cat design idea (need help)

Discussion in 'Multihulls' started by seymour2252, Nov 6, 2015.

  1. seymour2252
    Joined: Nov 2015
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    seymour2252 Junior Member

    im currently working on an idea to build a cat and i need some ideas/knowledge and expertise on the subject.
    the general design will be 5ft wide hulls and maybe an overall beam of 18-24ft, overall length will depend on how much it all costs im thinking anywhere from 22ft to 45-50 ft. the materials i have decided on using will be aluminium hull and wooden skeleton with as much locally sourced timber as i can to reduce the costs.
    i need to know average costs of everything, and really someone to say if it will or wont work and the best ways to get around it. im hoping for low costs and alot of the basic work to be done by a professional with me doing the main guts after the boat is functional. ill be using sail power 90% of the time so ill only have a small outboard motor and no high tech power steering or autopilot or anything of the type. ill be getting my power to power the lights/any electronic equipment i use from either wind power or solar.

    iv come to a stop with my writing and probably left a huge gap in the information that you guys probably need so please correct me and quiz me and so on, im looking for alot of information as im building my knowledge everyday and expanding on my ideas.
  2. Tom.151
    Joined: Jul 2009
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    Tom.151 Best boat so far? Crowther Twiggy (32')

    Before you go one step more... add up your budget numbers.
    Whatever the $$ are go on a detailed search for a used/neglected already built catamaran.
    Here in the USA there are more old boats for sale than there are buyers - so there are always excellent bargains coming on the market. But you have to look constantly in a very organized way in order to catch them when the hit the market - they don't last long.
    You cannot, OMNSHO from 50 years building/sailing multihulls, build for less than you can buy used/neglected.
    Not meaning to try to rain on your parade - just hoping to add a point of view.


    PS I just noticed you show that you hail from England. Prices there are typically substantially higher than the USA (used multis especially) - so don't ignore the USA market sources - wouldn't be surprised if you could ge a boat cheaper here and make the trip over to get the boat and still be far ahead on money.
  3. seymour2252
    Joined: Nov 2015
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    seymour2252 Junior Member

    thankyou and yes im trying to get a price list which is partly why i posted here, i have been looking up on used catamarans but they all seem to not fit my requirements, iv been looking for a short ish cat with room for 4 minimum and bedrooms in the hulls which i worked out would have to have atleast a 5ft width to be reasonably comfortable. would you be able to point me in the right direction maybe a website that is good to go on. so far the material prices for the basic structure is around £2k-3k thats excluding the sail and everything, im not so much as looking for any old catamaran im looking for something that has my own personal touch i can add. im a woodworker by trade so i want to incorporate that into it atleast if i build, but im still looking at others because as you said its more likely to be cheaper buying than building.

    edit: my budget will be as low as i can go under 10k for the initial boat but then as i make money i can add to it.
  4. waikikin
    Joined: Jan 2006
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    waikikin Senior Member

    Hi Seymour,

    looks to be a couple of issues so far, first is your bedroom requirements, the 5' wide beds will not fit within the confines of any cat that will sail at the short length, it may be possible to have the berths over the wing area but tough to get space over and have a boat that looks and sails ok at the lower length mentioned- the longer end of the range will run into the 100sK
    Second is your materials budget, given that pounds are bigger than dollars the 2-3 K mentioned is way way short, your construction sound "novel" although I have seen a large tri that lasted about 30 years that was timber framed and clad with light galvanised sheet... it to my knowledge never left port but "might" have done one reef trip when new.... but ended beached and abandoned on the shores of Botany Bay.

    So, if I was in your position I would look at established designs for sale or build and accept that someone else has done the work on design.... add your personal touches in fit out and styling.

  5. jamez
    Joined: Feb 2007
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    jamez Senior Member

    Having built I would echo the above advice and say don't think you will save money by doing it. Better to find an existing boat that will meet most of your requirements than to build to some some ideal that may prove impractical.

    Just as an example I found this Pahi for sale on a UK website, which if it stacks up, would seem pretty good value for money, way cheaper than build cost and not much more than your 10k budget.
  6. seymour2252
    Joined: Nov 2015
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    seymour2252 Junior Member

    im not sure how to quite so ill just answer them as i read them.
    the 5' width is more just the hull width and not the bed size, i have access to a whole range of internal materials which i can customize to fit in and create the bed out of and anything else so thats not really the issue.
    im lacking in practical sailing knowledge like what sizes will work. let me get this straight when i add more width to the hulls it creates more wetted area which in turn creates drag. then in turn you need more sail to compensate.
    the cost of materials im basing on the sheet metal, my first question would be how thin can i go? i have gone off what iv found in most places to be 1.6mm to 2mm thick? (back to googling) yes i did under buget the material cost the 2-3k was a guess and im recalculating is there a general list of structural materials and what they are for like say for a average 24' one you need 100 square feet for one hull (totally pulling random numbers there for an example) then another 100 square feet for the cabin and decks.
    the structural wood will be costing me nothing as i already have alot and i gain it from my work so thats not a problem so its really the sheet metal that im buying and probably around 1k worth of welding and fixings? maybe more. insides dont matter as much as the essentials but yes im seeing more as we talk how its better to buy a used one, as for designs iv had a poke about and theres nothing more than overviews and then they ask for money for the full print and im not even sure if looking at their design will help me.
  7. seymour2252
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    seymour2252 Junior Member

  8. Petros
    Joined: Oct 2007
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    Petros Senior Member

    Welcome to the forum Seymour,

    There are good reasons the typical cruising catamaran has length to width, and hull with sizes in the rangers you see on the popular designs. They are complex sailing and handling reason that all sailing vessels look the way they do. All sailboats of any type are always serious compromises in interior comfort and room as compared to similar length motor boats or cabin cruisers.

    to kind of franenstien together a hull configuration based on the accomodations you fancy would likely end up with a cat that will perform very poorly. It does not mean it will not be safe to use (though that could be an issue too), or it can not be made to behave resonably when under sail, it just it will be slow and possibly unmanagable in heavy seas. which means you will spend a lot of effort and cost building something that will not have any resale value when you are done with it.

    Find a poplular, but neglected existing used boat, that you restore and customize to your likely, will not only save you money, it will get you on the water faster, and it will have a good resale value when you are done with it. Either you decide a life at sea is not what you thought it would be, or you want to move up to a larger boat (or after your children leave the nest, move down to a smaller boat), there will be some time you will want to sell it. A poorly design, and poorly performing boat will have to be scraped.

    You would be money ahead to find something almost ready to go, that you can resell later. THe time you spend building a questionable boat, you could be spending at a second job, or earing extra income, to allow you to buy a better boat that is almost ready to go. You can than spend some time outfitting it to your liking, while you and your family can enjoy day sailing it, getting to know it, and learning how to use it.

    One thing you should consider is to find a local club and get some time on various sailboats. They often have weekend races which you can volunteer to crew (think of it as being their slave for the day, no hard feelings that way-a lot of yelling happens during a race). the best way to get familiar with sailing is to do it on other people's boats. Usually if you contact the local sailing club and talk to the commador or club president he can give you some names of boat owners that can use a slave, they will also have classes and group sails that are fun to go on, get to know other boat owners and learn about what it actually like to own, sail and live on a boat.

    good luck.
  9. gonzo
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    gonzo Senior Member

    2-3K won't even buy the rig. Buy plans from a reputable. designer, and it should include a list of materials. Study plans often have them too. That will give you a way to calculate the actual cost. Add to that tools, disposable materials, storage while you build it (a few years unless you are an experienced builder and are not working anywhere else)
  10. Teleman
    Joined: Oct 2014
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    Teleman Junior Member

    Alum on wood frame construction doesn't sound like a good idea for many, many reasons.
    A clue should be the fact that nobody uses it, and that nobody with boatbuilding/design knowledge has ever bothered trying it. The disadvantages are too many and too obvious.

    For decent performance, safety, and seakindliness, a cruising cat needs a hull L/B ratio no fatter than 9 : 1.
    So if you want hulls 5' wide on the waterline, you're looking at a 45'-ish boat.

    Built in ply/epoxy/glass, the most economical proven method, this size catamaran (complete, sailaway ready, not counting labour) would cost AUS$180K+.

    Built in all alum, more money, at least 50% more time (finishing/lining the inside of metal hulls is a bugger) and a lot more weight. On the plus side, you can leave the outside unpainted.
    It would take a solo home builder at least 3 years (if he was an experienced boatbuilder with a large well-equipped shed) or more like 6+ years if he was like most of us. Maybe a year less for a ply boat built from good plans.

    I would recommend going to Richard Woods' website and reading all the articles, FAQS, design descriptions. Very informative stuff.

    (Back in the late 60's I liked the look of big Wharram catamarans. I thought it would be easy to just add a big comfortable house on the deck, and I'd heard that ferro-cement was a cheap and easy way to make a boat. I hadn't done any ocean sailing, never been on a multi, didn't know any boatbuilders or multihull sailors..... The internet is a wonderful thing.)
  11. Mr Efficiency
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    Mr Efficiency Senior Member

    The old story of the shoestring budget and the boating dream. Does not dove-tail that well.
  12. Teleman
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    Teleman Junior Member

    My shoestring budget and boating dream eventually led to owning half of a 27' Wharram Tane. It was educational, but didn't end well.
  13. seymour2252
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    seymour2252 Junior Member

    okay, thankyou for all the info im now looking at used boats and as petros said im already working on getting experience sailing as i desperately need that. the max L/B ratio of 9 : 1 of the hulls, then how would the overall beam be at most would it be 3 : 2? i think thats mostly what iv seen maybe 4 : 3
  14. seymour2252
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    seymour2252 Junior Member

    and yup thats why im here to avoid the shoestring budget and boating dream accident.

  15. Tanton
    Joined: Nov 2003
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    Tanton Senior Member


    Then there is the Flat Cat.

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