Lose extreme weight in boats from 1990?

Discussion in 'Boatbuilding' started by George Lager, Jan 15, 2020.

  1. George Lager
    Joined: Jan 2020
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    Location: Spain

    George Lager New Member

    Hi

    Thinking of buying a 10-12 meter fiberglas motor boat from 1988-90 with a very big engine like 2 x 300 hk and almost 10 tons (10 000kg) that has NOT been renovated except the engines. Similar modern boats have almost half of the weight.

    Because of the extreme fuel consumption (like 2 x 35L/h) at 25 knots cruising speed, and because it’s old I have some thoughts of making 100% completely new interior from the hull and up.

    My plans are to use modern material and lose substantially weight which makes the boat substantially faster and substantially more fuel efficient.

    1. This is a very stupid question but where do all the weight on those boats come from? (-thick construction wood, thick fiberglas, kitchen countertop in stone and so on and so on?)
    2. It would be interesting to hear any thoughts if it’s possible to loose weight on an old motor boat?


    One boat example below:

    Cranchi mediterranee 40
    10 tons
    Cranchi Med https://www.boat24.com/se/motorbatar/cranchi/cranchi-med/detail/419546/
     
  2. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    And how much weight do you imagine you can lose ? I doubt that you could strip out enough "unnecessary" weight to make any appreciable difference to your fuel consumption. Do you have an example of a similar size modern boat that is half the weight ?
     
  3. BrissoDamo
    Joined: Dec 2019
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    Location: Brisbane

    BrissoDamo Junior Member

    Someone that wants a 10/12m boat and wants to spend a truckload of money to save 50lts/hr :rolleyes:

    Just kick it back to 6knts and you've achieved the requirement!
     
    fallguy likes this.
  4. BrissoDamo
    Joined: Dec 2019
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    Location: Brisbane

    BrissoDamo Junior Member

    throw that TV away first thing you do!
     
  5. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    You can't achieve a weight loss goal and if you did; the boat would float above her lines and possibly perform badly.
     
  6. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    A stone benchtop ? Seems a bit much.
     
  7. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    One thing you can do is install a fuel meter. This would help you find the sweet spot.

    For a planing hull; it is just off the hump generally, so you can also go by feel. Take it up on plane and back it off so she doesn't sit down.

    Most likely, you are running too fast.
     

  8. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    Cranchi boats are not really heavy for a cruiser. If you want light weight, a better choice would be something like a Fountain, Wellcraft Cigarrette or other performance boat with minimal interior.
     
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