Are small ships a thing of the past?

Discussion in 'All Things Boats & Boating' started by El_Guero, Oct 2, 2013.

  1. jehardiman
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    jehardiman Senior Member

    Yes, I worked there 1985 til closure in 1993. I had a SecNav transfer to MINSY from Norfolk to do a project, which was rare at the time. Up here at PSNS is the longest I've ever been in one place (93-present).
     
  2. heatedsoul
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    heatedsoul New Member

    Smaller ships must become faster in order to compete with the biggies. Since they cannot possibly compete with efficiencies of cost per load etc.. So around 40 knots should do the trick, they will either try to keep up or die trying... Ofcourse smaller ships also have better maneuverability they can take urgent pickups and move around easily and with much better flexibility.
     
  3. jehardiman
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    jehardiman Senior Member

    Nope, can't be done. The only reason to be faster is if the cargo (i.e. people, troops, fresh fish or fruit) has a time limit, and then it is better to fly it. Take a look at a modern Gabrielli - von Kármán line.
     

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  4. heatedsoul
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    heatedsoul New Member

    Fruits and vegetables are a very delicate commodity, and if speeds can be improved even slightly a few days can be cut off. For example here in UAE most of the produce is imported since there is no viable natural soil all desert.

    Now if someone is going to import a few tonnes of produce from lets say Bangladesh where rates are very low as it is much easily available. Normally it would take around 2 weeks and if you are to keep rates competitive with say India you are not going to send it by plane?! The fuel cost alone will be tremendous instead you stick it with preservatives and ship it still 25% rot. On the other hand if a smooth 30 knot or even 28 knot cruise can be maintained this will significantly bolster you with higher margins and keep rates lower than the planes. In the growing world such is the case..

    And you get what you ordered for in under a week this is near to the plane which also take approx 3 days to arrive and offload go through customs etc... Also small ships are usually good for transporting cars, to other countries I have seen this countless of times people don't like waiting for there cars.

    Large ships can have all the petroleum shipment as that is not time sensitive. There is a huge time sensitive market which you might have overlooked therefore I vote small ships to stay..
     
  5. jehardiman
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    jehardiman Senior Member

    Yes, but as you can see from the Gabrielli - von Kármán figure, it takes more energy (i.e. fuel cost) to transport them by small ship than it does to fly them. Since #2 diesel is about the same cost as Jet-A (NYC 2.95 $/gal vs Gulf 2.88 $/gal) it is actually cheaper (for fuel) to fly.
     
  6. rwatson
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    rwatson Senior Member

    Hang on - that doesnt compute.

    Sure, the cost per gallon is similar, but most of the jet fuel is keeping the plane n the air - while a boat floats.

    You have to provide the distance per tonne per gallon to make sense of that.
     
  7. jehardiman
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    jehardiman Senior Member

    Sigh....what do you think the Gabrielli - von Kármán graph is all about.

    Notice the line. That line is where the same amount of energy is required to deliver 1 gram or kilo or tonne over any distance. Above the line it costs more energy (i.e. high speed ship or truck), below the line it costs less energy (i.e. supertanker or modern efficient commercial air). The graph is in terms of delivered power, so if you want to get down to actual pennies, you would need to have the actual thermal efficiency of the prime movers (~46% for a medium speed diesel and ~55% for a high bypass turbofan) and the heating value of the fuels (LHV ~18,300 BTU/lb for diesel and 18,500 for Jet-A)
     
  8. gonzo
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    gonzo Senior Member

    I noticed there is no data for trucks.
     
  9. rwatson
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    rwatson Senior Member

    Sigh yourself ....

    You cant have been talking about the Graph.

    To think that its cheaper to send things by plane than small ships from that graph is inaccurate. Its not about cost of transport - just efficiency for fuel by time.

    Also, Fuel isn't the only cost factor in transport - there is capital infrastructure including docking or airport costs, purchase price and longevity of transport units, running costs etc etc

    That graph isnt about total cost of moving stuff ,just relative efficiency of energy per unit by transport type.

    Take a look at this graph, which DOES take into account those factors - based on real costs.

    http://richardtorian.blogspot.com.au/2012/01/cost-per-ton-mile-for-four-shipping.html
     

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  10. jehardiman
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    jehardiman Senior Member

    I haven't found a Gabrielli - von Kármán graph with tractor-trailers on it and considering that the original work was done in 1950, long distance trucking were not a big factor then (Once in school I had to laugh out loud when a fellow student pointed out that the US Interstates followed the main rail lines so railroads were redundent). Other data I have seen (hp/ton-mile) puts semi's below busses and automobiles close to the line, but still above it. Some data I've seen shows a modern Class 8 truck has been stated to be 130-275 ton-mile/gal while rail is given as 400-450 ton-mile/gal (and both would be using diesel). There are ways to up this for trucks, i.e. turn them into road trains; more trailers, streamlining, seals between trailers, etc.

    http://www.treehugger.com/cars/rail-versus-trucking-whos-the-greenest-freight-carrier.html
     

  11. jehardiman
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    jehardiman Senior Member

    I suggest you re-read post #20. I was only discussing fuel, not taxiation, regulation, infrastructure, or economic policy which drives a fair amount of total transpost cost. I only showed that from economy in energy that the fuel cost were cheaper to transport by air that by high speed vessel.

    You may be correct that other factors make the total cost higher, but that is a social engineering issue, not a technical one. Indeed, if the infrastructure cost of a single transport cycle is fixed, then that drives the transport to become larger, not faster. Which I believe is the whole point of this thread as well as being born out in the capacity growth of ships and aircraft in recent years.
     
    Last edited: Jan 26, 2014
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