Extreme Lightweight Aluminum Construction

Discussion in 'Boat Design' started by TealTiger, Aug 27, 2014.

  1. TealTiger
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    TealTiger Junior Member

    I appreciate your input TANSL; thanks.
     
    Last edited: Sep 5, 2014
  2. Emerson White
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    Emerson White Junior Member

    While thinner plate does mean more flexure smaller panels mean less. We could develop a curve (or series of curves) that described the ultimate hull strength as a function of the distribution of alloy in the framing versus the plate. Obviously on a ship of substantial size doing away with the framing all together your ship would be very weak and if you got your hull plate thickness down too thin you would similarly find yourself very wet. Now the relative high cost of framing pushes designers off of the high point on that curve towards a heavier hull that is faster and cheaper to construct, for any given strength benchmark.

    Given that we are in the middle of an explosion in the affordability and capability of CNC machinery the relative cost of producing framing has been falling. With this we should see a shift towards more extensive framing and thinner hulls than what was standard 20 years ago.

    It remains unlikely that you will see anything more substantial than single digit reductions in hull weight at any given safety factor, as a result of the correction.
     
  3. Ad Hoc
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    Ad Hoc Naval Architect

    Please explain and define what you mean by high cost and what "high point" are you referring to?

    Again, please explain what does:... more extensive framing and thinner hulls... mean? And what do you mean by a standard 20 years ago?

    Very confused?
     
  4. Emerson White
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    Emerson White Junior Member

    High cost- building lot of frames takes a lot of labor.
    High point- on the curve described, which compares the strength of the hull to the percentage of metal in the frames versus the plating, all plating and no frames will be very weak (on any large vessel) and all frames and vapor thin plating will be very weak. There are the twin low points. In between them there is a high point, a point where you have plating and framing both, and shaving weight off of one to apply to the other will result in a weaker craft.
    More extensive framing- more ring frames and more longitudinals
    Thinner hulls- hull plating that is composed of thinner pieces of metal
    Standard 20 years go- what people were building 20 years ago

    Good design is about more than just the ideal shaped pieces of material. It's also the process. Good designers 20 years ago knew how expensive and time consuming it was to make each individual framing element. With that in mind a good designer would choose to build a design with slightly fewer framing elements and slightly thicker hull than the ideal, because the extra labor saved would more than make up for the marginal reduction in strength.

    Today, there is less marginal savings to be seen from fewer frames, since it's so easy to have a 19 year old set up a computer to crank the pieces out for you via CNC plasma torch/waterjet/router/laser cutter (if you're working in wood) which is all way cheaper now than it was 20 years ago. Good designers respond to a limitation being lifted. The constellation of acceptably well designed boats now is probably closer to that ideal distribution of material in frames and in hull plating than the constellation of acceptably well designed boats was 20 years ago.
     
  5. TANSL
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    TANSL Senior Member

    Emerson White, I do not agree in general with what you say. I think you do not know the current and past situation in shipyards.
    I will point out only two ideas:
    In the early 70s (the last century) pieces were cut by CNC. Machines have changed but not the procedure. Cutting speeds are very similar and, therefore, the cost of the process is very similar. The cost of materials cut or oxidize, do not know.
    Often puting 1 mm thick plates can save a lot of manpower. As labor is more expensive than the materials it is possible that it is cheaper to increase the thickness. If we talk about the structure of minimum weight, the problem may be another, should study the specific case of each vessel.
     
  6. Emerson White
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    Emerson White Junior Member

    I did not intend to give the impression that CNC was invented in the last 20 years, only that it has gotten much much cheaper. The machines cut at comparable speeds, but the machines themselves cost much less. The software is more powerful, and the precision is much higher additionally. There is a lot less paying a highly skilled highly paid workmen to fiddle with each rib now there there was in the past. That is where the labor equation has changed.

    It still takes more time to make more welds, so the advances in automation haven't gotten us completely to the ideal distribution of material being the best design, but it's taken us closer.
     
  7. Ad Hoc
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    Ad Hoc Naval Architect

    Er not really.

    We had 1 guy, yes 1 guy, doing the CNC nesting manually, until we bought automated software. The cost of 1 guy is immaterial when you consider the other functions the person does as well as the overall cost of the boat. The automated software we bought, well, that was almost 20years ago now too...so, I think you need to go back further than 20years to make some kind of statement....but still unsure what it is you're trying to say?? Very muddled :confused:
     
  8. TANSL
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    TANSL Senior Member

    Emerson White,
    The price of the machines may be down, I do not know. What I do not know is whether the equipment depreciation is an expense or a cost. You seem to say that it is a cost, ????, I'm not an accountant.
    Current accuracy is no more at all.
    The waste produced by an automatic nesting are not appreciably lower (perhaps the opposite) than those generated with manual nesting.
    Shipbuilding low value added has shifted generally to countries low cost labor. That is the reality.
    Slightly increase the thickness means no more running meters or more welding material provided.
    I think you should get a little closer to reality of shipyards.
    Indeed, in the end I know not what you mean to us.
     
  9. Emerson White
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    Emerson White Junior Member

    How is it that every other industry is going nuts over how these advances are cutting costs for them, but the ship building industry is magically unaffected? The cost of tooling has gone way down, that has a huge impact on production. If someone had a high end system 20 years ago they may not have bothered to upgrade, but there are a lot of new players on the market who are now starting out with these machines, when they would have had to have started out doing everything by hand 20 years ago. They get to cut all of that overhead out of production costs. This includes overseas production with lower labor costs too.

    Waste is not down, in that offcut is offcut no matter what. But tolerances (accuracy) are certainly getting tighter. Machines that 20 years ago would have cost $250,000 are now making appearances in regular peoples garages and basements. The software now is much better at nesting than it was 20 years ago.

    I see yards that I do business with investing in this technology that was out of there reach decades ago, and cutting their costs, using it, and really have a hard time believing that I'm making a mistake because I'm too far removed from yards.
     

  10. TANSL
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    TANSL Senior Member

    I repeat the same things in my post # 53. Needless to say the same again every hour and a quarter.
     
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