Hydro Technical Features

Hydrostatics and intact stability

  • Interactive interface
  • Easy access from MultiSurf: go to View/ Offsets, then click Tools/ Hydro

Fixed position hydrostatics

Place the model in the water in any position and orientation; the program calculates all the integral quantities of interest to the naval architect.

Equilibrated hydrostatics

An automatic balancing algorithm will bring the model into a position of hydrostatic equilibrium under whatever conditions of heel and loading you specify — you can specify trim free or fixed when bringing the model to equilibrium.

Graphs and tabulated data

View and print graphs and tabulated data. Multicolored graphs can be marked with symbols for monocolor printing

  • Curves of Form
  • Stability Curves
  • Section Area Curve

Bonjean and dynamic stability (righting energy) data included.

Special calculations

  • Ballast weight and CG
  • ZCG from RMPD
  • Sink and Trim from Freeboards
  • Sink and Trim from Drafts

Critical points

You can name and key in the coordinates of up to six specific points whose heights above or below the waterplane will be reported in each condition.


  • English, metric, or other
  • Conversion between units or just label change

Interactive tabs

  • Offsets View (graphic display of vessel position in relation to waterplane, CG and critical points)
  • Hydrostatics View (text display of hydrostatics report)
  • Section Data (tabulated report of section data)

Change vessel position using sliders and/or numerical fields.

Change data in either the Offsets or Hydrostatics View and it is automatically updated in the other views as well as in the Section data table.

Color control

  • Port and starboard sides of the vessel
  • Center of gravity mark
  • Critical point marks
  • Graph backgrounds

Toolbar and keyboard shortcuts

Save Setup

How to... Examples

  • Position a boat to its design waterline
  • Get upright hydrostatics for an existing boat for which freeboards have been measured
  • Get upright hydrostatics for an existing boat for which drafts have been measured
  • Get total enclosed volume of boat
  • Get total skin area of hull and appendages
  • Get upright hydrostatics for a boat whose weight and center of gravity are known
  • Check the effect of adding a weigt at a particular location

Hydrostatic output quantities

  • Position: Attitude of vessel in terms of Sink, Heel, and Trim.
  • Center of Gravity (CG): X,Y,Z of CG.
  • Coefficients: Waterplane, prismatic, block, midsection, and displacement/length ratio.
  • Displacement: Volume, weight of displaced volume, and longitudinal center of buoyancy.
  • Dimensions: Waterline (WL) length, WL forward X, WL aft X, WL beam, draft.
  • Center of Buoyancy (CB): X,Y,Z of CB.
  • Waterplane (WP): WP area, and center of flotation.
  • Specific Weight: Specific weight of fluid in which model is being immersed (typically sea water or fresh water). For ballast and CG calculations, value is specific weight of ballast material (e.g. lead).
  • Wetted Surface (WS): WS area and the center of WS area.
  • Initial Stability: Calculated when heel is zero. Includes: moment of inertia (of the waterplane), metacentric height, and righting moment per degree (RMPD).
  • Heeled Stability: Calculated with trim free or trim fixed when heel is nonzero. Includes: transverse and longitudinal righting arms and moments.
  • Critical Points: The calculated heights relative to the waterplane.

Documentation and on-line help

  • Comprehensive, illustrated manual
  • “How to” examples
  • On-line help duplicates all the textual information and examples in the manuals

System requirements

Since Hydro is a MultiSurf utility, the system requirements are those for MultiSurf:

  • PC 64 bit system
  • Windows 7, 8, 10