefed as required like a junk sail.

    The batterns required 18 foot long strips of elm. None of the elm trees were straight, so Wayland again found a solution. He cut the timber to size then steamed the timber and stacked it to straighten the timber out. It worked. This guy works with what he has. Not what can purchased with a credit card at the local timber merchant, as Wayland could not get any credit anyway. The 7 batterns had a solid nose section then a flexible tail so the sail section changed shape tack to tack to form a very good aerofoil section. Result, a powerful, low centre of effort reefable wing sail. There were also some headsails. All the sails were made on a home sized treadle sewing machine with “sharp” needles and triple zigzag stitching. The sail cloth was purchased at a discount rate as per usual. The jpeg shows the batterns of the original single wing sail.

    Lateral resistance was provided by 4 leeboards (2 per hull) to provide lateral resistance and be able to help the balance of the cat when sailing. A central wing mounted rudder was used for the Transatlantic trip. A 12-horsepower auxiliary motor was also installed.

    So how does Taulua sail? On its Transatlantic trip it had from drifting conditions to gales. It averaged 180 miles a day on several days and took 25 days for the trip. Taulua can average 7 to 8 knots in cruising mode loaded for cruising. The cat and rig works. But as per usual things can be improved. After Taulua went through the Panama Canal to Costa Rica, Taulua was modified.

    To quote Wayland and Aruna: “During the first two years that we were travelling we had plenty of opportunity to observe Taulua´s performance and when we rented a place in Puntarenas we were able to make a few changes. We changed the sterns into transoms which gave a little more waterline length and a way to fit dual rudders, connected to a central wheel. We took off the lee- boards, which though effective were unwieldly in a seaway, and fitted a low aspect ratio keel along the bottom of each hull. These keels gave us the necessary lateral resistance and also made it easier to clean the hulls when beached. The sail was evolved into a twin, cantilevered mast rig with double-sided balanced airfoil sails, built on flexible wooden battens. Each mast was seated in the keel with a conical roller bearing and at deck lever a cylindrical bearing so it could rotate completely. No stays! The new rig was very efficient, we tested it well in the northerly winds off the coast of Nicaragua. Three point turns were even possible.”

    During the time in Costa Rica Wayland formed a partnership with Gifford Technology in Britain to develop and test the Tuna rig further. He built 2 small (about 20 foot) Bruce foil trimarans to test the improved Tuna rig against a conventional sloop rig. The learnings from this helped develop the new biplane rig on Taulua. Jpegs below. Also Wayland assisted in building the first “Constant Chamber” 1 ton pickup trimaran, he also did some mast building work for other wooden boats including building and repairing wooden masts etc.

    After 8 years of sailing (about 1990) Wayland and Aruna reached Banderas Bay in Mexico and decided this was their future home and beached Taulua. They then started a small restaurant which grew into a music venue and social gathering point for the community. Wayland and Aruna also took great interest in the Huichol indigenous people and started a project to build spinning wheels for them, financing it by printing Cultural Huichol Art T-shirts and employing 80 local residents for 20 years. As per usual Wayland could not afford the serious machinery for printing T-Shirts so invented his own at a low cost. In 2014 Wayland was fixing the roof on his property and fell of a 13 foot ladder damaging his spine and was paralysed from the chest down. Wayland died a few years ago.

    Again, I am amazed at the resourcefulness, intelligence, problem solving skill and persistence of some people to achieve very good things. Wayland and Aruna built an ocean crossing cat for very little money by using what was available in a smart way to achieve an outcome. Brilliant inventive work. The jpegs are limited but again the 5 part Youtube videos gives a lot of the idea.
     

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  3. oldmulti
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    oldmulti Senior Member

    Lorenzo Carrara was an Italian student of nautical/naval design at University of Genova when he did this design with a few class mates. I do not know if this design was ever taken further but what was done was reasonable. The biplane cat design is 76 x 44.9 foot with a displacement of about 67,000 lbs. The free standing masts are 82 foot from the deck with 1400 square foot of reefable sail per mast. The rig was chosen for its lower centre of effort and easier handling of the rig. The design is intended to be a fast cruiser not an outright racer. The length to beam of the hulls is 13 to 1. The draft varies between 5 foot and 11.5 foot depending on the daggerboards. The underwing clearance is 3.3 foot. The engines are 2 diesels of 85 HP with built-in 7kw alternator convertible to 10kw (peak) electric engine. Speeds up to 12-13 knots with the diesels.

    The biplane rig is widely spaced for less interference (40 foot between masts) with soft reefable wing sails. The masts are big (50cm diameter) unstayed masts buried deep in bilge (approximately 8 foot between low and top bearings). Winches for halyard & sheet are electrically assisted. The camber & vang are hydraulic with controls from the cockpits.

    Again, the accommodation is vast with 6 double berth cabins with ensuites in the hulls, also there are 2 single berth crew cabins in the hulls. The main saloon is vast with a large galley with several separate seating areas and navigation facilities.

    The construction is proposed to be aluminium (thick plate with few web stringers for the bottom, thin plate with web structure for the rest). The masts would be carbon fibre. I suspect the engineering of this structure would have to be very good to meet the estimated weight.

    An interesting design for 2010. There have been several other designers who have done similar cats that have been built. EG Kelsall, Chris White etc. There is a real market for biplane cats of all sizes. I think this remained a design study. Sorry for the limited jpegs.
     

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  4. peterbike
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    peterbike Junior Member

    Oldmulti, are you aware of any studies that compare a cat ketch to a biplane rig ?
    Thank you.
     
  5. oldmulti
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    oldmulti Senior Member

    Peterbike. I am not aware of any public studies of this specific combination. The closest would be contacting Bertrand FERCOT who built PHA (Tiki 30 biplane) and Grand PHA (Wharram Tiki 46 biplane cat) about his experiences against EG Tiki 46 conventionally rigged. One of Bertrand children live in Geelong Melbourne and Grand PHA was moored in Geelong for about 6 months. There have been several studies of the advantages of different types of single mast rig sail combinations by Gifford Technology in Britain and others. The built biplane cats in the water reports vary from very good to it has problems reaching. If the cat is light for its length and there are good sail mast combinations the cats can go very well. If the cats are overweight without good lateral resistance they do not seem to perform as well. Also look at Bernd Kohler designs and rig experience. The jpegs are of a few cats.
     

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  6. oldmulti
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    oldmulti Senior Member

    Sorry folks, but I have some issues and will be back in a couple days. Stay well please.
     
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  7. Burger
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    Burger Junior Member

    Best wishes oldmulti, and thanks for creating this great resource of information.
     
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  8. redreuben
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    redreuben redreuben

    I have issues too.
    After all this time I’ve gone and cought Covid !
     
  9. oldmulti
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    oldmulti Senior Member

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  10. oldmulti
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    oldmulti Senior Member

    Redreuben. Please take it easy and fully recover. This bug is stuffing a lot of people up. Please be careful out there.

    Mike Schacht has let his imagination produce an innovative simple multi purpose concept develop again. “Chetzemoka” is the latest idea, a small multi-purpose trimaran (described as a double outrigger) cruiser/cargo/expedition vessel designed for the Salish Sea. It’s a motor sailor, because the wind rarely blows when you’d like it to in these parts. “Chetzemoka” is 28 x 17.25 foot with a medium displacement 3200 lbs. The free-standing mast is only 19’-6” long and with the tabernacle it folds down to a bridge friendly air draft of 8’ and carries a crab claw auxiliary sail of 250 square foot (can be made from a flat sheet of poly-tarp if need be). The length to beam on the main hull is about 8 to 1 and on the floats about 16 to 1. The draft is 1.4 foot, there are no lateral resistance as this design is intended to be a motor sailor with the engine running most of the time especially to windward. The outboard is 15 to 25 HP.

    The concept of the design is to be a cheap effective small trading/charter vessel between many EG Indonesian islands to cheaply go to locations of the beaten track. There is little point in trying to make the tri go to windward well with all the associated deck gear and high stress rig components, foils etc when the motor will be more effective at meeting schedules etc. Also the rig is so simple to deploy that anything from a reach to a run will mean you can reduce your engine and fuel use to maintain your average speed.

    The accommodation is a shallow bow cockpit for anchoring and attending to mast raising and lowering small forward cabin for EG a berth or a toilet. A central cockpit/cargo storage space with good storage below the sole and an aft cabin with a steering wheel, double berth, mini galley, beer cooler, and CB radio or iPhone.

    I can understand the logic of this vessel as been a small trading/charter vessel between many EG Indonesian islands to cheaply go to locations of the beaten track.

    The materials for this are not specified but it would be easy to produce the dory main hull in plywood/timber or flat panel foam glass. The floats again could be plywood or foam glass as could the cross beams.

    This is a simple design that took a lot of thought to make as “simple” as it appears, but it is very functional design that took a person with a creative view of the world to develop the idea. Again, well done Mike.

    There are only limited jpegs.
     

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  11. oldmulti
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    oldmulti Senior Member

    And you thought biplane rigs were interesting. Today we will talk about a triplane rigged trimaran. In 1976 Roland Tiercelin designed and built a 40 foot trimaran named Trimama. Little is known of the dimensions beyond it was 40 foot long and Trimama had 3 aluminum masts on the forward crossbeam with each mast mounted near a hull. The masts were supported by a series of wires and struts between the masts. The initial sail plan was 3 mainsails with wishbone booms. Later, 2 roller furling genoas were placed on the outer masts to the float bows. The floats had angled hydrofoils on them to provide additional stability. The central hull had a conventional rudder.

    So how well did this rig/trimaran work? I will give a quote from Rolands son: “The mast on each hull which worked very well. In a multihull trophy regatta at La Trinité (about 1980), we had finished a few meters from Paul Ricard (the 54 foot foil stabilized tri sailed by Eric Tabaly). When Trimama converted from mainsails only rig, to additional roller furling genoas, the crew only needed to unroll only one of the genoas to gain between 10 and 20% speed. Trimama entered the Round Britain Race in 1982 with Patrick and Francis Tiercelin (sons) sailing the tri, but it dropped out with various problems after being competitive early.

    After a short period more advanced designs were sailing and Trimama with its problems was neglected. Trimama was bought for a pittance by 5 young people who were to restore it, but the project did not succeed due to the sails and all the fittings being stolen, then only 1 of the 5 people pushed on but the cost and work load became too much and Trimama was finally destroyed.

    An interesting trimaran of which little is known but it proved to work well after development. But the pace of multihull development in France from the early eighties made Trimama rig approach inferior to the wing mast light weight structures that started to do serious racing at that stage. There was a story in Voile magazine about Trimama but I have not found it. Sorry about the limited jpegs.
     

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  12. oldmulti
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    oldmulti Senior Member

    The Stow-Away 7.5 design is the next step up from the Stow-Away 6.5 model. The 7.5 is trailable during daylight hours in many areas. Craig Schoinning of Spirit design developed the design after he produced the 6.5 and 8.5 Stow-Away motor sailor designs. The Stow-Away 7.5 is 24.6 x 9.8 foot with a weight of 3000 lbs and a displacement of 4400 lbs. The rig could be a EG Hobie 20 but the real motive power is a 60 HP outboard. The draft is 1.9 foot over the hull and rudder. There is a centreboard case in 1 hull. The underwing clearance is 1.45 foot. There Is a 150 litre fuel tank. The claimed maximum performance under sail is 15 knots and under the 60 HP power is claimed to be 20 knots. This is the multihull version of a McGregor 26 monohull power sailor.

    The Stow-Away 7.5 overall 9.8 foot beam provides significantly more deck and internal space than the smaller Stow-Away 6.5m design. The 7.5 utilizes a pop-top to gain headroom in the main cabin. The pop-top produces low sleek lines which cuts down wind drag and provides clear vision when sailing. When at rest the internal layout is relatively spacious and more practical. The design allows for compact cruising for a small family over short periods. The accommodation is relatively comfortable with the pop-top raised and has a small galley to starboard with an L-shaped dinette opposite. Interior Forward of the dinette is a double berth in the main cabin area. A nice feature in the main cabin is a line of vertical windows in the front of the cabin for uninterrupted vision forward. The starboard hull forward is a single berth with the option of another quarter berth aft below the cockpit. The port hull has no accommodation and houses the centreboard case.

    Given the light weight structure this design will be manageable when towing, launching, docking etc. The construction is DuFlex Balsa/Foam/E-Glass or Plain Foam/E-Glass in Vinylester. Most of the structure is flat panels with minimal but simple curves. Craig has an understanding of how to build good hull shapes with minimal joints. The build time is claimed to be 750 hours for a basic boat with a semi experienced builder.

    This would be an interesting coastal cruiser for a person who wants reasonable accommodation for a couple for a month or 2. It is not an ocean crosser and for those who really want to sail it would probably be better to get a Farrier tri. This is a very good compromise for true cruiser that is relatively simple to build. Sorry about the limited jpegs.
     

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  13. tane
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    tane Senior Member

    pretty untangible what I have to contribute, but one of the Aussie may be knowledgeable:
    in the Brisbane area in the 80s there was this guy "Freddy", that built cruising cats out of aluminium. He must have been the builder with the very best effort-achievement ratio, bar none: the one cat I saw in 91 in the Brisbane river ("Amadeus", ~38-40', Austrian flag) loooked a little bit angular, but the proportions looked fine, aesthetics fine, a little on the rough side, but only a little. Overall it looked a very good world cruiser for a young couple. "Freddy" built it with a circular saw & a MIG welder beside a little hut right there in the mud. When I was shown the "building site" by a friend (Freddy wasn't around, so I never met him, I guess he was German or Austrian) I was very much astonished!
    Achieving a top notch vessel with a huge effort in manhours, tools, heated shed,...is fine, but having built cats like "Amadeus" there in the mud - extraordinary!
    Maybe someone knows more about it?
     
  14. oldmulti
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    oldmulti Senior Member

    This is about a fast day sailing catamaran that was used as the base of a very fast foiling day sailing catamaran. The standard Marström Composite AB M20 is 20 x 10 foot cat and weighs 257 lbs with a square head cat mainsail 237 square foot, no jib. Spinnaker 237 square foot. The standard build is Carbon fiber reinforced epoxy sandwich Nomex carbon fiber epoxy for the hull and deck. (First jpeg)

    The intention is/was to have an “open source” foiling development process to advance foiling cats without limitation. The Vampire project was conceived by William Sunnucks and boat builder Graham Eeles to develop foiling systems beyond current class cats and Americas Cup/GP 50 cats. An interesting aim. The cat initially chosen was a M20 from Goran Marstrom that weighs 322 lbs fully set up. After some initial racing to get a base line the cats beam was increased to 12 foot and a jib was added. The 34 foot carbon wing mast carries a 237 square foot mainsail and a 60 square foot jib. The 2 extremely flat spinnakers were 220 or 300 square foot. In this configuration this cat won the Texel race in 2009. After a short time foils were then added and the overall beam dimensions vary according to how the foils are deployed. With one hydrofoil down the beam is 14 foot with both foils down and full canted out (will explain later) the beam can reach 20 foot. The weight with the foils increased to 430 lbs.

    So, what is different between the foils on the Vampire project versus most foiling cats. The foils on Vampire are related to Moth foils with flaps controlled by forward wands which react to waves etc lifting or lowering the Vampire cat accordingly. The foils are also T foils that are canted out like the latest monohull AC boats. For the Vampire cats the canted flapped foils provide more stability and “automatic” control while sailing. This allows the stern T foils to just provide secondary lift and be used for steering. The forward T foils have a 4 foot span, the rear T foils have a 2 foot span. The Wand system is as far forward as possible to provide more pitch control. The system is by pull wire instead of push rod. The bias adjustment is through deflection of pull wire. There was modelling to get correct lever arm and bell crank dimensions requiring a wand length adjuster. Why gull wing (canting) foils? Advantages are more righting moment and therefore more speed, they also can be raised without disconnecting dynamic control system for light air sailing.

    During the development program some significant changes were made. The foil cant was increased to 30° then reduced back to 20°. The rig was reduced and sails were flattened. The platform beam was reduced from 12 to 9.6 foot. The main foils were moved back and the angle of incidence of the main foil increased. Also, calibrations improved the performance measurements.

    So how does a Vampire sail? To quote William Sunnucks: “We regularly see 30 knots downwind with two sails and we know that it has more to give. In light winds we use a spinnaker which (despite being super flat) is lower but slower – no more than 22 knots. Upwind we target 18 knots, bearing off when its less and heading up when its more. We have learnt that it’s not the top speed that matters – its consistency.” Top measured speed over 500 meters is 34.5 knots. That is an average not a peak speed over 500 meters. The Vampire cat is seriously fast for a 20 foot cat and is being developed into a high average speed device through improved foil and control approaches.

    The jpegs give the idea. For more information look at: The Vampire Project https://vampire-project.com/#post-30 and look at page 18 onwards of: https://www.ayrs.org/catalyst/Catalyst_N51_Jan_2017.pdf
     

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  15. oldmulti
    Joined: May 2019
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    oldmulti Senior Member

    The following is a conceptual design by Andrew Truillo Design. Andrew has worked with several large luxury yacht building organisations but now is doing independent aircraft and automotive design. As a result, he is not as locked in by convention as other people. The design we will discuss here is a conceptual 82 foot cruising catamaran Andrew has done. There are no dimensions beyond 82 foot length overall and a 115 foot masts from deck on the biplane rig version. The “Coriolis” is to have electric motors with onboard generators and deck solar panels providing the power.

    The twin mast configuration is to enable each mast to be more compact and less loaded, with the masts in the hulls to provide better support. The wing sail design is conceptual. It uses a NACA 2412 foil form but has a number of features that should mean that, in theory at least, the foil form could be varied by the use of cams inside the wing. The cams would act on the battens, which in turn would vary the section profile depending on the direction of the wind. The profile is controlled by the skipper. The sails are on unstayed masts and can rotate fully 360 degrees, if required. This means that the wing sails could be used as wings even with a following wind. The cams that are attached to the battens have loose fitting bearings that not only allow the wing to rotate, but the bearing surface also slides up and down on the mast, though the tolerances would not be very tight, removing therefore chances for the cam “vertebrae” to seize up. The mast would probably be made of pultruded Carbon fibre, meaning tubes that are consistent and can be very stiff. The masts do not taper. The cam system would probably be powered by electric winches or hydraulics. The sails would have a boom, inside which would be the hoisting mechanism, probably an electrically powered capstan winch. The wings can be raised in a similar way to a junk rig, so the uppermost part of the sail is hoisted, and it raises each segment in turn.

    The accommodation is vast and what ever you want. The designer says “The hulls are capacious rather than very slender, meaning that she is not intended to win races (though probably quite swift).”

    The build is meant to be environmentally friendly with the latest generation of more sustainable composites (vegetable sourced epoxy resin and flax fibre) with PET foams etc.

    There is an alternative sloop rig model proposed but the designer does not like to have a mast on the bridge deck structure, which is considered to be the weakest part of the structure according to Andrew.

    An interesting concept, the jpegs give more of the idea. The final jpeg is of a "sloop" type rig.
     

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