About this site

What this is

Knot & Rigging is a reference for the rope work that happens on and around boats: what a line is made of, how a knot behaves when it is loaded, how a splice differs from a knot, and how a load actually travels through a rig.

The site has 28 tool entries, three calculators that print the formula they used, a sortable database of ropes and knots, and four interactive 3D models. Everything is static — there is no account, no tracking script and no server doing anything with your input.

What it is not

It is not a shop. Nothing here is for sale, there are no affiliate links, no sponsored placements and no retailer relationships behind any recommendation.

It is not a certification. No figure on this site is a rating for a specific product. Ratings come from the manufacturer and from the standard the product was made to.

It is not a substitute for training. Rope work done badly hurts people. The site is written to help you understand what you are doing; it is not a course.

How the numbers are derived

Breaking strengths are typical catalogue values for new, dry line with a spliced termination, quoted to the nearest sensible figure. They are not measurements of any particular product. Knot retention figures are typical values for a correctly tied and dressed knot in nylon or polyester line, and they vary with the rope, the load direction and the age of the line.

The calculators use simplified models and they say so. The rope strength calculator fits a diameter coefficient to the catalogue figures used across the site; the knot calculator applies a retention factor and a condition derate; the rigging calculator uses the standard sling-tension relationship and takes the conservative assumption that a three- or four-leg sling is rated as a two-leg sling. Every one of them prints its formula on the page.

Editorial approach

• Say where a number comes from. If a figure is a typical value rather than a specification, it says so.
• Show the working. The calculators print their formulas so the arithmetic can be checked.
• Treat safety as the subject, not a disclaimer. Working load limits, inspection and retirement are covered as real topics.
• No product placement. Where a tool type is discussed, it is discussed generically.

Accessibility and performance

The site is keyboard navigable, respects a reduced-motion preference, and degrades gracefully: if a device has no WebGL, the 3D tools show a static diagram rather than a blank box. The 3D library is loaded only when you open a 3D tool, and on a small screen the tools open in their static form until you ask for the interactive version.