Cruising cat design

Discussion in 'Multihulls' started by Moewaka, Jun 25, 2016.

  1. Moewaka
    Joined: Jun 2016
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    Moewaka Junior Member

    Hi, I've been following this site for some time but only just joined up.

    I've been looking at cruising cat designs for a few years, but now getting close to making a decision and having the time and $ to start a build.

    I'd like a cat at about 50ft but there are only 2 of us and 1 or 2 crew to help out from time to time so accommodation requirements are minimal for a boat of that size. A large part of the forward hulls would be devoted to bouyancy as well as some sections of the stern.

    I've looked at some of the more reasonably priced designs (Waller, Woods, Tennant etc) and all the way up to the supposedly 'faster and up to date' designs where you pay tens of thousands just for the design.

    The way I see it there are many designs that have been around for 15 years or so that were successful at that time but would benefit from a little 'updating' to the superstructure.

    My question is this, have there been major advancements to cruising cat underwater shapes in the last 15 - 20 years or are they much the same?

    I've been working in design (not naval) and building, cabinetry etc and have been making things all my life. I feel I'd be fairly capable of taking an older design and doing a bit of 'tweaking'.

    Cheers.
     
  2. Corley
    Joined: Oct 2009
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    Corley epoxy coated

    You have to consider hydrodynamic concerns in concert with the nature of your personal requirements. A good way to do so might be to tally up honestly the weight of everything you feel you need to take with you when cruising and then use that as a clear eyed guide as to your payload requirements. Most designers are happy to discuss modifications of their existing designs to suit your needs.

    There are frequent threads on here about "Spartan" cruising cats personally I dont think they are a good idea. They have a poor resale value due to their low load carrying ability and lose their performance qualities when overloaded. Choose a design with enough payload to meet and exceed your requirements. On a cruising boat you want a decent galley and comfortable berths with enough capacity to sufficient stores for a comfortable trip. You also want decent tankage and the ability to carry plenty of anchor chain. They sound like boring issues but they can make or break the enjoyment that you have whilst cruising.
     
  3. aussiebushman
    Joined: Oct 2009
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    Location: Taralga NSW

    aussiebushman Innovator

    As Corley writes, "spartan" boats are not a good idea for many reasons. Please consider that most of the time you spend aboard will be on the mooring or at anchor not actually sailing, so comfort and practicality become highly important.

    As well as a workable galley with safe storage for consumables, things like fresh water and fuel storage, refrigeration (or at least a decent ice box) racks for books, CDs (or whatever) storage for wine or liquor, engine and rigging spares, tools and so on require a well designed layout and secure lockers to avoid having these items under foot. An enclosed head, a small but practical desk and the list goes on.

    Also, there may only be two of you, but good berths for at least 4 persons with storage for personal gear will make the boat far more enjoyable.

    Ultimately, your choice of course, but I hope this helps

    Alan
     

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  4. Moewaka
    Joined: Jun 2016
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    Moewaka Junior Member

    Thanks for the replies guys. I should explain a bit better. I definately dont want a spartan boat. Just a longer (safer, faster and more stable) boat, but I dont require the extra staterooms and bathrooms that a 50fter might normally have.

    I've seen plenty of 38fters with all the things you mention aussiebushman. This is rather like putting all of that on a boat thats 12 ft longer.
     
  5. Corley
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    Location: Melbourne, Australia

    Corley epoxy coated

    There are lots of good cats out there more or less in your size range. Buying an existing boat and refitting it to your own requirements makes sense and would certainly be less expensive than building a new boat. There would be some structural areas that could not be changed but most furniture is able to be remodeled without a problem. Sometimes furniture is installed in such a way that it contributes to panel stiffness by being tabbed in which is something to look out for.
     
  6. rberrey
    Joined: Oct 2010
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    Location: AL gulf coast

    rberrey Senior Member

    The K-design KD122 is only 40' but may be close to the concept your looking for , might need a mast redesign .
     
  7. Stumble
    Joined: Oct 2008
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    Location: New Orleans

    Stumble Senior Member

    If you want a larger boat for sea keeping, but really don't care for all the excess acomodations why not take a look at something like the Rapido 60 Trimaran?

    The major downside to trimarans is minimal acomodations for the size compared to a monohull or cat, but you gain a lot of performance at the same time.
     
  8. catsketcher
    Joined: Mar 2006
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    catsketcher Senior Member

    Gday Moewaka

    Welcome to the site. One of the problems some newbies exhibit is an inability to understand the design spiral. You may be well aware that updating the styling may require huge changes in the design. Plus be very careful of style over substance.

    Reverse bows are one style change that is big news. Some people think you can bung one on a current cat but once you have built a few hulls you realise that bow shape is a function of hull flare, not something you can add. So slab sided cats have vertical bows, flared hulls have raked bows and inverted flare hulls have reverse bows. So to get a reverse bow on an older design you have to totally change all of the hulls sections forward of the mast. (Read "Perry on yacht design" for a good read on this)

    But be careful about following a trend for style's sake. Up until the about 2005 some Aussie cat designers were putting very raked front windows on the cabins - looked very sleek on the drawing board and supposedly modern. The owners of these cats would sometimes put sunshields above the windows to stop them being greenhouses. Then the market flipped in Australia with the commonsense French approach (with smaller vertical windows) being instituted on most cats -some Aussie production cabins got the vertical front window update. The sleek style is not usually seen on modern cabins. Now the "sleek and modern" cats look dated because they followed a trend and sacrificed function for style.

    So update the style IF it will update the usability. Start with function and let things go from there.

    cheers

    Phil
     
  9. DennisRB
    Joined: Sep 2004
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    DennisRB Senior Member

    Gday. The simple answer is no, there have been no great changes in underwater shapes for more performance. Performance comes from light weight and not shape, well providing the shape has been competently designed to already well known parameters.

    A light competently designed shape will have less drag than a heavy one from a million dollar design studio. Eg the reverse bows greatest offering is very simply the longest waterline for the least weight. The shape underwater is not really any different but the boat is lighter and has less windage compared to a similar underwater shape but with a plum bow.

    It seems you already know that which is why you want say the amenities of a 38 footer in a 50 footer. I agree with you and my ideal boat is exactly the same.

    As you say a modern 38 foot cat is not spartan. If like me you actually plan on sailing a lot and not living in marinas the extra length just means more speed, safety and comfort.

    The cost and weight of this boat need not be excruciatingly higher if amenities, rig and engines are kept at a similar size to the original 38 footer.

    Google the Bob Oram "Colors". I almost purchased it. It was a 52 footer as you describe. Its price was low for a 52 footer, but it cost bugger all to build compared to most 52 footers to begin with. It was rigged and powered like a 38 footer. 2 x 10hp outboards. 16m rig yet probably weighed almost half of a lagoon 380.

    [​IMG]
     
  10. brian eiland
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    brian eiland Senior Member

    Dudley Dix 55

    Good advice there.

    I might also suggest you give this design some serious thoughts...
    Dudley Dix 55
    DH550-vanilla4.jpg

    ...and have a look thru the build photos
    http://www.dixdesign.com/dh550%20build.htm


    You are on the right path to make the vessel a wee bit longer than you might fill up with accommodations,....leave those bows empty, and a portion of the sterns as well if you can.
     
  11. brian eiland
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    brian eiland Senior Member

  12. DennisRB
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    DennisRB Senior Member

    That Dix boat is huge. Over twice weight, 3 times the space and with 2 x 50hp engines. I don't think its anything like what the op had in mind. Nice boat though.
     
  13. brian eiland
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    Location: St Augustine Fl, Thailand

    brian eiland Senior Member

  14. Corley
    Joined: Oct 2009
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    Location: Melbourne, Australia

    Corley epoxy coated

    I agree, It's too bad that Bob Oram threw in the towel on designing cats I think a brief like this would be right up his alley.
     

  15. DennisRB
    Joined: Sep 2004
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    DennisRB Senior Member

    legend has it if you are dead set on an Oram you may still be able to get a design from him and kit supplied. I imagine tyre kickers and time wasters are the majority of a designers inquiries which one may no longer want to deal with at some point. So if you are mates with an Oram design owner and committed you may be still be in luck.
     
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