100 feet aluminium semi plaining hull

Discussion in 'Boat Design' started by VexCore, Aug 30, 2014.

  1. Rastapop
    Joined: Mar 2014
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    Rastapop Naval Architect

    I don't like your chances of success VexCore, you're out of your depth. If you have no choice but to carry on the following is the best advice I've seen in this thread:

    Find a similar, successful design and use it as much as possible to generate your own GA.
     
  2. daiquiri
    Joined: May 2004
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    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    Vex, with a boss like that you are in deep trouble. Actually, the whole design office / yard you work at is in deep trouble. :eek:
     
  3. Tad
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    Tad Boat Designer

    The first step is as others have mentioned, you must develop a decent sized data base of comparables. Google long range patrol boats, coast guard cutters, crew boats, and motor yachts. Record all the data you can find, length, beam, draft, displacement light, fully loaded, GRT, power, fuel, speeds cruising and top, etc.

    Once you have some data points you can start to develop a weight factor. This will be length x beam x depth (main deck to keel) x w factor = displacement. Be careful about the consumable weights, best to separate them out. Once you figure out what your weight factor is you can estimate the weight of your projected vessel. Once you have the weight we can figure out power required and fuel consumption.

    Your GA does not have to float so don't worry about that, you just need a basic envelope. To do this in 2 weeks would be pushing it for someone with considerable experience and the database in hand. Your best bet will be to follow something already published. Think about centering heavier weights just aft of midships, and look at the volume required for the tankage.
     
  4. VexCore
    Joined: Aug 2014
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    VexCore Junior Member

    Ok thanks for the advice. I will try to do that.
     
  5. Tad
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    Tad Boat Designer

  6. VexCore
    Joined: Aug 2014
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    VexCore Junior Member

  7. VexCore
    Joined: Aug 2014
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    VexCore Junior Member

    Can you guys give me an approximate total weight for the specs i have? Or otherwise tell me how i can get it?
     
  8. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    It is very easy, just add the various items that make up the weight. Furthermore, if you calculate the moments about the coordinate axes, you'll also get the center of gravity of the whole.
     
  9. johnhazel
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    johnhazel Senior Member

  10. AndySGray
    Joined: Jun 2014
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    AndySGray Senior Member

    I am thinking the purpose is blindingly obvious - it is a great test for a junior engineer, and is much less about the challenge than about how Vexcore handles it, and, more importantly, what he learns along the way.

    50,000 litres of diesel would weigh about 42 (metric) tons...


    Design spec reminded me of ;-

    http://www.virginatlanticchallenger2.com/About/Boat-Spec

    but even those guys had only 12.5 tons onboard - refuelling half way was one of the reasons they did not get the blue riband.

    so I guess you ought to be coming to conclusions like "they want a transatlantic range" ?

    Show your working/thinking throughout and give plenty of examples, good and bad, explaining why the former is more applicable than the latter...
     
  11. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    Indeed. Not a small amount. As I noted here too.
     

  12. Village_Idiot
    Joined: Oct 2007
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    Village_Idiot Senior Member

    I've not seen any reference in the vessel requirements as to how seaworthy she needed to be. If she is only to be used in relatively calm waters, she can be flat-bottomed (the most efficient planing design).

    As a data point, I've personally run a 26-foot aluminum landing craft (72-inch flat bottom, 96-inch beam), carrying 3,000lbs+ of cargo, getting on full plane with a 150hp outboard (Merc four-stroke). Correct weight distribution helps a lot.
     
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