22m cruising cat design concept

Discussion in 'Multihulls' started by Becaris, Aug 3, 2008.

  1. Becaris
    Joined: Aug 2008
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    Becaris Junior Member

    Thanks for the prop picture suggestion. Here are the latest screenshots with all changes so far (including your new prop/hull change). Any thing else? Anyone? Beueller?
     

    Attached Files:

  2. rwatson
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    rwatson Senior Member

    I think I would like one of these!

    Question, why a boom when you have the wishbone sprit?

    If you beefed up the sprit, you would do away with the need for head crushing booms perhaps?

    Another thought out of left field, why not start that wave splitting edge under the bowsprit and extend it back under the cabin. That would give that little bit more of spray protection and lift from the odd big wave maybe?
     
  3. Becaris
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    Becaris Junior Member

    The shape of the mast, boom, wishbone, length of boom, height of mast, are all areas that I don't know enough about to create an efficient design. I was hoping that I could get some more knowledgeable people to chime in on this area.

    In my lack of full understanding, I added the wishbone connection to the boom to act as a kind of reverse boom vang to keep the boom from flexing down so that I could get maximum sail as low as possible to the coach. I was going with the idea of keeping the sails center of gravity as low as possible.

    If I'm headed off in the wrong direction, or if you can tell me anything else I've done wrong in the sails, masts or boom, please, jump in. I'll make the changes and repost the model pictures.
     
  4. rwatson
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    rwatson Senior Member

    You are absolutley right about the reverse vanging effect, and keeping the area down low.

    As long as you have two curved wishbones, you vould do away with the boom altogether - saves weight and expense, and on this rig, it seems to fit right in
     
  5. Grizz
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    Grizz Junior Member

    Will the sails blanket each other? Would the power of the sails be more efficient if one mast was forward of the other one? Like a piroge rig, or cat-ketch as it's more recently called. With the sails seperated by the hull CL distance the power of the slot effect is lost, no?

    Rambling,

    Grizz
     
  6. Becaris
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    Becaris Junior Member

    I don't know about the slot effect, could you (or anyone) address this in more detail? As for positioning one mast in front of the other, there will always be an angle of wind where one sail blankets the other, so I'll just keep them parallel.

    I've already decided to go with the two mast setup, using unstayed carbon fiber masts. I've done this to make the yacht easier to sail by a small crew, and safer. To gain these two advantages I've made the decision to suffer the drawbacks, one of which is the blanket effect when on a reach. While sailing her in that condition I would follow other people's advice and let out the windward sail to 'spill' into the other, and even more often, adjust my heading to get out of a strict reach.

    As for the other disadvantage, getting through the wind while tacking, I'm not concerned with this. Of course I hope she turns well enough to handle that, but I can always use a bump from the electric motors to pull her through. Finally, as for the 'fun of sailing' argument against twin unstayed masts, I enjoy being on the sea, but the sails are a means to an end for me, cheap propulsion.

    I'm seeking more automation so that I can control everything from a single location (flybridge or pilothouse), without having to venture out to the bow much during sailing, and to keep messing with winches and lines to a minimum. This is one reason the coach shape and forward flybridge and pilothouse look so different from other cats.

    Anyway, that's all I want to say about single or twin masts. What I really want to know is how to position my twin unstayed masts (more forward, more astern, which side and how close to each hulls center line?), how tall to make them, how long to make the booms, etc. Thanks!
     
  7. rwatson
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    rwatson Senior Member

    There are quite a few boats that have used this twin mast setup over the years, with all the types of comments you are making about the pros and cons of the rig.

    Unstayed carbon fibre on a boat this size will be enormously expensive, but hell - the boat wont be cheap either.

    I think you are going to have to turn the concept over to a naval Architect as soon as you have ironed out all your priorities and compromises. This will be required to do calculations like mast location, and general certification that will allow insurance companies to take you on. Asking for 'opinions ' on this site will get rid of some of the obvious flaws, but will not come close to providing the complete solution.

    You have about $20,000 of design work to be done after your concept drawings, and perhaps half a million to spend after that on the boat.

    It might have been another post, but the1much observed that the Naval Architect will just about start from scratch despite you hours of thinking.

    I think you are now at the stage of putting a request for an NA in the appropriate forum, and start to get some 'professionaly indemnified' work done. I got some great responses for my project, and as you know there are some very clever people on this site.

    Go for it! :)
     
  8. mikereed100
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    mikereed100 Junior Member

    The new drawings are an improvement and the flybridge and hulls blend nicely. To my eye, however, the cabin seems "clunky" and does not blend well wih the hulls and flybridge. I think this is mostly due to the large, flat panels, size of the windows and angle of the cabin sides. I would love to see a drawing with more vertical cabin sides in which the window height and width matches that of the windows on the flybridge. Perhaps a slight forward slope to the aft side of the cabin as well would help.

    I'm looking forward to comments on the nacelles. It looks like the shape you have drawn would go a long way towards alleviating bridgedeck slamming.

    Mike
     
  9. Becaris
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    Becaris Junior Member

    Yes, I agree. I already knew I'd have to pay a professional to do the actual design. However, I'm just trying to get the concept as close as possible so that they start with a concept of what I'm looking to build, then they can tell me I'm crazy. (it won't be news to me).

    So what I'm looking for now is just obvious adjustments (obvious to others, news to me).
     
  10. Nordic Cat
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    Nordic Cat Senior Member

    I would expect the masts to be a bit further forward in the hulls. Place them so you get the best possible bury in the hulls while still allowing passage past them below.

    The centre of effort for the sails need to be roughly above the CoE for the underwater sections including keel etc.

    I am not keen on the steps on the sides, they break up the lines of the boat....

    just my 2 cents

    Alan
     
  11. Becaris
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    Becaris Junior Member

    Thanks for the suggestion on the mast position. As for the stairs, I'll leave them for the moment, I'm going to show pictures of the interior layout and open a discussion on why I am putting what where soon, then once again have people tell me 'why not?'. Until I show those shots and open those discussions, I'm going to leave the functional aspects involving those parts of the design alone.

    You see, I'm not trying to just make a pretty yacht here. Now... don't get me wrong, I will try to improve the lines and look and take suggestions to improve the looks, but I am far more concerned with function than good looks. I have very specific needs in the yacht I will eventually build and sail around the world, which is why I'm busy with this early concept.

    This yacht needs to handle blue water sailing, but... it also needs to be ready to act as an almost motor yacht for when I reach various ports and places where I want to move around some while not under sail. This is part of why the design has a flybridge forward.

    Also... I plan to have her up in cold water zones at times, which is why there is a pilot house, and why I want her to sail or motor with the least amount of work on deck as possible. Hence the pilothouse configuration and bi-plane unstayed masts.

    I also want her to rarely use any diesel fuel. This is why there will eventual be a large array of solar panals on the coach roof, twin wind generators (one on each mast top) and electric motor propulsion/charging.

    Much of the design is predicated on the idea that new better, lighter batteries are on the horizon, and should be available in five years (about the time I might be finishing the build of my yacht (whatever that ends up being past the prototype stage).

    So... it's a different kind of yacht, and therefore a different kind of layout. Now, if all this will all work together... maybe?
     
  12. brian eiland
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    brian eiland Senior Member

    Eco Trimaran vs Kite Assisted Powered Multihull

    From the sounds of what you are after, you might pay a visit to this site:

    The Eco-Trimaran - a motor ship powered soley by renewable Energy

    http://www.oeko-trimaran.de/eco%20trimaran.htm

    ...but I suggest you have a healthy wallet. I think this fellow has already spent a lot of money and time.



    On the other hand you might consider something more realistic:
    New Age Trawler/Motorsailer; Kite assisted PowerYacht
    http://www.boatdesign.net/forums/showthread.php?p=171356#post171356

    Back to those design concept drawings by Humphrey’s (attached PDF). I can fully imagine a scaled-down version of this tri-hull design, in the 65-70 foot range, with a wonderful rear ‘swim’ platform deck incorporating a sportfishing arrangement and/or a Scuba diving platform. Just inside could be a tender stowage as shown; or rather a complete diving & fish tackle facility. The tenders could then stow up on rear deck, or one forward, one aft.

    The power would be a single main engine sized to develop the vessel’s desired top speed, and it could transmit this power by conventional shaft/prop arrangement, or with a azimuthing Volvo IPS dual prop unit, or via a retractable azimuthing Rim-Drive prop unit as I included on my latest dynarig motorsailer design.
    1) Volvo IPS : http://www.yachtforums.com/forums/y...rld-debut-volvo-pentas-new-ips-750-850-a.html
    2) Rim Drive : http://www.yachtforums.com/forums/te...ropellers.html

    Supplementing this single main engine would be a single DC diesel/electric power unit to provide for:
    1) Ships electrical requirements
    2) Slow speed operation by electric (wing) motor belted to main prop shaft
    3) Maneuvering thrusters as required depending upon azimuth capabilities of main prop.

    The entire ship would be powered by only two engines, basically sized to provide:
    1) Full main diesel power, unimpeded by interceding diesel/electric conversion
    2) Slow speed operation and ship’s systems via the smaller diesel/electric unit
    3) ‘Twin power’ emergency backup as either engine can run all gear
    This configuration more ideally meets the latest thinking for the new diesel/electric DC technologies onboard smaller vessels. Alternatively, two identical diesel/electric plants might be sized such that in combination they would supply the max power required of the vessel, and half power for lesser times.

    Only two engines and no conventional sailing rig should make this a more affordable vessel, both in construction, in maintenance, and in operation. However the SkySail kite arrangement will probably more than offset the conventional sailing rig in cost. Possibly a less expensive alternative to this ‘brand name’, with less computerization could be found (no integrated weather/navigation features, etc). Light-weight construction would be desirable but not necessary. Third world hull construction materials are a possibility.

    I’ll call it a KiteSail Motorsailer for now.


    This is doable now, and maybe in affordable epoxy saturated wood. And it would have a resale value when you want to upgrade...everyone does eventually.
     
  13. Becaris
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    Becaris Junior Member

    The problem with that yacht concept it is just too radical for me. Even though I'm interested in as 'green' a boat as possible, I'm also looking to go with more tried technologies. There are already electric motor powered cats, and several biplane rigs. I'm just looking to combine these two existing designs into one and add some of the better battery storage coming from the hybrid car boom. Finally, make use of the biplane rig with unstayed masts to add a flybridge and pilot house control area. Nothing on my concept is that radical. Right now I think it is only about 30% of the way there, I'll be trying to reduce the size some, make it lighter and more streamlined. Add a few small innovations, etc. Nothing too radical.
     
  14. brian eiland
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    brian eiland Senior Member

    I assume you are speaking of the Eco-Tri rather that the Kite-Assisted vessel??
     

  15. Becaris
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    Becaris Junior Member

    Yes, sorry, I was talking about the Eco-Tri. As for the Kite-Assisted vessel, the problem there is that it is primarily a motoryacht, while I'm seeking primarily a sailing yacht. That vessel is also just way to large for what I need. Even my current concept is too large.

    I'm currently scaling her back to about a 16 or 17 meter version. I want the vessel to make an ocean passage without ever having to fire up diesel engines and be crewed by only two to three people. When she is under power I'd like it to be electric motors running off batteries and solar power (with a diesel genset in reserve for emergencies).

    I'll post pictures of the new size concept soon.
     
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