Editor: Otto Tromm | Test date: 13-4-2026
A cord with a 1.5 mm diameter sounds fragile. Barely thicker than a shoelace, thinner than a pencil tip.
But what if a cord that thin can handle a load you simply would not expect at this size? That is exactly why this SK78 Dyneema cord was placed on the universal testing machine.
What is the breaking strength of 1.5 mm SK78 Dyneema cord without coating?
In our test, this cord broke at an average of 2.51 kN (256 kg) — based on 5 repetitions.
For a cord of one and a half millimetres, that is a notably high figure.
What type of rope is this?
This is a braided SK78 Dyneema cord of 1.5 mm without coating and without core.
SK78 is a specific variant of HMPE fibre (High-Modulus Polyethylene), also known under the brand name Dyneema.
The construction is a single braid without protective sheath and without core.
The cord has a diameter of 1.5 mm and is white in colour.
Typical applications for this size and material include:
- Scale modelling and drones (guide lines, tension wires)
- Fishing hooks and fishing tackle (trace lines, assist cords)
- Kite applications and flying lines
- Jewellery, bracelets, and craft applications where high strength in a thin profile is required
- Trace and marking cords in technical environments
Test methodology
The tests were carried out on a universal testing machine with cord-specific clamps. These clamps are suitable for measuring rope strength without the need to splice the rope.
Each sample was loaded to complete break at a constant test speed of 20 mm/s.
No pre-tension was applied prior to the test.
A total of 5 separate samples were tested. The average, highest, and lowest measured values are reported below.
The results were measured on dry material, in accordance with common practice for mechanical tensile tests on fibre ropes (ISO 2307).
Test results
The average breaking strength of the 1.5 mm SK78 Dyneema cord is 2.51 kN (256 kg). The highest measured value was 2.64 kN, the lowest 2.37 kN.
This spread spans a range of 0.27 kN, which for a cord of this size represents a reasonably consistent series.
During the tests, a characteristic sound pattern was observed. Just before complete break, a faint crackling sound was audible — an indication that individual fibres were beginning to fail while the cord as a whole was still holding.
The final break itself sounded like a whipcrack: abrupt and sharp. This behaviour is consistent with the low-elongation characteristics of HMPE; there is virtually no energy build-up through stretch before the break point, which means the release of tension is immediate and forceful.
Comparison with cords of equivalent diameter
To put the performance of this Dyneema cord in context, it is useful to compare it with another 1.5 mm cord also regarded as high-strength:
- Kevlar: 1.05 kN
- SK78 Dyneema (this cord): 2.51 kN
The difference is substantial. At equal diameter, the Dyneema cord is 2.4 times stronger than the Kevlar cord in our test.
This is not a marginal difference — it means the Dyneema cord at this size is in a different class altogether.
Kevlar does offer other advantages (heat resistance, cut resistance), but purely on breaking strength per millimetre of diameter, the Dyneema clearly comes out ahead here.
When to use this rope
This cord is best suited for applications that require the thinnest possible profile combined with the highest possible breaking strength. Specifically:
- Kite and flying lines: best suited for high-load lines where weight and diameter must be kept to a minimum.
- Precision scale modelling and drones: best suited for structural connections in lightweight frames where steel is too heavy and nylon lacks sufficient stiffness.
- Craft and jewellery with high strength requirements: best suited where a thin cord is subjected to sustained load, without knots or abrupt load changes.
Because SK78 Dyneema does not absorb water and shows no strength loss when used wet, this cord is also suitable for marine and humid environments.
Limitations
This cord has a number of properties that make it less suitable for certain applications. It is important to be aware of these before use:
- Minimal elongation: HMPE has an elongation at break of less than 4%. This cord absorbs virtually no shock energy. Under sudden impact loads, it may fail at a breaking strength below the statically measured 2.51 kN.
- No coating or sheath: Without a protective outer layer, the cord is more susceptible to cut damage and abrasion. Contact with sharp edges or rough surfaces can cause localised fibre damage.
- Knots significantly reduce strength: A standard overhand knot reduces the effective strength by 40–55%. For this cord, that represents a drop from 2.51 kN to potentially less than 1.4 kN at the knot. Where possible, use a suitable terminator or swaged end fitting.
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Creep at elevated temperatures: HMPE exhibits creep (permanent elongation) under sustained load above 60 °C.
Do not use this cord near heat sources or in environments where the ambient temperature is structurally above 50 °C. - Cut sensitivity: Dyneema is strong under tensile load but has low resistance to cutting. In combination with sharp objects, a low transverse force may be sufficient to cause failure.
Alternatives
For applications where this Dyneema cord is not the right choice, two alternatives are worth considering:
Polyester cord 1.5 mm: Polyester has higher elongation (10–15% at break) and is therefore better suited for applications involving shock loading. However, the breaking strength at 1.5 mm is considerably lower than that of Dyneema. Polyester is more abrasion-resistant and lower in cost. Suitable where some degree of stretch is desirable.
Nylon cord 1.5 mm: Nylon has the highest elongation of all synthetic fibres (20–35% at break) and absorbs shock energy most effectively. It loses 10–15% of its strength when wet and has a lower breaking strength than Dyneema at equal diameter. Nylon is the appropriate choice when the cord is intended to act as a shock-absorbing element, such as in small lashing applications or anchor lines on light vessels.
Conclusion
The 1.5 mm SK78 Dyneema cord is best suited for applications that require an extremely thin line combined with high static tensile strength — such as kite lines, precision scale modelling, or technical cords in humid environments.
With a measured average of 2.51 kN (256 kg) — more than twice the strength of the comparable Kevlar cord at 1.05 kN — this cord delivers performance that is exceptional for this size.
The abrupt break (the crackling sound followed by a whipcrack) confirms the low-elongation character of HMPE: those who need shock absorption should select a different material; those who need raw tensile strength in a small profile will find this cord fit for purpose.
This test was carried out by Otto Tromm, who afterwards spent a moment wondering whether he had pulled the cord or the cord had pulled him — because 256 kg from one and a half millimetres does make you think.
The test data were collected by Prorope. This text was generated using AI on the basis of those data and has been verified for factual accuracy. Read how we test and publish →