PSModel a look inside

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Introduction

Quick Start

Quick Series
Facts

PSModel
Program

Data Input

Data Output

Importing a
Data file into
MS Excel

Main Menu

Main Screen

Printing
Graphs
and Data

Screen Colors
and Fonts

Screen
Graphs

Shortcuts

Working
with Data

Testing:

Test Sheet

Examples

19' Ski Boat

34' Sailboat

41' Utility Boat

Technical

Blade Area
Ratio

Calculating
the Cavitation
Number

Horsepower
Losses

Hull Speed

Kt Breakdown

Propeller
Geometry

Propeller Law

Wake Factors

Glossary

References

Data Input:

Before asking PS Model to calculate Horsepower, Torque, and Thrust, select the density of water that the propeller is operating in.  This is  done by selecting Tools \ Density Table from the main menu. 

Density Dlg Box

In the water Density dialog box that opens, enter the water temperature and check either Salt or Fresh Water.  If the water is brackish, check Fresh Water (brackish water usually has more fresh water near the surface).  If in doubt about the temperature, guess.  Water density, also called Rho, is not a critical parameter in the calculations, but if known increases the accuracy of Horsepower, Torque, and Thrust predictions. 

Check the Default Rho check box if the temperature or type of water is not known.  Once selected, the density value is used until changed by opening the dialog box and selecting a new density value.

Series Dlg Box, J input selected

To enter propeller data, select Series on the main menu then choose the propeller series you would like to use.  A Series Dialog Box opens, allowing values to be entered.  The following is a description of the controls (or input windows) located in the Series Dialog Box:

1) [Append Row] -- Clicking on this text allows the following selections:

-- Append the next data row to the end of the data in the Data Window.  This is the default action.

-- Insert the next data row above the highlighted or selected row in the Data Window.  If Insert is selected, [Append Row] changes to a yellow highlighted [Insert Row].

-- Edit the highlighted or selected data row in the Series Dialog Box.  After editing in the Series Dialog Box, click the Calculate button to see changes in the highlighted row.  If Edit is selected, [Append Row] changes to a yellow highlighted [Edit Row].

-- Read the highlighted or selected data row into the Series Dialog Box.  Once the data is read into the Series Dialog Box, it can be changed then Appended or Inserted into the Data Window.

2) [Change Series] -- Clicking on this text allows selecting another Series.

3) [Current Rho = ... ] -- Text shows current water density (Rho), Salt Water (SW) or Fresh Water (FW),  and water temperature used for calculations.  Clicking on this text causes the Density dialog box to open.

4) Adv. Coef., J -- If this checkbox is checked, then the Advance Coefficient (J) is input: Torque, Thrust, and Horsepower are not calculated.

5) MPH / RPM -- If this checkbox is checked then MPH and engine RPM are input; propeller RPM can also be input by setting the Gear Ratio value to 1.0.

Note: text above some of the following input windows may change to show ranges of possible input values.

6) Enter P/D -- Pitch/Diameter of the propeller:  Diameter and pitch are usually stamped on the hub of small propellers.  For example, the stamp 16 x 12 indicates a 16 inch diameter by 12 inch pitch  (P/D = 12/16 = 0.75).

7) Select Blade Number -- Allows selection of the number of propeller blades if the Series has more than one choice.

8) Enter BAR -- Blade Area Ratio of the propeller. 

9) Sigma -- Cavitation Number:  If the Series was tested at several different Cavitation Numbers, this window allows Cavitation Number input.  If not, this window is grayed.

10) Select Cupping -- If the Series supports cupping, this input window allows selection of the amount of cupping.  Choices may include None, Light, Medium, Heavy.

11) Enter J -- If the Adv. Coef. J checkbox is checked, this window is active and a  J value has to be entered.  Kt, Kq, and Efficiency values are interpolated from the propeller curves at this J value and displayed in the Data Window after the Calculate button is clicked or the Return Key pressed.

Series Dlg Box, MPH input selected

12) Depth of Prop -- Enter the depth of the propeller hub below the water surface, in feet; if not know, guess.

13) Wake Ftr. -- Enter the Wake Factor or (1-w).

14) Propeller Dia. -- Enter the propeller diameter in feet.

15) Gr. Ratio -- Gear Ratio is equal to the engine RPM divided by the propeller RPM.  For example, an engine that turns at 4000 RPM while the propeller rotates at 2000 RPM has a gear ratio of 2.0 (4000/2000 = 2.0).  For an outboard engine or an inboard-outboard (I/O) drive, the gear ratio is usually the same as the gear ratio of the lower gear pod.  This value can be obtained from engine literature, a local retailer, or the manufacturer.  For inboard engine installations, the gear ratio is the same as the reduction gear or transmission ratio.  The manufacturer's name, model, and serial number should be on the reduction gear case.  Write this information down, then check on the Internet or contact the manufacturer\retailer to determine the gear ratio.   If the propeller turns at the same RPM as the engine, the gear ratio is 1.0.     

16) Boat MPH -- The speed in Miles Per Hour recorded during testing or trials.

17) Eng. RPM --  The engine Revolutions Per Minute associated with the Boat MPH value entered.  If propeller RPM is entered, the Gr. Ratio entry should be 1.0.

18) Calculate --  Clicking this button or pressing the Return Key causes PSModel to calculate data, and to add or modify (if Editing) a data row in the Data Window.