Aerodynamic and Hydrodynamic Performance
design for Powerboats

1) Variable Deadrise Longitudinal (Warped Plane) - variation in deadrise angle of running surfaces, where deadrise changes through the planing length of the running surfaces.  This is also called 'Warped Plane' deadrise.  So, through the length dimension of sponson of vee surface, the deadrise angle changes through the length of the wetted running surfaces.

Longitudinal variable deadrise hulls (warped planes) vary deadrise along the length of the hull, with higher deadrise forward that progressively flattens toward the transom. This design excels at reducing resistance and enhancing lift at speed by aligning the aft bottom more favorably with the local flow, while the deeper forward sections improve wave penetration. However, warped planes can introduce trim sensitivity, pitch-coupling effects, and less uniform pressure recovery, requiring careful balance of CG location and buttock curvature to avoid porpoising or inconsistent handling across speed ranges.

2) Variable Deadrise Lateral (Progressive) - variation in deadrise angle where deadrise changes in the lateral dimension (width) of running surfaces.  This is also called 'Progressive Deadrise'.  A sponson/vee inboard deadrise angle is defined and an outboard deadrise angle is defined. So, across the width dimension of the sponson or vee surface, the 'effective deadrise' angle is variable.

Lateral (Progressive) deadrise can be designed in 2 ways...

Case 1: Steeper deadrise at keel, flatter at chines - The deep keel section cuts through waves smoothly, reducing pounding and improving ride comfort in rough water. Flatter chines provide good planing lift and contribute to high-speed stability, helping the hull plane efficiently. The combination offers a balanced ride and good lateral stability. However, Lateral lift is concentrated more outboard, which can create complex flow patterns and slightly more sensitivity to weight distribution. Spray deflection may be less uniform, requiring careful chine shaping.

Case 2: Shallower deadrise at keel, steeper at chines - Flatter keel allows quicker planing at lower speeds, with good initial lift and responsiveness. Steeper chines add roll stiffness and lateral stability once on plane. This configuration can feel more agile at moderate speeds. However, Shallower keel increases the likelihood of pounding in waves, reducing comfort in rough water. The hull may be less smooth when encountering chop and could generate harsher impacts along the centerline.

Average Effective Deadrise - TBDP/VBDP calculates 'average effective deadrise' of wetted planing surfaces.  This unique presentation shows the 'combined' hydrodynamic effect of variable deadrise surfaces, based on the portions of the planing surfaces that are actually ontributing to lift/drag.  As speed, trim and loading change the differing deadrise surfaces become wetted or unwetted - even when operating with dynamically changing complex variable deadrise designs, including 'variable deadrise longitudinal', 'variable deadrise lateral', 'round pontoon', with 1 step, 2 steps or no-steps with unique deadrise features.

Performance Analysis - as a hull design changes velocity, trim angle and wetted length (LWet) and wetted width (bWidth) also change, which changes the 'effective deadrise' of the planing surface.  Many inter-dependant Lift/Drag contributors - such as 'longitudinally variable deadrise', 'laterally variable deadrise', 'vee-pad', 'center-pod', local step combinations - must be considered in the determination of each surface's wetted length and bWidth, and hence resulting performance and stability.

TBDP/VBDP dynamically calculates the changing wetted surfaces, automatically assessing the 'active' deadrise portions of wetted surfaces - 'Effective Deadrise' throughout the velocity range is used for performance analysis and is reported for the entire velocity range, in Performance Results and graphically in Performance Graphs