How do I use NavCad's Method Expert to check hull form validity?

What Method Expert Does

Method Expert checks the entered hull data against the published applicability ranges of each available resistance prediction method. For each method, it reports which parameters are within range, which are out of range, and by what margin. Methods with out-of-range parameters can still be used with engineering judgment, but the confidence plot reflect reduced reliability.

For planing hull configurations, Method Expert also evaluates whether the hull has sufficient power-to-weight characteristics to actually sustain planing. This is a practical check before committing to a planing resistance method if the hull is too heavy relative to its projected bottom area, empirical planing methods may return unreliable results.

Running Method Expert

• Complete hull data entry (or perform hull CAD import) before running Method Expert. Validity checks require complete parameter values.
• .
• Review the table. Methods within range for all parameters are highlighted as valid. Methods with one or more out-of-range parameters are flagged with the specific parameter and the degree of exceedance.

Interpreting the Results

A method flagged as technically out of range is not automatically invalid. Some methods have been successfully applied to hulls modestly outside their stated ranges particularly where exceed a less sensitive parameter. Use the Method Expert flag as a prompt to review the specific parameter and decide whether the extrapolation is defensible for the application.

Where multiple methods are valid, running and comparing . ivergence between valid methods indicates a hull form or speed regime where empirical scatter is high.

Planing Hull Loading Check

For planing hulls, Method Expert evaluates a loading parameter that reflects whether the vessel to actually achieve planing. Hulls that fail this check may transition poorly to planing speeds, and the selected planing method may not produce physically reasonable results. In such cases, consider whether the ITTC-78 scope is more appropriate, or whether the hull geometry data should be reviewed.

Related Articles

• How do I choose a resistance prediction method in NavCad?
• How do I import hull geometry from Orca3D, PROLINES, or an STL file into NavCad?
• Savitsky method error low deadrise / planing station geometry troubleshooting