Deadrize question

Discussion in 'Boat Design' started by claydog, Feb 13, 2013.

  1. claydog
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    claydog Junior Member

    A simple newbie question, when talking of deadrize in a boat hull, is the angle calculated using one side of the hull center line against a horizontal plane or the combined angle of both sides of the hull?
     
  2. michael pierzga
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    michael pierzga Senior Member

  3. claydog
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    claydog Junior Member

    Thank you.:)
     
  4. DCockey
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    DCockey Senior Member

    I've always seen the angle between horizontal and the bottom on one side used as the deadrise angle. A more precise definition is given in the ITTC Dictionary of Hydromechanics. http://ittc.sname.org/CD 2011/Dictionary/ITTC Alphabet Dictionary 2011.pdf
     
  5. tunnels

    tunnels Previous Member

  6. PAR
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    PAR Yacht Designer/Builder

    Most deadrise specifics published is at the transom.
     
  7. rxcomposite
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    rxcomposite Senior Member

    How is it defined when the keel is rounded and the chine is reversed? I have seen this somewhere but could not recall.
     
  8. Manfred.pech
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    Manfred.pech Senior Member

  9. Eric Sponberg
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    Eric Sponberg Senior Member

    The bottom surface is projected to the centerline, so the vertex of the angle is in space below the hull. If there is a lifting strake with a downward angled surface to the outside corner, the upper extent of the deadrise, at least as far as I have worked, is taken to the inside corner of the lifting strake. If the bottom is slightly rounded (usually convex--bowed outward, but can be concave--bowed inward) the deadrise is taken as the chord of the curve from centerline to inside corner of the strake (or chine if there is no strake).

    Eric
     
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  10. Leo Lazauskas
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    Leo Lazauskas Senior Member

    If you are interested in slamming, would the deadrise at midships, or further forward, be more useful?
     
  11. tom28571
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    tom28571 Senior Member

    It depends on how specific you need to be on a particular boat. A true deep V will have the deadrise equal all along the waterplane. A warped bottom normally has varying deadrise all along the waterplane, so one number will not make much sense. A monohedron will normally be warped from the stem to 60% aft of the stem and constant from there to the transom. The warped bottom will need a minimum of two stations defined, with one at the transom and another about 25% aft of the stem. The more complicated the bottom shape, the more stations will need to be defined.

    Another measure that is common is the bow half angle. This is a horizontal half angle taken at the stem along the waterline. It defines the deadrise at the bow better than a single vertical measure in that area. Unless the hull bottom has an unfair shape, these are all that are necessary for most purposes.
     

  12. rxcomposite
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    rxcomposite Senior Member

    Thanks Eric.
     
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