Rope 101: What is Constructional Stretch?

While many people outside the industry would expect ropes of the same fiber, size, and strength to equally perform, other factors at play will impact the performance. When assessing rope performance, it is also important to consider its constructional stretch.

What is a Constructional Stretch?

Constructional stretch refers to the elongation that occurs within the construction of a rope while it takes on the load/force in its application. The best way to picture constructional stretch is a . When pulled apart, the device tightens on your finger as the force of pulling straightens out the weave of the trap. This causes the device to narrow and tighten your fingers.

Rope constructions function similarly. As force is applied to the rope, the fibers will move within the construction to realign parallel to the force. In many common rope constructions, the strength is supplied by the jacket fibers. These jacket fibers are not linear and need to be straightened out before the load is taken up completely.

Our proprietary construction uses internal linear strength members in the core, which provide strength and resistance to constructional stretch. These linear core strength members are already aligned with the direction of the forces, reducing how much they need to shift to engage the weight/tension. This results in a rope that has an overall lower stretch when compared to a different construction style with the same strength.

Key Factors Affecting Constructional Stretch

• Construction Type: Traditional solid braided ropes and other non-core ropes will tend to have higher stretch. Reinforced ropes and those including a linear core will tend to be lower in stretch, making them the preferred choice for most applications.
• Diameter: Typically Diameter and Strength are related, so another technique to cut down on constructional stretch would be to use a larger product. This will help mitigate the effects of the constructional stretch by overcompensating with additional strength.
• Manufacturing: Pre-stretched ropes during manufacturing often show reduced constructional stretch in use. Some manufacturers will pre-stretch their ropes, though this is an additional step so it does impact the cost.

Why It Matters

• Load Distribution: Significant constructional stretch can impact how a rope takes up a load, potentially leading to uneven load distribution.
• Efficiency: Excessive stretch can required modifications to compensate for. This could mean additional time re-tensioning or adjusting the cord to get it tight. This is why Quality Nylon Rope’s low-stretch cords are the preferred cord for many lacing applications. Avoiding the need to retention cords can lead to more installment time or to return to tighten the cord.
• Accuracy: For tasks needing precise control, understanding constructional stretch helps in making accurate calculations, ensuring optimal performance.
• Bonus: Strength is derived from the core members, abrasion to the jacket will have less impact on the rope’s lifespan. With that in mind, the jacket can be viewed as an extra line of defense against failure when the rope is in a challenging environment.

Managing Constructional Stretch

By understanding and managing constructional stretch, you can improve safety, performance and efficiency in your applications.

• Choose Wisely: When selecting a rope, consider how the stretch may impact your requirement. For applications where extra elongation is a concern, a linear core rope will provide extra holding power to count on.
• Inspect Regularly: Check ropes regularly for wear and performance changes.
• Unsure? Ask!: Please reach out if you have any additional questions on constructional stretch, or how this factor may impact how you are using your rope. Contact us at sales@qualitynylonrope.com, Send us a request, or give us a call at 800-519-4878