Difference concept of cruising catamarans

Discussion in 'Multihulls' started by AdrianN, Apr 10, 2023.

  1. AdrianN
    Joined: Mar 2023
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    AdrianN Junior Member

    Hi all

    After living a couple of years on catamarans I started to carve out what an good cruising catamaran would be for me.

    I have no intention to build a boat myself, I simply don't have the time to invest anything between 5000 and 10000 hours. Though at the moment I also don't have the money to pay someone to build it for me, so it's more a mental exercise...I'm basically looking for feedback on my thought process - what are good ideas, what doesn't work etc. (and yes, I'm well aware this project would need a good naval architect before being taken anywhere...)

    To set the scene: I have lived aboard with my wife and our dog for a few years. First was a Leopard 38 (2010) that we owned, currently a 2019 Bali 4.3 that we use in a co-use agreement.
    Living aboard means for me to have the boat as only home, living on the boat except for "holidays" off the boat. Personal belongings are on the boat with (maybe) a small storage of stuff I don't want to give away for various reasons. We are both more the collector type of person opposed to "empty bag" or "I don't need anything": I want my tools, diving gear etc etc...so not travelling light. I don't mind if the boat looks a bit like a house on two hulls, because it is basically that.

    Things I don't like about the boats I sailed so far:
    - Saildrives: I carry this thing which is so fragile I can't even use ordinary antifouling on it. The propeller induces drag while sailing and fosters all sorts of creatures 100% of the time the boat is not moving. Also, a crucial part can only be serviced with the boat out of the water (shaft seal)
    - I'm in general no fan of any piece installed under the waterline, be it saildrive, propeller, rudder etc (I have changed rudder bearings in the water, which was not fun)
    - Rig: The mainsail is overall just a hassle, which makes is very inefficient (I always reef deeper than necessary to be on the safe side, if I set it at all). Heading up into the wind (and waves) for reefing is also neither comfortable nor safe. Downwind the rig is so inefficient that I need dedicated downwind sails.
    - Sailing Performance: The Leopard was not that bad (except for being overloaded), but the Bali sails like a fridge. As I don't want to sail forever I mostly motor-sail to get anywhere. Sailing upwind is impossible under sails unless the water is flat.
    - Flybridge (Bali only): This is a totally silly concept, it is like sailing open bridgedeck, just without performance. Who wants an exposed helm?

    Overall
    - I want a boat for 2 that can accommodate occasional guests. I need a lot of storage to have a place for the things I do not need on a daily basis (kind of a basement)
    - I need to be able to sail single handed easily. I don't want the boat to top out at 20+kn, because even if the boat can, I cannot do that more than a couple of hours. But I also don't want to sail forever, so 200 miles a day would be nice.
    - I would love to visit places like Denmark or Sweden, so colder climate is a topic for me

    What I came up with:
    - Long and slender hulls for good sailing and easy motion.
    - The rig consists of two junk sails, one mast in each hull
    - Two outboards that I can lift out of the water when I don't need them
    - The accommodation is in the deckhouse only
    - To not assume unlimited budget I set a 46 foot production cat as a benchmark

    So I started with the deckhouse: Two cabins, a "large bathroom" with head and shower, a "small bathroom" with head only, a galley, dining table and "living area" (sofa). I concluded I'd need about 7 by 7 meters for a nice layout, which gave me a total width of 9 meters (some deck space to walk around the deckhouse) So that makes a overall length of about 18 meters.

    The hulls do not contain any accommodation, their only job is to float the deckhouse. and be easily driven through the water with nice motion. They are 18m long and have a length to width ration of about 12:1 at the waterline. I was thinking of building them of tortured foam panels (like tortured plywood, just foam panels), a single chine more or less box shaped hull gives me panels that only need to be tortured slightly and the majority of the chines remains under water. The panel can be infused on a laminating table, which gives me one finished side (outside) and the inside doesn't have to be too nice because the hulls are only basement and do not contain any accommodation. This saves a lot of finishing work.
    I don't like rudders under the hull and stern-hung interferes with the swim-steps so I thought of hanging them on the sides of the hulls, similar to what I have seen on harryproas. They are lifting like daggerboards, if they collide with something they would be break-away and not swing up. As I found out that I sail a lot more upwind than I would like to I opted for daggerboards, but I don't want fouling in the case so my case exits through the hull side just above the waterline (this extends the unsupported daggerboard, making the daggerboard more expensive, but everything is a compromise...). I would add mini-keels of just a couple of inches for beaching and for the boatyards (I have seen boatyards have no problems with cats that have keels, but they struggle to support a cat without keel). Draft incl mini-keels is about 95cm, over daggerboards 2.4 meters, displacement is close to 20 tonnes.
    As I mentioned above the rig is a bi-plane with junk sails, which are easy to handle and don't require any additional downwind sail. The sails are 100m2 each. Having the masts in the hulls gives them enough bury to be free standing and keeps the forces out of the deckhouse.

    The deckhouse is more or less a square, with sides and roof only slightly curved to be build from flat panels. Fitting out a rectangular space is very easy (compared to conforming everything to a hull curve) and I even thought of using standard furniture to speed up the building. A kitchen from IKEA might be heavier, but will be a lot cheaper and faster to build (and if I don't like it after 4 years, I can replace it in just a weekend). I put everything that requires water on one side, so the plumbing can be in that hull where it is short and easily accessible. One advantage of accommodation on the deckhouse is that waste water can be all gravity-drained into the blackwater tank and overboard (no shower pumps that need to be cleaned regularly, no black water tank to pump out, gravity does everything).

    The cockpit is as wide as the deckhouse, as I don't need the space in the hulls. The helm station is raised, accessible from "inside" the cockpit (no need to go "around" as on the flybridge) and is fully enclosed so I don't need oilies for my watches even if it is raining. I put a generous sitting area behind the wheel that can be used as a bed by the on-watch person and at anchor can be used to dry the laundry. All lines are led to the cockpit, so the junk sails can be controlled from there and there is usually no reason to leave the cockpit (especially at night).
    The rest of the cockpit is more like open space without built-in furniture, so can be used very flexible. For example the outside table can be moved wherever needed, but needs to be lashed down for sailing. The area between the outboards is a big storage box, simply because storage in the cockpit is very handy and I really don't like the cockpits that are totally open to the sea (for example like the Leopards).

    Sorry if the above is a bit messy, I'm trying to sort of explain my thought process, I hope it makes kind of sense...I did think a lot about my ideas, much more than I can write down in a post...A few drawbacks of my design:
    - Big and bulky deckhouse, aerodynamics similar to a fridge. Most people won't consider it "nice", but as the saying goes "beauty is in the eye of the beerholder"
    - Hull shape is hydrodynamically not the best
    - Accommodation in the deckhouse brings CG up compared to having some accommodation in the hulls
    - Outboards come with all sorts of drawbacks and may suck air in short waves. The diesel outboards I want (no aspiration to carry a large amount of gasoline) are very expensive an there is no choice between 50hp and 150hp...so it would need to be 2x50hp, but I think this should be enough even with the windage
    - Daggerboard as mentioned above
    - Overall dimensions are not marina-friendly, especially not marina-fee-friendly...

    But, there are also some advantages:
    - Long and slender hulls should sail considerably well and have good motion without hobby-horsing
    - Sails are easy to handle, bi-plane rigs brings CE down
    - The panels are easy to produce on a large laminating table, producing the structure should be fairly quick
    - Fitting out is much easier than in a normal build because of the shapes in the deckhouse and all the electric/plumbing is easily accessible in the hulls and doesn't need to be hidden (also easy for later troubleshooting and fixing.

    I'm not good at CAD, so I'm sticking to 2D drawings right now....but I hope they give a picture.

    Thank you for reading through all this and I appreciate any feedback.
    Adrian

    side.jpg top.jpg back.jpg
     
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  2. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    Some interesting ideas there Adrian.
    Various cats have been built with bi-plane junk rigs as you have shown, and they seem to work well.
    Re your displacement of about 20 tonnes, is this calculated from the hull shape (ie, have you also drawn an initial lines plan?)?
    And have you done a rough initial weight estimate yet?
    @oldmulti said he would be back tomorrow, and I am sure that he can give you some expert thoughts about your design - along with the many other knowledgeable cat designers and sailors on this Forum.
     
  3. peterbike
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    peterbike Junior Member

  4. guzzis3
    Joined: Nov 2009
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    guzzis3 Senior Member

    Rhea 40 cruiser with central cuddy by Woods Designs https://www.sailingcatamarans.com/rhea.htm

    In theory only 1.5 ton but could be stretched 10% V or rounded bottoms. Building you'd make a mold for the bottoms and panel the rest in flat infused foam. You could probably mold in solid glass to teh chine, or go V. I don't know how badly a 44' cat would pitch with V hulls.

    As Mr Woods says you could live entirely in the cuddy cabin.

    He has retired his bigger designs but would sell you plans if you wanted them. He's got a giant full bridgedeck cabin boat as well.

    Biplane unarigs have just as many issues as sloops. It's probably more that you have sailed boats who's design did not prioritise sailing but rather pretty finishes and enormous accomodations.

    Ondina and Cirrus, 45' ocean cruising catamarans by Woods Designs https://www.sailingcatamarans.com/ondinacirrus.htm

    Look at cirrus..
     
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  5. AdrianN
    Joined: Mar 2023
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    AdrianN Junior Member

    @bajansailor the 20 tonnes are on the one hand a figure derived from "comparable" boats like a Lagoon 46 and considering that cruising boats are always overloaded. On the other hand I have drawn hull sections every 2 meters and based on those each hull displaces ca 9'700 liters.

    All, thanks for point out the different boats. For me they are pretty far from my ideas and I'm not looking urgently for a boat to get on the water (I am on the water right now, even if a Bali is far from what I consider ideal). I was more looking for feedback on my ideas, like torturing foam panels (I didn't find much information except for a thread here on boatdesign forum) or the daggerboard cases ending above the waterline.
     
    Last edited: Apr 11, 2023
  6. guzzis3
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    guzzis3 Senior Member

    Daggerboard cases too close to the waterline will cavitate, you might as well fit leeboards.

    Building hull skins is the easy bit. It's the details that take all the time. Tortured foam has been abandoned by most, for lots of reasons. The amount of work building a mold to the waterline or chine is trivial in the scheme of things.

    Maybe take a look at Harryproa ? Those boats are quick to build and there are some enormous ones now that can be sailed short handed.

    Orbiter 80 – Harryproa
     
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  7. rberrey
    Joined: Oct 2010
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    rberrey Senior Member

    If I were you I would start with Hans Klaar,s Ontong Java and do some updates . 70' , sail single handed , no motor , used as a cargo vessel so lots of storage , cheap to build . I think you first lighten it up using foam for the build , then add a center pod to live in and you have your boat .
     
  8. oldmulti
    Joined: May 2019
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    oldmulti Senior Member

    AdrianN. Your ideas are built on your experience, and your logic is sound. See if you can contact the guy below, as you can see from the jpeg below, this has similarities to your thoughts. This guy did a lot of design work and built parts of this boat. His description is below with a name. Bigcat1950 was active on the multihull thread previously.

    65' Catamaran, radius chine, wing sail
    Radius chine, wing sail, unstayed masts, vinylester, balsa, hard chine, full floatation, buoyancy, amateur construction, home built, vacuum bagged, vacuum infusion, resin infusion, junk rig, Polynesian, http://www.dunnanddunnrealtors.com/Catamaran.html , laminating table, tandem rig, bi-plane rig, catamaran, multi-hull, polyurethane, shoal draft, balanced rudder, keel, skeg, Tim Dunn, Seattle

    Also Multihull Structure Thoughts tread received a response from him "I'm the BigCat guy, but the money for the project fell through. I don't have a web address for yachts any more. I'm busy with earthnurture.com . My old webpage is still on the Wayback machine, of course. BigCatCatamarans.com on archive.org - from 2010. Someone else bought the web name later."

    I can do more analysis if you want but in summary you already understand length, lighter weight, 12 to 1 hulls and large sail area equals performance. Biplane junk rigs work especially downwind but have less performance upwind. You trade simplicity of handling for performance but several junk rig biplanes have gone long distances. Look up Grand PHA (Tiki 46) and some others like China Moon (38 foot cat) both of which have sailed from Europe to Australia. Hope this helps.
     

    Attached Files:

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  9. AdrianN
    Joined: Mar 2023
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    AdrianN Junior Member

    Guzzis3, I think tortured foam is a lot more than just not building a mould, it's creating a hull side "ready to paint" in one shot, avoiding all the sanding and fairing. Do you know why tortured foam has been abandoned?

    I also considered changing my design to use constant radii (gunnel and bottom, so top and side view) so that one mould could be used to create both hull sides. Bow left in the mould is a starboard side, bow to the right a port side. The constant radius version lacks a bit volume in the forward half (gut feeling), but otherwise I think it might be worth investigating further...See image, black are the original lines, amber/brown whatever colour it turned out is constant radius. I would use a mould for half-hulls (one side plus half bottom). so that deck and deckhouse would need a flat laminating table.

    compare.jpg


    Oldmulti, thanks a lot for the Big Cat, I will try to contact Tim. Amazing, how you always have a design ready for every question, much better than Google could ever be...I enjoy your Multihull Structure Thoughts thread, thanks for all the effort you put into it!
    I believe that junk sail, if cut with some profile instead of flat panels, sail considerably well upwind. For me, the ease of handling offsets the penalty and bottom line probably give me more miles/day because I dare to keep sails up according to wind and not according to what the wind might be.
     
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  10. guzzis3
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    guzzis3 Senior Member

    Constant radii has been done. The hulls end up looking a bit odd but whatever. Tortured hulls have limited beam and thus limited load carrying and as I said all these techniques shave minimal time on teh build, and no money. How much time do you spend fairing the bottom 3rd of a hull compared to the whole build time ? The whole hull build is maybe 1/3rd of the time. There has always been an obsession with it by people who have never built a boat. It's the fitout that will kill you.

    Here is a current example. Read the ad carefully and read between the lines. Got neck deep into a project then broken by it. He will be lucky to recoup half his investment.

    SCHIONNING CATAMARAN Wilderness 1100 | Sail Boats | Gumtree Australia Murray Area - North Yunderup | 1308097300

    He paid big money for someone else to do the fun bit for him. Now he's into thousands of hours of tedious fitout sanding finishing. Saving 5 minutes torturing hull skins for a compromised shape just doesn't make sense. As I say look at Rob's boats. He's addressed the important thing, making furniture fact, make simple rigs. And because they shunt the keel has no rocker so load carrying, pitching and you can use the same mold to make both sides of the hull.

    There are those who have no clue but are good "salesmen", there are those who understand the problem properly and will steer you straight. Then there are the ones who know but have something to sell. You can't know who you are talking to here but there isn't anyone here anymore who has money to make from you, so all the thoughts will be well intentioned. I've never built a hull, but I've fixed and restored too many boats and I'm a mech eng, or was. Now I'm broken and useless. But I still know something about physics and process management...

    If you are that concerned about hull fairing build a huge table and infuse whole hull sides for a V hull. You will only have to fill and fair around the keel. RW has some old designs for that, Ondina is the biggest I believe.

    Ondina and Cirrus, 45' ocean cruising catamarans by Woods Designs (sailingcatamarans.com)
     
  11. guzzis3
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    guzzis3 Senior Member

  12. AdrianN
    Joined: Mar 2023
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    AdrianN Junior Member

    @guzzis3, thank you for your explanations. You mentioned somewhere you suffered a stroke and you may be more limited than before, I think that's what you mean by broken - but you are for sure not useless! I only see your activity here on the forum, you are posting a lot and helping other people (for example me) and I absolutely appreciate that.

    Regarding build times I understand the 1/3 rule, and I'm looking to reduce the effort in every third. For the fitout I have a square (more or less) deckhouse, so I can use standard furniture. I cannot imagine a faster way to get a wardrobe than buy one from IKEA and assemble it. Screw it to the wall and add a pushlock for each door. Done. Chipboard (I think that's proper English term) may not be the lightest material but as I don't want to build superlight anyway that's fine. The hulls are all "open space" so I can easily install all the plumbing and electrical, that also saves a lot of time.

    @oldmulti, thanks for posting the Hitchhiker 52. Good to see the Owner is happy with the Dtorques, but I have also been contemplating moving the engines forward because I fear they might ventilate in short steep waves because the long and narrows hulls will not follow the waves too much.
     
  13. guzzis3
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    guzzis3 Senior Member

    I wouldn't worry about cavitation in a boat that size but putting the props deep is no bad thing. You can place the engine anywhere and run a V drive forward to wherever you want the prop.

    Standard furniture is a great idea although I'd look for solid pine or similar rather than chipboard. Ikea etc sell such things.

    There seems to be a trend towards fatter cat hulls. Mr Woods and Mr Waller are both drawing boats that are 9:1 on the waterline. 20 years ago 12:1 was more common. Reports from owners indicate these boats sail well. I don't know that I'd go fatter than that on a cat though. I wouldn't be in a hurry to go extremely long and slim though...Works for beach cats but they are a completely different proposition. You shouldn't get too hung up on trivial differences though. Anything within the normal range of things will be good.
     
  14. waterbear
    Joined: Mar 2016
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    waterbear Senior Member

    Adrian,

    I suspect you're thinking about this a bit wrong. You say you want to have a boat that is easier to handle, and at the same time you want to make it larger, fill it with heavy particleboard, and also somehow travel 200 miles per day under sail? I could be wrong, but I believe these stated goals are at odds with each other and not really possible to achieve without compromising somewhere.

    The boats you mention owning are aimed at the charter industry and are basically floating condos. Interior volume and amenities are the priority which of course means these boats are fat and heavy, with lots of windage an lackluster sailing performance.

    To achieve good performance, ease of handling and reasonable accommodation I believe you need a boat with a more holistic approach. That means keeping the weight of the boat down, keeping the weight of your possessions down, keeping the windage down, etc. Having a light boat means the hulls don't need as much volume and can be made more slender. It also means the boat will have a better power to weight ratio for a given sail area, which is limited by what you can handle. All of these factors are dependent on each other, and you often can't change one without the other. Interior furniture should be made out of foam core like the boat itself, or out of lightweight occume plywood.

    If you take the Richard Woods Transit 38, for example, and compare it to the Leopard 38, the Transit weighs 40-50% less than the leopard, depending on fitout. The lighter weight allows the hulls to be relatively narrow, and a flare above the waterline (known as a knuckle) allows good accommodation in the hulls. This means the bridgedeck can be smaller and the overall windage is low relative to the size of the accommodations. The Transit also has 20% less sail area, but because it's lighter it has a whopping 70% more sail area to displacement than leopard. I think if you really want to achieve your stated goals, your boat will need to be more like this.
    transit.png transit2.gif
     
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  15. rberrey
    Joined: Oct 2010
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    rberrey Senior Member

    I will go back to the Ontong Java , 65 / 70' LOA , can do 200 mi per day single handed while being built heavy and capable of a heavy payload . I believe Klaar,s first boat had Junk rigs in both hulls , his second has one mast , maybe for a reason . Klaar may not be the best of men , but his sailing ability is beyond question . I doubt there are very many people in the world with his sea time and or sea miles on a catamaran . His boat is beyond basic , but built with modern materials and holding the design to it,s basics , adding better living conditions , would keep the boats abilities and give you everything you ask for with the exception of mast in each hull .
     
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