Description: This boilerplate spreadsheet performs planing boat powering calculations using Crouch's formula (a planing boat power prediction method).  Result graphs are automatically generated and show speed in knots versus brake horsepower required.  Because the input weight is important, this spreadsheet is setup to conveniently calculate the vessel's weight in various operational conditions.  This template also checks to see if the vessel will go it's intended range, if the installed horsepower is adequate and if the stern's quarter butt exit angle permits the input speed.

These calculations apply to planing vessels that operate at a speed length ratios, V / LWL^1/2, of 3 and greater.  Vessel's must have a aft quarter butt exit angle of 2 degrees or less for these calculations to apply.  A example drawing of this angle is provided with the calculations.

These computations are based on procedures described by Skene's Elements of Yacht Design and Dave Gerr's Propeller Handbook.  Unless otherwise noted, the calculative procedures contained in this spreadsheet are primarily adapted from Reference D.  This reference is recommended reading.  The other references contain supplemental information, but they are not required for implementation or understanding of these calculations.  This template is designed to be used with English units.

There are advantages and benefits associated with this calculative method.  First this approach saves time.  Numerous computations are automatically and quickly done on your input data.  This approach is also cost effective because the calculations are already setup for you.  As a result your research time is minimized to familiarization of concepts when necessary and not in time consuming procedural development activities.
 

Electronic Document Type:  Microsoft Excel spreadsheet           Cost: $25 US funds
 

Number of Pages: Inputs Sheet, Output Sheet, References, Figure and Notes Sheet, Use Terms Page and Instructions Page.       
               

Inputs:  

• Hull characteristics

  • Length Over All, LOA, feet (optional input)

  • Length of Waterline, LWL, feet

  • Beam on Waterline, BWL, feet (optional input)

  • Exit Angle, q_AFT, of Aft Quarter Butt, an explanatory diagram is provided on the References Sheet of this template.  This value is critical for proper hull operation and it is therefore checked in this analysis.  For complet details about this requirement refer to Pages 12 and 13 of Reference D. 

  • Constant for Crouch's formula, representative values given on outputs sheet.  Alternatively this value may be calculated based on input (speed, weight and horsepower) provided from a similar vessel.

• Weight information

  • Vessel light ship weight, pounds, the weight without any people, luggage, personal gear, provisions, stores, fluids or cargo on board

  • Weight margin on light ship, percent.  This is optional input and default values are provided.

  • Cargo weight, pounds, usually can be left at zero default value.  Examples of cargo weight are fuel drums on deck, weight of fish and ice on board.

  • Number of crew and number of passengers, integer

  • Additional equipment not included in light ship, pounds

  • Duration of voyage, days, for calculating provisions and stores, this value can often be left at it's default value which is equal to zero

  • Personal crew gear and passenger luggage, pounds, can be set to zero

  • Portions of total fluid capacities to be applied in analysis, default values that are set at 2/3 are provided, however these values may be specified as inputs.

  • Main propulsion fuel tank capacity, gallons, & fuel type (diesel or gasoline).  This is a highly recommended input value, if provided an estimate of the vessel's range will be automatically computed by this spreadsheet.

  • Potable water tank capacity, gallons

  • Sewage holding tank capacity, gallons

  • For catamaran hulls a convenient input factor is provided so as to facilitate calculation of maximum displacement speed length ratio, based on the displacement of one hull.

• Propulsion Plant Details:

  • Installed brake horsepower, if unknown guess an amount, this value can be easily changed once these calculations are done.

  • Parasitic loads, horsepower, for pumps, generators, etc.

  • Continuous operating rpm, percentage of maximum, guideline values are given on the input sheet, simply select the applicable rpm percentage

  • Shafting efficiency, ratio, guideline values are given, select appropriate value

  • Propeller efficiency, ratio, a default value is present, however another value may be substituted in the calculations

  • Vessel range required, nautical miles, optional input.  If this value is specified this spreadsheet will automatically determine if the tanks provided are adequate to make the voyage distance specified by this input.

Outputs:  

• For each of the input speeds the following is output are computed by this template:

  • Effective Horse Power, EHP

  • Brake Horse Power, BHP

  • Continuous Horsepower, BHP₀

  • Estimated Range, nautical miles, from fuel consumption rate and tank capacity

• The total operational weight is automatically computed based on light ship margin selected, cargo present, persons aboard, voyage duration which affects stores and provisions, selected operational tank capacities and gear on board.

• Supplemental values like displacement length ratio, estimated maximum possible displacement speed, estimated fuel consumption rate, speed length ratios.

• Calculative Checks are made for the following criteria:

  • Check if installed horsepower will meet the required horsepower needed for continuously operating at the speed computed.  It is important to know that If the speed involved is not a continuous operating speed this check should be ignored.  These speeds include those used for burst mode operation (operations only for short periods at this speed) and transitory speeds (when accelerating or decelerating towards a continuous operating speed).

  • Check if range requirements will be meet at the speed evaluated.  If this check is met the fuel tanks are adequately sized, if not the fuel tanks should be increased in size, but only for continuous operating speeds.

  • Check if hull bottom aft exit angle at quarter butt is appropriate for speed computed.  If this check is not met the bottom shape at the aft end of the hull should be flattened more so this speed can be reached by the hull.

Recommended Reading:

• Reference A: Doug Shryverk, article entitled "Making Sense of Engine Options," Motor Boating and Sailing, February 1977 issue. 

• Reference B: Valentine Jenkins, article entitled "Building Fast Boats that Don't Break," Professional Boatbuilder Magazine, Oct.-Nov. 1997 issue.

• Reference C: Lorne Campbell, Letter to Editor regarding article entitled "Building Fast Boats that Don't Break," by Valentine Jenkins, Professional Boatbuilder Magazine, Oct.-Nov. 1997 issue.

• Reference D: Dave Gerr, Propeller Handbook, International Marine, 1989, Camden, Maine.

• Reference E: Dave Gerr, Nature of Boats, International Marine, 1995, Camden, Maine.

• Reference F: John Teale, article entitled "Teale on Trawlers," Motor Boating and Sailing, June 1981 issue.

• Reference G: Robert P. Beebe, article entitled "Trawlers - Designing by the Numbers," Motor Boating and Sailing, January 1977 issue.

• Reference H: Alfred D. Isaacson, paper entitled "Sewage Polution Control: A Guide for the Ship Owner & Design," SNAME Marine Technology, July 1977 issue..

• Reference I: S9086-C6-STM-010/CH-096R1 "Naval Ships' Technical Manual Chapter 096 Weights & Stability," NAVSEA, 2 August 1996.

• Reference J: Detroit Allison Diesel, article entitled "Calculating Hull Speed," Motor Boating and Sailing, February 1978 issue.

• Reference K: Robert P. Beebe and James F. Leishman, Voyaging Under Power, Third Edition, International Marine, 1994, Camden, Maine.

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Minimum System Requirements: Windows 95/98/NT/2000/XP/Vista/Windows7

Sample: A sample of an output page is shown below.