Can NavCad be used for sailing yacht design?

Overview

NavCad addresses the auxiliary propulsion system of sailing yachts the engine, gearbox, and propeller that provide power under sail-down or restricted conditions. The analysis workflow is identical to a powerboat analysis, but with sailing-yacht-specific models for hull resistance, propeller drag under sail, and engine sizing for range requirements.

Hull Resistance

• Monohull sailing yachts: Standard ITTC-78 methods with appropriate hull form inputs. The low-drag sections typical of a sailing yacht hull are generally within the applicability ranges of common methods.
• Sailing catamarans: Use the catamaran configuration with appropriate demi-hull parameters.
• Trimarans: Can be approximated using a hybrid approach the primary ama treated as the principal hull with a correction for the float contributions.

Propeller Options

Sailing yachts typically use folding, feathering, or fixed two-blade propellers to minimize drag under sail. NavCad includes:

• Folding and feathering propeller drag models based on HydroComp in-house R&D these are important for accurate performance prediction in the mode.
• Standard B-series and Gawn propellers.

Engine and Gearbox Selection

NavCad's propulsion analysis sizes the engine and gearbox for the required motoring speed and endurance. The yacht's resistance curve determines the power demand at motor-sailing speeds, and the propulsion analysis finds the optimum propeller, gear ratio, and engine combination.

Racing Rules Compliance

Some racing classifications require minimum auxiliary performance under power for example, the Category 3 Monohull rule requires that the vessel achieve at least 70% of hull speed for a minimum of 8 hours under engine power. NavCad's fuel consumption and range prediction can be used to verify compliance with such requirements and to size the fuel tank accordingly.

Notes

For sailing yacht analysis, appendage drag (deep keel, rudder) can be a substantial fraction of total resistance. NavCad's appendage component models should be populated with keel and rudder geometry for accurate total resistance at motoring speeds.

Related Articles

• How do I choose a resistance prediction method in NavCad?
• How does NavCad predict resistance for catamarans?
• How do I import hull geometry from Orca3D, PROLINES, or an STL file into NavCad?