The fisherman’s bend, also called the anchor bend, attaches rope to a ring using turns around the ring and a hitch tucked through those turns. The calculator compares an entered rope strength, assumed knot-retention percentage and selected design factor. Its result is an arithmetic comparison, not a rated capacity for an anchor or rope system.
Fisherman's Bend Hitch Interactive Calculator
Compare the effect of assumed knot-strength retention and a selected factor. The result does not establish a certified working-load limit.
Equation Used
The entered MBS is multiplied by the assumed retention percentage and divided by the selected factor. Neither the retention nor the factor is validated by this tool. Use rope-specific termination data and application requirements to establish allowable working loads.
- Knot routing and suitability must be checked separately; the calculator does not inspect a knot.
- Rope MBS is the manufacturer's unknotted minimum breaking strength.
- Efficiency is entered as a percentage and converted to eta = percent / 100.
- The selected factor is an arithmetic divisor, not a validated choice for this application.
The ring turns and trapped hitch
The rope turns around the attachment ring, and the working end forms a hitch through the turns. This distinguishes the anchor bend from a plain round turn with hitches outside it.
The rope must be compatible with its attachment and intended use. Knot form, dressing, tail treatment and inspection depend on the rope and applicable instructions. This page does not provide a complete tying or installation procedure.
Rope-to-ring attachment
The anchor bend is associated with attaching a rope to a ring in marine rope work. That association alone does not specify a suitable rope, hardware connection or anchoring arrangement for a vessel.
Actual line loads depend on the complete arrangement and operating conditions. The calculator has no vessel, wind, wave, anchor, seabed or hardware inputs and cannot predict dragging or holding performance.
Strength-retention comparison
For entered rope minimum breaking strength B in kN and assumed retention η as a fraction, assumed strength is S = Bη. The displayed comparison load is S/f, where f is the selected factor.
Assumed strength loss is B − S. The second comparison-load output converts kN to lbf using 224.808943 lbf/kN.
This calculation does not establish a knot's tested breaking strength. It also does not select a design factor or permit shock loads above a rated working load. Those decisions require the actual rope, termination and application data.
Example with assumed inputs
Enter 49 kN, 70% retention and a factor of 5. Assumed strength is 34.3 kN, comparison load is 6.86 kN or about 1,542.19 lbf, and assumed loss is 14.7 kN.
At 65% retention with the other inputs unchanged, comparison load is 6.37 kN. At 75%, it is 7.35 kN. This is a sensitivity comparison: the percentages are not measurements of old or new rope and the results do not define allowable vessel or weather conditions.
Knotted and manufactured terminations
A knot, splice and manufactured termination have different requirements. Their strength and suitability depend on the rope construction and the particular termination, not a single universal percentage.
Use the selected rope manufacturer's data and instructions for the chosen connection. Account for condition, bending at the attachment and dynamic loads through the applicable design process. This tool cannot choose a knot or replacement splice for a working system.
Frequently asked questions
Does Comparison load give a rated WLL?
No. It divides an assumed retained strength by a selected factor. A rated working-load limit needs appropriate rope, termination and application data.
Where does the efficiency percentage come from?
It is entered by the user. The tool does not infer it from material, age, dressing or ring size.
Is a factor of five always suitable for anchoring?
No. The tool does not select or validate the factor. Application requirements and equipment data determine the appropriate design criteria.
Can this compare wind or wave limits?
No. It has no vessel or environmental-load model and cannot determine anchor holding or dragging.
Does a knot retain the same strength on every rope?
No. Rope construction, condition and knot configuration affect performance. Use relevant test data rather than transferring a percentage between products.
Can I use the drawing as a complete tying instruction?
No. Routing, tail treatment, dressing, compatibility and inspection must follow appropriate instructions for the actual rope and application.
Rope-selection reference
Samson Rope: minimum breaking strength, working loads, design factors and application conditions.
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