Wave-peircing & Axe bows, how about Saw bows?

Discussion in 'Boat Design' started by Squidly-Diddly, Aug 30, 2020.

  1. Squidly-Diddly
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    Squidly-Diddly Senior Member

    20200830_154333[1].jpg Wave bow.jpg
    Inspired by this interesting Italian ship with a Wave Piercing bow TOPPED by conventional spray defecting and nose dive arresting bow.

    Saw Bow theory is you'd get most of the benefits of Wave Piercing, throughout the range of bow going into wave, but also most of the benefits of a final spray defecting upper bow. Theory is also that spray and bow wave generated by teeth would be proportional to the (not as big at conventional flared bow) tooth above ability to mitigate. In top flared bow example, could also reduce loading spikes a typical flared bow generates when hitting a wave, and reduce popping up and thus reduce porpoising.

    My crude drawing tries to show how the indents would recess into the hull. Figure they would be smoothed and hydro-streamlined there the light pencil lines on are the field of the hulls. Size of teeth, number of teeth, angles, etc are all just my first best guess. Figure things would need to be adjusted to finer entry from the drawing's red indicator lines.

    Would this work without creating prohibitive new drag? Would it work at all? Would it work but only create lots of drag in certain rough conditions where its working would be worth it?
    Could it become the latest craze in boat design, like putting a row of six big outboards on your status symbol powerboat? "Mr Customer, just like lumber mills don't use axes but instead use SAWS, this new bow SAWS the waves in more manageable smaller pieces".

    Which one of the 4 examples makes most and least sense?
     
    Last edited: Aug 30, 2020
  2. Will Gilmore
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    Will Gilmore Senior Member

    What are the advantages over the bulb bow? There is no WL extending effect, but otherwise, looks very similar.
    [​IMG]

    -Will (Dragonfly)
     
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  3. bajansailor
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    bajansailor Marine Surveyor

  4. Squidly-Diddly
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    Squidly-Diddly Senior Member

    apples and oranges

    Bulb bow is to decrease drag by canceling bow wave with bulb wave when cruising on calm waters at specific speed. Doesn't function if ocean waves of any consequence or if ship's speed AND water line not within narrow limits.

    Saw bow is about finding happy-medium between spray defection and wave piercing across wide range of wave heights and boat speeds, rather than optimized for laboratory conditions for a large ship.

    Note the Italian warship in 2nd pic doesn't have a bulb but "wave piercing". My guess is because WP works in wide range of waves and speeds. Bulbs are good for tankers, cargo carriers, nuclear powered aircraft carriers and other ships big enough that 95% of time waves are small compared to bow size and ship travels at same speed 95% of time.
     
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  5. bhnautika
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    bhnautika Senior Member

  6. Will Gilmore
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    Will Gilmore Senior Member

    I like how they title the article, as if real swans have detachable heads.

    -Will (Dragonfly)
     
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  7. Squidly-Diddly
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    Squidly-Diddly Senior Member

    ay yai yai, it looks like it has a bow 'viewing porch' above the wave piercing bow.

    My Saw Bow concept is all about mitigating waves AND spray where it would be encountering max size waves on regular basis.
     

  8. cracked_ribs
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    cracked_ribs Junior Member

    That is a fantastic take on that article. Complete with detachable head, just like you'd expect on a real swan!

    I mean technically every head is sort of detachable, depending on your available tools and skillset, but...I still don't usually think of myself as having a detachable head, no matter how attractive Robespierre might have found my neck. Swans do have a very convenient arrangement for the guillotine, though.
     
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