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    Design Controls in VBDP Version 8   

 

  About VBDP | VBDP© Features | Design Inputs | How it Works | Perf Reports & Graphics | Testimonials | Magazine Reviews | Upgrades | Order  
  Here's the kind of (70 ) Design controls you have available with VBDP© to help optimize your tunnel hull performance…There's a lot here, and still more in the program! [Screen Samples]
 
1.  Design Data Input 2. Weight & Measure Input Four full, user-friendly input screens, with over 70 input variables, for very precise control of your design and setup. Excellent for any size of boat - from Recreational Vees to Vee racing hulls and from modified Vees to 60ft offshore Vee hulls and utility vees - and even RC model vee hulls. Size, speed and setup conditions all accounted for by the software.
3.  Boat Setup Input 4. Design Detail Input
Design for: Multiple Step design Vee Pad designs Hull design dimensions Deck & cowling/cockpit design Acceleration mode
     Spray rails          Deck design Complex Weight distributions Drive Unit design Aerofoil design selection Altitude & water type
 
 
1. Design Data Input      [see Input Screen Sample
NAME UNITS DESCRIPTION                                                                                                                      
Hull Design

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Vee Deck Height (In) Height of the deck at the highest location, measured from the deck surface to the (virtual) water surface.
Non-Vee Width (In) (not normally changed from Default value when using VBDP©)
Vee AeroChord (Ft) length of the deck surface or "wing"/aerofoil, measured from the leading (front) edge of the deck to the trailing (aftmost) edge.(not normally changed from Default value when using VBDP©)
Vee AeroThkness (In) (not normally changed from Default value when using VBDP©)
Vee Type (select) Select whether design has a Symmetrical or Assymetrical sponson shapes
Hull Wet Length (ft) Maximum wetted Length of running surfaces. Must be less than BoatLength and greater than zero. Default is BoatLength. Consider using only the length portion of vee planing surfaces that are ‘flat’ or are likely to contribute to Lift in normal applications.
Vee 1/2 Width (In) Width of 1/2 of vee section surfaces (bottoms), measured from effective sheer (inside) to effective chine (outside).
Vee Deadrise (Deg) Angle of vee running surfaces, measured from sheer to chine.
Deck Width (In) Width of the hull deck at the widest point.
Steps  

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Step Select (Selection) Select the use of vee bottom design – no steps, one step, two steps
Step Length1 (Ft) Length of first (or single) step fore of transom (in feet), must be less than boat length
Step Length2 (Ft) Length of second step fore of first step (in feet), StepLength1 StepLength2 must be less than boat length
Step Height (Ft) Height of STEP in sponson running surface, if one (or two) exist(s).
Vee Pad  

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VeePadSelect (Selection) Select whether the hull design includes a Pad-Vee style CENTERPAD lifting surface (Yes/No)
PadLength (Ft) When it exists, the length of Pad-Vee style CENTER PAD lifting surface, located centrally in the hull.
PadWidth (In) Overall width of Pad-Vee style CENTERPAD, from chine to chine.
PadHeight (In) Height difference between Vee planing surfaces and Pad-Vee style CENTERPAD, positive means CENTREPAD is higher from waterline than Vee planing surfaces. (Most Vee-Pad designs have the VeePad at a slightly incrementally “lower” height as compared to the Vee planing surfaces)
PadDeadrise (Deg) Angle of CENTREPAD running surfaces (bottoms), measured from keel to chine.
PadWAngle (Deg) Incremental VeePad Angle of attack relative to Vee planing surfaces ( /-). This feature is used when the angle of incidence of the Pad-Vee style CENTERPAD running surface is different than the angle of incidence for the vee planing surfaces. (Some Vee-Pad designs have the VeePad at a slightly incrementally “higher” angle of incidence as compared to the Vee planing surfaces)
 
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  2. Weight & Measure Input      [see Input Screen Sample
NAME UNITS DESCRIPTION                                                                                                                        
Lengths  

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Boatlength (ft) Overall length of hull, measured from foremost deck tip to aftmost deck or vee planing surface point.
BoatCG (%) Location of static CG of boat only, measured as a % of total BoatLength ahead of transom (%). Default is 45% (0.45) of total BoatLength
Driverlength (ft) Location of the driver, measured from the transom to the driver centre.
Motorlength (ft) Location of the motor, measured from the transom to the motor centre. May be either fore ( ), or aft (-) of the transom.
Fuellength (ft) Location of the fuel, measured from the transom to the fuel centre.
Misclength (ft) Location of additional equipment that is concentrated mostly in one location, such as hydraulic systems, ballast, etc., measured from the transom to the (average) load centre.
Motor Height (%) Height of MOTOR from water surface to the top of the engine casing/housing.
Lower Unit Height (%) Height of lower unit "bullet" above/below sponson running pad. ( ) is above, (-) is below.
Hint: Most high performance setups start with as little of the lower unit bullet in the water as possible, thus reducing drag significantly. Surface piercing propellers and low level water pick-ups make this fiesalbe. LwrUnitHeight values of 0.5in to 1” (above sponson running surfaces) are possible in very high performance applications. Without low water pickup, or when low end torque is a requirement, then LwrUnitHeight values of –0.5 to -2” (below sponson running surfaces) is applied.
Weights  

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Boatweight (lbs) Total weight of hull (only), including rigging, but excluding motor, fuel, driver, and other significant additional equipment. This weight should include all rigging weights that have not otherwise been accounted for.
Motorweight (lbs) Total weight of motor, drive unit, propeller, and accessories such as hydraulic trims, plates, etc that are attached to or built in at the motor.
Driverweight (lbs) Weight of driver with all clothing and safety equipment.
Fuelweight (lbs) Weight of fuel tanks and normal fuel supply.
Miscweight (lbs) weight of additional concentrated equipment such as hydraulic systems, ballast, etc., that are located at LENGTH MISC .
 
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  3.  Boat Setup Input       [see Input Screen Sample
NAME UNITS DESCRIPTION                                                                                                                        
Design Analysis

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Optimization
Configuration
(-) CONFIGURED FOR VELOCITY OPTIMIZATION - the program will find the maximum velocity attainable for the specified Angle of Attack, while satisfying the specified power rating (POWER MAX). The input value of STARTVEL will be used only as the first "guesstimate" of the solution. [Often used for the 'first run check' of potential design performance]

CONFIGURED FOR ANGLE OPTIMIZATION - the program will find the optimum Angle of Attack required to attain performance at the specified velocity, while satisfying the specified power rating (POWER MAX). The predictive performance solution will be presented for each of ten (10) specified velocities as defined by STARTVEL and VELOCITY INCR'T. [Most powerful and used most frequently for performance evaluation, since this feature utilizes full power and minimizes the required trim angle to achieve balanced performance]

CONFIGURED FOR POWER OPTIMIZATION - the program will find the required (minimum) POWER at the specified velocity, for the specified Angle of Attack, ANGLESTART. The predictive performance solution will be presented for each of ten (10) specified velocities as defined by STARTVEL and VELOCITY INCR'T. In addition, full power (POWER MAX) will be used to estimate ACCELERATION rates and elapsed TIME to each VELOCITY increment. This feature is a most powerful tool in evaluating detailed design and hull setup performance characteristics.

Accuracy (%) Selected allowable percent deviation for the OPTIMIZATION analysis, will define how close the program iteration process will attempt to come to specified maximum power rating, before printing a solution; a smaller ACCURACY DEF gives higher accuracy, but takes longer; too small an ACCURACY DEF may make it too difficult to optimise a solution.
Minimum VeeLength Wet (ft) Set minimum allowable vee planing surface wetted length. Default is 0.01. Set to larger number to limit realistic wetted contact and unrealisticly high velocities.
Start Velocity (Mph) Starting (lowest) velocity of a series of ten (10) velocities that ANGLE OPTIMIZATION or POWER OPTIMIZATION analyses will use. The predictive performance solutions will be analysed for this velocity and the increasing velocities at specified increments (VELOCITY INCR'T).
Velocity Inc (Mph) increment used in the series of ten (10) velocity steps analysed with ANGLE OPTIMIZATION or POWER OPTIMIZATION analyses. Ineffective if VELOCITY OPTIMIZATION analysis method is used.
Velocity Range
Calculator
(Selection) [HELP TOOL]   You can use the Velocity Range Calculator to automatically determine the incremental velocity steps to be used in the analysis. Change any of the variables, and the others will be changed automatically. Close the window to transfer the values back to the input screen.
Start Angle (degrees) For ANGLE OPTIMIZATION, this is used by the optimizing algorithms as a starting estimate for the Angle of Attack of the running surfaces (sponson pads). The program will find the angle of attack for the specified velocity while still satisfying POWER MAX. The closer your first "guesstimate" of ANGLESTART is to the optimum angle of attack (WANGLE), the faster the optimising analysis procedure will be.For VELOCITY OPTIMIZATION, the program uses this specified angle of attack to calculate the velocity that will satisfy POWER MAX. For POWER OPTIMIZATION, the program uses this specified angle of attack to calculate the POWER required to maintain specified velocity increments, or it uses the WAngle input in the ACCEL MODEL (see below).
Acceleration
Model
(selection) [HELP TOOL]   This is an optional input. The default (Constant WAngle) is used for analysis if you don't change it. Input the WAngle of attack for each Velocity in the performance range. For POWER OPTIMIZATION, the program simulates acceleration and elapsed time based on power available, and the WAngle of attack. Three (3) selections are available: (1) Constant WAngle: Uses the same WAngle for all velocities. StartAngle input is used automatically. This gives a bounding simulation of achievable acceleration.(2) Straight-Line WAngle: A more realistic acceleration and elapsed time simulation can be modelled by inputting a specific WAngle for each Velocity in the performance range. A reasonable representation of this WAngle is provided as a "Straight-Line" increase of WAngle from zero (0 degrees) up to the input Startangle(3) User-Fit: A third simulation "User Fit" can be selelected, allowing the user to input a specific WAngle of attack for each velocity in the performance range. This will be most accurate, but is for advanced users.
Conditions  

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Power Max (Hp) shaft horsepower used as basis for all OPTIMIZATION analyses. (Note that shaft HP is usually about 10% less than the maximum powerhead HP on an outboard). Predictive performance solutions will be based on this HP rating, within the specified solution tolerance (ACCURACY DEF).
Powereff'yfac (%) efficiency factor in the transmittal of POWER from prop shaft into propulsive force. This includes efficiency losses due to gear/transmissions as well as propeller inefficiencies, and is usually between 0.5 --> 1.0. This value is used in the calculation of ACCELERATION and estimated ELAPSED TIME to accelerate between incremental velocities, and will not affect any other performance results.
RPM Max (RPM) Maximum RPM setting/allowable on engine (input directly or from MotorSelection Wizard database).
Altitude (ft) altitude above sea level, of expected performance conditions.
Water Type (Selection) expected water conditions - sea water or fresh water.
Drive Unit  

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Drive Type (Selection) [HELP TOOL]   Select the type of lower unit (outdrive) you are using, from a drop-down list of all manufacturers.  All of the dimensional detials (below) of the selected drive are automatically input to the remaining fields, when you make your selection.  You can also select to input your own specific outdrive design dimensions.
Drive Number (Selection) The number of lower unit drives (no. of engines). Select: One (default); Two or Three drive units.
Skeg Width (In) average width of motor lower unit/outdrive skeg (leading edge of skeg to back of skeg).
Skeg Length (In) length of motor lower unit/outdrive skeg (top of skeg to bottom of skeg).
Skeg Thickness (In) thickness of motor lower unit/outdrive skeg (thickness of the skeg plate).
Torpedo length (In) length of motor lower unit/outdrive torpedo housing (leading edge of torpedo to aft edge of torpedo, at prop shaft).
Torpedo diameter (In) diameter of motor lower unit/outdrive torpedo housing (in section).
Gear Ratio (ratio) gear ratio of Lower Unit/drive unit (input directly or from MotorSelection Wizard database).
 
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  4.  Design Detail Input      [see Input Screen Sample
NAME UNITS DESCRIPTION                                                                                                                        
Spray Rails  

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Spray Height (In) Height of outer sponson SPRAY RAILS, if they exist, measured from aftmost bottom of sponson running surface. Usually are seen about 1/2 way between sponson bottom and deck (sheer clamp). Outer spray rails can improve hydrodynamic lift at lower CLW's (lower velocities) and reduce spray drag.
Spray Width (In) Width of outer sponson SPRAY RAIL, if they exist. Usually about 2 inches wide on IOGP and family (Mod-VP) type hulls - wider on Ocean racers.
Sprayfac (-) Factor of influence of water spray on hydrodynamic lift and drag. Affected somewhat by effectiveness of spray rails, chine steps, etc.
Include Inside Spray Rails (checkbox) check box to ALSO include Spray Rails inside sponsons. Outside (only) spray rails is default.
AeroFoil  

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VeeAero Type (Selection) Aerofoil design TYPE, or configuration. Can be selected from five (5) TYPE's: [performance data researched by AR®]
(1) Positive Camber - upper lift surface has a camber to positive (upward lift) side of aerofoil chord. This is the normal default tunnel boat aerofoil TYPE.
(2) Medium Camber - both upper and lower lift surfaces have camber to positive (lift) side of aerofoil chord. This can produce higher lift, but also more dynamic changes to aerofoil Centre of Pressure. This TYPE of aerofoil shape should be used with some caution, but can produce good results.
(3) High Camber - both upper and lower lift surfaces have camber to positive (lift) side of aerofoil chord. This can produce much higher lift, but also bigger dynamic changes to aerofoil Centre of Pressure. Also can generate significant interference with water surface and can cause EXTREME dynamic instability. This TYPE of aerofoil shape should be USED WITH CAUTION, but can produce excellent results when properly tuned-in.
(4) Zero Camber - upper lift surface has positive camber, lower lift surface has negative camber. When the amount of cambers are the same on both surfaces, aerofoil has what is called a zero camber. This generates less lift, but also less drag, and is somewhat more aerodynamically stable. It can create interference with water surface in some conditions.
(5) Low Camber - upper lift surface has positive camber, lower" lift surface has slightly negative camber. This Aerofoil TYPE is often seen in competitive designs, but is not particularly efficient. This TYPE generates less lift than TYPE's with more" positive camber, and not that much less drag. It is fairly aerodynamically stable, although can create interference with water surface in some conditions.
Vee Angle Inc (Deg) (not normally changed from Default value when using VBDP©)
AngleInc
Calculator
(Deg) (not normally changed from Default value when using VBDP©)
Cowling  

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Cowltype (-) type of cowling design, either:(1) OPEN faired front and rear cowlings, with exposed driver cockpit. (2) CANOPY type with integral or closed, faired cockpit enclosure, like with a safety cell. (3) NONE open cockpit with no fairings. (4) Cuddy Cabin
Cowlheight rear (in) Height of REAR COWL/COCKPIT from the deck surface to the maximum point above the deck surface.
Cowlheight front (in) Height of FRONT COWL/COCKPIT from the deck surface to the maximum point above the deck surface.
Cowlwidth (in) Width of COWL/COCKPIT or fairing at the widest point.
Open Deck (ft) Length of open (unobstructed) deck fore of the cockpit.
 
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