This application is a running rigging size calculator for historical sailing ship models, based on classic ship modeling principles and proportional methods commonly associated with the Mondfeld approach. It calculates rope diameters for running rigging elements such as halyards, sheets, braces, lifts, and other control lines used to operate yards, sails, and spars on square-rigged and fore-and-aft rigged vessels. The calculations are derived from traditional proportional relationships used in scale ship modeling, ensuring consistency between standing and running rigging systems.

The tool is intended for ship models representing sailing vessels from the Age of Sail, covering the period from the 16th to the 19th century. It is suitable for caravels, galleons, frigates, ships of the line, and other classic sailing ships where accurate depiction of running rigging is essential for both functional realism and visual balance. By providing precise rope diameter proportions, the application helps modelers maintain correct scale relationships between masts, yards, sails, and control lines.

Correctly sized running rigging significantly improves the authenticity and readability of a model, preventing visual overcrowding or disproportionate line thickness. Accurate rope dimensions also enhance the overall harmony of the rig and support faithful reconstruction of historical vessel layouts. The calculator is especially useful for advanced modelers, scratch builders, and competitors preparing models for exhibitions and contests, including NAVIGA Class C-1 sailing ship competitions, where precision, proportional accuracy, and historical correctness are required.

This tool serves as a practical reference for improving build quality, ensuring consistency between rigging systems, and achieving higher standards in professional and competitive ship modeling.