Aluminium boat out of one piece - self casted, one big mold...

Discussion in 'Boat Design' started by congoriver, Jun 23, 2010.

  1. kerosene
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    kerosene Senior Member

    congrats. not to be a negative nancy but can you take a decent sized hammer and give the hull a serious whack.

    Alu plate boat would dent, steel would make noise, decent thickness wood would also just make noise. 3mm cast shell might say crack.


    Test it properly before you send big crew across distant waters.
     
  2. kerosene
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    kerosene Senior Member

    oh yeah - and post pictures or it didn't happen!
     
  3. cthippo
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    cthippo Senior Member

    Just a random thought, but would it be possible to do some sort of a deep draw pressing process to stamp a hull out of Al? Probably not practical for a developing country, but an idea.

    Something else I've toyed with is using 2L plastic bottles for flotation. If you filled some sort of a bag or space with them they would act like a single flotation space, but one that would be very puncture resistant.
     
  4. Jeremy Harris
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    Jeremy Harris Senior Member

    IIRC a boat building company (Australian?) was making alloy boats this way from sheet aluminium, but using explosives. I can't remember the exact process, but I think they dug a big boat shaped hole in the ground, lined with reinforced concrete as a mould, then laid a big sheet of alloy, made from welded up smaller sheets, over the top. They then covered this with explosive and some sort of tamping mass. The pressure from the explosion pushes the alloy down into the mould, forming the hull shape (minus the pointed bow, IIRC).

    I may have some details wrong, but that's how I seem to recall the process worked. It'd probably work OK in a developing country, too. The mould should be easy enough to make, there already seem to be metalworking skills there and the explosive could probably be something as cheap and simple as ANFO, easily mixed on the spot from materials (ground ammonium nitrate fertiliser and diesel) that are almost certainly freely available, even there.

    That's quite an achievement to have cast such a thin shell. I'd have thought that technically casting such a shape without using a pressure casting technique would have been pretty hard to do. It just shows that perseverance pays off. I'd make sure the casting is malleable enough, and free from major flaws, before entrusting lives to it, but overall it may well be stronger and as safe as any other local boat building technique.

    Jeremy
     
  5. liki
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    liki Senior Member

    Linder in Sweden atleast uses pressure forming, no idea though do they use explosives though, for little aluminium boats and canoes.
     
  6. Mr Efficiency
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    Mr Efficiency Senior Member

    The pictures are coming, yes ? It will be fascinating !
     
  7. HJS
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    HJS Member

    As I understand it, Linder is stretching the plate over the elastic limit and thereby also harden it.

    js
     
  8. Pierre R
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    Pierre R Senior Member

    I am a we bit skeptical to say the least. 3mm is about 0.12 or so. That is very thin to cast and probably has defects. How are you heat treating it?

    Pierre R
    Alumalloy Metal Castings
    Avon Lake, Ohio USA.
     
  9. HJS
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    HJS Member



    ALUSCOPE, Dec 2010:

    One of a kind: the Linder production process

    Linder follows its own path when it comes to the production process. “First we pull the aluminium sheet over a die that shapes one half of the boat hull. This procedure is repeated with the other half. Subsequently, any protruding material is trimmed off and both halves have to undergo a heat treatment in a special furnace for about 8 hours. Finally, the two halves are screwed together using an accurately fitting aluminium profile which makes the boat 100 % watertight”, Cecilia Linder explains the production technique which is, arguably, second to none in this industry. According to her, the achieved stability is greater than on any traditionally welded hull. The process,called “stretchforming” by Linder, is only possible thanks to certain aluminium alloys, which had originally been developed for the automotive industry.

    http://www.aleris.com/sites/default/files/Aluscope 2010_2_english.pdf
    http://www.linder.se/?lg=2
     
  10. kerosene
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    kerosene Senior Member

    I don't think Pierre had doubts on the Linder process but the one sancast from scrap to a uniform 3mm shell.
     
  11. SamSam
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    SamSam Senior Member

    An 8.5 meter FAO boat is too small, so you make a 6 meter boat.
     
  12. kerosene
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    kerosene Senior Member

    well - I think its understandable to make smaller prototype 1st...

    But again I would be quite worried about hitting a rock or a log 10 times in the same spot. Rather do that on a 20ft/6m boat with 4 people on board than 10 meter boat with 30.
     
  13. rwatson
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    rwatson Senior Member

    I would bet a boat twice as large would be three time as hard to build using this technique. The explosion formed hulls worked fine at smaller scales, but got problematic for larger ones. Also, if he is refining aluminium from scrap, its not marine aluminium, and wont be very robust.

    Its a case of getting excited about non workable solutions, after all the best ideas get ignored.


    I think the economic arguments have been well presented, and its not a technological problem, so all he is left with is doing what we all like to do - playing around with boats.
     

  14. RAraujo
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    RAraujo Senior Member - Naval Architect

    Hi Congoriver!

    Me, and I'm sure almost all members are deeply expectative about those photos.

    Please let us have them.

    Rodrigo
     
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