A Carrick bend joins two ropes with an interwoven pattern. The flat inspection view makes the continuous strands and alternating crossings visible; a real unseized bend changes shape as it tightens. The calculator below compares entered strength assumptions, rather than assigning a tested rating to the knot.
Carrick Bend Interactive Calculator
Compare a supplied rope breaking strength, an assumed retained fraction, an entered divisor and a pull load. The drawing traces each rope through the flat weave. The numbers are an assumption comparison and do not establish a working-load rating.
Equation Used
- Breaking strength and applied pull use the same force unit.
- Retention and design divisor are entered assumptions, not values certified by this calculator.
- The computation is an algebraic comparison with no dynamic loading, slip or failure model.
- Flat knot topology is displayed to inspect crossings; tightening and material deformation are not simulated.
- The retention slider lets you compare assumed fractions; its range does not describe tested Carrick-bend performance.
- Both margin and utilization are measured against the factor-divided limit.
Trace each rope through the flat Carrick weave, with alternating over-and-under crossings and diagonally opposite tails. The calculation compares an entered pull with a limit derived from your assumed strength retention and divisor; it does not establish a tested knot rating.
Follow the two continuous ropes
The flat Carrick-bend layout has two interwoven ropes and diagonally opposite tails. The diagram distinguishes the standing parts from the tails and separates every overpass from the strand beneath it. Tracing either rope encounters alternating over and under passes.
The reference photographs show the flat form changing into a compact form when tightened. The animation deliberately keeps the flat inspection layout so its crossings remain visible. The moving highlight is a visual guide, not rope sliding through a loaded knot.
The model has eight crossing locations: two self-crossings and six between the ropes. Following either rope passes through eight crossing encounters because its own self-crossing is encountered twice.
A topology illustration and an assumption comparison
The diagram is intended to make the Carrick weave recognizable and inspectable. It is not a full tying or load-testing simulation.
Enter breaking strength, an assumed retained fraction, pull and a design divisor to compare those assumptions. They do not identify an actual rope or establish a permitted use, towing load, lifting capacity or climbing system.
Use one consistent comparison limit
Let B be entered breaking strength, η the assumed retained fraction, F the entered divisor and P the applied pull. First S = ηB. Then the illustrative comparison limit is L = S/F. Margin is L−P and utilization is 100P/L.
Margin and utilization both compare the pull with L. Increasing the divisor F lowers that comparison limit. Retained strength S is shown separately as an assumed intermediate value.
These relationships are arithmetic. They do not determine η from knot shape or validate the chosen divisor. All load entries and results use tonne-force consistently.
Read the default assumptions
The sample entries are B = 100 tonne-force, η = 0.62, F = 2 and P = 20 tonne-force. They give assumed retained strength S = 62 tonne-force and a factor-divided limit L = 31 tonne-force.
The margin to that limit is 11 tonne-force and utilization is 20/31 × 100 ≈ 64.5%. The values illustrate the equation; they are not attributed to a tested rope-and-knot combination. Doubling the divisor halves L and doubles utilization at the same pull.
What the entered fraction leaves unknown
The model has no input for rope construction, damage, material, diameter, dressing, contact behavior or loading history. It therefore cannot calculate a real knot’s retained strength or infer that a particular fraction is appropriate.
The weave drawing also does not predict deformation, slip, failure or the shape under load. A flat diagram clarifies the crossing sequence but does not substitute for information about the actual rope and application.
Questions about the Carrick-bend model
Does the drawing show the loaded shape?
No. It is a flat inspection layout. An unseized Carrick bend changes shape when tightened; that deformation is not simulated.
What moves in the animation?
A highlight follows the stationary ropes to make their continuous paths and over/under crossings easier to inspect.
Is 0.62 a guaranteed retained-strength fraction?
No. It is a sample assumption, not a measured or guaranteed rating.
Which limit do margin and utilization use?
They compare pull with the displayed factor-divided limit: margin is that limit minus pull, and utilization is pull divided by that limit, expressed as a percentage.
Crossing references
Scouting Resources: Carrick Bend, original step photographs, especially the flat completed weave and tightened form. Animated Knots by Grog: Carrick Bend confirms diagonal tail placement and the distinction between flat and tightened shapes. These references support the topology, not the calculator’s retained-strength assumptions.
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