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

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

  1. congoriver
    Joined: Jun 2007
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    Location: Kinshasa

    congoriver Junior Member

    Hi, I'm still trying to find a solution to the huge transportation crisis in Congo, where a large part of the logistics of this country is based on river transportation. There's not enough boats, except pirogues that require human power.

    Because of this situation farmers remain dead-poor because they can't get their products to market, and city-dwellers are condemned to rely on expensive imports from abroad. This is a bad situation for everybody, and I can't stand it.

    We need a mass of simple boats:

    -The main requirement is to make medium-sized boats capable of transporting agricultural products (and their small peasant owners) over distances of 200 to 500km.

    -I've explored many options, even such radical ideas like polymer rotomolded boats (because someone once told me that U.S. Patrol Boats used during the Vietnam War were made out of one single piece of a type of plastic).

    Now I have a new idea. It came to me when I visited artisanal aluminium workshops in Kinshasa...:eek:

    What they do in this workshop -mainly used to make cooking pots -is very simple:

    -they gather scrap aluminium from all over the city/country
    -they melt it in simple forges
    -then they pour it into molds made out of sand
    -and out pops up a functional cooking pot, rather heavy, but apparently strong

    This is the inspiration for my mildly absurd idea: why not make medium-size boats from this scrap material, in one go, with one huge mold? Mass production would be possible.

    Some calculations on cost:

    -a 3 mm aluminium pot measuring 26cm diameter and 15cm height has a surface area of around 1756cm²; that is, you need about 5.7 pots to make a plate of alumium with a surface area of 1m²
    -a single pot costs about 2500 FC (around 2.5euros/3US$); so a 3mm plate of 1m² would cost around 14.25euros/17,1US$

    If we make a boat with a rough dimension of:

    -keel: 5m X 12m = 60m²
    -sides: 1.5m height = 36m² long sides / 15m² short sides

    Then we'd have a box with a surface area of around 111m².

    Now add some frames and stiffeners with a total surface area of about 40m².

    Say our total aluminium need is 150m² of 3mm thick. Based on cooking pot prices, that would cost approximately 2137euros/2565US$.

    Big question marks (as you can see, I'm not a boat designer at all, I'm a social scientist!):

    -I'm not sure if this is cost effective.
    -I'm not sure at all if the idea of making a boat out of one piece is even feasible; but the aluminium is there (a huge quantity, because a workshop can produce hundreds of pots a day), and the simple forges are there (they can be placed anywhere, they're mobile and ultra-simple, so several of them could be brought together in one site)
    -I'm not sure if this aluminium is "boat-grade" or that it is even robust enough

    But I'm just exploring all ideas, even the most bizarre ones.

    Because of all these basic question marks and doubts, I ask your opinion.

    Don't hesitate to put down the idea at once, if you think it's utterly unfeasible! :) :!:

    Like they say in Congo: merci mingi!
    1 person likes this.
    Joined: Mar 2009
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    Location: Ontario, Canada Junior Member

    I won't comment on the aluminum molding aspect, as I don't know enough about the process. I can, however, imagine some possible pitfalls trying to mold an aluminum boat with simple tools. In fact, I don't think I've ever seen a molded metal boat (barring some hydro or explosive molded crazies).

    However, my thoughts on the problem behind your query go something like this: If the raw materials, the labour, and simple tools all exist, then I find it hard to imagine a scenario where simple wooden boats will be beat. The tools to make them can be transported to where the materials are (no lugging aluminum around a country with a transportation problem), they can be repaired with the tools and wood already present, and all of the logistical problems of introducing new technologies are avoided. Also, unlike a solution such as roto-molded plastic, there is no increased reliance on outside technology, skills, or resources (another of your stated goals, I think).

    You mention the traditional pirogues that already exist (the photos in your other thread are great). Your comment is that they rely on human power. Is it boats, or engines, that are needed most? I'm not trying to be rude, but the two lacks seem like very different problems. (Also, your other thread seems to be about getting boat OUT of the Congo!)

    If the problem is that the current traditional forms can't transport the goods needed, then finding an appropriate model of boat should be relatively simple. If the needs (amount of cargo, type of water conditions encountered, etc) are identified, very capable people here on the forums will be able to identify an appropriate boat (possibly even a set of free plans). The course of action from that point might be to open a boat building school in a central region, and run workshops for boat builders and local entrepreneurs from different regions of country, with an eye to spreading the plans and skills as far as possible.

    Keep us updated on your ideas, and post more pictures of the pirogues - we like looking at boats! I'd personally like to see some pictures of them being made.

    And, I'm sure someone will come along soon who can properly explain the problems with molding an aluminum boat.
  3. NoEyeDeer
    Joined: Jun 2010
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    NoEyeDeer Senior Member

    Hell, what an idea. Sand casting a cooking pot is one thing. Sand casting a 12 metre long boat is a different ball game. Ask the foundrymen about that. You have to build an internal and external mould and the gap between them has to be pretty accurate (to one or two millimetres) over 12 metes. Frankly I don't think it's practical. Somebody will probably prove me wrong on that. :D

    Suggestion: if you have the aluminium why not just cast flat sheets (much easier) and just rivet them together?

    The sheets wont be nearly as strong as some marine grade alloys but extra thickness can compensate for that if the weight penalty isn't a problem.
  4. Starman

    Starman Guest

    It would be nearly impossible to cast such a large object because earlier aluminum would solidify and new molten aluminum reaching it wouldn't stick to it so there would be a huge number of cracks and weak points. It would also be impossible to get the aluminum into far reaches of the mold unless the entire mold was heated to above the melting point of aluminum during the pouring process. Also it is best to keep oxygen out because of the length of the pour.
  5. capt_jack
    Joined: Jun 2010
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    capt_jack Junior Member

    You might look into using several Fresnel lenses to focus the sun. I've been working with them to convert solar energy into intense heat for charging a thermal mass which then drives a Stirling engine w/ linear alternator.

    You can easily reach temperatures of 3000 degrees F but the area of focus is 2-3 inches with a small lens.

    If you were to line up a dozen, two dozen, etc lenses you could create a series of focal points in a long line. The trick then would be what to use as your container and where to focus the heat. My project partners have come up with a wide variety of uses for this system which include metals casting, cutting, cooking, etc.

    Your only other choice would be to build a large gas driven appliance, very large and no doubt using a lot of gas which may be an issue. The other concern would be materials - I would think wood might be easier and cheaper to obtain in that region than marine grade aluminum. Come up with the right boat design, something simple and easy to build and look into the open source CNC robot projects to cut the panels.

    Think about possible long term implications to this, however.

    In the Amazon, fisherman traditionally used rough kayak / canoe type boats of small size. There were plenty of fish but the available technology made harvesting them difficult.

    Enter modern fishing boats and fishermen began to organize businesses using larger, traditional type fishing boats w/ outboard motors. Now they were able to harvest large amounts of fish and years later the population of those species is declining to the point where they are not sustainable. This is because the fisherman refuse to obey limitations on the size, sex and seasons for fishing. This same exact story is playing out in quite a few regions around the World. (African Lakes especially)

    In Haiti, the poor harvest trees to make charcoal which they sell for cooking. Because of this the island is almost completely deforested. This makes the seasonal storms more deadly as the soil washes away easily now creating mud slides and exposing the solid rock base of the island. Areas which can grow crops are declining, imported rice brought in to help is cheaper than local which destroyed the farming economy and the cycle of poverty has gotten so much worse that most of the population depends on foreign aid. (Which has created a huge population of people with no solution other than monthly food hand-outs) Even as children starve to death the parents continue to have more.

    There are no easy solutions to poverty and many "solutions" lead to bigger, worse problems. Be very, very careful and consider long term implications is all I'm saying.
  6. RAraujo
    Joined: Apr 2010
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    RAraujo Senior Member - Naval Architect

    I would agree with Cameron on the use of wood. It's available, people are used to work with it, not specialized tools required and people have been using it for millenia.

    You can have a look at the models FAO has developed for use in less developed countries. I know they were intended to be used as fishing boats but they can be adapted and they are easily built.

    Have a look at

    As for the propulsion outboards could be used or adapted car engines like those used in Thailand's long tail boats.

    And I'm prety sure users of this forum can give a couple useful suggestions...
  7. capt_jack
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    capt_jack Junior Member

    Other wild ideas:

    DIY RIB: recycle plastics to melt down and treat sewn cloth to make inflatable "pontoon" type boats / rigid inflatable boats

    Pontoons: recycle any metal or plastic containers which could be used to build pontoons. LP / gas cylinders, plastic water / pop bottles sealed and combined into a larger container which forms the pontoon.
  8. NoEyeDeer
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    NoEyeDeer Senior Member

    I have a better idea. If you get a stack of gas cylinders and focus your fresnel lenses at the pile, the resulting explosion should be big enough to lob the cargo 200 to 500 km. Aiming might be a bit of a problem but practice makes perfect.
  9. Pierre R
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    Pierre R Senior Member

    I guess I can comment on this thread as a real expert since I am a metallurgist, have and aluminum foundry and I am the inventor of a unique sand casting process.

    The alloys that would not corrode out quicker than wood rotting problems cannot be cast in this matter so there is the first problem. Alloy 319 would be the easiest but its not corrosion resistant.

    Making the bottom mold would not be a big deal but making the top mold (cope) would be a serious problem due to the weight of the sand. Placing the correct risers on the boat to prevent unwanted shrinkage and hot tearing would be another problem that I think would be near impossible to correct. In short the molding process for this would be very technical and require heavy equipment.

    The final problem is pouring the metal fast enough. You would need the entire boat including the risers, gates and pouring cups to be melted all at the same time. Then you would need to make the pour quickly all at once.

    I think the logistics of trying to make a boat in this way would require more expensive equipment and labor than building the boat from plate.

    Now I have to go to the foundry.
  10. apex1

    apex1 Guest

    Would like to second Raraujo´s recommendation.
    That is the way to go.

    As Pierre made very clear (thanks), The cast Al is definetively not possible.

  11. Village_Idiot
    Joined: Oct 2007
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    Village_Idiot Senior Member

    Sounds like your biggest need is cargo-carrying capacity, like a barge. Inflatable boats offer the largest carrying capacity for given resources. Obviously, their weak spot is puncture resistance. Enter the RIB, which Cap'n Jack mentioned earlier. Modern mfr'd. RIBs are expensive because they are designed to be fast, which you don't need. Your job is to build an inflatable barge, then cover it with a protective coating, be it sheets of aluminum or plastic cloth or fiberglass or wood. Numerous discrete inflatable chambers should be incorporated into the hull, so that you have a safety factor should one or more chambers be compromised (punctured). Along those same lines, make sure that the inflatable chambers are easily accessible topside for maintenance reasons.

    Now, if your protective covering is strong enough, you could eliminate the inflatable chambers, and your covering becomes the hull of a traditional boat/barge. However, it will need to be watertight or you will need several very good bilge pumps. Your bigger problem will be overall strength of the hull - you would likely need to add stringers and longitudinals to gain required strength, all of which add weight, complexity and expense. Therefore, best to stick with protected inflatable chambers. You may need to add water ballast chambers or outriggers for improved stability if cargo cannot be balanced or rough waters are expected.
  12. Chris Ostlind

    Chris Ostlind Previous Member

    Pierre doesn't say it's not possible. He says it would take serious equipment and knowledge to do so.
  13. jonr
    Joined: Sep 2008
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    Location: Great Lakes

    jonr Senior Member

    I'd look at wood, fiberglass or steel in slow moving diesel powered boats - perhaps pulling a barge/raft.
  14. congoriver
    Joined: Jun 2007
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    Location: Kinshasa

    congoriver Junior Member

    Wow, thanks to everybody, this forum generates a lot of interesting comments, rapidly. This is exceptional on the internet! So congrats to you all.

    -Now, I've looked at the wooden FAO boats, and they're fine. But their capacity is rather limited. Still, I agree that working with wood would be the least costly and most resource effective strategy (in the sense that it's available everywhere, and relatively easy to work with);

    -How large can a flat-bottom wooden boat be made, practically, and what loads can it carry?

    -Apparently the aluminium casting idea is off the table. Good. I wanted to throw it in here, just to know whether to discard or keep it in my list of options.

    -The inflatable idea might be too risky, because there's a lot of objects floating in the rivers that might easily puncture the boat.

    -I have a friend boat-builder in Kinshasa who has worked for the only boat-building facility in Congo, and he has already made large barges. He's willing to look at alternatives, but quite frankly he sticks with the big steel barge idea. In the long run, this is the way to go. But lack of capital puts this off my current list.

    -This man has also suggested just working with steel to make a 12m type boat that would cost between US$6000 and 8000 (that is: hull only); I will delve into details with him, because it seems to be rather low cost.

    -Maybe we could explore the idea of a steampunk barge based on "pirogues", which are plentiful, rather durable and very low-cost. Take several large pirogues, attach them to each other, and build a platform on them to carry the cargo...

    -Finally, perhaps most interestingly, I should look at refurbishing boats that have been abandoned; there are hundreds of them anchored in Kinshasa, rusting away

    -Any other ideas are really welcome, because I will not leave Congo before finding a really workable solution. So guys, don't get me stuck here in Congo forever!! :D

    Below, some pics of the current situation:

    Attached Files:

  15. apex1

    apex1 Guest

    ...which of course is easily available in the middle of nowhere.:mad:
    If we would´nt have to do with all the IF..s, a Helicopter could be a very sensible solution! Yes, if.......

    You are not happy when you cannot contradict................
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