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

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### claydogJunior 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?

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### michael pierzgaSenior Member

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### claydogJunior Member

Thank you.

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### DCockeySenior 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

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### PARYacht Designer/Builder

Most deadrise specifics published is at the transom.

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### rxcompositeSenior Member

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

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### Manfred.pechSenior Member

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### Eric SponbergSenior 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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### Leo LazauskasSenior Member

If you are interested in slamming, would the deadrise at midships, or further forward, be more useful?

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### tom28571Senior 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.

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### rxcompositeSenior Member

Thanks Eric.

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