Hydrostatics for One Waterline (U. S. A. Units)

Description: This spreadsheet automatically computes hydrostatics characteristics for one waterline.  If the waterline is level this data may be used as an input source for the vessel's "Curves of Form."   If the waterline is not level (and/or includes sag or hog) this template can also be used.  It is ideal for cases where the vessel exceeds the one percent allowable trim at a stability test (inclining experiment).
     This spreadsheet combines the three Hawaii Marine Templates into one. These are the Displacement Sheet (Product Disp-e), the Waterplane Sheet (Product WP-e) and the Waterline Input/Output Sheet (Product WL-IO-e).  This combination facilitates faster and easier computation for a given waterline.  These combined case calculations are more automated, significantly minimizing entry input time.

Electronic Document Type:  Microsoft Excel spreadsheet           Cost: $15.00 US funds

Number of Pages: single sheet                        

Inputs:  

• The following dimensional and property input data are required on Sheet 1:

  • The vessel name, project description, client name and calculation date.

  • Define the WL condition to be evaluated by entering the forward draft (T_FWD), midships draft (T_MID), aft draft (T_AFT) and maximum draft (T).

  • Then enter in the waterline length (LWL), waterline beam (BWL), station spacing (s) and maximum hull cross sectional area (SA) below the waterline.

  • Then enter in the specific gravity (S) of the water that the vessel is in. If this is in regard to a stability test enter the average specific gravity taken at the time of stability test.

• The following sectional area dimensional input data are required on Sheet 2:

  • Enter in half the hull's cross sectional area (SA) for each station.   Note the vessel must be divided into ten stations (this yields eleven cross sectional areas) with a half station at each end (this adds two more cross sectional areas).  This means a total of thirteen input cross sectional areas are required.  Bonjean Curves may be used to quickly determine the cross sectional areas.  They also may be determined by calculation, a CAD program or some other means.

  • For each cross sectional area the vertical distance from the Baseline to the centroid of each cross sectional area is required.  For the template this value is called a vca and thirteen of these values are required.  These values may determined using a Lines Drawing, through a CAD program or through some other acceptable means.

  • For vessel's with overhang; add in the aft overhang volume as well as the longitudinal (from Station 5) and vertical centers (from Baseline) of buoyancy for this volume.  This data is often needed because many vessels that end their LBP (in the Lines Drawing) at the center of the rudder post.  This correction compensates for the volume that is displaced aft of the rudder post, which may be substantial.

• The following water plane dimensional input data are required on Sheet 3:

  • Enter in half beams (y) for each station.   Note the vessel must be divided into ten stations (this yields eleven half beams) with a half station at each end (this adds two more half beams).  This means a total of thirteen input cross half beams are required. 

  • For vessel's with overhang; add in the aft overhang waterplane surface area as well as the longitudinal center of area for this surface from Station 5.  The longitudinal and transverse moments of inertia for this overhang area are also required.  This data is often needed because many vessels that end their LBP (in the Lines Drawing) at the center of the rudder post.  This correction compensates for the area that is aft of the rudder post, which may be substantial.

Outputs:  

• The automatic output generated are: from Sheet 2 -displaced volume (V), displacement (W), longitudinal center of buoyancy (LCB), vertical center of buoyancy (VCB), from Sheet 3 - waterplane area (AWP), longitudinal center of floatation (LCF), longitudinal moment of inertia about the LCF (ILCF), transverse moment of inertia (IT), and from Sheet 1 - tons per Inch (TPI), longitudinal metacentric radius (BML), transverse metacentric radius (BMT), distance from keel to longitudinal metacenter (KML), distance from keel to transverse metacenter (KMT), bock coefficient (CB), prismatic coefficient (CP), and miship's coefficient (CM).

Suggested Reading (see References page for more detail on these items):

• Microsoft Excel user manuals

• Principles of Naval Architecture, Edward V. Lewis, SNAME

• Basic Ship Theory, Rawson & Tupper

• Applied Naval Architecture, Robert B. Zubaly

• Introduction to Naval Architecture, E. C. Tupper

• Introduction to Naval Architecture, Thomas Gillmer and Bruce Johnson

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Minimum System Requirements: Windows 95/98/NT/2000/XP/Vista/Windows7/later Windows OSs including Windows 11

Sample: A sample document is shown below.