Affordable cruising yacht design ?fiber reinforced concrete

Discussion in 'Boat Design' started by Laphroaig, Jul 18, 2012.

  1. Laphroaig
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    Laphroaig Junior Member

    Hello all,
    I am looking to get a cruising yacht built. Ideally for a modest cost without compromising structure or form. This would be for use in a temparate climate. And currently favor a 28ft bristol / falmouth cutter type hull such as BCC 28 or Atkin fore and aft but would opt for a dipping lug rig. ( Mainly for some odd historical preference but also cost ).

    I have a few questions I need some advice on which I have been unable to find any information on.

    1. Is fiber reinforced concrete a suitable hull material?

    It would appear to lack some of the draw backs of ferro cement discussed in previous forum threads. Rust and construction of rebar being less of an issue, potentially being able to be applied shotcast to a mould or shealthed to an inner framing as a core material or laminate. It is also advocated as having flex in certain configurations and being much more resistent to cracking.

    2. Does anyone know of anyone with experience of fibre reinforced boat building or design?

    3. For afforability of a hull would one be better of sticking to fibre glass construction, ie. the Bristol channel cutter hull? Where are the costs in hull construction?
     
  2. gonzo
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    gonzo Senior Member

    Fiber reinforced concrete may allow you to put less mesh in the hull, but you will still need rebar or other metal reinforcements.
     
  3. ocean_groover
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    ocean_groover Junior Member

    At 28 feet, I would think that you will pay a heavy weight penalty using concrete as a hull material.
    Hull and deck can be just 30% of finished boat price. And if you look forward to the time you come to sell, a concrete boat won't get near the price you'll get for the same boat in glass/timber/composite.
    Major cost in hull construction will be labour, unless you're building yourself and choose to ignore this cost. If you're looking to save money, look for a chine construction that can be assembled from say foam/glass panels taped together over simple male frames. Everything cnc cut and delivered gives a good head start.

    Of course we all know you get more boat for your money buying second hand. But for some the build is a part of the process of getting on the water.

    Whichever way you go, good luck, and enjoy!
     
  4. PAR
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    PAR Yacht Designer/Builder

    With out a substantial steel armature, the concrete hull shell will have to be significantly thicker. The only reason ferro works, is it's considerably lighter then a less reinforced mixture, for it's strength to weight ratio. I'd hate to have to calculate the hull shell thickness, on a fiber reinforced hull shell, particularly on a yacht that size. Lastly, the hull shell itself on a build that size, will account for about 15% of the total materials and labor involved in the project, so you're not really saving much, by skimping on materials there. In fact, one of the worst places you can cut corners on is the hull shell.
     
  5. dinoa
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    dinoa Senior Member

    They are using it in precast panels for building construction with considerable weight advantages.

    http://www.buildingonline.com/news/viewnews.pl?id=3782.

    It's widely used to reinforce damaged ferro cement structures but usually with a polymer matrix. Often used to repair earthquake damaged ferro cement.

    Dino
     
  6. PAR
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    PAR Yacht Designer/Builder

    I've seen do data on TechFab's use to repair ferro. Are you sure you know what ferro is? The TechFab product is intended for static structures, I've seen no use in dynamic loading situations.
     
  7. dinoa
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    dinoa Senior Member

    True.

    But it never the less is being done. Maybe in time the technology will improve so that it will be used when dynamically loaded if it hasn't already.

    I would think though that it will be hard to overcome the weight advantage of polymer matrix verses cement.

    Dino
     
  8. dinoa
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    dinoa Senior Member

    Tech fab was a link found that sells carbon/cement prefab panels for buildings. Carbon/polymer is widely used to repair damaged ferrocemet structures in bridges and earthquake damaged buildings.

    Dino
     
  9. Manie B
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    Manie B Senior Member

    Please take note - very important

     
  10. Laphroaig
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    Laphroaig Junior Member

    Thanks for your advise. Its very useful indeed. The hull being approx 15% of the total price noted.

    I had originally invisioned using fiber reinforced concrete over a strip planked hull as a means to add impact resistance and retain watertightness in the event of collision. I wouldnt have thought in this configuration it would need to be particularly thick to be effective. Could be applied over a fibre or metal rebar but I expect this would be tricky and labour intensive to construct.

    The hull shape I had had in mind like the bristol channel cutter 28 are often described as being heavy or overbuilt.

    http://www.wavetrain.net/images/stories/subdir8/bcc.1.jpg

    The mould for these boats are in Australia and they were built in fibreglass "handlaid laminate composed of up to 10 layers of mat, woven roving, and cloth. Laminate thickness varies from 3/8 inch at the sheerline, 1/2 inch at the waterline, to nearly 1-1/2 inches at the bottom of the hull"

    Displacement: 14,000 lbs.
    Ballast: 4,600 lbs. (lead)
    Sail Area: 673 sq. ft.

    I think steel would fit the bill probably better, but I have little idea how much achieving the curves in steel would cost.

    There is a similar vessel the "Puffin" produced in Holland I think from alluminium or fiberglass. The alloy boat has a different keel. But certainly there is an abundance of aluminium boat builders of trailerable runabouts where I live. Some with good reputations.

    However in my experience aluminum can both tear and with enough time become brittle and prone to crack. Cracking unlikely to be an issue in a boat that dosn't pound and with little internal vibration.

    Resale value is not a concern. And certainly I see a massive potential in building rather than buying secondhand from an enjoyment point of view.


    An additional question would be how much would rigging a boat cost as a percentage of the total. Would a dipping lug rig reduce this noticably? I appreciate the rigs limitations when it comes to tacking up wind and in shorthanded sailing. But I certainly like the look. And it would be otherwise useful.

    http://www.mbla.co.uk/index.html

    Not sure if these photo links work. Havn't posted here before sorry.
     
  11. Laphroaig
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    Laphroaig Junior Member

    Also please don't get we wrong on the cost aspect. I have no concerns paying for value. Just some indecision figuring out where the value lies.
     
  12. Laphroaig
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    Laphroaig Junior Member


  13. FAST FRED
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    FAST FRED Senior Member

    "And certainly I see a massive potential in building rather than buying secondhand from an enjoyment point of view."

    Purchase a used production boat and sail it as you enjoy creating a hull.

    When finished take all the rig , engine and equipment from the donor and stick it in your hull.

    Used boats can be had for very little , and new is almost insane in price today.

    FF
     
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