Deep V-bottom

Discussion in 'Powerboats' started by HJS, Dec 20, 2009.

  1. HJS
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    HJS Member

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  2. PAR
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    PAR Yacht Designer/Builder

    Almost anything is going to be more efficient then a deep V hull form.
     
  3. Yellowjacket
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    Yellowjacket Senior Member

    The a deep v obviously gives a better ride than a flatter hull of similar beam, but it also makes sense that if you narrow the beam you are going to get less slamming and therefore improve the ride, and the narrower beam but flatter hull could be more efficient than the fatter deeper v.

    What this says is that the payoff in efficiency is there for the narrower, flatter hull. We don't often see an "apples to apples" comparison of things like this. This is why boats are interesting, lots of ways to skin the cat so to speak.

    What is also not mentioned is that the narrower boat is going to have less interior room, so nothing is for free.
     
  4. PAR
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    PAR Yacht Designer/Builder

    The premise I read was efficiency not comfort. Comfort is a much more complex equation. Flat bottoms are the second most efficient hull form in terms of efficiency. Of course given beam, available power and power to weight remain the same.
     
  5. Tad
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    Tad Boat Designer

    Which is exactly why I used the form in my WoodenBoat/ProBoat Design Challenge entry....... This form is fine for a mostly empty hull, for a heavily loaded boat you need to be careful you don't run out of planing surface at too low a speed.

    View attachment SS185Lines.dwf
     
  6. HJS
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    HJS Member

    Soft ride with a slim bottom

    The boats have, as mentioned, the same volume and weight.
    The difference is the length, deadrise and beam, especially the chine beam, 1.95 respective 1.34 meters.
    The chine beam makes the different in vertical acceleration more than the deadrise.

    More in my contribution to the PBB design challenge, Victoria


    HJS
     

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  7. kengrome
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    kengrome Senior Member

    What is the most efficient hull form?
     
  8. fcfc
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    fcfc Senior Member

    Efficiency, but for what purpose ?

    What you gained by reducing chine beam has been lost in stability. And the lengthening of the hull is detrimental to parking the boat and the trailer.

    Is it worth it ?
     
  9. HJS
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    HJS Member

    The purpose of a more efficient boat.

    An efficient boat needs a smaller engine, uses less fuel, less emissions and therefore a cleaner world to live in. Furthermore, my approach is more seaworthy than a deep V-bottom.
    This is the positive purpose of optimizing my crafts.

    Stability is the same as on a normal boat with 17-degree V-bottom.
    This has been both calculated and checked on the boats in the water.

    That the boat is 10% longer and 10% slimmer than the normal boat hardly affects manageability on a trailer. In addition, the boat is intended to be used primarily in water and not on land.

    As I see it, I have not lost anything of what is important to me.
    Therefore, I see that the result is worth all the work behind these designs.

    I do not know what calculations and practical experience you are basing your opinion on that my boat would be unstable and unpractical. I look forward to concrete calculations and descriptions.

    js

    www.sassdesign.net
     
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  10. Tad
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    Tad Boat Designer

    JS.....

    Your Victoria comparison seems to indicate differences of much more than 10%, both in length and chine beam. What are we missing? Are you meaning that the waterline beam difference is 10%?
     
  11. HJS
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    HJS Member

    I am referring to the report in the first post of this thread
    not the Victoria design

    js
     
  12. gonzo
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    gonzo Senior Member

    The graphs show boats of different displacement. The beam is the same, but the cat has the same beam on deck. The added waterline beams are much less. It is a misleading claim typical of bs sales brochures.
     
  13. HJS
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    HJS Member

    The graphs in the first post shows two boats with the same displacement 1200 kg and the same volume around 8 m^3 and about the same stability.
    Otherwise the comparison would be meaningless.

    js
     
  14. gonzo
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    gonzo Senior Member

    Volume and displacement are not related. It says that the graph is dimensionless. The narrow boat has lifting or dual chines, something not explained properly. It is not a valid comparison.
     

  15. HJS
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    HJS Member

    Latest testrun

    This is a powerboat concept with high efficiency and excellent seaworthiness of the entire speed range. The new slim and flat bottom requires 15 - 25% less power than the deep V-bottom. The new boat has equal vertical accelerations at 29 knots as the deep-V boat at 20 knots in all sea conditions. These figures are scientific mesured by students at Marina System Kungliga Tekniska Högskolan in Stockholm

    http://www.youtube.com/watch?v=cXDfQqxJ_pM
     
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