Multihull Structure Thoughts

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

  1. tane
    Joined: Apr 2015
    Posts: 244
    Likes: 79, Points: 28, Legacy Rep: 10
    Location: austria

    tane Senior Member

    could it be that these our sentiments are not shared by the younger generation?
    sad as this is, maybe we should view it as "there is a time for everything"?
     
  2. oldmulti
    Joined: May 2019
    Posts: 2,565
    Likes: 1,639, Points: 113
    Location: australia

    oldmulti Senior Member

    This catamaran/trimaran appears to be a design done for long distance cruising. The designer is K Reinke of Reinke Yachts (who mainly do mono metal yachts). The interesting part of this design is it really is a motor sailor with a central hull pod that allows a permanently immersed central hull pod with 3 bladed prop to be used for sailing support. The cat/tri named “Inzula” is 56 x 31 foot with an unknown displacement (I am guessing 60,000 plus lbs). The A frame mast is capable of folding to deck level. There is a roller furling mainsail of 1200 square foot and a roller furling genoa. The hull shape is a chined hull form with a length to beam of about 8 to 1. The draft is 5 foot over the low aspect ratio keels and rudders. The engine is a centrally mounted 140 HP diesel driving through a fixed 3 blade propeller.

    The accommodation has a total 12 fixed sleeping places (+4 for kids) in 4 double cabins for guests, 1 double captain cabin and 1 double crew cabin in the midhull forward. In one hull is a full galley with easy access to main saloon. There The main saloon has seating, a bar and entertainment areas. The jpegs do not do show the layout in the best light because the cleaners did not go through first.

    As I said this cat/tri is a cruisier and the rig is simple to handle with roller furling sails on the main and jib. The cockpit has a large sun shade solar panel array over it. The solar array has 3 kw of panels leading to a 5000 watt inverter and battery set. There is also a 0.4 Kw wind generator. This boat can be generator free while on a mooring while cruising.

    The construction of the cat/tri is mainly aluminium with limited internal timber and foam glass. The A frame mast structure can be seen in the jpegs. The design and build of the mast structure would have to be very good as the forces of effectively 2 “forestays” carrying over 2000 square foot of sail would be substantial. Also the hinge points between the masts and mast support stubs would be another interesting engineering challenge. Also this is a serious cruiser as indicated by EG anchors: 1 x plow anchor, 52 Kg with 90 meter 13mm chain Galvanized and 3 extra 21 Kg anchor with chain and rope rode's with an electric windlass.

    The jpegs give the idea of a solid motor sailor cruiser.
     

    Attached Files:

  3. oldmulti
    Joined: May 2019
    Posts: 2,565
    Likes: 1,639, Points: 113
    Location: australia

    oldmulti Senior Member

    Mike Schacht. Thanks for the words. I agree an Evergreen 6 mtr biplane square top main rig would provide better performance upwind and would still be relatively easy to handle. Tacking headsails going upwind in narrow waters is great for exercise but annoying for relaxing, especially with my bad back. For the Evergreen 8 have you an idea of the overall beam and an approximation of the loaded displacement. I understand this is still a conceptual design at the moment.

    Burger , good comment, but remember the largest aircraft in the world for years was the Spruce Goose (about the wingspan of a 747), Howard Hughes built timber aircraft built and flown once. Yes it could be possible to do a plywood version of the above aircraft tri sailor, but the 100,000 plus hours of build time and 4 very expensive engines may be a bit limiting.

    Tane, sailing as a concept peaked in the 80's and 90's and home building has declined since. Wharram is the most successful designer of large multihulls and they claim to have sold over 10,000 plans. This in a world of 8 billion people is relatively small. Maybe the modern world has more interest in virtual sailing on television screens etc or just go down the street and purchase a production multihull. People appear to be financially strained and time poor and do not have the desire to spend several years building their dreams.
     
    Last edited: Nov 16, 2022
  4. Michael Schacht
    Joined: Aug 2021
    Posts: 4
    Likes: 10, Points: 3
    Location: Port Townsend

    Michael Schacht New Member

    Thanks for the interest in the boat. A few specs (sorry for the Imperial Units):

    LOA: 26’
    LWL: 25.4’
    BOA: 16.6’
    Hull beam: 4.2’
    L/B ratio: 9.5:1
    Headroom: 5.3’
    Draft: 2.1’
    SA: 388 sq. Ft.
    Mid-load displacement: 4,134 lb.

    The boat has no folding mechanism to narrow the beam for trailering or to fit into a slip, which makes finding a place for it a bit problematic these days. I could see the design working for a world cruiser though, maybe scaled up a bit. Cruisers hang on the hook anyway. Attached is a view of a layout.

    Evergreen-8-ghosted.jpg
     

    Attached Files:

    Flotation and oldmulti like this.
  5. redreuben
    Joined: Jan 2009
    Posts: 1,999
    Likes: 223, Points: 63, Legacy Rep: 349
    Location: South Lake Western Australia

    redreuben redreuben

    Michael, to my aesthetic the Evergreen bow and sheer is much cleaner, the lug boat bow looks a bit … um, clumsy is the only word I can find.
    And a conventional single mast sloop is just fine, although a Wharram style Wingsail would fit real nice. Enough beam for a deck pod and I’ll send you money.
     
  6. Ron Badley
    Joined: Aug 2020
    Posts: 30
    Likes: 11, Points: 8
    Location: Madeira Park, British Columbia, Canada

    Ron Badley Junior Member


    What a lovely boat this is. Thanks Micheal. I’d move the shelter forward and have the option of closing off the front. …and maybe the back. This would make a great year around cruiser here in BC.
    RonB.
     
  7. oldmulti
    Joined: May 2019
    Posts: 2,565
    Likes: 1,639, Points: 113
    Location: australia

    oldmulti Senior Member

    Kenichi Horie is probably Japan's most famous sailor, he has done several adventure sails across oceans in many varieties of boats. EG smallest boat, a wave powered catamaran, a mono built from wooden beer barrels (broken down to form planks) etc. He announced plans in 1998 to sail a beer barrel catamaran single handed across the Pacific. Again, there is minimal detail of the cat but here is what we know. Horie's boat, “Malt's Mermaid II”, is a 32.8 x 17.4 foot catamaran of unknown displacement. The rig is a biplane junk rig with a 35 foot aluminium mast on each hull that carries a 300 square foot junk sail on each mast. The masts are interconnected at the mastheads and stayed with wires going from the mast heads to the opposite mast base. The cat has low aspect ratio keels.

    This would not be a fast cat as the structure would be relatively heavy and the hull shape is less than ideal. Combine this with a Junk rig and the cat would sail OK but this is not a “performance cruiser”. The vessel's junk-rigged, full-batten sails, trampolines and other canvas gear are manufactured from reprocessed plastic bottles. The accommodation is minimal and limited to a recycled plastic pod on the wingdeck. There is a wind generator for the minimal power required on the voyage and the cat had windvane self-steering.

    Kennosuke Hayashi, a top Japanese designer, came up with the two-masted catamaran design with a biplane junk rig. Even then, the shipyard balked and only finished the vessel after what were described as "animated discussions." The basic structure is uses five rows of small stainless steel beer kegs (528 in all) welded together end-to-end to form the sides of the two hulls. The cross beams are also small beer kegs welded end to end. As mentioned, there is much recycled plastic bottles to form plastic fabrics for sails, nets, the deck pod etc.

    I like this man’s humour. He said the cat was going to be built with 528 small beer barrels, 500 would be empty at the start of the voyage but he said all 528 would be empty at the end of the voyage. The trip was successful. The sponsor Suntory Malt, a leading Japanese beer maker, were very happy with publicity and sponsored other trips. The Malt’s Mermaid II is now on display in Japan. The jpegs give the idea.
     

    Attached Files:

  8. Russell Brown
    Joined: Jul 2012
    Posts: 256
    Likes: 152, Points: 43, Legacy Rep: 25
    Location: washington state

    Russell Brown Senior Member

    Anyone watching the Route Du Rhum? I'm interested in the tri "Jess", used to be "Jessica Rabbit", which is doing extremely well right now. I hear it has an interesting history.
     
  9. patzefran
    Joined: Feb 2011
    Posts: 376
    Likes: 55, Points: 28, Legacy Rep: 10
    Location: france

    patzefran patzefran

  10. oldmulti
    Joined: May 2019
    Posts: 2,565
    Likes: 1,639, Points: 113
    Location: australia

    oldmulti Senior Member

    Jess, Jessica Rabbit. Page 188 Multihull Structure Thoughts, item 2819, 18 September 2022. Top speeds in the mid 30 knot range. I hope it succeeds against the big budget boats.

    Jessica Rabbit is a 40 foot performance cruising trimaran designed in 2009-10 by Benoit Cabaret, John Level and Martin Fisher. If any of those names seem familiar think Flying Fantom, Groupama 4 the 60' Orma, AC-45, Fujifilm, etc. Jessica Rabbit was built by Marine Performance Noumea in 2012, New Caledonia. After some ownership changes and name changes to Jessie then in 2017 changed to Jess. The tri is still a fast cruiser that occasional lead its class in things like the Route De Rum in 2019. OK.
    Jess is 40 x 39.5 foot (LOA 45.5 over the bowspirit) with a displacement of 8,300 lbs. The rotating carbon wing mast is 60 foot high with an upwind sail area of 1,400 square foot and a downwind sail are of 1,830 square foot. The Mainsail 753 square foot, Gennaker: 1,075 square foot, Solent: 540 square foot, Code 0: 860 square foot, Staysail: 330 square foot, Storm jib 194 square foot. The draft is from 5 foot to 11.5 foot. There are 3 rudders with T foils on them, 2 lifting C section foils in the floats and daggerboard in the main hull. The engine is Lombardini 27CV engine with a folding two-bladed propeller.
     

    Attached Files:

    Last edited: Nov 18, 2022
  11. oldmulti
    Joined: May 2019
    Posts: 2,565
    Likes: 1,639, Points: 113
    Location: australia

    oldmulti Senior Member

    This is new variation of Bernd Kohler KD 860 catamaran. Bernd has designed an open bridge deck variation of the KD 860 catamaran with a biplane rig. The cat is 28 x 18.5 open bridge deck cat that weighs 2900 lbs (this version is 1100 lbs lighter than the full bridge deck KD 860) and displaces 6200 lbs. The biplane rig has a carbon fibre mast in each hull with each mast having a 230 square foot mainsail. The length to beam is 11:1 and the prismatic coefficient is 0.57. This is a performance cruiser. The hull draft is 1.3 foot and over the rudders 2.3 foot. There is vortex keels, but low aspect ratio or daggerboards would be possible. The rudders are stern mounted kickups. The outboard can be 10 HP.

    The accommodation layout is a large double berth and separate toilet area in one hull and in the other hull a dinette that can be converted to a double berth with a large galley area. The headroom in each hull is 6 foot. This cat could be a relatively cheap long term cruiser for a couple. The open cockpit is between the 2 hulls. This boat is not designed to be transportable, it’s a permanent mooring cat.

    The KD 860 parts can be built separately for assemble near a shoreline built once launched it is a single integrated unit. I am assuming the majority of the build is very similar to the KD860 bridge deck shell, therefore the hull skin and decks will be 8 mm plywood and is covered with light glass epoxy. There are 25 x 38 mm stringers at 400 mm centre lines and 8 plywood 8 mm bulkheads. I am guessing here but the underwing is likely to be 12 mm with 32 x 50 mm stringers at 800 mm centre lines. The main cross beam and rear crossbeam bulkheads are 12 mm ply with 450 gsm 45/45 on either side with top and bottom flanges of timber. The rudders are NACA 4412 sections. The blades are 1470 mm long and 250 mm wide. The skins are 4 mm ocume ply placed in a V mould of 52 degrees then epoxy is poured into the bottom of the V to 15 mm deep. A 20 x 20 mm spar with 2 layers of 400 gsm uni directional on the length of the spar. The spar is placed 78 mm back from the bottom of the nose V. The tail pieces of the ply are pulled together to meet a tapered 25 mm piece of timber to form a foil. The entire outside is covered with 2 layers of 240 gsm cloth. Construction time is estimated by the designer to be about 1200 hours. The KD 860 Open is by its very nature is simple which results in a lighter better performing cat that is also more affordable than the KD 860 bridge deck.

    The difference between the KD 860 Open and the Evergreen 8 mentioned earlier is the Evergreen 8 is a slightly smaller, lighter and is possibly more transportable (that does not mean trailable for a weekend, it means you could take it home for yearly maintenance). Both would be excellent cats, both are designed to be easily built in ply epoxy but I suspect the Evergreen 8 will use less materials and has a smaller rig and therefore will be cheaper. The KD 860 has more interior room and slightly more performance potential. Your choice, the cheaper simpler Evergreen 8 or the slightly larger higher performance KD 860.

    The limited jpegs give the idea. The 2 hull build jpegs are of a KD 860.
     

    Attached Files:

  12. oldmulti
    Joined: May 2019
    Posts: 2,565
    Likes: 1,639, Points: 113
    Location: australia

    oldmulti Senior Member

    This is an update to an Item on Page 123 about Open water yachts ESC 40. The ESC 40 is 39.5 x 23 foot that displaces 12,000 lbs. That means it should weight about 8,000 to 9,000 lbs. The 55 foot mast carries a 635 square foot mainsail, a 280 square foot self tacking jib and a 1300 square foot gennaker. The hull draft is 2 foot. The rudders are retractable transom hung and with curved retractable daggerboards providing better upwind handling and performance at speed. The length to beam at the gunnels of the hull is 10.3 to 1 which makes the hulls 3.85 foot wide. I am guessing that the length to beam at the waterline is about 11.3 to 1 judging by Hal Whitacre other cat designs.

    The ESC 40 can be had as a kit boat to a fully finished cat. This allows for EG 2 hulls to be put in a container shipped to a location then a final assembly done or have a transportable component cat for transport to new sailing locations. The design is innovative and I hoped it would come to reality. As the jpegs indicate it is a real design and has been put into production. The hulls are put in one container with the cross beams stored inside the hulls during transport.

    The build of this cat is full carbon foam epoxy. The core is a structural-grade foam with a high shear strength characteristic: if the part is of a complex shape, we cut the foam into sections, thermoforming it to the required shape. They use five different sizes and densities of foam on the boat, optimized for local strength requirements. Each cat takes 35 rolls of stitched carbon fibre to complete and the cat parts are epoxy resin infused under vacuum. Final finishing such as taping and sanding is hand done before painting.

    The accommodation is unusual. A hull has 3.7 foot wide “double” berth aft, either a galley and or a berth centrally and a toilet forward. The wing deck cabin can have either a double berth or a dinette. Plenty of deck space though.

    This is an interesting design that has the capability of going fast.
     

    Attached Files:

  13. oldmulti
    Joined: May 2019
    Posts: 2,565
    Likes: 1,639, Points: 113
    Location: australia

    oldmulti Senior Member

    When you get high paid professionals involved in catamaran design some of the outcomes are interesting. EG Ker designs do many high performance monohull racing yacht and multihull designs. To analysis a design concept Ker Yacht design use: “Ker Yacht Design uses state-of-the-art technology, techniques and processes throughout the research and design processes. Most of the research work is conducted in-house, however where a certain speciality skill or knowledge is required, we have a strong network of consultants who include our software suppliers. We use software to both make the process faster and the results better and allow us to carry out repetitive tasks automatically and through the time saved, we are able to focus our attention on the creative aspects of the job where the real gains are to be found.”

    Examples of the type of software are: 3D CAD - Siemens NX. All Ker designs are entirely modelled in the computer in 3D using NX, to ensure a high degree of accuracy of the surfaces which gives the boat builders a more precise model to work from. NX is a best-in-class tool chosen by other users such as Red Bull F1, SpaceX and Mercedes Benz.

    Computional Fluid Dynamics – CFD: Ker Yacht design use of CFD for yacht optimization has used Numeca's FINE/Marine CFD code for hull and appendage optimisation. Continuous improvement in techniques and validation over the years using experimental data means they can rely on CFD data to guide and validate improvements. Ker Yacht Design runs its own compute cluster and has used external super-computers when timescales have demanded it. Notice the final words here, Ker Yacht design have used external super-computers when required. This equipment is not cheap to hire, but the results can be very good as several very wealthy global yacht race owners have found.

    Next is FEA to quote Ker Design: “Finite Element Analysis – FEA. Ker Yacht Design use an FEA package – NX Nastran – that is fully integrated with our cad system – allowing the design team to assess the structural integrity of components or an entire vessel structure with a high degree of accuracy and as a routine part of our workflow. This process allows the structure and its load paths to be better understood and for excess material to be removed whilst ensuring that highly stressed areas of complex geometry are sufficiently reinforced, making the Ker designs stronger and lighter.”

    To use very good FEA design tools can cost real money to do the runs that approximate real world stresses on a vessel. Once you have the theoretical information and you truss it (very important), the structural design becomes easier as you can strengthen and lighten the structure as required to meet the global forces.

    If you go to Ker Designs you get a good solution for a price, you get value for money. Unfortunately for a custom design both the value and the money are large. Only the personally rich and companies are able to pay. But the benefits are large. We will use the MC 50 catamaran design to give an example.

    The MC 50 was designed in about 2017. The design sails very well and is 50 x 26.5 foot with a fully loaded displacement of 33,000 lbs. The MC 50 comes equipped with a square-top 1,120 square foot mainsail and a 535 square foot self-tacking jib. Downwind sail area can be up to 3,540 square foot. The draft is 4.5 foot to 12 foot over the foils. The power is two 57 HP diesels.

    The builders went to Ker to develop the design and the associated structure to achieve a high performance cruising catamaran. The result is a 50 foot cat that sail at or exceed wind speed. Tests “She will consistently sail at 75 to 100% true wind speed, so yes she moves alright. Polars from the manufacturer point to speeds of over 10 knots in 25 knots of wind at 30° off true. Come off the wind onto a broad reach and she´ll manage 21 knots-plus if handled well.” And also “Owners have reported that this cruiser exceeds true wind speed from time to time. Breeze was between 5 and 12 knots true and the MC50 was responsive to the lightest helm input and eager to accelerate in the slightest breeze. After short tacking – easy with the self-tacking jib – the enormous Code-0 weapon was unfurled to see if the boat could actually sail faster than the wind. The MC50 consistently sailed at 75 to 100% true wind speed, but could she, in fact exceed it.”

    To allow this to happen you need a light strong structure with a big rig. This is where FEA comes in. When done very well a production boat builder can build a strong stiff boat with minimum of well placed materials and structure. The original MC 50 was carbon/e-glass/epoxy/foam. McConaghy (the builder) used around 60% carbon in the construction for weight savings, and prioritized stiffness in the build. The later version of the MC 50 was extended to 55 foot and used E glass, core cell foam with vinylester resin construction in the lengthened MC 55. Combine the FEA structure with a CFD hull shape and a very experienced group in rig design you end up with a light very high performance cruising catamaran.

    The first 2 jpegs are of the FEA outputs for a cat and the following jpegs are of the MC 50.
     

    Attached Files:

  14. oldmulti
    Joined: May 2019
    Posts: 2,565
    Likes: 1,639, Points: 113
    Location: australia

    oldmulti Senior Member

    If you have a few minutes to spare please have a look at the thread Taulua - The Movie "All for a Horse"

    This is about a couple who built a 35 foot catamaran out of a wood frame with leather, paper and tar covering in 1982. The rig was a very advanced reefable wing sail. The tools used to build the boat were basic and the guy used hand tools to create timber from trees he cut down etc. This is a very well though out old build concept with a very advanced rig. The couple then sailed the cat across the Atlantic without much problem. This guy is inspirational but there are easier ways to build a boat.

    The 5 parts to the movie are on youtube and if watched fully will take about 90 minutes. The above thread will give you part 1 of the movie.
     
    Last edited: Nov 21, 2022
    Russell Brown likes this.

  15. oldmulti
    Joined: May 2019
    Posts: 2,565
    Likes: 1,639, Points: 113
    Location: australia

    oldmulti Senior Member

    Taulua the 34 to 36 foot leather, paper and pitch skin cat interested me, not so much for the hulls but the “Tuna” rig. But first a little investigation into the creators of the Taulua catamaran. Wayland Combewright and his girlfriend Aruna were “mini circus” people who lived in London with their horses and wagon. They made a very modest living and knew they needed more horses to improve their income. They search England for suitable horses then found some were available in USA. They could not afford to travel to the US by other means and pay for accommodation therefore they opted to build a “cheap” boat and sail to the US. You now understand the thread title “Taulua All for a horse”.

    Now folks when I say “cheap” you will be amazed at how cheap we are talking. Wayland and Aruna are smart hard working people who research ideas, test them, understand the problems and develop solutions for them. Wayland has developed solutions for problems that others have not even realised exist. This man is an innovator and carries through with his plans.

    Let’s start with the design concept. He could have started with a Wharram plan in 1978 and built the boat. Small problem, after he sold up everything in London, he had 800 pounds (about $1000 US 1978 dollars) to his name. If he had to pay for a design and some plywood, he would not even finish the hulls. Also during his research on boats, he kept reading about Irish curraghs (animal skin on timber frame small cheap boats). Also, he read about pitching problems of fine ended catamarans and wanted fatter bows and sterns to minimise pitching. He wanted to have a minimum wetted surface hull with more room in them than the prevailing V shapes. He decided to build an accurate 6 foot scale model of his ideas and test what was possible. He wanted a catamaran as they were more stable and he could build a “lighter structure” that could be made from cheap materials and timber. The rig was conceived from the start to be as aerodynamically efficient and easily handled as possible.

    Wayland knew he needed timber, so he offered to demolish a house if he could keep any salvageable timber, next he needed somewhere to build which was very cheap. He found a farmer in the Cotswells that lent him some land and said he could cut down 12 Elm trees for additional timber. His accommodation was a tent for the next 2.5 years including some very cold winter snows etc. Next, he tested some structural ideas. He wanted cheap and curraghs were made from hides or canvas and some with added paper and pitch for sealing. After testing pitch with some asbestos strengthening, he then tested pitch and canvas and found he could easily pierce this with a knife. He then tried a layer of canvas with sheets of pitch paper then another layer of canvas on top with pitch all over and found he could not pierce this with a knife. Next, he loaded 100 lbs of stone on a test piece of the skin on a timber frame and dragged it along the ground, minimal damage. Next he drove a tractor over it whilst it was laying in rough stones. Virtually no damage. He had confidence to build the hulls. Wayland is learning from history and applying modern approaches to get a viable solution.

    The timber frames and stringers for the hulls was built using wooden pegs to hold the frame together. There were heavy timber keel lines to form the main strength elements. The hull frame was then covered by the first layer of 15 ounce cotton canvas and tar then between 8 to 20 layers of kraft paper and pitch (tar) were laid on the hulls followed by 1 or 2 canvas layers and tar. We are not talking about newspaper paper, we are talking about cement bag type quality of paper that has long strong threads in it. The tar are blocks of regular wood tar which is boiled down to boil of lighter water soluble constituents then some creosote is added until it becomes a thick tarry residue (the pitch) that is used as a paste/glue for the canvas and paper. The pitch, paper and canvas were all gotten very cheap to “no cost”. The timber frame was from the demolished house or hand milled from the elm trees. Wayland used a chainsaw and hand tools to cut the tree trunks down to the correct size of timber. There is an old art of “cleaving” used by some old farmers etc to create timber fence posts from cut down tree logs. Wayland refined the process to create EG 50 x 50 mm timbers. Any curves were steam bent into the timbers and any connectors were dowel timbers. There is a minimum of plywood in the design mainly in the decks. The cost of the hulls so far was 200 pounds. I said this cat was cheap.

    The crossbeams are solid timber with bolt connections. Any metal was at best, galvanised steel but the majority is steel. Instead of drilling holes Wayland heats up the metal then uses a punch to hammer a hole in the metal. Faster and cheaper than drilling a hole. After 18 months of work, the couple had produced hulls and deck shell of a catamaran. PS folks like all boat building this boat uses toxic flammable materials. Don’t try and emulate the build process until you understand the risks of some of these materials. EG is the boiling of the tar was to boil over and catch fire you have a real problem.

    We are half way there. The rig is next and what happened after the transatlantic run. Please view the you tube videos to get the concept. Wayland got a really cheap deal on a camera and filmed a lot of the process with the idea of producing a film to help pay for the boat. Sorry only I jpeg more tomorrow.
     

    Attached Files:

    Last edited: Nov 21, 2022
    kdifzero and bajansailor like this.
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.