Stretch vs. Creep

A post by Ryan Scott on the West Marine Rigging-Newport site that might be helpful as you prepare your boat for the coming season.

One common misconception that I am asked about, is whether stretch and creep are the same thing. They are not. I saw an analogy a while ago describing the difference, and I still think it is one of the best ways to demonstrate it. Rubber bands stretch, taffy creeps.

Stretch is measured as a percentage of length at a percentage of breaking strength. It is elasticity, or recoverable elongation. Say you have a halyard, that when the sail is hoisted, has a 100′ working length. And say the halyard has a breaking strength of 2000 lbs, and a stretch characteristic of 2% at 20% of BS. When that sail exerted a load of 400 lbs. on that halyard, the halyard would stretch 2′. However, when the load was removed, the halyard would return to its original 100′ length.

Creep on the other hand is non-recoverable elongation. It is the permanent long-term elongation which occurs until the line reaches breaking strength. Creep is not as large of an issue in most applications of running rigging, where loads are not constant, as it would be in standing rigging, where a constant load on a line would continually creep it, and make it longer.

If you have any questions about this, are looking for ways to eliminate stretch on your boat, or have any rigging needs or questions, feel free to contact us at ryans@westmarine.com .

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