Multihull Structure Thoughts

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

  1. oldmulti
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    oldmulti Senior Member

    Francios Perus is a multihull designer that originally worked for Tony Grainger then for himself in France (his home country). He has designed or been involved in designs for Corsair, Seawind 1350, Ita 15, Overboat foiler, Pandora, Corthinx CX 450 etc. I recently viewed a 2 hour video of him speaking to the NWMA which was informative.

    He owns a Pandora 8.50 catamaran (which he designed) and sails from his beach front home. The Pandora 8.50 was featured on Page 86 of this thread. The Pandora 8.50 is 27.9 x 16.5 foot that weighs 1900 lbs and displaces 3250 lbs. The 40 foot rotating mast carries 312 square foot main, 150 square foot jib and a 400 square foot gennaker. The hull length to beam is about 12 to 1. The production boat has low aspect ratio keels that draw 2 foot. Daggerboards are an option. The Pandora 8.50 is built as a PVC foam sandwich with e-glass and is fully infused with vinylester resin. The cross beams are full carbon epoxy for stiffness and low weight. The rudders are carbon fibre. There is a semi bridge deck pan. The cat can be disassembled for transport by container or on a trailer. Cranes are required for assembly. The Pandora is now built by a Polish company Walby.

    Francios made comment the cat can only reach 21 knots with the low aspect ratio keels, where as the dagger board version was designed to hit 25 knots. He said under most circumstances the LAR keel version will sail as well as the dagger board version but misses on peak performance EG upwind. His views on Reverse bows are if the design is designed to handle them good, otherwise it’s a marketing situation.

    He was asked to update the Corsair 28 design by Corsair to make the 880 trimaran. New crossbeams, floats and deck. But the real interest was in the structure. Perus did structural design work on eg crossbeams, some of it was accepted by Corsair but in other parts Corsair said from our experience we think this is best. Perus listened. He explained that FEA analysis (Finite Element Analysis) etc is great at predicting loads, material characteristics, best layup options etc but ONLY if the input information of loadings are correct. 1000’s of sea miles and many boats have taught Corsair where weak points are in structures that were not predicted by theoretical models etc. Design is working with facts but also needs some intuition about the wind and wave forces involved. All is not obvious, as Nigel Irens found in his 60 foot tris when the wrong type of foam core (not flexible enough) caused failure in a wing deck to beam joints.

    The video is a meeting of the NWMA and Francios was guest who spoke at that meeting. The video is at: https://www.youtube.com/@NWMA/videos Look down a bit too the 9 jan 2021 Cosair 880 designer Francios Perus.

    The jpegs are of the Pandora 850.
     

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  2. SolGato
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    SolGato Senior Member

    For me, the biggest take always from watching the presentation on the new Corsairs was the difference in beam positioning and float volume when compared to the 28.

    A few times Francois showed scaled overlays of the boats to show just how far back the beams have been shifted on the newer models.

    And then if I remember correctly, the floats have something like 600% more volume!

    I knew bigger volume floats were the new trend, but I didn’t quite understand the real theory behind them, and never would have guessed they were that much bigger in volume.

    As he explained, the large volume floats help to convert the energy of strong puffs into forward momentum versus a float submerging increasing drag causing the boat to heal and spill wind as Farrier originally designed his boats to do as a safety precaution.

    One thing I’ve been asking myself is if these bigger volume floats pose a more dangerous risk to capsizing in the event of a catastrophic failure, especially in heavy sea states, if say the bulkheads fail and the float fills with water.

    And @Phlames that folding Cat sounds interesting, maybe a little ahead of its time.

    I like the idea of a single hand riggable/sailable/trailerable big beach-like Cat, although the one you spoke of sounds like it even had some accommodation.

    The neat thing about A-frame folding is I think it is possible to keep the hulls low on the trailer between the width of an axle which makes towing easier with center of gravity low, and makes launching in shallow water easier as well. One challenge of telescoping type trailerable Cat’s is the hulls want to live about where the trailer wheels need to live, requiring the boat to sit very high on the trailer.

    Some designers have had to go to great lengths to design complicated systems to allow for folding/expanding on trailer that don’t hold up well with too many moving parts, etc.., whereas folding and unfolding on the water makes the trailer design a more simple affair.
     
  3. oldmulti
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    oldmulti Senior Member

    SolGato. Agreed, Corsair had bigger volume floats and that creates more stability. Yes, it puts more strain on the structure but the designer was employed to allow for that (hopefully). Like all things its a compromise, greater float volume may also mean more water in the float if there is a problem but again its the designer builder responsibility to build a structure that doesn't fail. The insites that Francious provides give an idea of what is involved and Seawind guy comments on testing everything to breaking point before production tells another side of the story. Yes modern tri with fuller floats are generally faster under most circumstances.

    I will be doing an item on folding cats in 2 days. There are many approaches already tried and actually put into production. Again each has its advantages or downsides but all are possible to do by an average person. But I suspect this ends up like open wing deck cats. They are good at the start but many people want more cabin space and put a bridgedeck cabin on. Trailable boats, unless they are small or permanently set up, start out OK then a mooring is found and they are left on a mooring. But thats a discussion in a few days.
     
  4. oldmulti
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    oldmulti Senior Member

    This is a update on an item on page 96 of this thread had an article on the pH 850 which is an open bridgedeck performance cruising catamaran that measures 28 x 17 foot and weighs 1200 lbs. The 44 foot carbon fibre wing mast carries a 302 square foot mainsail and 128 square foot solent for an upwind sail area of 430 square foot. The length to beam ratio at the waterline is 12 to 1. The hull beam at the gunnel is 3.25 foot. The design has curved daggerboards that draw 5 foot when down. The curved daggerboards in each hull generate upward lifting force to increase the righting moment which helps the cat point well upwind. The wave piercing bows and wide underwater transom section helps the hull ride smoothly though choppy seas. There are outboard rudders that can be raised for shallow water or trailing.

    The design is a transportable cat more than a trailer sailor and can be broken down to 8.5 foot wide package for trailing. The central beams/hard cockpit section with integrated engine pod can be unbolted from the hulls allowing the hulls to be pushed together for trailing. The 8.5 foot central beams have end flanges that bolt onto the hull wing shelf sides.

    The update is about the hull structure. The entire structure is built is pre-preg carbon fiber foam construction in epoxy. A bit of background about the designer/builder, Jay Phillips who has about 40 years in the boating business including time at Gunboat and was the founder and product developer of the Stiletto X Series Catamaran Design. He established the production facility and built new prepreg carbon design demountable trailerable 33 ft high performance catamaran. He has some serious background.

    The pH 850 hull from the inside has 2 layers of 7 ounce Eglass, reinforced with load path directionally oriented 150g unidirectional carbon fiber, and some additional thickness in areas of high foot traffic and rigging load points. A PVC foam core then outside is covered with a 411 Carbon (~12 ounce) + 200 g Woven Carbon + 150g Unidirectional Carbon in specific load path areas. The components are heat treated to fully cure the epoxy pre-pregs. The hulls are built with inner and outer hull halves joined at the keel and deck “centreline” line. The inner halves have an accommodation shelf moulded in. There is a moulded centre platform that incorporates the beam structure again in foam carbon fibre.

    Again, Jay’s experience has come to the fore with some learnings from is Stiletto experience. EG “One of the costliest mistakes in the Stiletto X Series was to not have asymmetrical molds. To add the necessary parts to the form the asymmetrical hulls once out of the mold, we were spending up to an additional $60,000 in labor and materials to make the symmetrical inner hull sides have asymmetrical characteristics for holding the beams and cockpit together. While it will cost more initially to have 4 hull tools for the pH 850, the production savings will quickly outweigh this additional cost.”

    The pH 850 has just enough interior space for 3.1 foot “twin berths”, a head and a galley. The twin berths would be good singles and “honeymoon” doubles. To quote the builder “While the interior is sparse in order to reduce weight, it is useful for light cruising and camping adventure, featuring twin births in each hull with head and galley options”.

    The jpegs give the idea.
     

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  5. oldmulti
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    oldmulti Senior Member

    Plhames and SolGato made comment about catamarans that can reduce their beam for trailing. The Farrier trimarans are the gold standard for trialability and catamaran owners have always wanted a similarly easy approach.

    The best trailable cat solution so far has been the 8.2 to 8.5 foot wide fixed beam cats that range from 16 to 32 foot long. But they have one problem less stability than is desirable. So, people sought to have wider beam trailable catamarans. Now we will look at the first batch of 6 (of 12, 6 more tomorrow) trailable catamaran solutions that have been designed, the majority have been built are sailing.

    The first approach was to have the parts of a cat arrive at a launch point then assemble them into a cat for sailing. If the components are light it works OK but once the parts are over 50 lbs each it starts to become a problem. This is used by EG Wharram, Firebird etc.

    Next was developed by the 10 foot wide Tornado cats. Tip the cat on an angle for trailering, to reduce the beam to 8 foot. Works well for beach cats but once you have hulls that can accommodate a person the geometry limits either the beam or hull size.

    The next model is the sliding crossbeam cats that can expand from 8 foot to about 14 foot. More stability but after a very short time, difficulty in the expansion and contraction process, as tubes that need tight tolerances bind unless the hulls are pulled apart exactly parallel. EG Stilletto, International 23

    Rob Denny then designed W a 40 foot cat that had a single crossbeam that slide one half into the other half to compress the cat down to a marina width berth. Not trailable but the idea could be used on a smaller catamaran. W has an unstayed balanced rig on one hull and the single telescoping beam, which allows the hulls to pitch independently can vary the beam from 23 to 13 foot beam. W displaced 1350 lbs.

    The hinge in the centre of the crossbeams to allow the cat to fold the bridgedeck up and angle the hulls inward started back in the 1960’s with early British and Attunga cats. It has been refined by the Viva 27 and Thomas firth Jones Brine Shrimp cats. In each case the limitation is not the folding system as it can be done on the water. The limitation is the limited headroom you can achieve in a hull as there is a geometric limit to the hull shape that can be fitted when folded.

    Next came the expanding trailer approach, where hulls on the trailer were positioned by the trailer expanding or put on sub trolleys so they could be positioned for the cross beams to be manually put in position and the mast etc raised. A minimum of 2 hours of work and lifting some heavy components around. Strider, Coral Coaster 25, Seawind 24 etc.

    All of the above catamaran trailering solutions work but anything that requires assembly of separate crossbeams and attaching trampolines require hours of set up time before putting up the rig. Rigging time is similar irrespective of the folding or assembly system.

    Boats like the Stilletto 27 or International 23 take less time to setup IF, and I repeat IF, you can expand and contract the cat with the crossbeam tubes binding as you are changing the beam of the cat. I have watched an International 23 take about an hour to expand as the 2 guys could not work in perfect synchronisation.

    The hinged centre bridgedeck model used by the Viva 27 and Brine Shrimp take minimal time to set up and can be done in water. The real design issue with the centre hinge model is how the hinge is engineered especially is the hinged beam supports the mast. In the case of Brine Shrimp the folding beams with a strengthening support panels are independent of a secondary mast beam attached later. The Viva 27 has a hinge on the beams but also has a cap covering over the hinge joint where the mast sits to help spread the mast load over more of the beams length. Point loads in multihull design always need good engineering.

    The jpegs give the idea of some of the trailing solutions.
     

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  6. oldmulti
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    oldmulti Senior Member

    Additional folding cat jpegs of expandable trailer then position cross beams etc.
     

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  7. oldmulti
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    oldmulti Senior Member

    I thought folding catamarans was going to be in 2 parts but it has turned into 3 parts. This part will be about folding catamaran that have vertical hinge systems where the cross arms fold but the hulls remain upright. These cats can have large hulls with good headroom and the crossbeams have a central hinge pin and hinge pins at the hull sides to allow folding. Good solution with a major downside. There have been many design attempts and a few very successful cats doing this approach but in each case the engineering on the hinge joints and cross arm gates is critical.

    The point loads in this approach are large. There are two sets of point loads. The mast base, if it sits on a hinge point on a cross beam and the second more difficult to handle, torque effect of the hulls working through a seaway as one bow is lifting and the opposite stern is sitting on a wave. The twisting effect goes through every hinge joint creating point loads. Next is the loads going on the hinges as the cat is being folded or unfolded. Ok if you unfold in flat water, not good if you unfold where there are small waves. A half open hinge gate puts a point load at 45 degrees to the intended direction. Finally, when trailering the hulls need to be well strapped down as any movement between the hulls on the road can again strain the hinges. All of this can be accommodated by good engineering but it has to be considered. Plhames spoke of the British catamaran. Other designers such as Kurt Hughes with his proposed 30 foot catamaran folder cross arms and Tim Clissold with his TC 750 proposed folder have done some detailed design on hinged gate cats (jpegs attached). Also there have been some cats in Russia that have been built using the hinged gate approach.

    Now we come to the best of the big hull, folding crossbeam models. In Australia the Simpson designed Takeaway was built and has been used as a trailer sailor. As you can see from the jpegs Takeaway works well but notice the hinge joint jpeg. The dimensions of the pins and aluminium supports for the pins are substantial. The cross beams are square aluminium tubes which have a 2 mm aluminium plate welded onto one face. Very strong and has worked over the 20 plus years of existence. The hulls are roomy and have near full headroom. This cat can be trailed and used as a short term cruiser.

    Next is the best thought out solution in this type of trailer sailor catamaran. Phil Thompson is a family man, teacher, part time boat designer, prolific boat builder, writer, blogger (Catsketcher) enjoys sailing and gets bored with all his free time. He decided to do a trailable catamaran for when he was not cruising on his 38 foot cat. He really thought through the folding system and realised that the folding system with associated bridgedeck could unfold on the water in a way that would strengthen the joints and act as a mast step. There is a video of the launching of the cat (Page 45 of this thread) and it is impressive. All the hinged gates on the Breeze 7 were design to strengthen the cat as they unfolded especially the angled front main cross beam gates. Breeze 7 is the catamaran equivalent of the Farrier trimarans in trialability and usability. This cat also sails well and has nice features like a real double bunk in a separate hull away from the kids etc. If you are interested, I will leave it up to Catskecher to describe more of the detail if he is not off sailing somewhere.

    Trailable cruising cats that are as easy to use as a folding tri are out there but it will take a courageous manufacturer to produce them in volume. The jpegs give the idea.

    Tomorrow we will discuss other cat folding systems some of which can be home built.
     

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  8. SolGato
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    SolGato Senior Member

    Great collection of folding Cat designs there OldMulti!

    I think the ME22 is worth a mention as it is IMO the most refined example of a bridge deck folding design with handsome lines.

    If I were to take my pick for a single hand trailer day sailor, I think it would be the winner.

    I missed an opportunity to see one in person, but from photos it looks like a comfortable dry boat with a wide beam and good amount of freeboard that is easy to rig single hand, and what little video footage I have found of it sailing shows it moving along nicely, flat and drama free. I can’t imagine Newick would ever designed/build something for production that didn’t sail well.

    And my pick for trailerable and expanding with some accommodation would be CatSketcher’s Breeze.

    I think his folding design and the way he incorporated the bridge deck is very clever and offers the most no fuss from trailer to sailing experience. I also think his design would lend itself well to a Solar Electric Power Cat version with the addition of a large bimini solar hardtop in place of a mast.

    I have two expanding Cat beam designs that I have been working on.

    One is a design that has swinging floats like a Dragonfly, but instead of a central hull the bridge deck is suspended like a Pod Cat between the floats supported by articulating half beams, so when expanded the boat can be used for cruising and lounging at anchor with side wingnets between the hulls and Pod to provide more lounging space and more stability at anchor.

    Then when collapsed, the floats come together swinging forward tucking under to support the deck converting the vessel into a narrow beam power Cat that can better handle rougher conditions with improve high speed efficiency, and of course reduce the beam width for narrow water navigation and trailering.

    The second design I’m actually in the process of building for my big Solar Electric Cat using the modified Viva 27 hulls I purchased last year.

    It is a telescoping design but will use roller bearings and linear actuators to allow the Cat to expand from 9’ to 14’ on the water with a push of a button.

    The system will be made from square aluminum tube with all mechanical parts housed and protected within, and it will convert to 6” round tube sections at the ends that will clamp and bolt down to the hulls just as the original cross beams did. The design basically consists of overlapping beam housings that are stacked and attached vertically with the ends offset on center to keep the telescoping sections in a parallel plane. I will be over-engineering the beams because I can afford the extra weight with the design being open bridge deck slow speed cruiser, and because I may want to add more superstructure like an enclosed cabin in the future.

    The basic concept is the same as the swinging beam design -to have a Cat that is narrow enough to trailer and launch at a narrow ramp and get in/out of a narrow river, that can remain collapsed when underway to reduce windage and increase efficiency while getting to a destination, then is able to open and expand for more comfortable lounging at anchor.

    The other important design feature is the allowance of a large one piece articulating bimini solar hardtop that spans the beam width of the boat on trailer and is adjustable in height by the push of a button providing standing headroom, but is also able to be completely struck and bolted down to near deck level to enclose and protect the interior and reduce windage during tropical storms, whether on water or on the hard.

    The renderings below show the beam system and my basic design plans for the superstructure shown with the bow hull sections expanded out 30” to max beam width, and the sterns sections collapsed and tucked under.

    43ED379D-FB4E-4BE3-B718-7B1EDE2E3B22.jpeg
    5ACA7EA9-D113-48DB-B20D-FFF32E36ACAA.jpeg
    12BD664D-13C8-420A-89E4-E47D30065215.jpeg
     
    Last edited: Jan 22, 2023 at 10:57 PM
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  9. oldmulti
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    oldmulti Senior Member

    Part 3 of folding catamarans that are trailable. The real breakthrough was done by Malcolm Tennant when he designed the Turbo 6 (see first jpeg). A really trailable catamaran with bunk and limited accommodation. The design did not gain much acceptance. Richard Woods developed and refined a similar concept with his Wizard 22 and Sango 25 which have more accommodation. The centre bridgedeck remains in position and the hulls fold under the bridgedeck. A 14 foot wide sailing cat cab be trailed at 8 foot wide. Richard Woods refinement was shape the hulls so that they would automatically unfold and fold as you launched or recovered the cat. This allows the bridgedeck cabin to have EG a dinette/double bunk and small galley area that stays vertical. The hulls can have bunks and storage. These designs are popular with many built.

    The main advantage of the Woods approach is that the cross arms do a similar task as a Farrier tri. The cross arms spread the loads depending far less on the hinge pins than other concepts. This is structurally the most “reliable” concept.

    Another variation of tuck the hulls under the central bridgedeck was mentioned in an early AYRS booklet but first patented by Dennis Conner of America Cup fame. The hulls were stored vertically under the central bridgedeck section. The hulls and bridgedeck were connected by cross arms that controlled the motion. A New Zealand company EZIFOLD were intending to patent a similar system. I have not seen any of these boats produced. The only down side is the high centre of gravity during a launch and trailering.

    Some designers used a fixed bridgedeck and hulls that folded upwards above the bridgedeck. This allows the bridgedeck cabin to have EG a dinette/double bunk and small galley area that stays vertical. The hulls are general left as light as possible as they have to be lifted up and when trailering they are stored high creating windage and raising the centre of gravity. EG Twist 6.5, Surtees 29 (also did a cruising 22 footer).

    Bernd Kohler designed the KD 800, a fixed bridgedeck catamaran, but with hulls on swing arms that fold the beam from 12.8 foot to 6.5 foot for trailering It works like a Dragonfly trimaran swing arms. The technology of hinge points etc are well known and proven but each design again needs to be well engineered.

    The Fold Cat 36 has a patented X beam folding system that allows the cat to be launched and unfolded on the water with the x beams unfolding into 2 continues crossbeams. There have been some variations of this but have a similar result EG latest version of Evergreen. This system again depends on pivot bolts as a major strength component with a secondary bolt to lock it into position. The pivot bolts need to be supported in such a way as to not pull through the cross beam material. The Seaclipper tris depend on the same sort of pivot bolts and need big washers and stainless steel insert tubes in the wood cross beam segments so the bolts don’t pull through the timber.

    There are other folding systems out there but I have tried to keep it to systems that have been proven or are practical. The jpegs give the idea.
     

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  10. oldmulti
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    oldmulti Senior Member

    There is a concept called the Green Flash. A Green Flash is when the sun is setting or rising but just below the horizon the sun rays shine "through" wave tops to create a green flash. Very rare but seen occasionally. Here is one seen off Tampa Bay in the Florida.
     

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  11. oldmulti
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    oldmulti Senior Member

    The Twist 6.50 catamaran was built by the Naval Force 3 shipyard and designed by the naval architect Samuel Boudon. The Twist was the winner of a design competition to produce a contemporary trailerable cruising catamaran. Its construction began in 1986 and is basically a trailable camp cruising sports catamaran. The Twist is 21.3 x 10.8 foot (foldable to 6 foot for trailering). The Twist weighs 890 lbs and carries a 26 foot aluminium mast with a boomless mainsail of 183 square foot, a furling jib of 65 square foot and a spinnaker of 260 square foot. The draft over the low aspect ratio keels and rudders is 2 foot. The outboard is 4 HP.

    The cat is trailed with its hulls inverted on the trailer but still connected to the bridgedeck cross arm tubes by hinges. When you arrive at your launching site the hulls are folded down and short aluminium tubes are inserted into the crossarm tubes on the hulls and the bridgedeck crossarm tubes. Simple, effective but turning a 150 lbs to 200 lbs hull even though it is hinged is not easy. Finally, the LAR keels have semi-circular recesses that accommodate axles with attached wheels. The boat can be set up completely on land and then rolled into the water, on the “stub keel wheels” so that the trailer never has to be in the water. The wheels can then be removed before sailing.

    The Twist claims to have 4 berths on four spartan cane berths (kids at best, cramped for adults) but the main accommodation is a bridgedeck tent that can be 6 foot high. There is some hull storage.

    The hulls are made of a solid GRP full laminate, the decks are made of GRP with a balsa core sandwich all in polyester. The crossarms are aluminium. Everything is solidly built.

    The performance is good with no handling problems and the cat tacks without the need to back wind etc. This cat may be the same size as a Tiki 21 but performs a lot better around a course due to better hull shape, keels and rig. Also, it is a very practical trailer sailor. But this is a fast camp cruiser not an outright performance or cruising cat.

    The jpegs give the idea.
     

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  12. oldmulti
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    oldmulti Senior Member

    Trimarans come in many forms but the following 2 tris have surfboats as their main hulls. A surfboat is generally used in surf lifesaving competitions now as jet ski’s do most of the rescue work. A surfboat is generally rowed by 4 people and has a person on an oar at the rear for steering. The surfboat is 26 to 28 foot long about 5.4 foot beam at the gunnels with about 3 foot beam at the waterline. These boat are built from various materials but weigh about 500 lbs. There are few restrictions on the design beyond its ability to go through waves and the boat is easy to row.

    So occasionally a surfboat comes up for sale very cheaply and some guys are inspired to build a tri. The first surfboat tri here was done in Sydney Australia and is named WTF (no I will not explain). The surfboat hull was 28 foot long and was modified to have a small cabin forward. The rowing seats were removed to provide a cockpit. Next, a 16 foot Hydra beach cat provided the hulls to act as floats, daggerboards in floats and rudders on the sterns. The cross beams are aluminium tubes, The mast from the Hydra is 26 foot tall. This tri is fun day sailor, not an ocean sailor as the cross beams, rudders and boards are day sailing strength not ocean sailing strength.

    As I said surf boats have been built from either cold molded plywood, strip plank cedar, foam glass or aluminium. The cheaper older surfboats are mainly molded ply and timber.

    The next conversion was done in New Zealand was a more substantial conversion. The 26 foot surfboat hull was moulded plywood with a substantial top side and cabin built on. Next the floats from a Buccaneer 24 trimaran was added the surf boat main hull via custom built cross arms. The rig looks as thought it came from a Buccaneer 24 as well.

    There have been several other surf boat tri conversions in Australia of which many sailed well and if properly refurbished lasted for years. But this conversion process is not limited to surfboats. The final jpeg is a MacGregor Venture main hull with Hobie 20 floats which is just one of many combinations. There is a point where you may as well build a new design from the start as converting old boats into a parts build does not always sail well or have any resale value.

    The jpegs give the idea.
     

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  13. oldmulti
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    oldmulti Senior Member

    Old boats never die, they just disappear from view. Not always, Russell Brown at about age 15 wanted to do his own thing and developed his first ocean going proa named Jzero. Russell didn’t have much money but was resourceful and built the proa from left over parts from other boats, some plywood and timber he purchased or obtained from others. Jzero was kept small in all dimensions to keep cost down. Jzero was 30 x 18 foot with a mainhull that was 2 foot wide. The ama was 16 foot long. Jzero weighed about 800 lbs. The first rig had a Hobie mast that carried an 80 square foot jib and 120 square foot mainsail from a mono. Jzero sailed from Virginia to Florida in 1978 then to Puerto Rico, then over time made it to Sainte Croix.

    The Hobie mast broke off the Florida coast after Jzero hit something in the dark causing an aka failure. Jzero was towed to shore then a repair was done to make the ama and akas stronger. A new stronger mast was also fitted. The initial boat was built for about $400 with its first rig then was rerigged and upgraded in Florida for $800. Total cost $1200 for an ocean crossing proa.

    The build was mainly 6 mm plywood and timber. Simple, cheap and fast boats generally have one downside, a lack of accommodation. Jzero was a tight squeeze for one young person but when you had 2 people on board you better be good friends. Jzero raced and sailed offshore a lot, often with 2 people aboard and there is not a lot of space. This was an adequate but minimalist boat.

    Jzero performance for a 30 foot boat was very good. In the St. Maarten Tradewinds race on a leg from Virgin Gorda, around St. Croix, to Martinique, about 350 miles essentially a one tack beat, Jzero finished third, less than 2 hours behind the leaders. The 2 lead boats were Rouge Wave, 60 ft tri sailed by Phil Weld and a 60 ft Peter Spronk cat. On another occasion it covered 360 miles in 2 days under working sail of about 200 square feet. This was after a storm that where it did 31 miles in 2 hours running downwind and handled flawlessly. Jzero and more importantly the crew had no problems handling heavy weather, impressive for an ocean crossing 30 foot light proa built for $1200.

    Back to now, so after 40 plus years in existence we find that Roger Hatfield (Gold Coast yacht fame) has been involved in the restoration and upgrade of Jzero and has renamed it Lazarus. Jzero/Lazarus is the same general dimensions but now has an open cockpit and more integrated cross arms and an improved float design. For someone to put the energy and money into saving this proa says a lot about the original design and build. If a boat is well conceived and well built to start with then it will be “loved” and used by many and therefore maintained. Its not about expensive materials etc. It is about effect use of materials in a good starting design.

    The jpegs tell part of the story. PS Any additional information or corrections are welcome.
     

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    Last edited: Jan 26, 2023 at 11:47 PM
    patzefran, redreuben and revintage like this.
  14. SolGato
    Joined: May 2019
    Posts: 236
    Likes: 155, Points: 43
    Location: Kauai

    SolGato Senior Member

    I don’t know what the narrator is saying, but the video footage is fun to watch, especially the opening scenes of them sailing that Cat like it was a dinghy:
     
    revintage likes this.

  15. Burnside Style
    Joined: Apr 2019
    Posts: 14
    Likes: 1, Points: 3
    Location: Ocean Spring, MS USA

    Burnside Style Junior Member

    Anyone seen or have any experience with the bora bora 28? Looks like it is the only multihull offering from B and G Yacht Design.

    "The symmetrical hulls are of multichine design and are built using ¼” thick sheets of plywood over 3/8” bulkheads and semi-bulkheads.
    The whole interior should be impregnated with epoxy resin prior to the painting process and an important fiberglass lamination, using epoxy resin must be applied externally.
    The cross-beams are made of wood using a box-type technique, similar to wooden mast building."

    https://bgyachtdesign.com/boat-plans-designs-easy/boat-plans-borabora-28/

    BB28-saildeckinterior-1-501x1024.png construc3.jpg DSCN7918.jpg flor-pronto4-prnhce9z2gpjs0w7jies1hl3wzah45b2xt2g3x43hc.jpg
     
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