Advanced Aerodynamics and Hydrodynamics for Powerboats

Performance analysis of any hull design can be completed to determine 'Economy' operation settings and performance results.  TBDP©/VBDP© software's 'Optimize=Economy' analysis completes a series of performance checks, to find the lowest Power and the lowest Trim Angle (WAngle) required to satisfy the setup at each velocity step through the operating range. Other performance values are resultant of these settings.

This setting is most often utilized to consider the boat's performance at best fuel economy.

'Optimize=Economy' default analysis examines performance starting at 30% (max) power level, testing up to 100% power level, optimizing for LOWEST Power level and LOWEST trim angle (WAngle) for each Velocity.  User can also set the 'minimum' power level desired for the analysis (10% through 99%).

Optimize=Economy' versus 'Optimize=Angle'

• Analysis using 'Optimize=Economy' will find (specified) minimum power required using minimum trim angle (WAngle) to satisfy a solution at each velocity.
• Analysis using 'Optimize=Angle' will use maximum power to find minimum trim angle (WAngle) to satisfy a solution at each velocity.

These options will usually determine similar results at higher velocity range of the hull design.  At lower velocities, since 'Optimize=Economy' will use the minimum power setting possible, then higher trim angles will be required to achieve sufficient lift to balance the design setup.  As a comparison, 'Optimize=Angle' will use maximum (100%) power available, and so lower trim angles will be required for the same design to achieve sufficient lift to balance the design setup.

Some observations 'Optimize=Economy'
In practical operation, a lower trim angle is normally desired.  As boat starts to plane, however, operators may apply less than maximum power, and often a bow high attitude will result if less than full power. With bow high, more power can lower bow down attitude. Operators may find that applying more power allows for a more desirable, lower trim angle.

Here's why....
More power allows a lower trim angle, more visibility, better control - but may be less efficient lift (CLW) and thus, increased required wetted surface (SWet) and wetted length (LWet).  The additional wetted surface results in more drag (DW). Operators will notice that applying lower power settings when starting to plane, can generate sufficient lift, using less wetted surface, even though this lift is at a needed high trim angle.  Applying higher power settings when starting to plane can generate required lift at lower trim angles but needs more wetted surface, thus more drag at the same velocity.

Same hull design/setup at same velocity: