Foldable catamaran

Discussion in 'Boat Design' started by skatun, Nov 20, 2018.

?

Feasible?

  1. Yes

    1 vote(s)
    50.0%
  2. No

    1 vote(s)
    50.0%
  1. skatun
    Joined: Sep 2010
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    skatun Junior Member

    So we have currently a monohull, but we need more space and also like the idea of going into shallow waters and less movement. Hence we think its time to switch to a catamaran. But a catmaran comes with some catches.

    We have two demands and that it needs to fit inside a shipping a container and it should be electric motor. So the question is how can we achieve this? The idea is to take the floaters off during shipping and fold the whole thing up like this:



    So I started to read up on DNV shipping design standards and making some 3D model based on aluminium beams as shown below. However it would be nice with some feedback if this project sounds feasible and the question is also should it be folded up during sailing and just expended at anchorage, or should it be fully extended the whole time except of during transportation inside the shipping container?



    upload_2018-11-20_17-19-33.png
     
  2. Niclas Vestman
    Joined: Aug 2017
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    Niclas Vestman Junior Member

    skatun likes this.
  3. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    It doesn't need to fold if you can install a beam.

    Need to know your length n beam desires.
     
  4. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    Richard Wood's has two beautiful folding power catamaran designs. I especially like his Skoota 24, but not a fan of the aft cabin.

    He probably has a few sail designs that break down as well.

    You ought to connect with him about your wishes and he can recommend if any of his designs work.
     
  5. skatun
    Joined: Sep 2010
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    skatun Junior Member

    What size:
    It needs to fit inside a standard 40' container, so 11800mmX2300mmX2300mm when folded. By using the Tenfolding principle it can then have a beam of around 6000mm unfolded.
    Weight: Well as light as possible, I am still working on the mass budget but aiming at 4000kg empty
    Style:


    image.png


    Whithout the second floor... and foldable like tenfolding.

    Fast or slow?
    cruising speed aim of 20 kt.

    I will update with more pictures in the following weeks.
     
    Last edited: Nov 21, 2018
  6. Niclas Vestman
    Joined: Aug 2017
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    Niclas Vestman Junior Member

    I'm sorry. Still far to little info to understand your questions. Is it a weekend cruiser or a live aboard? Is it a sailer or strictly motor propelled. The picture shows accomodation spanning almost the entier length. Looks like a summerhouse on water more than a boat. Electric? Do you meen mainly solar powered? My guess would be that you'd need 2 containers for that size. That weight would be double. Around 8000kg. And that you'd need around 2x100kW motors for 20kts. If you have 50sqm solar panels, they whould produce 10kW under ideal conditions, ie 5% of the total continous power requirement.
     
  7. Niclas Vestman
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    Niclas Vestman Junior Member

    Search this site for the thread posted by "groper", and looks at page 26 to start. Very Good info om power needed for very efficient hull design.
    efficient 10m displacement powercat (build thread)
     
  8. Niclas Vestman
    Joined: Aug 2017
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    Niclas Vestman Junior Member

    Another problem. The 40'HQ is about 2,65m internal height. The pontoons need to be shiped in a separat container. To be safe, depending on cruising waters and design, pontoons need a minimum height of 1,2m up to 2,40. Why is the folding option important? Is it because it is an interesting engineering chalenge? Or because world wide shipping is important? Or just because you have limited dock space? Or mostly coz it is a cool and unique concept?
     
  9. Niclas Vestman
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    Niclas Vestman Junior Member

  10. JamesG123
    Joined: Mar 2015
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    JamesG123 Senior Member

    I don't think as you envisage via the tenfold video its practical. Joints and pivots introduce structural weaknesses and flex. What might work for a popup camper isn't going to work on a boat that has to resist all sorts of loads that a camper designer never has to worry about.
     
  11. skatun
    Joined: Sep 2010
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    skatun Junior Member

    I am trying to dimmension it after this:
    http://rules.dnvgl.com/docs/pdf/dnvgl/ru-yacht/2016-10/DNVGL-RU-YACHT-Pt3Ch1.pdf Quite some reading needed:)

    Well I am considering operating it folded and then at dock unfold it, I need to do some calculation both of strength and stability according to DNV first to conclude on it though. The pantoon can be used to stiffen the construction, and the folding could take a 0-2h to complete, i.e bolts can be used to get the desired stiffness. However folding should be doable by two person without a crane!
     
  12. skatun
    Joined: Sep 2010
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    skatun Junior Member


    The idea is to go for around the world trip, but to skip the atlantic crossing and other long crossing(not fun to do with small kids) Also when winter comes its way cheaper to store it in your back yard then at a shipyard(also easier to pop out in the backyard to do maintenance after work then going to a marina)
     
  13. skatun
    Joined: Sep 2010
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    skatun Junior Member


    I am at some point going to install hydrofoil on it to reduce amount of power needed . I still havent figured out the ideal range any suggestions?, but my girlfriend says she gets bored if it moves slower than 20kt, thats why that number is set as a target for now.

    The plan is to use some solar power to charge it as well as kitepower in the future, below are my formulas for battery capacity calculations:


    upload_2018-11-21_16-41-14.png
    Code:
    Public Function boat(Optional boatSpeedKt As Double = 20, Optional rangeNm As Double = 200, Optional boatMassEmpty As Double = 4000) As Double
        Dim pGuess As Double
        Dim rangeM As Double
        Dim speedMS As Double
        
        'constants
        dBattery = 100 '[Wh/kg]
        pGuess = 10000 '[W] - initial power requirements in W
        LD = 30 ' Glide ratio estimate
        pricePerKwh = 190 '[usd/kwh]
        
        ' Calculations
        rangeM = rangeNm * 1859
        speedMS = boatSpeedKt * 0.51444
        timeH = rangeM / speedMS / 3600 'needed time
        
        'finding needed power
        j = 1
        Do While Abs(pGuess - pReal) > 0.001 And j < 1000
            L = (boatMassEmpty + pGuess * timeH / dBattery) * 9.81
            D = L / LD
            pReal = D * speedMS
            pGuess = (pReal + pGuess) / 2
            j = j + 1
        Loop
        
        
        Mbattery = pReal * timeH / dBattery
        Price = pricePerKwh * pReal * timeH / 1000
        batteryCapacity = pReal * timeH
        
        Debug.Print String(65535, vbCr)
        Debug.Print "Battery price: " & Price & " [usd]"
        Debug.Print "Battery mass: " & batteryCapacity / 1000 & " [kwh]"
        Debug.Print "Battery capasity: " & Mbattery & " [kg]"
        Debug.Print "Drag force: " & D / 9.81 & " [kg]"
        Debug.Print "Power Needed: " & pGuess / 1000 & " [kW]"
      
        If j < 1000 Then
            boat = batteryCapacity / 1000
        Else
            boat = -9999
        End If
    End Function
     
  14. Squidly-Diddly
    Joined: Sep 2007
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    Squidly-Diddly Senior Member

    See my gallery for my modular container catamaran concept. I didn't include any expanding X beans but I guess they could be used to separate the two holes until the main cross beams are bolted in place. It's not only contain orible but comes with a trailer that becomes a mast. The concept is you could tow it with a heavy duty pickup such as an F-350 then build the boat roll the pick up onto the boat and transport the boat possible using the trucks engine as power source on the boat. Then on distant Shore reverse operations and start Towing again. Do a round-the-world trip. LOL maybe get sponsorship. Also shown in one drawing is a double-wide container sized hull. Living space close to 8 feet wide is a whole lot better than a living space close to four foot wide. Add or subtract hulls on the water as needed.
     

  15. Niclas Vestman
    Joined: Aug 2017
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    Location: Malmoe, Sweden

    Niclas Vestman Junior Member

    Ok, thanks for the info. I think i have a good enough picture of you idea. First. I know very little about these things, so don't take my word for it. But with that said; No! It will not work. But some aspects of it might. 1) It will cost you 10 times more, than renting luxury yachts and flying 1st class around the world. Also meaning, no need at all for winter storage or maintenance. 2) You will never go more than 10-12kts max on electric. Never ever! So if you want a happy wife/family, you need a different concept, or better yet, rent a yacht. 3) Spending 1000s of hours on a project like this, only drawing and commissioning, will seriously conflict with the happy wife/family criteria. But just developing the idea as a hobby in it self might work, if you don't forget to take your family on vacation. I love developing ideas myself. Actually as it happens, a cat that is container transportable with good accommodation. But a more conventional design, with slightly less "wild" wish list. 4) Even if you decide in building or ordering this boat. It will cost between 200k and 1000k euros. And resale value will be max 25% of that. Meaning you will loose 75% instantly. 5) Foils and electric don't mix except for in light experimental craft. Totally impossible. 6) I see no point in saving money on back yard storage if you are wasting 1000 times more on a difficult and commercially unprofitable build. Also most building code regulations in Europe do not allow for giant foldable boats to be stored on properties in residential areas. 7) It is important to have access to good accommodation while sailing. Makes absolutely no sense to fold while under way, also regarding stability and wave interference (resistance). Meaning, better to investigate a different concept. Also, shipping is still a large cost. I guess around 5000€ minimum for 2 containers cross Atlantic not including handling and port fees. I really love new creatibe ideas. If only as an intellectual exercise. And I like the idea of foldability or better defined as "shipability". But for avoiding longer blue water crossings, it makes no sense at all. At least not in that format. As for electric, it isn't a choice of economy or speed. But ecology and excellent long range motoring in sub 10kts speed. Lastly, there is a very good reason for why 35-40' cats are designed the way they are, meaning accommodation in hulls, and bridgedeck saloon. Having an expandable container as a base for this concept is based ok 1 or 2 benefits, but ignores about a 100 more important reasons for why it is a terrible idea. ...... And it has not been my intention to be offensive, only to give as good feedback as possible. Best wishes /NV
     
    rwatson likes this.
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