A step-by-step guide to choosing the right shock cord for your project

The inherent versatility and performance of our shock cords here at Ibex Marina Ropes means that they play a crucial role in a wide range of applications across a variety of key sectors, from marine and aerospace to military or outdoor adventure. Primarily, their elasticity and strength makes them useful for securing, fastening, and load management – but it is far from their only usage.

If you are looking for the very best shock cord for your own applications, you may have already found that it is not necessarily a straightforward process. Choosing the correct type requires careful consideration of a number of factors, including (but not limited to) load capacity, environmental resistance, and installation requirements. If it is not a decision you have made before, it can be particularly challenging – but that is where our team can help here at Ibex Marina Ropes. Here, we have collated a quick guide to getting you started on choosing the right shock cord for your project, whatever it may be.

1. Assess your project’s shock cord needs

The specific demands of your industry will strongly influence the type of shock cord you need. Depending on your intended application, your shock cords may need to endure constant tension, or alternatively they may stretch and retract repeatedly. Environmental exposure to moisture, extreme temperatures, or UV rays will also affect their overall durability, so that is also worth bearing in mind. (We will come onto this in more detail in just a moment.)

For example, if you are transporting goods, you may be looking for shock cords best suited for securing goods in transit, requiring durability and a predictable stretch pattern to maintain load stability. If your application falls more within the aerospace or defence sector on the other hand, you may be looking for shock cords made with advanced materials that offer resistance to extreme pressure and temperature variations.

Marine-based industries require shock cords resistant to saltwater and sunlight, whereas construction and manufacturing environments may involve abrasive surfaces, so additional protective sheathing could be beneficial. These may not be universally hard and fast rules, but they provide a good place to start.

2. Choose the correct diameter and length

Essentially, a shock cord’s diameter determines its strength and stretch potential. A thicker cord provides greater resistance to stretching but is less flexible, while a thinner cord allows for more give – the trade-off is that it may not handle high tension effectively.

This means that the correct choice of diameter will be strongly influenced by the level of strain the cord will experience. In applications where the cord must hold a static position under tension, a thicker diameter can be helpful in preventing excessive elongation over time. On the other hand, applications that require regular stretching and relaxation can benefit from a thinner diameter with a higher stretch ratio. If your application involves lighter loads or frequent adjustments, you may find that a cord between 5mm and 8mm is effective. Heavy-duty industrial tasks (such as securing cargo or supporting mechanical components) typically require diameters of 10mm or more.

Determining the correct length is equally important, as it allows for the necessary level of stretch. A cord that is too short may become overstressed, while an excessively long cord could reduce stability.

3. Take a moment to think about load-bearing capacity

The ability of a shock cord to handle tension and weight is also a crucial factor in its overall effectiveness, helping you to avoid the risks of excessive stretching or sudden failure under stress.

When you are considering load-bearing capacity, you will need to factor in an additional margin for safety, particularly in environments where sudden force could be applied. For example, industries such as warehousing and distribution often use shock cords for securing goods on racking systems or within containers, where uneven weight distribution can place additional strain on certain sections of the cord. For that reason alone, it is a good idea to ensure that the cord’s rated capacity exceeds expected loads, so it can prevent the risk of premature wear and unexpected failures. (Load ratings are usually specified according to the cord’s core construction.)

It is also important to ensure that you are taking into account both static and dynamic forces. A static load refers to a constant force applied over time, such as securing tarpaulins, while a dynamic load involves repeated stretching and sudden force – as seen in industrial fastening applications. In both cases, a cord rated above the expected load reduces the likelihood of premature wear.

4. Consider environmental factors

As we touched on above, the environment in which a shock cord is used has a direct impact on its lifespan and effectiveness. Exposure to moisture, UV light, extreme temperatures, and chemicals can weaken materials over time.

This is one of the reasons why different sectors often require subtly different solutions – essentially, various industrial environments often introduce their own unique stress factors that impact shock cord performance. For example, in cold storage facilities, it is essential to choose a cord that retains elasticity at sub-zero temperatures, so that you can be sure of its long-term reliability.

On that note; temperature also affects performance. Some materials lose elasticity in cold conditions, becoming brittle, while excessive heat can weaken structural integrity. Manufacturer specifications indicate which cords are suited to different environments.

5. Select the right material for durability and performance

The material of a shock cord plays a key role in its longevity and ability to withstand demanding conditions. Natural rubber cores provide exceptional elasticity, allowing the cord to stretch and retract efficiently under load. In particularly intensive environments, shock cords are often encased in a protective sheath that enhances durability and resistance to environmental wear.

Polyester sheathing is a common choice due to its high abrasion resistance and ability to withstand prolonged outdoor use. It protects the core from mechanical damage and helps maintain consistent performance even in rugged environments.

6. Ensure compatibility with fittings and attachments

Ultimately, a shock cord is only as effective as the fastening system that secures it. It is therefore worth putting extra time aside to assess compatibility with hooks, clamps, toggles, or tensioners to ensure the cord integrates seamlessly into the intended application. This is again where the diameter of the cord plays a major role, as some fittings require a specific thickness to achieve a secure grip. If the cord is too thin, it may slip under tension, while an oversized cord may not fit properly within fasteners or attachment points.

Industrial shock cords often feature reinforced loops, crimped metal ends, or pre-moulded plastic fittings to improve their reliability under repeated use.

This is not an exhaustive guide, but designed to be a helpful primer to help get you started. If you need any specific advice about choosing shock cords for your own application, or any queries about their technical specifications, feel free to contact us here at Ibex Marina. You can give us a call on 01706 360 363. Our expert team is always happy to help!