Knot & Rigging MARITIME TOOLKIT
3D Studio

∞ SEAMANSHIP

Rope, knots and rigging, explained properly

What a line is doing, what a knot costs you in strength, and how a load actually travels through a rig. Four free 3D tools and three calculators that show their working.

Explore the tools Open the 3D Studio

Independent education

Written as a seamanship reference. No brand is promoted and no product is sold.

Nothing for sale

No affiliate links, no sponsored placements, no retailer relationships behind any figure.

Free 3D tools

Four interactive simulators that run entirely in your browser, at no cost and with no sign-up.

Safety first

Load limits, rope inspection and working aloft are treated as the serious subjects they are.

∞ CATEGORIES

Five areas of rope work

Every tool on this site belongs to one of five areas, from choosing a fibre to knowing when a line has reached the end of its life.

Rope & Cordage

Fibre, construction and how a line behaves under load.

6 tools

Knots & Splices

The joinery of seamanship — what holds, and what costs strength.

6 tools

Rigging Hardware

Shackles, thimbles, blocks and the metal that carries the load.

6 tools

Sailing & Lines

Halyards, sheets, dock lines and anchor rodes in service.

5 tools

Safety & Maintenance

Inspection, protection and knowing when to retire a line.

5 tools

∞ THE WORKING ORDER

Four steps, in order

Most rigging failures trace back to skipping one of these. The order matters as much as the steps.

  1. Choose Line — illustration
    STEP 1

    Choose Line

    Match the fibre and diameter to the load, the stretch you can tolerate and the environment.

  2. Tie & Splice — illustration
    STEP 2

    Tie & Splice

    Terminate the line with the right knot or splice, and know what it costs in strength.

  3. Load & Test — illustration
    STEP 3

    Load & Test

    Work out the tension, apply a safety factor, and stay inside the working load limit.

  4. Maintain & Inspect — illustration
    STEP 4

    Maintain & Inspect

    Inspect on a schedule, record what you find, and retire on evidence rather than on hope.

∞ 3D STUDIO

Work it in three dimensions

Four interactive tools that run entirely in your browser. Drag to rotate, change the parameters, and watch what happens to the numbers.

INTERACTIVE

Try it here

Drag the rope to turn it. Tighten the knot and watch the bight draw in — the same geometry the simulator uses, with the same strength figures behind it.

Knot Tying SimulatorRope Load SimulatorSplice SimulatorRigging Load Visualizer All 3D tools

∞ MOST USEFUL

The tools people reach for

All 28 tools
Nylon Rope — nautical chart line drawing

Nylon Rope

High-stretch synthetic with excellent shock absorption — the default for anchor rodes and dock lines.

Rope & Cordage Select
Polyester Rope — nautical chart line drawing

Polyester Rope

Low stretch, strong ultraviolet resistance — the working line for sheets, halyards and general rigging.

Rope & Cordage Select
Manila Rope — nautical chart line drawing

Manila Rope

The traditional natural-fibre line — good grip and a classic look, but it rots, and it is far weaker wet.

Rope & Cordage Select
Dyneema Rope — nautical chart line drawing

Dyneema Rope

Ultra-high-molecular-weight polyethylene — the strongest line by weight, with almost no stretch at all.

Rope & Cordage Select
Shock Cord — nautical chart line drawing

Shock Cord

Elastic bungee cord for holding, tensioning and absorbing small movements — never for load-bearing duty.

Rope & Cordage Select
Paracord — nautical chart line drawing

Paracord

Light nylon kernmantle cord — 550 lb rated, seven removable inner strands, endlessly useful ashore.

Rope & Cordage Select
Bowline — nautical chart line drawing

Bowline

The fixed loop that will not jam — the single most useful knot in seamanship.

Knots & Splices Tie
Figure-eight — nautical chart line drawing

Figure-eight

A strong, symmetrical stopper and loop knot — the standard where the load matters more than easy untying.

Knots & Splices Tie
Clove Hitch — nautical chart line drawing

Clove Hitch

Two crossing turns that grip a post or rail — fast, adjustable, and only trustworthy under constant tension.

Knots & Splices Tie

∞ CALCULATORS

Three calculators that show their working

Each one prints the formula it used. No black boxes and no numbers you cannot check.

Free tool

Rope Strength Calculator

Fibre→Breaking strength

Breaking strength, working load and stretch for a given fibre, diameter and duty.

Calculator
Free tool

Knot Strength Calculator

Line breaking strength→Strength at the knot

What a knot costs you, and what the line can safely hold once it is tied.

Calculator
Free tool

Rigging Load Calculator

Load weight→Tension per leg

Sling tension against angle — and why a wide angle multiplies the load so fast.

Calculator

∞ READING

Start here

All articles
How to Start Sailing: A Beginner's Guide to Lines and Knots — illustration
Beginner

How to Start Sailing: A Beginner's Guide to Lines and Knots

The first things worth learning are not the knots themselves but what a line is doing, and which four knots cover almost everything on a small boat.

Mara Ellison9 February 20269 min read
Article
Understanding Rope Materials: Nylon, Polyester, Dyneema — illustration
Beginner

Understanding Rope Materials: Nylon, Polyester, Dyneema

Four fibres account for almost every line on a boat. They differ in stretch, sunlight tolerance, and how they behave when wet — and those differences decide where each belongs.

Tomás Reid22 January 202611 min read
Article
The Five Essential Knots Every Sailor Should Know — illustration
Knots

The Five Essential Knots Every Sailor Should Know

Five knots, what each one is genuinely good at, what it costs in strength, and the specific way each one fails.

June Okafor27 February 202612 min read
Article

∞ ONE PLACE TO LOOK THINGS UP

Every rope and every knot, side by side

The database sorts by fibre, diameter, breaking strength and elongation, expands each entry, and compares up to three at once.

Open the database About this site