Coastal Cruiser

Discussion in 'Boat Design' started by Guest625101138, Oct 25, 2007.

  1. Guest625101138

    Guest625101138 Previous Member

    One of the load case we are designing for is the buoyancy of a fully submerged bow and obviously the bigger the volume the more force.

    I have no experience of a hull like this in a seaway. My objective is to get a good balance between wave piercing and lifting so there is not continuous green water over the bow.

    The idea development, which possibly incorporates some of what you are thinking, is shown in the attached. This is the evolved version without windows and internals. It does show the keel for the batteries, wider beam, shorter length, Sunpower solar panels, slight flare in bow, lifting surface at nose, near vertical cabin windscreen etc

    The idea is still evolving but this hull is being used for load analysis.


    Rick W.
     

    Attached Files:

  2. Thunderhead19
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    Thunderhead19 Senior Member

  3. captaintrue
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    captaintrue Junior Member

    Nice design. Similar to something I've been toying with for a while--especially since keeping them narrow means they can more easily be trailered. You might want to put some mechanism for an outrigger on there to enhance stability. Alternatively you could a specific portion much wider in the back than in the front to the extent that section acts like an outrigger. That bow is designed for wave-piercing no?
     
  4. Guest625101138

    Guest625101138 Previous Member

    The underwater shape is a product of Godzilla optimised for speed of 10kts with displacement and stability constraints. I have added above water level shape to sort of fit in with underwater shape. I did not want the bow to have a lot of bouyancy. Aim was to get a good balance between pitching and burying nose.

    The stability is quite good. The long keel is almost entirely filled with batteries. I expect in most sea conditions it will ride better than a cat around the 30ft mark at 7 to 8 kts. I expect the long keel will also add some roll damping. The wind turbine will also dampen roll.

    Others may be able to work out what it will actually be like. I will need to try it to know. One comfort factor I have used to assess it indicates it will not be the most comfortable boat.

    Rick W.
     
  5. rwatson
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    rwatson Senior Member

    NOt having read all the previous comments, my impression of the current design is that you could benefit from some serious streamlining in the cabin front - a bit of a head wind would severely impact performance, not to mention encountering a big wave (maybe a bow wave from a large vessel on a nice day).
    I know the intention is to operate in moderate conditions, but I wonder why you emphasise reduced bow bouyancy. Certainly windage doesnt appear to be a concern given the bulk of the accomodation.
    You could keep the bow lines "fine" to about the middle of the freeboard for moderate weather efficiency, and then flare it somewhat to cope when you get caught in more severe sea states.
    I can imagine the craft having almost permanent "underwater viewing" in waves of a metre or two as it stands at the moment.
     
  6. harry tams
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    harry tams Junior Member

  7. Guest625101138

    Guest625101138 Previous Member

    Harry
    Yes but only in thinking. In terms of detailed design I went furtherest with the above.

    These links to images show two further iterations:
    http://www.boatdesign.net/gallery/showphoto.php/photo/14408/size/big/cat//ppuser/18624
    http://www.boatdesign.net/gallery/showphoto.php/photo/15019/size/big/cat//ppuser/18624
    Both of these are based on stabilised slender monohull underwater and a single cabin with the stabilisers incorporated into the cabin. This concept is superior to what I started out with. A shorter boat can have a cabin of more normal proportions. A 10m boat would be good for a couple for overnight cruising. A 13m boat would be suitable for family holidays.

    I am currently thinking that I might do something much more streamline more as a solar day boat as an interim stage. That could be my solar boat project. I can give you reasons for this but there are many factors.

    I have been somewhat distracted with improving the basic hull design of my pedal boats that have been used as test platforms for ideas that will go into the solar boat. Linked is my V14 design:
    http://www.boatdesign.net/gallery/showphoto.php/photo/15138/size/big/cat//ppuser/18624


    Rick W
     
  8. harry tams
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    harry tams Junior Member

    Both designs are significant. They could easily be built using the origamiboats method in alloy. What kind of material would you consider? Impressive.
    Harry
     
  9. Guest625101138

    Guest625101138 Previous Member

    Harry
    For the 10m boat I was initially thinking only carbon fibre on foam but I have seen some really impressive work with fibreglass and I think the weight would be tolerable if you took care with the fitiout to keep amenities to bare minimum.

    If you were to go up to 13m then I believe you could get away with aluminium. I have not done enough iteration to confirm this. The 13m would not be trailerable without a permit and is bigger and more expensive than I am interested in doing.

    The motion of these hulls even at speed tend to pass through waves as much as over them so there is little tendency for the pounding you get with fuller bows. Would be very wet if not protected from the elements but no different to most fine entry sailing boats.

    I did some work on hull shape for a fellow considering a 4HP displacement racer and I was taken a bit by that design. It was more like a grown up version of one of the pedal boats I build. A fast point-to-point boat using solar power with the aim of taking time to recharge in protected locations in order to pick weather windows. I have not looked to see if I can get it self-righting, which is something I regard as essential for this size boat for coastal cruising. The three earlier concepts were self-righting:
    http://www.boatdesign.net/gallery/showphoto.php/photo/16439/size/big/cat/500
    I would be looking at something with a bit more room and space for large solar panels on the wings or on top of a partial cabin top. It would also have some form of sealing for the cockpit.

    A scaled down version of the original design on this thread has since been built for an ocean crossing using pedal power and, in the initial testing, it has worked to expectations. It still has to spend some time on the ocean for a decent shakedown but I am happy with it so far:
    http://www.boatdesign.net/gallery/showphoto.php/photo/16440/size/big/cat/500
    It is capable of setting the sort of pace with a single person similar to what is achieved with 4 or 6 man rowing boats.

    Rick W
     
  10. harry tams
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    harry tams Junior Member

    Here in Tasmania one can trailer anything that cannot be easily disassembled if it is under 3.5m wide without a special permit. All you require is 'oversize signs' front and rear, marker flags, and an amber flashing light that can be seen 360 degrees. I imagine the road rules elsewhere in Australia would be similar. Worth checking.

    What are the proposed dimensions of the 13m craft? Do you have any more details? I'm intrigued and very interested. harrytams@gmail.com
    Harry
     
  11. Guest625101138

    Guest625101138 Previous Member

    Harry
    I had only made rough sketches. I was thinking around 3m beam but had not got into any detail.

    My aim was a day trip cruise around 10kts with a more conservative overnight rate between 6 to 8knots. A waterline length of 13m allows reasonable accommodation, and associated weight, while still achieving these speeds efficiently. The 10m boat has to be built very light to get these speeds efficiently.

    With low drag hulls you have to be mindful of windage and I intended to have something more like the ocean boat that has been built already but scaled up for standing head room. It would also have a small aft deck for a bit of outdoor area and steps for access.

    It was not something I ever contemplated building for myself but just to look at a size that would make a zero fuel family cruiser that would match sail or other fuel powered displacement boats for weekend and holiday cruising.

    I did not even determine optimum hull shapes and power requirements other than rough projections from what I have already looked at.

    I doubt Tasmania would be the best location for a solar boat. I expect for realistic cruising you would want wind collection as well.

    If you had a serious interest I could do performance calculations and weight estimates. It is something you would really need to have passion about it. It could be powered by other than solar I guess that would make it less experimental.

    From my perspective, I am happy to spend AUD10k to 20k on something that occupies my mind for a couple of years as a hobby but a 13m boat with family accommodation will be well beyond this. Certainly more than I want to put into a hobby over a couple of years.

    To get 10kts efficiently with 10m it has to be very light. Anything with accommodation is hard to get the weight down low enough. That is why I am toying with the idea of the day boat. I can build a hull like that in CF that will weigh less than 100kg. All up with two crew would be under 500kg including batteries and commercial solar panels. Top speed would be around 16kts.

    Rick W
     
  12. BertKu
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    BertKu Senior Member

    Hi Rick, lovely project. Did you consider those flexible solarpanels. Glass is damm heavy and you would on 4 panels save quite some weight. Unfortunately I have no experience with those flexible panels, how well they last under salt seacondition. Forgive my ignorance, what is CF?
     
  13. Willallison
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    Willallison Senior Member

    HT - The Tasmanian regs are not quite as simple as that. For instance, a vehicle or it's combination must be accompanied by a 'pilot vehicle' if the vehicle is used at night and is more than 22 metres in length (total) or 3.2m in width.
    The regs can be found here:
    http://www.thelaw.tas.gov.au/tocvie...T@EN+20090818080000;histon=;prompt=;rec=;term
    The pertinent section being Part 7.

    Can I ask what it is you are looking for....?


    RW - I'm by no means a solar expert, but given that Tassie has some of the most intense sunlight in the country, I wouldn't have though that this was the case. Is there a reason (beyond the common misconception that it never shines here;) ) that solar is not viable in Tas?
     
  14. harry tams
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    harry tams Junior Member

    Thank you Will
    RE: road rules- What I said though was basically true... but not at night, and not on some roads.
    Are you in Tasmania?

    Harry
     

  15. Willallison
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    Willallison Senior Member

    Yes - sorry, I wasn't contradicting, just wanting to point out that like most legislation, it's not as simple as it 1st may appear.....
    And yes, I'm in Hobart - how about you?
     
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