Multihull Structure Thoughts

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

  1. pironiero
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    pironiero Junior Member

    excuse me guys, don't want to create new topic for a single question

    can you please help me to find catamaran manufacturer and model?

    it was built around 2000s and distinct feature it had was that it had somewhat round walls of the hull
     
  2. oldmulti
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    oldmulti Senior Member

    Do you have a picture? What was the length? Did it have a single mast. Did it have a big mainsail and small jib? We need more information.
     
  3. pironiero
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    pironiero Junior Member

    if i had a picture id found it already, single mast, sails were off lenght about 45-55ft
     
  4. oldmulti
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    oldmulti Senior Member

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  5. pironiero
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    pironiero Junior Member

  6. Clarkey
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    Clarkey Senior Member

    I really like this boat. It seems to have been designed by people who actually like being at sea (but not in the rather masochistic way typified by Sven Yrvind) and understand what is necessary to be in comfort, if not luxury. It looks like a tremendous amount of thought has gone in to every aspect.
     
  7. oldmulti
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    oldmulti Senior Member

    You start with a man with an ambition of owning the fastest racer cruiser cat in New Zealand, so he created X Factor. It is a 54 x 34.25 foot open bridgedeck cat that weighs 16,800 lbs and displaces 20,400 lbs. The 70 foot rotating mast carries a 1,150 square foot mainsail, 505 square foot jib, 1,050 square foot code 0 and a 2,250 square foot gennaker. The daggerboards 8 foot draft helps windward performance. The original X Factor was designed as a coastal and offshore race catamaran, so it could win NZ premier race, the 300 mile Coastal Classic. The cat has sufficient accommodation for enjoyable cruising.

    The hulls are made of fibreglass with carbon reinforcement and carbon composite construction in the beams and full length center girder that take the mainsheet loads from the curved aft beam direct to the forestay base. It was built to the highest standards in New Zealand (2003/4), designed by TC (Tim Clissold) Design, engineered by High Modulus with foils by Bakewell-White Yacht Design.

    It won the Coastal Classic at the first serious attempt along with many other races. What do I do with it now? Sell it. The new owner shipped the catamaran via cargo ship from the Pacific to Italy and at the end of almost two years of studies, modification and tuning, a new X-Factor was born. The new version of X Factor had a bridgedeck cabin attached to it and other modifications to become more of a cruiser without much weight gain.

    H3O Yacht Design and Brett Bakewell White did the redesign. The modifications included removing most of the internal panels and internal furniture replacing them with very light carbon sandwich panels and mouldings. The new bridgedeck cabin was also a carbon fibre foam sandwich structure. The rudders and daggerboards were modified and lightened. The result is the modified X Factor is a very similar weight to the original.

    The accommodation had the galley and dining arrangements moved from the hulls to the main cabin, the hulls are now focused on 2 bunk cabins and a bathroom in each hull. The main bridge deck cabin has the galley including a washing machine (have I missed this memo that washing machines were vital requirement for a fast cat) and good central cockpit as well as the hull based sailing cockpits. The rig was slightly modified with a self tacking jib to make the cat easier to sail. But all things are relative.

    The Italian delivery skipper who has raced on MOD 70 and ORMA 60 trimarans reported “On this trip we faced different weather conditions. Between Tarragona and Palamos we found 35 knots of wind and waves of 2.5 meters (8 foot), X-Factor reached peaks of 27 knots bouncing wildly between the waves, we covered 50 nautical miles in less than three hours, we tried to slow down X-Factor to not excessively stress it, but X-Factor is naturally a fast boat…”

    The jpegs give the idea of how you can turn a racer cruiser into a cruiser racer with very similar performance and a fair amount of cash. The first 3 jpegs are of the original X Factor, the remainder are of the modified X Factor. Back to reality tomorrow.
     

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  8. oldmulti
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    oldmulti Senior Member

    Want a relatively cheap and easy to build 24 foot multihull that is difficult to capsize and is fast? We will talk about Coconut. Coconut is a 24-foot sailing proa design built in Honokaa, Hawaii. It is only takes 185 pieces of shaped wood, some fiberglass, some epoxy resin and paint. Simple.

    Ok you think this is just another person random thoughts. Tim Mann first built a Searunner 37 and then designed and built a 56 foot sailing fishing trimaran, 24 foot sailing fishing trimaran, a 40 foot charter/cruising catamaran and several power boats. His advisors and friends include Jim Brown, Russell Brown and John Marples. Hmm.

    Coconut is 24 x 16 foot overall, weighing 1000 lbs and displaces 2100 lbs including crew and 400 lbs of fish (this is a commercial fishing proa). The rig is a sloop with aluminum spars and dacron sails and roller furling jibs at each end. The length to beam on the 22 foot waterline main hull is 12 to 1. There’s a daggerboard in the ama (outrigger) which helps with leeway. There are rudders at each crossbeam that can steer the boat in either direction. Coconut is bolted together, and can be disassembled and trailered in about two hours from on the trailer to in the water ready to sail.

    Coconut is built with marine plywood and timber for frames, stringers and crossbeams. The proa is covered with fiberglass and epoxy. The construction jpegs give you a very good idea of its structure including its central fish tank capable of holding 400 lbs of fish. The fish tank has 50 mm foam and is lined with 3 layers of 330 gsm cloth in epoxy.

    But the elephant in the room is the claim that Coconut is not completely capsize-proof, but she’s practically uncapsizeable. A statement that Tim backs up with practical sailing demonstrations and logic. “During sea trials we once got her up to a 75-degree angle of heel, and she was still quite stable, and came down by herself. Coconut is relatively non-capsizeable when compared to the 24-foot trimarans, and probably faster under sail. These are VERY positive improvements for a small boat like this.” And the following. “Once we were sailing off Kawaihae on the Big Island of Hawaii when we got some 25-30 knot offshore winds with gusts to 40. We got up to a 75-degree angle of heel during one of these gusts, riding on the pod, of course. And she came right back down after the gust passed, of course.”

    Thanks to Dick Newick for the concept of the pod on a proa, Russel Brown for evolving it on his proa’s and Tim Mann for demonstrating its practicality on smaller Pacific Proa’s. This is an excellent practical small proa that has the capability of being turned into a small fun fast cruiser. The jpegs give the idea. the next entry will have jpegs showing how it resists capsize.
     

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  9. oldmulti
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    oldmulti Senior Member

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  10. oldmulti
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    oldmulti Senior Member

    The 24 foot proa Coconut featured yesterday was followed by an 18 foot pacific proa version. Pocket Rocket is 18 x 12 foot that weighs 350 lbs and displaces 850 lbs. The dual mast freestanding rig (I suspect is 2 windsurfer masts) with mainsails only. It has twin rudders that act as rudders and “daggerboards”.

    The 18-foot long Pocket Rocket is the prototype for two different lines of boats Tim Mann building, one that we call The Little Teaching Sailboat, and the other we call the ARC (short for Autonomous Research Canoe). The ARC is a robot sailboat that does oceanographic and weather research at low cost, without risking human lives. The ARC will have added sensors for wind, steering and sails so a microcomputer (Raspberry Pi) can control the Pocket Rocket. The sailing course, sails etc can also be remotely adjusted with an iPhone app.

    Pocket Rocket can also be used for sail training with a person standing on shore with their iPhone if the students get into trouble. This means the training sailor is always dry and comfortable. If they get a big gust of wind, Pocket Rocket goes up onto her "leeward buoyancy pod" and spills wind (just like a ballasted monohull does), rather than capsizing and dumping you in the water. As you can see from the jpegs the proa can carry 2 people for normal sailing. Again, Pocket Rocket is unsinkable, practically uncapsizeable, and she steers the same way a bicycle or car does. Notice the 2 small steering wheels.

    Again, the proa is built with marine plywood and timber for frames, stringers and crossbeams. The proa is covered with fiberglass and epoxy. This size of boat can be built from 4 or 6 mm ply, 25 mm square stringers and eg 50 x 75 mm laminated cross beams.

    The performance claims are interesting and if true would be very good. Tim Mann states “15 knots top speed in ideal wind and sea conditions of 10 knots, 12 knots speed in 15 to 20 knots of wind, 8 to 9 knots speed in 25 to 30 knots of wind, 6 to 7 knots of speed in 35 knots plus wind, and can make progress to windward in 45 knots or more of wind and 10-12 foot seas”.

    The jpegs give the idea but the following web page gives some video’s. Our Pocket Rocket - Ocean People https://oceanpeople.org/pocket-rocket/
     

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  11. catsketcher
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    catsketcher Senior Member

    Great stuff
     
  12. oldmulti
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    oldmulti Senior Member

    Yesterday we spoke of a 18 foot proa that could be used as an unmanned research vessel with one being offered for hurricane research as the proa is virtually “uncapsizable”. Now we deal with the problem of this offer.

    I need to ensure people understand what keep designers awake at night. The jpegs give the hint. When you sail a multihull you try to avoid bad weather, but occasionally bad weather gets you. It can hit you in coastal sailing or crossing oceans. Anywhere there is a long fetch sea swells can build up to large size and then have wind driven develop waves develop on top of them. This combined with currents that may be against a sea swell can create the sort of mess that the Fuji trimaran jpegs is sailing into. Big messy seas like this can pitch pole, capsize or break boats. For a cruiser the safest path is to stop the boat and throw out drogues or a parachute from the bow. Now we will get to the components of a multihull in rough weather.

    The wind speed can be handled by most multi’s to a degree. If you have a cruising multi with a bit of weight reefing down will solve most issues. A drogue or parachute will solve the majority of the rest. If you have a big crew onboard, you can steer downwind if you have sea room and time. If you have a light multi with a wing mast and a very strong gusty shifting winds be very careful. I know of one cat that scared its owner who could not deal with gusty shifting winds as the wing would power up before he could adjust course or depower the wing mast. He swore he would buy a drogue for the next trip to throw out the stern to slow the boat down and have the wing “the wrong way” to minimize its power.

    Seas have 2 versions. Long big swells which are generally not too much of a problem. Yes, there not fun but you can generally steer your way through them, but wind blown waves with breaking wave tops are just plain dangerous. I have sailed in 50 knot winds and 8 meter (26 foot) seas and with breaking wave tops on a 37 foot cat when I was young and silly. We had a really good crew who steered there way through the waves but we still have several breaking waves land on the boat. Not only was the cat pushed sideways (no daggerboards down) but there were leaks developing around windows being hit by wave tops. Do not underestimate the wave forces that can happen. Good designers should give you good detail as to how to fit windows etc to maximize strength and minimize leaks. If a designer says 10 mm Lexan windows do not put in bigger 6 mm polycarbonate as a substitute to improve the view.

    Capsizes can be wind driven but are also be wave driven. The worst type of capsize is the combination of wind and wave. EG you’re going downwind with an apparent wind of 15 knots but a boat speed of 15 knots. The real wind speed is 30 knots. You go down a big sea and bury your nose. You guest it, 30 knots on your main and headsail results in a cartwheel and you are fighting for survival.

    Rouge waves are real. They happen more often than you think. They impact big boats more than smaller boats but if you are in there way, I hope your bow is pointing into them and the back of the wave has a reasonable slope on it. I have sailed over some seas and found a steep back on them which allows the boat to just drop. This tests the boats structure and your nerves.

    The majority of people will never go through really extreme conditions at sea but the longer you sail the greater the chance you will get hit. I have not been in a hurricane, but those who have, say at 75 knots plus wind speeds the seas start to flatten due to the windspeed. Back to the light unmanned 18 foot proa for hurricane research. 2 things, the wind may just blow the proa over and wave conditions when getting to hurricane strength will just throw the proa on its head. Size helps in hurricanes but even big ships break in these conditions.

    What is being said here respect the sea, build a boat as the designer specifies and have heavy weather reefing gear fully set up and practice using it. Next have drogues or a parachute available and finally LISTEN to weather forecasts and learn to read the sky and weather around you. You may not get into extreme conditions often but please be prepared.

    The jpegs give some idea and please read the PDF which has been shown before which analysis’s multihull action in big waves and the characteristics to minimize capsize.
     

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    Last edited: Oct 21, 2020
  13. redreuben
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    redreuben redreuben

    Just read the whole Minimus II post, while I am a fan of minimalism 4 masts does not fit the concept, 4 masts to build, 4 hull points to reinforce, 4 sails to trim and 4 places to be at the same time when a gust hits. I think it would be a fine boat with a sloop rig.
     
  14. Russell Brown
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    Russell Brown Senior Member

    Anyone who claims their boat is uncapsizable or virtually uncapsizable is probably not being kept awake at night by anything.
     
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  15. oldmulti
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    oldmulti Senior Member

    The Smart Cat S 280 is Korean designed and build production cruising catamaran. The Smart Cat S 280 is 28 x 17.4 foot that displaces 10,000 lbs in the open cockpit version and 11,200 lbs in the hardtop version. The 40 foot fixed aluminum mast carries a 417 square foot mainsail, a 174 square foot self tacking jib and a 344 square foot genoa. The length to beam for the hulls are 6.5 to 1. The cat has fixed low aspect ratio keels with spade rudders.

    The above numbers indicate a cruising catamaran with reasonable performance that only occasionally will see 15 knots. Its a 7 to 8 knot sort of cat. It will be capable of reasonable progress to windward and judging by the hull lines has reasonably full ends to help minimize pitching. Translation, it will sail better than older style British cats like the Catalac 28 but will not be in the same performance league as EG Kohler’s KD 860 or Woods Gypsy.

    The cat has been designed to be able to be “disassembled” to transport in two 40 foot containers. There are 2 hulls with some wing, a central wing pod, 2 aluminum crossbeams and if required a central cabin component. The hulls, deck and cabin components are foam sandwich in polyester resin and externally gelcoated. The fibreglass hardtop is fitted with fixed toughened glass forward and side windows. The forward crossbeam section is a 125 x 3mm tube. The Smart Cat S 280 can also be had as a FRP kit version. Customers can customize their own boat from the kits assembly to finish. There are two 9.9 HP outboards as engine power.

    The Smart Cat S 280 comes in 2 versions. The open version has a Bimini hardtop and open cockpit and is 1200 lbs lighter than the fixed hardtop version. The fixed hardtop version only provides a cover for the cockpit with no other accommodation changes. The design has 2 internal accommodation layouts, a 2 double berth and an optimistic 3 double berth version. The galley and loo are in the hulls. There is 6 foot headroom in the hulls and the hardtop version. The demo boat has such cruising requirements as an 18,000 BTU air conditioner, microwave, electric stove top, electric fridge, electric coffee maker etc. The cockpit roof will need to be covered by solar panels, a large battery pack and a backup generator to power that lot of electrical equipment.

    Now getting 6 foot headroom in a 28 foot cat and still have an underwing clearance of about 2 foot requires something to give. The high freeboard tries to visually hide the height of the hardtop but I am reminded of a term used in buildings “Brutalist Architecture”. This design emphasis function over style, but it is very effective at providing a lot of accommodation in a small design. This design claims to be affordable. The base price is $US150,000 but rises to over $US240,000 when fully fitted out with the electrical goodies etc.

    The Smart Cat s 280 is the classic dilemma that was first described by Richard Newick. You can only have 2 of the following 3: Accommodation, Performance or Cheap to build. In the trade off between accommodation and performance in this design favors the accommodation side, but you could live on this boat and if wanted, cruise across an ocean in a reasonable time if required.

    The jpegs give the idea.
     

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