Constant deep V deadrise. Powering up angle.

Discussion in 'Powerboats' started by cyclops2, Sep 18, 2011.

  1. cyclops2
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    cyclops2 Senior Member

    Thank you Daiquiri.

    Your statement about slender boats having narrower " hump" speed ranges is exactly what I needed to know.

    My 19' Chapperall is a 5.0 L V 8 of 200 hp 18.5' WL 8' beam.
    Fantastic safe, load carrying, 6 people in 6' waves. Ran it at maximum safe trim out for 5 miles. However. It has a MASSIVE wide "hump" speed range.
    It is impossible to run with the old Garwood woodies at their normal cruising speeds. I either am a high speed tugboat or a minimum on plane speed that is constantly leaving them behind.

    That problem of modern hull shapes is why I have a need to build a dedicated deep V hull with a vertical, slender, bow.

    I have the time, money & other boatbuilders to build the boat to look like a 1918 Ditchburn above the waterline.
    Is there a optimum % point from the stern of that the V should begin to fold inward to the vertical bow.

    The boat is designed as a 2 seat Gentlemans Racer with rear seats only.
    Errors on this post will occur due to my medications.

    Thank you.
    Cyclops2
     
  2. cyclops2
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    cyclops2 Senior Member

    Is there a preferred thru the hull, shaft angle for deep V boats ?
     
  3. daiquiri
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    daiquiri Engineering and Design

    Take a look at these graphs posted by Ad Hoc in this thread: http://www.boatdesign.net/forums/hy...laning-hull-low-speed-35799-3.html#post426942
    The first graph, in particular, shows the importance of slenderness ratio for the reduction of resistance hump.

    I'm affraid there is no universal answer to this question. Hull design will depend on speed, LCG position, power, seakeeping and maneuverability requirements, slenderness ratio - among other things.
    I could tell you to keep at least the aft 45-50% portion of the buttocks flat, but it should not be taken as a general rule.

    Flatter is always better, but no firm rules there either.
     
  4. cyclops2
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    cyclops2 Senior Member

    Thank you daiquiri.

    Since I am not a naval designer. I will do it the possibly hopeless way. Seat of the pants & best logical combination.

    Parameters desired.
    Cut ( pierce ) thru the waves.
    Lean up to 30 degrees in a panic, evasive, tight turn at full speed.
    Maximum speed of 50 mph. GPS.
    Weight of 1,000# to a maximum of 1,500#.

    I will be going to see a 23' Hunt designed deep V boat. I hope it has the ability of my first 2 parameters required. Copying a winner is always more sucessfull in any new projects.

    Rich
     
  5. daiquiri
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    daiquiri Engineering and Design

    Will be quite difficult to achieve, imho. The engine alone will be around 700-800 lbs.
    Cheers
     
  6. m3mm0s rib
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    m3mm0s rib Senior Member

    My opinion. can a boat with deep V to develop high speed but must be to have lee-boards that will lift out of the water. Like boats with short V without lee-boards can not develop the same speed
     
  7. PAR
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    PAR Yacht Designer/Builder

    m3mm0s rib, I'm sure it's just a translation issue, but what you've posted doesn't make any sense.
     
  8. m3mm0s rib
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    m3mm0s rib Senior Member

    What do you mean it makes no sense.
     
  9. IMP-ish
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    IMP-ish powerboater

    Post a picture of what you mean when you say "lee-boards".
    That is not translating right.
     
  10. Mr Efficiency
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    Mr Efficiency Senior Member

    He's likely talking about strakes or risers that create extra lift.
     
  11. daiquiri
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    daiquiri Engineering and Design

    LOL !!! :D :D :D
     
  12. daiquiri
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    daiquiri Engineering and Design

  13. Mr Efficiency
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    Mr Efficiency Senior Member

    "Constant deadrise deep-vee" ? Maybe he is alluding to trim tabs, it's a thread for people who like guessing games.
     
  14. m3mm0s rib
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    m3mm0s rib Senior Member

    The lines you see along my boat called lee boards.How do you call it in your language?
     

    Attached Files:


  15. daiquiri
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    daiquiri Engineering and Design

    I don't know how did you arrive to translate that Greek word (whatever it is) into "lee board" in English, but those things in the pic are for sure not leeboards. The stuff in the pic are called "strakes" in English.

    These are leeboards: http://www.leeboards.com/
     
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