Aerodynamic and Hydrodynamic Performance
design for Powerboats

Based on expertise developed by SAVITSKY/DELORNE/DALTA and CLEMENT, Jim Russell (AR) has applied unique Whisker Spray drag analysis to the total hydrodynamic performance analysis of Vee hull and Tunnel hull powerboats. The analysis shows that Whisker Spray drag is HIGHER at LOW trim and HIGH deadrise settings. It can be reduced by using Below-Chine Spray Rails.

Jim Russell applies these advancements in newest versions of AR's TBDP©/VBDP© performance analysis software.
 

Figure 3 - Below-chine spray rails can reduce whisker spray drag and increase performance.

Figure 4 - Whisker Spray drag contributes to total hydrodynamic drag of high performance Vee hulls and tunnel hulls [Tunnel Boat/Vee Boat Design Program©].
 

The performance effects of friction drag, profile drag, induced drag, sheer spray drag and whisker spray drag generated by all Vee hull, Vee-pad hull, tunnel hull and modified-tunnel hull types of powerboat applications is developed by Russell. The results are accurate representation of hydrodynamic drag associated with all performance powerboat arrangements, using Russell's analysis techniques in the "Tunnel Boat Design Program" and "Vee Boat Design Program" software.

How it Works - When a typical Vee hull is planing, particularly at higher speeds, the hull gets it's lift from the wetted lifting area of the hull bottom. The forward portion of this lifting area is a triangular shape (simply due to the geometry of the veed hull). Behind this triangle, defined by the "stagnation line" is the lifting area – this is the wetted surface that does the good work of lifting the hull out of the water. Ahead of the stagnation line, there is an area that experiences spray from the high velocity water that flows along the hull surface. The "whisker" spray from highly loaded lifting surfaces can wet a significant portion of your hull surface, causing additional drag without the benefit of any lift.  Tunnel hull configurations can also generate whisker-spray drag components that affect performance and stability.

For higher deadrise hulls and at higher velocities, this "whisker spray area" can be large, causing additional drag on the hull. This added drag steals valuable horsepower and reduces the efficiency of the hull.

 [also see Jimboat's article on Spray Rails and Lifting Strakes]