BREAKING STRENGTH 0.8 MM DYNEEMA 0.51 kN — thinner than a shoelace tip
Five tensile tests on 0.8 mm Dyneema with polyester sheath. What does such a thin fibre deliver — and when is this rope the right choice?
In five tests, this 0.8 mm Dyneema with polyester sheath broke at an average of 0.51 kN — equivalent to 52 kg.
At a diameter of 0.8 mm, most people assume this is decorative material — suitable at best for a label or a piece of jewellery. That assumption is incorrect. Dyneema has the highest strength-to-weight ratio of all rope fibres, and that holds true at this size as well. But exactly how much breaking strength is contained in a cord thinner than a shoelace tip? That is what we measured.
Five samples, all tested on a universal testing machine with rope-specific clamps, at 20 mm per minute. The lowest break was at 0.48 kN, the highest at 0.55 kN. The spread across the five measurements was 0.07 kN. That is a difference of approximately 14% between the weakest and strongest measurement — acceptable for this thin format, where even small variations in the sheath can influence the result.
A distinctive pattern was observed at the break point: after the main break, a secondary smaller break of the polyester sheath followed. The rope therefore did not break in a single step.
The average breaking strength of 0.51 kN is the measured value.
0.8 mm Dyneema with polyester sheath — what is this rope made of?
The core of this rope consists of HMPE fibres, better known under the brand name Dyneema. HMPE stands for High-Modulus Polyethylene: a synthetic fibre with the highest strength-to-weight ratio of all synthetic fibres.
It does not absorb water, floats on water, and loses no strength when wet. Over the core sits a braided sheath of polyester. That sheath protects the core against wear and makes the rope easier to handle.
This rope is part of our Dyneema cord collection.
How we test
The breaking strength tests are carried out in-house by Otto Tromm on a universal testing machine with a capacity of 50 kN. Two sets of specially developed rope clamps are available for this machine, selected based on the diameter and material of the rope.
These clamps allow rope to be tested without first requiring it to be spliced.
All tests are carried out in accordance with the guidelines of ISO 2307:2019. This includes testing five times and using a test speed of 20 mm per minute.
Each rope is secured in such a way that it sits taut. No pre-tension is applied, as elongation is not measured in these tests.
Two recordings of each test are made with a Sony camera on a tripod. In addition, the exact progression of the graph is recorded separately on video.
This allows the stress progression and break behaviour to be matched precisely against the graph from the breaking strength test machine.
For each of the 5 tests, observations are also recorded in writing by the tester, documenting aspects such as the degree of elongation, the manner in which the rope breaks, and the loudness of the snap when the rope fails.
Test results: 0.51 kN average across five measurements
The five measured values ranged between 0.48 kN and 0.55 kN. The average is 0.51 kN — equivalent to 52 kg. The spread of 0.07 kN indicates that the measurements were reasonably consistent, but not identical.
For a diameter of 0.8 mm this is expected: minor deviations in sheath thickness or rope position in the clamps already influence the result at such a small diameter.
In every measurement, the break pattern was two-stage. The Dyneema core broke first, followed by a second, smaller break of the polyester sheath.
This two-stage behaviour means the measured breaking strength does not represent a single break event. The value of 0.51 kN is the peak prior to the core break and is the governing breaking strength.
Comparison with other ropes
In this test, only the 0.8 mm Dyneema with polyester sheath was measured. No other ropes are currently included in the same test set, so a direct comparison is not possible.
A relevant reference point: polyester rope of 0.8 mm typically has a considerably lower breaking strength than Dyneema of the same diameter.
Dyneema fibre is 2 to 5 times stronger than polyester of the same diameter. A specific figure for that polyester rope is not available in our test data — that comparison will follow once that rope has been tested.
Conclusion: 0.51 kN in 0.8 mm — strong for its size
This 0.8 mm Dyneema with polyester sheath achieves an average of 0.51 kN (52 kg) in a straight tensile test without a knot. That is notably high for such a thin cord. The polyester sheath protects the core and provides grip, but also produces a two-stage break pattern.
The rope is best suited to lightweight precision applications: kite and model building, and as a repair cord for (pleated) fly screens.
Otto Tromm carried out the tests, counted the break stages, and wrote this report. He confirms that the rope is thinner than his patience on a rainy test day — but stronger than most people expect.