Multihull Structure Thoughts

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

  1. oldmulti
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    oldmulti Senior Member

    Historical Multihulls thread has just produced some very interesting photo’s of the original Cliffhanger cruiser racer tri by Lex Nicol. I spoke of Cliffhanger (Ben Bolt) on the first page of this thread. Sorry for repeating some information. The tri is 42 x 28 foot displacing 7000 lbs carrying 900 square foot of sail. The main hull has an aluminium tube space frame around the gunnels and along the keel and stem. When the hull was built and the internal frame attached glass was wrapped around the tubes which then "shrank" fit the hull tubes to the tubes. All rigging loads were basically taken by the perimeter tubes allowing the hulls just to deal with water forces. The tubes are 100 x 3 mm 5083 H32 (high strength aircraft grade). The 3 cross beams were also 100 mm tubes for the top and bottom trusses with 50 x 4 mm tubes acting as truss frames. The inner ends of the cross beams where they leave the main hull are 1 meter high, the outer end of the cross beams where they enter the float are 400 mm high. This boat has done thousands of miles of racing and cruising and looks as good as new but the cross arms need constant inspection for stress cracks as they have had to do some minor repairs on them over time.

    The main and float hulls were constructed from 200 gsm kevlar 12 mm airex foam 200 gsm kevlar (doubled outside on main hull bottom to waterline). The decks were 330 gsm cloth, 300 gsm cloth 12 mm airex foam 200 gsm kevlar on the inside. The BH's were foam glass. The dagger board was aluminium with a 25 mm leading edge tube, 3 mm aluminium walls second vertical tube 75% aft of cord and some shaping bulkheads at stress points and to handle uphaul and down haul.

    The tri is now doing the Queensland coast as a live aboard cruiser under a new owner and his family after a mild refit. The aluminium crossarms had some strengthening done a few years back due to cracks in some of the welds but the same basic structure has lasted over 30 years, some of it very hard racing. If well conceived, multi’s can be built very lightly and if well maintained, be very effective long term cruiser racers.
     

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  2. catsketcher
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    catsketcher Senior Member

    Cliffhanger is now in Lake Mac - I buzzed the owner in a light day when she went near my mooring. He has put new sails on her and removed the front daggerboard. She looks good.
     
  3. oldmulti
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    oldmulti Senior Member

    A Russian man wanted a version of “Miss Cindy”. Miss Cindy is an ocean crossing 16.25 foot cat designed, built and sailed by Tony Bigras from Canada. The Russian cat is a 16.25 x 10 foot cat that displaces 1320 lbs. (Miss Cindy fully loaded was 1100 lbs).

    The Russian tried to get a bit more stability with slightly more beam (10 foot versus Miss Cindy's 8.5 foot) and putting the hulls further apart (hull centre lines 7.6 foot versus Miss Cindy's 5.8 foot). Result is the Russian cat has 30% more stability for a given displacement than Miss Cindy. The Russian cat has a length to beam of 10:1, Miss Cindy has a length to beam of 13:1. The hull shapes between the two cats are similar. The Russian also wanted more deck space and put more accommodation in the hulls which also slightly lowered the centre of gravity of the cat. The maximum hull width is 2.5 foot at the gunnel with 3 foot headroom.

    So, what sort of performance would you get from the Russian cat? If we again use Miss Cindy’s sail area and a similar displacement the performance would be very close. Miss Cindy top speed was 15 knots, averaged between 3 and 7 knots under sail with a longest day run of about 130 miles. Miss Cindy sailed up to 200 miles offshore, crossing up to 430 miles of open water in 4 days and completed over 4000 miles of sailing. If you are well setup, choose your weather well and have a lot of sailing experience it is possible to sail a small boat a long way. But these cats do have limits, please do not try and cross the North Atlantic in boats like this, choose the Gulf of Mexico or the Pacific during the non cyclone/hurricane season.

    This boat could be built with 6 mm ply over the majority of the hull and deck with 9 mm plywood keel plates and bridge deck bottom. The rig was going to be from a “beach cat“ but the design would be easy to convert to a bi-plane lug rig the same as Miss Cindy.

    An interesting fun design. The first jpegs are of the Russian design, the final jpegs are of Miss Cindy.
     

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    Last edited: May 22, 2020
  4. oldmulti
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    oldmulti Senior Member

    The Class 4 design is basically a development of Erik LaRouge 46 foot cat range built by a Latvian company O-Yachts. Erik LaRouge has had over 500 of his designs built and sailed globally and Erik really knows how to design and structurally specify a fast yacht. The Class 4 is a 46 x 25 foot with a shell weight of 11600 lbs a float weight of 13900 lbs with rig, interior, deck gear etc and a maximum displacement of 18400 lbs with crew, water, food etc onboard. The mast is 62 foot high with a mainsail of 870 square foot, jib of 470 square foot and a genoa of 800 square foot of sail area. The rig plan is in the jpegs. The hull length to beam is 11:1 when loaded and the cat has large low aspect ratio keels for upwind work.

    This cat is fast for a fast and easy to sail being able to achieve 250miles/day in comfort. In the 2014 ARC Class 4 “Ena” sailed over 4000 miles going upwind 25% faster than wind from 3 to 9 knots real wind. Then when wind is about 10 to 15 knots, the Class 4 did over 10kts. At 20/25kts the boat will go 14 to 19 knots with reduced sails area and perfectly balanced. The maximum speed reached was 27 knots.

    The Class 4 is a fast yacht with a light displacement of 6700kg thanks to the composite material and build. Build method is a 100% infused sandwich composite in female moulds for the hulls and decks from eglass and vinylester. There is a 2 layer Kevlar shield from the bow to keel/dagger wet area. There is carbon fibre in beams and high strength areas such as a the front and central beam, bowpole, mast pilar, pilar beam and aft beam. The bulkheads, beams and much of the interior furniture is also infused.

    The yard also assembles by hand all composite panels that are not structural. This way, they become structural after hand lamination. The process represents hundreds of labour hours. Sofa, kitchen, stairs, floor, bed, are structural and will not produce a single “sound” when the boat is sailing as they are an important component of the cat’s structure.

    This is a good fast design that appears to well built. An interesting design. PS I do not know if Erik has retired as I could not find his web site, in France they have a rule that if a yacht designer is no longer active, they cannot advertise or sell boat plans.
     

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  5. Dolfiman
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    Dolfiman Senior Member

    It is Lerouge, not Larouge, started his career in 1976 and still in activity :
    Erik Lerouge http://erik.lerouge.pagesperso-orange.fr/catamaran.htm

    PS : Erik Le Rouge (=The Red, due the colour of his hairs and beard) is also the name of a famous viking, he installed the first colony in Greenland by years ~ 1000, Greenland so named by him because of the favorable climate in those days (already a climate change!) and also to attract more settlers.
     
  6. oldmulti
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    oldmulti Senior Member

    VMG design submitted the following visions for the Volvo In-Port Series. They were inspired by the famous D35 cats used in Swiss lake racing. They kept thinking if the Volvo and Swiss Lake circuits could race with the same platform. So, they proposed two designs, one that matched the Swiss Lake circuit and another that answered the Volvo tender. Design 1 is for the Volvo circuit requirements. Design 2 is for a “improved Volvo approach” with an eye on the second need of the very specific wind conditions on Lake Geneva.

    VMG 35 Design Proposal 1:
    This 35′ feet flying catamaran that includes all the latest features. This catamaran is a “limited risk project” and is an evolution of the current trend of foiling catamarans. This boat can race in either of the following mode: Non Foiling or Foiling. Therefore, this boat is somehow a “3 in 1” boat that is compliant with the specificity of being a full foiling boat on short In-Port Series, an exciting one design boat for long distance racing and a boat that can deal with very light winds encountered on some lakes.

    Design 1: 35.5 x 23.25 foot (total length with prodder 38.8 foot). Displacement (weight) 2000 lbs with an upwind sail area of 915 square foot including the wing mast. The cat is constructed of Carbon – Nomex – Epoxy.

    VMG 35 Design Proposal 2:
    The second project is the result of a brand new approach to the concept of foiling multihull. The concept is the foils are the central piece of the boat. This 39‘ catamaran is light and efficient with a twin rig with soft wing sails. The hulls are only to maintain the boat afloat when not foiling. The overall flight stability is clearly enhanced as the distance between the main foil and the rudder is at a maximum.

    Design 2: 38.8 x 27.85 foot. Displacement (weight) 1680 lbs with an upwind sail area of 970 square foot including the wing masts. The cat is constructed of Carbon – Nomex – Epoxy.

    These designs were done in 2017 and were not selected by Volvo but are interesting. Design 1 jpegs first. Design 2 with twin rigs second.
     

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  7. oldmulti
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    oldmulti Senior Member

    VMG Carpe Diem 42' was designed in 2009 as a fast cruising catamaran. The cat is 42 x 23.5 foot with a weight of 8500 lbs and a mainsail of 645 square foot, a solent jib of 322 square foot and a gennekar of 800 square foot. The hulls are 5.5 foot wide at the gunnels. The length to beam at the waterline is about 10:1.

    This fast cruising catamaran was designed to be light and efficient while being affordable. The simple chine hull shape of plywood would be reasonably fast to build. The materials are plywood covered with e glass and epoxy. There are epoxy and carbon reinforcements in crossbeams and foils. Strip planking and epoxy can be chosen as a good compromise between structural properties. The cross beams are plywood timber boxes reinforced with some carbon fibre. The project was to be a series design for Cédric Müller (Navalia). Plans and CNC plywood kits were to be made available.

    The accommodation is based in the hulls and is sufficient for simple cruising. Its wide cockpit can be closed using a removable tent system to temporarily expand the accommodation in port.

    This cat is a simple design that could be home built and the sail and displacement numbers would indicate the cat would have good performance.
     

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  8. oldmulti
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    oldmulti Senior Member

    We spoke of the Class 4 catamaran designed Erik Lerounge and I said the design was a development of many cats. Here is one of his original designs from 1989 that helped make Erik famous. Freydis 46 which is 46 x 25 foot weighing 13,200 lbs and displacing 17,600 lbs. It has a fixed low aspect keels that draw 3.6 foot. The mast is a 60.3 foot aluminium mast that weighs 485 lbs. Alternatively the 63 foot carbon fibre mast has 2 options, a high modulus carbon fibre that weighs 210 lbs or a standard modulus carbon fibre which weighs 310 lbs. The sails are on the carbon fibre rig is 920 square foot mainsail, 520 square foot 115% jib, 800 square foot drifter and a 1580 square foot spinnaker. The hulls length to beam is 13.5 to 1 in light displacement mode. Please study the hull lines. This hull shape has a minimum wetted surface and is very good across the wind range. How good? When tested in 1999 it could match the wind speed up to 15 knots reaching and do 10 to 12 knots upwind in 15 knots of wind. The top speed reached on the test was 22 knots. The test crew sailed the cat for 3 days and commented on its good controllable motion. Freydis has since circumnavigated and is considered to have a very good motion and is easily controllable in rough weather by its owners.

    The same size French cat would displace twice as much and often only sail at half the wind speed with maximum speeds less than 18 knots. The accommodation provided by the French cat would be similar but have air conditioning, washing machine, more water, bigger engines etc.

    I prefer performance over air con, big engines and enough water to have a shower every day.

    Freydis is built from vinylester resins, e glass and foam. There are selected Kevlar reinforcements on the hulls below the waterline. There is very little wood/plywood in this boat, the bulkheads etc are also foam glass and the interior is kept light.

    I have spent time sailing and cruising on 45 foot cats, this is a magic size for Australian conditions. These cats, if kept light and have relatively thin hulls, are fast capable of high average speeds across the wind range and have a good motion through a seaway if they have relatively full ends.
     

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  9. oldmulti
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    oldmulti Senior Member

    Kurt Hughes drew an interesting trailer design for this swing arm trailer that was Ken Lincoln's idea. He 3D modelled it to see if it would really work. It makes more sense to keep the folding equipment on the trailer and not on the boat. The parts Ken Lincoln thoughts are drawn in blue. The arms and amas are winched up from the top of the dagger board. It all fits in 8.5 foot wide. The same concept could be done in an 8 foot wide version. Kurt has several approaches to trailable trimarans. He has designed swing wings, sliding tube cross arms or his preferred approach which is to have a solid continuous beam that is added to the tri after you arrive at your sailing location.

    The single continuous cross beams often are lighter and stronger than folding or sliding beams. The difficulty of the continuous beam system main is the movement of hulls and final assembly of the tri at the sailing location. That is where this trailer design adds real value. It allows the hulls to be controllably put in position for the continuous often fairly light beams to be attached. How light can the beams be? Even 33 x 24 foot 6000 lbs tris only need 100 lbs aluminium beams with water stays. If the beams were carbon fibre tubes with water stays, they could weigh less than 60 lbs. Warren designed a 35 foot tri that had half cross arm that bolted to the main hull and floats that weighed 20 lbs each. Smaller tris, eg 25 foot, have aluminium beams that weigh less than 50 lbs.

    Good thinking and design by Kurt Hughes and Ken Lincoln.
     

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  10. oldmulti
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    oldmulti Senior Member

    The following foiling cat is the IFly 15 which is 15 x 8.3 foot without foils attached. The minimum weight with foils is 190 lbs. The carbon fibre mast is 25.5 foot high carrying 135 square foot of sail. Also, there is an optional 108 square foot light wind jib. There is another rig with a 28 foot mast and 156 square foot sail for light wind areas. Arno Terra developed the double luff Heru sail for the iFly 15. The main is a deck sweeper onto the aerodynamic air tight cloth wing deck to minimise any air leakage and maximise the mainsail lift capability. All ropes and cords are hidden within the aerofoils wing deck to minimise secondary drag. The IFly 15 is optimised to be as aerodynamically efficient as possible to minimise secondary drag. The hulls are optimised for “take off”.

    The boat is able to sail in 1 foot of water with foils raised but when foils are fully down the cat requires over 4 foot of water. The cat can be disassembled or permentaly bonded together. The foils range from 10% thickness and have a maximum span of 3.5 foot.

    Why the interest in this cat? Try a boat speed around double wind speed with tested top speeds of 26 knots and claimed top speeds of 30 knots. Besides having a very light weight and a lot of sail which helps speed the combination allows the boat to “take off” to foiling mode in 6 knot winds.

    Now we get to the heart of the matter, the item that allows these speeds the scientifically developed carbon fibre submerged T-Foils. There is no need to operate the foils while sailing as they are self-regulating automatic foils. The foils are operated by wand sticks that are the automatic foil control system attached to the forward main lifting foils flaps. These flaps adjust the lift coefficient of the foil adjusting the height of cat above the water. This is a “copy” of Moth foiling technology. The system is hidden within the hulls and foils except for the wands protecting the mechanism from mechanical damage.

    High speed can only be accomplished in a small boat when rig and foil efficiency is high. The submerged four foil active system appears to be a worthy alternative for the four foil Z board system (fixed foil system that depends on amount submerged to vary the lift). Both systems have their own strengths though. The active system adds complexity and costs but is easier to handle for the non experienced sailor. Foiling gybes are also quite easy with the active system as the flaps can effectively double lift and keep you foiling in a gybe.

    The strong point of the active foils is pitch stability and the ability to have foiling gybes and foiling tacks. The pitch stability is why you see such high consistent speeds.

    The carbon fibre foam hulls and carbon fibre beams are built by a company that supplies Airbus plane manufacturers. This is a very interesting fast same cat design that can go very fast. Enjoy.
     

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  11. oldmulti
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    oldmulti Senior Member

    Sylvestre Langevin designed the Trial 1100 tri in 2009, a 34 x 32.3 foot “swing-wing” tri intended for fast comfortable cruising. The Trial 1100 weighs is 7000lbs and the displacement is a maximum of 9200 lbs. The aluminium mast is 47 foot high with 680 square foot of sail with mainsail and 100% fore triangle. The Trial can be folded to 15 foot but as the floats extend beyond the stern it increases the total length to 43 foot for docking. The float cross arms have water stays. The design has wide lines aft (above the water-line) for maximum cockpit space, a clean deck devoid of raised coach-roof, multi-chined hull constructed in aluminium; and a self-tacking jib for easy handling while cruising.

    Designing a fast trimaran with an efficient hull and internal volume sufficient to allow long-term cruising requires a real knowledge of trimarans. On the Trial 1100, he decided to create a "step" in the main hull above the waterline while maintaining a fine and powerful hull with minimum wetted surface. The main hull includes a double berth aft, a forward cabin with double berth, two raised beds in the main cabin, a spacious L-shaped kitchen, a bathroom, a navigation station and many storage areas. The intended engine is an inboard shaft-drive 20 HP diesel. On deck, the useable deck area is impressive and equivalent to a monohull larger than 18m. Beaching is facilitated by a pivoting rudder and centre-boards placed in the floats to allow for easy movement in the central hull.

    The Trial 1100 is mainly built of aluminium construction which provides great strength and durability but contrary to general thinking, is not heavier than conventional molded fiberglass construction.

    The Trial 1100 will according to the designer “provide speeds of 15 knots under sail and 10 knots under power, and if you like to moor right on the beach, all while keeping a comfortable living environment”. Another interesting design.
     

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  12. oldmulti
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    oldmulti Senior Member

    The following is not about the cats that are built, but the way they are designed and built. Day 1 catamaran manufacturers can from design conception to launch, build an 85 foot 190 passenger charter catamaran in 8 months with a professional crew. Day 1 design and build charter cats from 50 to 90 foot using basically the same method and working tools. All the cats have simple chined hull shapes that can carry a load but still have decent length to beam ratio’s for performance. The rigs are large enough to drive the boats but the deck houses are for user comfort not good looks or low windage.

    All the cats are flat infused polyester e glass foam panels which are laid up on a marble table that is full length and width. The keel panels are then placed on a series of preshaped frames (jpeg 1) which are high enough of the floor to allow the adding of low aspect keels later.

    Next are added the main cross beam structures with attached bulkheads. These are taped to the keel panels. Next all the secondary bulk heads are placed along the keel plates. There are no side panels in place yet. All “hidden” hull plumbing and electrics are done at this point. Next are the full length side and chine panels of the hulls placed in position and taped to the bulk heads. Now the panels are glassed on both sides and the hull shape curves are soft enough to allow the foam glass to “bend“ enough to the hull shape. At this point the low aspect ratio keels can be built and attached.

    The bridge deck under wing is “halves” are attached to the cross beam structures followed by the bridge deck bulkheads forward and aft wing frame structures. Again, all plumbing and electrics are done whilst the wing deck is an “open structure”. Then the final decking and bridge deck cabin structures are done.

    This design and build approach require a very accurate design up front as any hull shape inconsistences will not be found until you are a long way into the build and may not be easy to “fix”. Also, you have to understand where you are going to route your plumbing and electrics etc up front or it could be a painful job to install or fix it later.

    I have witnessed a large cat build, where the electrics were installed as the structure was built. Pity a deck fitting hole drilled through part of an enclosed wiring loop, that cause intermittent then total electrical failure on the electrical recharge loop on this build.

    The advantage of this method is all you need is a single large flat moulding table for 95% of the boat panels. The down side is you have hundreds of feet of taping to join the panels together. The following website has a construction sequence video in it. Catamaran day charter - Catamaran day charter et passenger - Day 1® https://www.day1.fr/en/

    This build approach may not produce the “perfect rounded hull and deck shape” but you will be on the water sailing in a lot less time. This is the only boat build method I know that has one down side, it not as easy in smaller boat designs with fuller hulls unless you use thinner cores in your panel construction. Smaller boats with full hulls have relatively “larger” bends in the panels and a 12 mm core foam panel with glass on both sides does not bend well over a short distance. The reason why Kellsal does cuts and reduced glass in his panels until the hull is fully shaped.

    But if the cat/tri is appropriately designed with thinner hull shapes and thin cores this construction method can be used on any size boat. Finally there is a reason that some designers use simple hull shape cheap female molds for there designs as it minimises taping and any hull panel compromises to achieve a hull shape.
     

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    Last edited: May 30, 2020 at 8:21 PM
  13. oldmulti
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    oldmulti Senior Member

    On page 5 of this thread we had Phalmes speak about his Tennant Spyder an 8 meter tube cat. The original design was 25 x 15.75 foot with a 38 foot mast built from 6 mm wrc and 280 gsm uni glass and expected to weigh 1000 lbs. Phalmes version was 27.3 x 18 foot and carried a 40 foot mast which was built with 8mm Western Red Cedar/epoxy with 280 gsm unidirectionals on both sides. The glass is doubled on the bottom. The original design had aluminium main cross beams but was found to be “floppy”. A 100mm forebeam with 'seagull striker' and an intermediate beam between main and rear beams to support a central pod for outboard/battery, etc. PHalmes Spyder weighed 1340 lbs but sailed at 2000 lbs with crew etc and had 450 square foot.

    Another Spyder was built in Sweden “Scarlattikvarten”. It is 26 x 18 foot displacing 1820 lbs with a 40 foot mast and a 322 square foot mainsail and 125 square foot jib. It is also built with 8 mm WRC and uni glass epoxy with a heavily curved 3 mm ply deck covered with 4 mm obeche and 1.5 mm mahogany. Minimal internal framing with bunks as stiffeners and some bulkheads under beams. Again it was built with aluminium beams but was found to be “floppy”.

    “Scarlattikvarten” Had new main cross beams built to stiffen the cat up for sailing. The cross sections of the new cross beams are attached. The mast beam is 350 mm deep. Materials are 6–7 mm birch plywood oriented with the veneers at ± 45° to maximise shear stiffness. Spruce stringers and some UDWR glass are used to improve bending characteristics. The original box beam had a dolphin striker but had carbon fibre added later to replace the dolphin striker.

    The main x arm is inserted into a slot attached to the hull (see jpeg). The main beam end inserts are a 100 mm deep. When the beam is positioned the main attachment, points are 4 stainless steel attachment bolts that are on each corner of the main beam. The bolts attach to metal rods through the beams and hull attachment points. This is a very smart way of having a transportable cat that is strong and reasonably rigid.

    A jpeg of the reinforcements where the mast beam end interfaces with the hull. The underside of the beam and the hull sheer line are located at the very top of the photo. The task of the plywood patch is to transfer compression forces into the hull structure. The carbon does the opposite.

    The aft beam is bolted down in a more conventional manner. These threaded (M12) studs are 'only' bonded to the wood using over-sized holes penetrating almost 20 cm into the wood reinforcement. Unidirectional glass is wrapped over the wood reinforcement on each side of each stud and spread out down the in- and outside of the hull.

    Phalmes cat and “Scarlattikvarten” are fast boats. The jpeg of “Scarlattikvarten” has it doing 9–10 knots while close-hauled in 10 knots of wind. It tacks through less than 90 degrees in those conditions resulting in a VMG of 6–7 knots. The top speed of these boats are over 25 knots. Seriously fun boats.
     

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    Last edited: Jun 1, 2020 at 5:11 AM
  14. oldmulti
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    oldmulti Senior Member

    There are some people who are not professional boat designers but have an innate understanding of design and space. EG Oleg Safari is a furniture designer, but is designing a 40 foot cat (initial length) that grew to 42 foot long as his design evolved. A very famous Australian multihull designer started the same way, he had a good eye for shapes, space and style but his technical knowledge of boat design was lacking.

    Oleg Safari "finalized" his 40 ft catamaran project on drawing board. As Oleg, who has excellent CAD drawing skills, then planned the 40 foot design in detail in 2016. The 2016 “final” design evolved as further detail was drawn in CAD. The length went to 42 foot with an “axe bow” (reverse bow), the hulls had a step inserted above the waterline, the aft of the hull was redrawn etc. Over time Oleg also has developed a good knowledge of the technical aspects of boat design and appears to be capable of the maths etc required to do a good design. The cat ended up being 42 x 23.5 foot with 10.6:1 length to beam hulls with a weight of 12500 lbs and a displacement of 18000 lbs. The sail area is 1000 square foot with genoa.

    His intended construction technique is sandwich construction with PVC closed cells foam core and epoxy resin infused hulls, decks etc.

    The first group of jpegs are of the initial concept then a 4 item “initial” final design. The next are the “structural” jpegs of that initial version. The next set of jpegs is the 42 foot design. The final jpegs give an example of Oleg Cad skills in detailing a rudder. Excellent work of a good conventional home design. If the cat can be built down to the weight he wants and can sail at the displacement specified he will have a good cat. He has not tried to load the cat with vast cabins and island beds etc. It is just a good sensible design. Hopefully he can/is building the cat.
     

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  15. oldmulti
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    oldmulti Senior Member

    Chris White has designed a series of forward cockpit cruising catamarans named the Atlantic series. The cat we will look at is the Atlantic 42 which is 42 x 23.3 foot with a weight of 14,500 lbs and a half load displacement of 16,500 lbs, maximum displacement would be about 19,000 lbs. The aluminium mast is 55 foot high from deck with a 620 square foot mainsail and 370 square foot jib. The underwing is 2.4 foot of the water and the cat has minikeels and daggerboards with a draft of 7 foot. The hulls have a length to beam of about 12 to 1.

    These numbers indicate the Atlantic 42 will be reasonably fast with an owner reporting “She instantly hit 13-14kts with the wind at 16-18kts---60 degrees apparent gusting to 19kts with slight chop. I eased off the main to open up the leech and she settled in at 11-12kts popping up to 14kts on the gusts”. The Atlantic 42 has the ability to carry enough gear and stores for comfortable long term use and is still an excellent sailing cat, often making more than 200 miles per day. (The best days run reported is 267nm.) In the right condition’s steady speeds of 15 to 17 knots are fairly easy to achieve and occasionally 20 knots is reported by owners. However, the big selling point is the ease and comfort in the 8 to 12 knot boat speed range. This is a good size cat that can carry 4 crew and get you places.

    Chris White’s specs the hulls are strip cedar with biaxial and unidirectional e-glass and epoxy. The main beams can be timber ply or foam glass with unidirectional flanges top and bottom. The build time estimate is 6,000 to 7,000 hours. Production hulls are molded from vacuum bagged Knytex glass fiber bi-axial glass and epoxy resin (SP Systems, Ampreg Resin) with 3/4" Core Cell foam core. Additional lamination's of reinforcing glass fiber applied in the area of shroud chainplates, daggerboard fin and crossbeam bulkheads. Custom “catwalk” aft of pilothouse between hulls. All exterior surfaces are spray painted with AwlGrip™ polyurethane coating.

    The forward cockpit design allows you to steer in comfort from inside the main bridge deck cabin but allows fast access to the mast and winches for sail control. If the day is good you can steer from the forward cockpit. This is the best of all worlds. I can assure you a well protected steering position is a real asset in long term cruising. You are completely protected in this sunken cockpit and you are a good 8 feet from the edges of the boat.

    An accommodation layout like the Atlantic 42 really can work at sea. People heads while sleeping on the double bunks are near the pitch centre and their feet are facing forward. Really important when travelling fast in a seaway. The galley can be in the hull or on the bridge deck. The total concept of the Atlantic series is very smart.

    The Atlantic cats can leave even “performance” big French cats behind. This is a very practical boat that highlights sailing capability over island berths and massive load carrying capabilities. A very good design.
     

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    Last edited: Jun 2, 2020 at 6:36 PM
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