Multihull Structure Thoughts

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

  1. oldmulti
    Joined: May 2019
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    oldmulti Senior Member

    You think you cannot afford a boat to sail? Here is one mans solution to a mini cruiser. Due to his age and a wife who decided the land life was more comfortable, he was left with a big catamaran, which proved to be too much to maintain and handle alone. So, he started to think of what was available for an elderly singe-handed sailor.

    The smallest possible boat he could think of was a canoe. So, he bought a used canoe and designed a trimaran. The initial floats were sewage pipes and a rudder was added. The two windsurfer rigs were put on the forward parts of the outriggers. The boat also got two small leeboards, one in each outrigger. This time the boat sailed OK, although when it got some wind, it tended to heel and to take water over the outriggers.

    The next step was to make the tri into a "mini cruiser" selecting simple and low-cost solutions as far as possible. The canoe stem and bottom need an external reinforcement to take grounding and provide some extra strength. The cabin was built from the understanding that the human body does not need more space than what is in a coffin with sitting headroom. This insight keeps cost down and makes it possible to build a small cruiser.

    The cross arms are two aluminium ladders fastened to the sides of the hull. The ladders were bolted to fasteners on each side of the hull and to the pontoons. On each side of the front outrigger was placed a mast foot. The two windsurfer rigs were placed in these foots without stays.

    The floats were sewage pipes and were heavy and have little buoyancy. They were replaced by floats built in Gaboon plywood with wooden reinforcements for fastenings and leeboards. The leeboards were built from wooden stringers, glued together. They are angled 45 degrees inwards in order to give both a lift to the pontoon and a force to prevent leeway. They are also angled with a five degrees angle of attack, something that is possible when only one leeboard is in the water at one time. The rudder and the rudder head were built from wood and can kickup. The motor is a 2 hp Honda. Cost was kept down through buying some used equipment but still cost two thousand US dollars. Building time was about one and a half month of part time work.

    As can be seen from the pictures, the boat sails and goes to windward. It is slower than a full-size multihull cruiser or a beach cat. The boat has so low weight that it has difficulties to change tack without help with the paddle. The mast may need to be moved and reinforced as the masts tend to bend too much and to spill wind.

    Just one mans simple solution to a sailing as an older person so he can have some fun.

    The final jpeg is another mans simple solution to sailing with a Tiki 21 cat hull. The rig is cheap and simple for downwind and broad reaching courses. There was no comment about upwind performance.
     

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  2. oldmulti
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    oldmulti Senior Member

    The C3200 catamaran is an odd mix of a determined designer builder who wanted a cheap effective cat but did not fully understand how the materials could be used to produce a good hull shape. The cat is a tube cat that is 26.3 x 15 foot that weighs 1900 lbs. With the forward prodder in place the boat length is 31.5 foot. The mast height is 32 foot with 2 headsails with a total of 540 square foot. The length to beam of the hull is 13 to 1 at the waterline and is 2.6 foot wide at the gunnel. The hull shape is literally a flat bottom fore and aft for 80% of its length. It is basically a dory shape with a sharp short rise aft. This cat depends on its light weight, fine hulls and reasonable sail area to produce its speed. If the hull shape was improved, I am confident the cat would be faster. The rig was planned to be an A frame headsail only rig but morphed into a central mast leant back to carry the headsail only rig.

    The designer owner builds GRP boats as his profession and he is a big catamaran-fan. The catamaran had to come out of the water after every sailing trip because the local harbours are completely full. Therefore, the catamaran had to have wheels on its keel in order to pull it across the beach for boat storage. The wheels are removal whilst sailing.

    The cat had to be built on a very low budget, initially planned at 7000 euros and finally cost 12000 euros. It took 7 months and 700 hours to build part time.

    The hulls are marine plywood planking (7 mm), vertical frames (22 mm thick) and stringers (10 & 15 mm). The beams came from a 46 foot mast (200 x 125 mm profile) off a Beneteau. The keels have to be strong because the wheels have to be fastened on the ends. A supporting frame from welded stainless steel square pipes which was glued to the individual frames. Both sides of the keel were covered with 15 mm plywood. Building the gondola to support the outboard and provide a steering station. The building materials were 15 mm and 8 mm plywood. For the fillets he used 30 liters of wood flour. Epoxy total used: 90 kg. 2K-PU yacht paint used 20 Kg. The hulls as well as the gondola were not completely fiberglassed over - only the stressed points - but they were given three coats of epoxy resin.

    The wing mast was an aluminium 80 x 6 mm pipe as leading edge with cut ribs for the profile from PU-foam then covered with 3 mm plywood and had 2 laminations of 300 gsm fiberglass and finished the wing mast for €200. Well, the weight wasn’t too good. With a length of 32 foot x 1 foot chord. It weighed without spreaders 55 kg. The mast is inclined at 15 degrees aft.

    The owner’s comments “In the spring the new sails from Stravsails in Slovenia arrived and we set out for the next test drive. At about 20 knots of wind, the vessel reached 8-10 knots speed to windward. Not superfast for this fast looking design but enough for the cheap sailing system.”

    The structure appears to be OK and was a fast build design. A small refinement in hull shape could produce a faster boat. Sorry about the jpegs size.
     

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  3. oldmulti
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    oldmulti Senior Member

    SIDECAR is one of 2 Proa’s using this name. The first Sidecar is a Harryproa Elementary 25 foot. This SIDECAR is built in Tasmania and is a Pacific proa of 31.1 x 19 foot displacing 2650 lbs carrying 505 square foot working sail and a maximum sail area of 678 square foot. The main hull length to beam is 14 to 1 with a prismatic coefficient of 0.53. The main hull has a flat bottom because after doing some drag analysis calculations the owner did not find a round hull section did not gain you much. The owner said “My proa is flat bottomed all the way and will have a sprayrail and has a spray step. The weather rail will extend and blend into the bottom sidehung rudder gantry. The leeward step is in the form of a full length leeward pod. Flat bottoms save weight (no floorboards) are easier to build, enable shallower draught and should provide some dynamic lift.”

    The mast is a 34 foot carbon fibre C-Tech mast tube 92 mm outside diameter with 3 mm walls and no taper. The mast and associated gear is supported by dyneema rigging. The bare extrusion weighs 32 lbs. The additional supporting sail booms are carbon fibre. The wall thickness was chosen by “a rule of thumb” of 3% of the mast diameter suggested by Eric Sponberg. Rob Denny suggests this “rule of thumb” is just that. Rob says a well engineered mast will have a wall thickness required depending on many factors eg is it a thin diameter mast or a large diameter mast. Chainplate reinforcing was multiple layers of scrap material from hull sheathing.

    The owner is relying on an uplift / downlift pivoting foil that provides +/- 100kg @10 knots to help maintain stability. Also, the inverted aka wing should be a lot drier, provides storage and hopefully provide some down lift righting moment. The righting moment gain is minimal at low wind speeds, but over 30 knots apparent, the potential gets quite interesting.

    The build is using strip planking. The strip planking is 190mm x 12mm ( 8x1/2 inch in old money) paulownia glassed on either side for the hulls with 6mm wide half depth U shaped grooves into the back of it when the curves get difficult, and then fill the grooves with lightweight bog. All the bulkheads and frames are 14mm paulownia panels and all the stringers and other framing is also paulownia.

    This is an interesting variation of a Pacific proa which appears to sail well. I applaud the effort the owner builder has put into the design build and development of the proa. We can all learn something from it. The jpegs include some of the initial design and the final sailing boat.
     

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  4. oldmulti
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    oldmulti Senior Member

    Michael ONeill's launched his Schionning Wilderness 1230 with biplane wing mast rig. The Wilderness 1230 is 40 x 23 foot weighing 14200 lbs and displacing 18200 lbs. The standard rig sloop has 1010 square foot. The biplane rig started with 2 x 485 square foot main sails plus about 75 square foot wing masts each side. The 51.8 foot freestanding carbon rotating wing masts came in at 400 lbs (180 kg) each, booms about 110 lbs, mast posts 130 lbs and sails 78 lbs each. Total mast, posts, booms and sail are about 730 lbs each side or 1460 lbs all up. The conventional Wilderness design allowed 780 lbs for rig and hardware. The bi plane rig needs less gear so the total weight difference is probably 550 lbs of the heavier biplane rig. The masts/rig are placed one bulkhead (1960 mm) forward. The original biplane rigs cost about $70,000 Australian all up. That is the rig included the masts two fully battened mainsails and all the hardware, battens and cars that involved.

    Now the fun starts. The cat had a slight bow down trim when sailing in flat water. The rig also proved very powerful capable of driving the boat at near wind speed across most of the wind range. In about 8 to 10 knots of wind and at one point we were doing 8 knots. It was sailed in 20-25 knots when it did an easy 18 knots and tacked without problems. But there were some initial problems, to quote the owner “Finally got the sails up in a good breeze but before long discovered the sail track coming away from the mast. We did have a bit of sailing with one sail up and it was good to learn that the boat sails quite ok and tacks easily under one sail only. Also discovered that there are big forces wanting to over rotate the masts which I hadn't anticipated so will have to beef up the rotating mechanism. The mast tracks were glued on with screw fastenings at the top and bottom. Theoretically gluing should be much stronger than screw fastenings so I must have done something wrong for the track to separate so easily. I've taken the masts off to put screws in the tracks from top to bottom so there will be no doubt now. I did use a high strength specialist epoxy from ATL for the mast track. The track may have been contaminated or maybe I didn't carry out the correct preparation. I have just left the tracks in place, most of the adhesive is intact, and put in ss screws and backing nuts from top to bottom.”

    The performance was so impressive that the owner cut 12.3 foot of the top of each mast which has made a big difference to the windage, handling and manoeuvring under power. There was minimal effect on the performance of the cat. He settled on the 12.3 foot amount because it coincided with the sail reefing point and minimised alterations to the sails.

    The rig is now has 39.5 foot masts above deck carrying 300 square foot mainsails and a 60 square foot wing mast either side. The cat completed a trip from Melbourne to Tweed River 1100 nautical miles. He had the full range of sailing conditions from a rugged night time rounding of Wilson's Promontory in 35 knot wind, with a wild 15 knot and up to 20 knot sleigh ride through the Bass strait oil fields also at night, a fantastic day long close reach at 10kts under autopilot and flat seas, and quite a few hours of motoring. The rig was great allowing the booms to be sheeted out wide downwind with no spreaders or rigging to worry about. The boat was easy to handle in strong winds with the sails very deeply reefed giving little loads on the sheets, all the forces taken by the wings which are massively strong especially because they were designed to be 25% longer than they now are and for a bigger sail area.

    The cat was sold in Queensland to a WA client and was sailed the 3000 nautical miles by a delivery skipper who was scathing about the cats sailing characteristic is ocean swells. He claimed when running downwind or broad reaching the cat would bury its bows lifting the rudders out and the cat would spin out of control. I am trying to find out more details.

    This is getting to long a second installment will arrive about some of the structure and other similar cats. The jpegs are of Ozone and the Wilderness 1250 (almost the same as 1230) PDF provides the original sail plan plus the biplane sail plan with standard round masts.
     

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    Last edited: Jul 6, 2020
  5. oldmulti
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    oldmulti Senior Member

    After yesterday’s discussion about Ozone, the Schionning Wilderness 1230 biplane wing masted cat, we will try and analyse what is going on with Ozone. There are several other biplane rigged cats by several designers that work very well across all sailing conditions. More on them later.

    Let me say up front, any sailing issues of Ozone cannot be laid on any one person. The cat designer, mast advisor, mast maker, the builder and the sailmaker all did there function but there was no overall design conceptual coordination. We have a series of decisions made independently of each other and an owner who had a pragmatic “make it work” attitude which made the cat relatively effective.

    Ozone was a standard sloop rig stock design which the designer was asked to do a biplane rig. The biplane rig that appears to be suggested by Schoinning was a duplicate of his Radial Bay cats. A round tube mast bent (built that way) back at the tip with a full battened main and long boom. The original concept was done to keep the centre of effort roughly in line with the original centre of lateral resistance of the cat.

    Ozone wingmast rig did 3 things. The wing masts weighed more. The leading edge of the mainsail is close to vertical and the booms were shortened from the original Schoinning biplane concept moving the sails centre of effort forward without any adjustment to the centre of lateral resistance. Finally, the forward positioning of the mast required them to be placed 1960 mm forward to the next available crossbeam bulkhead. Result 5% of the boats weight (the wing mast rig weighed twice the standard rig) was moved 15% forward. This does not help the centre of gravity of the boat which could lead to a bow down sailing attitude.

    If going downwind the sail “pull” is further forward and the weight is further forward which could result in bow down attitudes and reduced rudder control.

    All of this adds up to the concept not matching the reality. Ozone was appears to be modification of an existing design not an integrated new design from scratch. EG Cool Change is a very good Kelsall biplane in New Zealand that has sailed 10 of thousands of miles very well and rapidly. It was designed from day one as a biplane cat with a more central mast location and an appropriate lateral resistance location.

    Ozone rig came from 3 Wilderness builders getting together and said they would like this rig option. Ozone was the first cat to be completed and rigged. “Yikes” the second Wilderness intended to have a biplane rig took 12 years to build from 2005 from a kit. The rig for “Yikes” was to be Schoinning original concept but has not been finalised yet. PS this boat has cost about $120,000 so far without the rig. The final intended builder was a WA guy who I cannot find any detail about beyond his boat was to be named “Whimsical”. All of the above adds up to a committee design approach resulting in many interpretations of the “same thing”.

    The Ozone wing mast is a unit that is placed onto a stub mast structure that is glassed into a hull. The 200 mm stub mast has a bottom bearing. Inside is ring machined s/steel self aligning. Outside machined ring of acetal all held together by a ring of glass. The bearing is glued to the post and bolts to the bottom of the 700 mm chord mast. The top bearing is a metal self aligning bearing on a s/s stub at the top of the carbon post and slips inside a rib inside the mast.

    The deck reinforcement was straightforward consisting of replacing the core with plywood where the post went through the deck and applying multiple layers of 450 double bias e glass on the outside of the deck centred on the post hole. The builder thinks it was something like 6 layers extending out to about a metre around the hole and tapering down to one layer. The reinforcing at the bottom of the post was similar with multiple layers on the cabin sole and extending up the chamfer panel.

    The materials used in a 120 kg unstayed tube mast suitable for the biplane rig mast is roughly: epoxy resin 40 kgs, e glass 20 kgs, Unidirectional carbon 60 kgs. Buying carbon tow is half the price of the unidirectional carbon.

    I will say Mike of Ozone did an excellent job of pioneering the approach and solution with what he had to deal with. He took decisive action to ensure he had a reasonable boat that could sail reasonably well. But as I said there are many other biplane cats that work very well indeed. The majority have been designed from the start to use a biplane rig (with or without wing masts) with masts more centrally located and the lateral centre of sail effort and lateral plane in alignment. EG Chris Whites 70 foot “Saphira”, Kelsall 54 foot “Cool Change”, “Cactus Island” a 45 foot cat, Ray Moxley 40 foot cat (launched and sailed by its 90 year old owner), Schoinning Radical Bay 8000 series of cats even a 15 foot cat “Roonio” etc. We will talk about a few of these boats in later posts. The jpegs are shown below.

    Each of the specialist designs work and sail very well and as Gary Baigant said, when he did a biplane rig on his trimaran, after being asked if the windward rig blanketed the lee rig. “On Misguided Angel the only time the leeward rig was slightly blanketed was on a true 90 degrees AW reach ... and to counter that you either head up or down only a few degrees." We are talking about two una rigs with wing masts on a fast and light boats here, which always dragged the apparent wind forward. On such a boat, you can virtually say blanketing doesn't exist. More to learn folks.
     

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  6. Dolfiman
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    Dolfiman Senior Member

    One can also mentioned the Hydraplaneur of Yves Parlier, launched in 2003 : the cata had some up and down, she held a 24 h record in 2004 but was never competitive in front of the racing trimarans in ocean races. For this project, Yves Parlier created in 2000 the Acquitaine design team with yet young naval architects which later became famous, the Guillaume Verdier team.
    2002 - Hydraplaneur - Yves Parlier - Plan Verdier https://www.guillaumeverdier.com/projects/2002-lhydraplaneur-mediatis-region-aquitaine/
     
  7. oldmulti
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    oldmulti Senior Member

    Saphira is a 70 x 32 foot cat, designed by Chris White, that is aimed at 300 mile days with a 2 person crew. It weighs 33,000 lbs at its day sailing weight and can go to 42,000 lbs in full cruise mode. The biplane wing mast rig is (guess) two 1300 square foot wing mast sail combinations for a total of 2600 square foot. The hull length to beam is about 13.5 to 1 and the hulls have daggerboards with small keels to protect rudders. The masts are full carbon fibre wings designed Southern Spars New Zealand who applied their considerable engineering experience to the rig. The mast rotation is controlled by electric motors and a press button.

    The owner Peter Francis wanted understand the pros and cons of the rig before embarking on a full blown design/construct of the project. Peter found two Stiletto 23' beach cats for sale. He rigged one with two masts fore and aft on center line and sailed that against the identical cat with the original conventional rig.

    After weeks of ‘match racing’, the fore and aft rig was changed to a freestanding side by side, bi-plane configuration and again sailed against the conventional rig. Considerable performance data was collected during this process and ultimately Peter decided that the bi-plane rig offered the advantages he was looking for.

    The A70F is long, lean and light, built in all pre-preg carbon fiber. The boatbuilder Eric Goetz, an old friend of Peter's, built the boat in all pre-preg carbon fibre foam composite. Extensive 3D computer modelling was used to CNC cut and mill moulds and parts. Large ovens were built to vacuum bag and cure the hulls and other large parts at the required 200 degrees F. The 100% Carbon Fiber/Epoxy Resin construction utilizes extra thick foam cores for strength and insulation. Robust uni-directional carbon fiber reinforcing laminates in all critical high load areas increase strength and stiffness for superior longevity.

    The performance of the cat is very good. As the designer said: “The wind was quite light but slowly increasing – good conditions for a first sail. By the time the sail was set and the luff and foot tensioned, the wind was hovering around 8 knots. With the engines off, and under only half her working sail area, Saphira sailed happily to windward at 5 knots or so. Steering and tacking seemed fine. After a little more time fussing around with various sailing controls, the port mainsail was hoisted to its working (single reef) position. By then the wind had built to about 12 knots. And with her full working sail, Saphira sailed very happily at 10 knots hard on the wind. Her narrow and light hulls made hardly a ripple in the water. Working our way toward the Newport bridge, the wind picked up a little more and Saphira started ticking off 12 and 13s on the GPS hard on the wind, with probably no more than 15 knots true wind speed. Turning down wind the sheets are eased way off into a simple “barn doors” configuration with booms projecting outboard. Saphira again made spectacular speed in the light conditions. Sailing a dead run at 10 kts with an estimated 14 knots of wind is pretty impressive. And both sails were still single reefed!”

    An outsourced company, Outradius, calculated the loads required for each piece of sailing hardware for the yacht based on the maximum possible loads on the running rigging. Using these loads and a baseline factor of safety, the team specified all production pieces of hardware to be installed on the boat. In some areas such as lines exiting the mast and entering the daggerboard trunks, the team at Outradius designed custom aluminum and stainless steel sheave boxes and ferrules, optimizing their designs using finite element analysis. From prior catamaran sailing experience and input from the owner, the hardware design globally defined the ergonomics of how the yacht is to be sailed.

    This is a very well designed “cruiser” for people who wanted a fast cruiser. It has no problems with 15 knot averages and over 20 knot top speeds. There are video’s of it sailing at 16 knots with bottles of water just standing on a table. This is a dream boat. The jpegs give the idea. The very close sloop sister ship study plans are included to give an idea of accommodation etc. The sail plan is not “Saphira” plan.
     

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  8. InetRoadkill
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    InetRoadkill Junior Member

    I got too much time on my hands due to the virus situation. So I'm toying with trimaran design. I have a couple of questions. First, there seems to be a lot of opinions on how thick a hull should be. I know that the hull can be made quite light using foam composite construction. But I also know that boats tend to get banged around a lot (flotsam, sea life, marina crashes, rough handling on the dry, etc.). So there's the issue of how to resist these unexpected abnormal loads. That said, what's a good practical thickness to resist these abuses? (Sketch is for 14 meter hull, around 14,000lbs displacement.)

    The second question is more concrete. I have a folding mechanism for the amas sketched up that allows the amas to fold and remain level horizontally while staying in their normal vertical orientation. (Not a swing-wing like the Dragonfly. More closely like the Farrier system.) But I noticed that Rapido also seems to have a setup that does this as well which is patented. I'm curious if I've re-invented the wheel. Can someone point me to the patent. My google-fu failed me on this quest.
     
  9. brian eiland
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    brian eiland Senior Member

    Thanks for posting this design, I was unaware of it.
    It so intrigued me that I spent the whole afternoon reading some very interesting submissions on the subject of freestanding, biplane (twin mast) on multihull vessels.

    Bi plane rigged wing mast cat pros and cons? http://forums.sailinganarchy.com/index.php?/topic/214126-bi-plane-rigged-wing-mast-cat-pros-and-cons/
     
  10. oldmulti
    Joined: May 2019
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    oldmulti Senior Member

    Gerald Barrink is an interesting man. He doesn’t like to get bored. In 1992 he designed, built and launched a 32 foot pod cat called Nusa Dua. He then said let’s design and make a trailable 30 foot trimaran Lukim Yu, after which he designed and built the transportable 34 foot pod cat Pork Chop. All these boats were creative in approach and raced successfully under Gerald’s ownership. The boats were progressively sold to other owners to fund the next project and all are still successfully racing. Now Gerald said, I need a house, so in his usual style proceeded to “restore” two old houses into one big house (translation, virtually built a new house). Now he had finished that sideline house project, it was time to get a new boat.

    Gerald then designed and built a radical 45 x 28 foot catamaran, Cactus Island, launched 2012. It weighs 10,000 lbs ready to sail and carries a biplane rig with a total of 900 square foot sail area (330 square foot in each main and 120 square foot in each jib). The sails are on 2 aluminium masts that are 46 foot long with 40.2 foot above the deck and 5.8 foot buried in the hulls. The cat is built in foam glass with some plywood. The accommodation is in a central pod with a double berth cabin forward the a dinette with seats (convert to berths either side of a central walkway) and a galley either side of the walkway befre the cockpit. The hulls have a loo and some berths and storage.

    The rigs are of Gerald’s own design and are balestron style. He built the masts for approximately $7000 (for both) and they took about 8 months work. They are constructed from two 23 foot lengths of 150 mm diameter aluminium tube with 4.75 mm walls which were internally sleeved together to form a mast, to which he laminated divinycell foam up to the hounds, then tapered the foam from 20mm at base to nothing at the hounds. Then laminated carbon uni's (toray 6oz) at 12 layers up to a metre above the deck bearing tapering down to 1 layer at the hounds. This was consolidated with double bias glass, one layer after 6 layers of carbon then another after 12 layers, also one layer over foam before the carbon. All the laminating was done by hand (no vacuuming etc, all very low tech). Because the tubes were joined he decided to put spreaders at the join (for diamond wires) as the 46 foot tubes seemed quite floppy. In hindsight this was probably not the best way to go as the diamonds transfer all the loads below the spreaders so it bends at the lower half of the mast instead of from the top down as a full tapered carbon tube would. Despite this, the masts work well and appear strong, being only 40' above deck helps a lot in this respect. He has been out in 30 knots and hit by a few big gusts without any scary noises or abnormal bending happening. The masts weigh about 170 kg each.

    The bearings are pvc pipe of around 10mm wall which were machined so the inner and outer bearings had about a 1 mm clearance. The inner bearings were then glued to the mast using a straight edge to align them. He made a conduit out of 3 layers of d/bias glass using some larger pvc pipe as a mould, the outer bearings were then glued to the conduit in situ on the mast which allowed the bearings to align. When cured the conduit was then removed and fitted to the boat knowing that the bearings were aligned. So, to do it this way you need to build the masts before fitting outer bearings to the boat. The bearings are 80mm high and I have fitted s/s grease nipples (3) around each set, Innox makes a grease which is suitable for use with plastics. They spin freely but the top bearings (which are more highly loaded) start to make noise when under load. Stainless steel shims at the top inners stopped this noise.

    Beefing up deck and sole had the conduit pass through what would be mast bulkhead (if standard rig) which is quite substantial giving it plenty of support sideways. To support the mast forwards and at 45 deg he heavily glassed tapering timber ribs (internal only) on the outside (deck) and glassed heavily (uni's and d/b) about 750mm out from mast. Also the decks core is removed for around 500mm around mast and replace with ply. The main things to be aware of with beefing up decks and sole is that the major loads on freestanding rigs at deck level go sideways and forwards with smaller loads going aft and at sole level the loads go backwards and sideways with smaller loads going forward and there is bugger all compression load. There is a drain at the bottom of the conduit into a small bilge but it has never needed emptying, he thinks the small amounts just evaporate.

    Gerald is very happy with his bi-plane rigged cat in all conditions after sailing her since 2012. No problems with the rig flopping around in any conditions. Her masts are round tubes so don’t give any drive at anchor or docking. Her Achilles heel is when the breeze is on the beam (or around 15 degrees either side) but this is compensated by her excellent close and broad reaching ability, her square running speed without use of a spinnaker, and her fine windward ability. Her cruisability was well proven during our 5,000 mile beat to Christmas Island and French Polynesia and downwind voyage back to Australia in 2016/17.

    PS Before heading off he built a new tender which is a folding cat 15’ long 9’ wide which hangs off davits on the back of Cactus. At the moment he is in the process of bi-plane rigging it (we only had outboard power 2hp for the trip) and making foils and hopefully getting the tender to fly on its foils.

    The jpegs are of Gerald’s first boats and then Cactus Island. One jpeg has the tender on the stern folded up.
     

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  11. oldmulti
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    oldmulti Senior Member

    Wayne Barrets M80 trimaran design is 26 x 19.35 foot (can be folded to 8.2 foot) and weighs 1900 lbs with a displacement of 2700 lbs. The mast can be either 36 or 41 foot high with a sail area of main and jib 409 square foot. The main hull length to beam is 7.4:1 with a float buoyancy of 150%. Main cabin headroom 6 foot.

    The M80 trimaran, is designed for the home builder in mind who has limited time and basic experience with small hand tools. The M80 trimaran uses the simple stitch and glue system with 6mm and 9mm plywood being the main components. All exteriors are covered with glass cloth of 300 gsm with the hull bottom having one extra layer for protection from grounding or running up onto the beach. The folding mechanism uses standard aluminium extrusions without any welding. Epoxy work on the structure is predominantly cove and fillet. A build page about beams is available at December, 2019 | Build Your Own Trimaran https://trimarankit.com/2019/12

    The trimaran kit is available in CNC Gaboon plywood with a comprehensive set of assembly plans. An option is also offered for Duflex, Duracore panels or foam core.

    Built weight will depend on fitout and the focus on saving weight and the sail area may be increased if desired.

    Multi chine construction from foam core or plywood panels with option for dagger board or pivoting centre board which increases draught by 100mm. The reasons for the small keel is to locate the pivot pin outside the hull (centre board option only) and to ease maintenance and provides extra protection on grounding. Dagger board and centre board have sufficient area for working to windward and the rudder blade has sufficient area for control in light winds.

    The 26 foot MOJO is an update on Wayne’s original design with accommodation is basic for two, for a couple of weeks cruising, up to six for a day sail. Very easy and safe to handle and above all be simple and economical to build.

    The MOJO is trailable for simplicity of building demountable not folding, although in the trailing position it will look the same as the folding system, I have attached a drawing of the beam socket system, beams and trampoline stay intact, could be done single handed with a trailer modification.

    It was an initial thought to make the MOJO available as a kit only, however due to the number of requests for plans, DXF files are available for those who wish to take that path.
     

    Attached Files:

  12. oldmulti
    Joined: May 2019
    Posts: 900
    Likes: 469, Points: 63
    Location: australia

    oldmulti Senior Member

    InetRoadkill. My basic thought is there is no bullet proof boat. You make choices. A thin skin foam glass hull which you repair each time you get a ding. This approach is required for a lighter boat. At 14,000 lbs for a 46 foot boat it is light. A more solid boat would be either solid glass below the waterline or strip plank cedar glass hulls. If you can afford it or know how to weld, an aluminium hull is the better prospect for maltreatment. There is no magic formula for a minimum hull thickness to resist most dings. Some of the better solutions are things like rub rails for docks and sacrificial keel strips for running up on a beach. I do not know of any material that will resist the edge of a semi submerged floating container. Watertight bulkheads helps. Most designers double the external glass layup over the bottom of hulls to help resist damage. But again a light boat will need a minimum layup.

    Folding cross arms require real engineering especially in larger sizes of tri's. If your 14,000 lbs 46 foot tri is eg 33 foot wide you will be generating a righting moment of over 200,000 foot lbs. A Farrier F32 AX righting moment is 60,000 foot lbs. 50% larger tri requires over 3 times the strength to handle normal sailing loads. I know a 40 foot tri the had steel swing wing folding arms that, tore a 9 mm steel brackets. This was not a fatigue failure but an actual tear of the 9 mm steel. Make sure your engineering is up to doing a folding system.
     
  13. brian eiland
    Joined: Jun 2002
    Posts: 4,940
    Likes: 178, Points: 73, Legacy Rep: 1903
    Location: St Augustine Fl, Thailand

    brian eiland Senior Member

    Do you have a contact email for Gerald Barrink ? or some other way to contact him??
     
  14. oldmulti
    Joined: May 2019
    Posts: 900
    Likes: 469, Points: 63
    Location: australia

    oldmulti Senior Member

    Brian. I do not have a direct link but several years ago, in one post about biplane rigs on "diy boats" I think he listed a hotmail link. Multihull structure thoughts thread is read by several guys who would know him so may help or go to the following thread Crowther X10 https://www.boatdesign.net/threads/crowther-x10.60364/page-2 and send a private mail that way.
     

  15. oldmulti
    Joined: May 2019
    Posts: 900
    Likes: 469, Points: 63
    Location: australia

    oldmulti Senior Member

    This man makes me feel ashamed. Ray Moxley launched his newly built 40 foot biplane catamaran RA in 2015. Not only has Ray drawn every inch of this remarkable boat and overseen its construction, but he also celebrated his 90th birthday in 2015. Ray is an Architect who designed London's Chelsea Harbour and has been working on catamaran designs for over fifty years. The boat is now for sale at £250,000 GBP.

    So, what is RA. A full bridgedeck catamaran 39.2 x 22.2 foot that displaces 21,300 lbs. The rig is a biplane rig with 2 masts side by side. The wrap-around the mainsails are on carbon masts without shrouds or spreaders. The double leaf non-rigid wing sails give better aerodynamic performance. The bigger area of sail cloth is divided between equal wing sails make reefing easier and in smaller stages. The parallel masts and strut are stronger and lighter than the alternative free standing solution and make possible the aerodynamically effective wing sail design. The furling jibs are on ProFurl furlers. The cat has lifting daggerboards and rudders.

    The cat is built to EC RCD Category A (Ocean) classification and its main structure is GRP foam sandwich construction.

    The accommodation has 4 double or twin berth cabins, a good loo and very big main cabin and cockpit.

    This cat has entered races like the Round the Island and sails well but it is a cruiser that will take some learning to optimise its performance. The jpegs give the idea. Sorry I do not have more detail.
     

    Attached Files:

    bajansailor likes this.
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