AmatsunawaUSA works hand-in-hand with our jute rope experts every step of the way, from planting to processing.
This relationship with our manufacturers starts with understanding jute ply and lay, and launches us towards producing the best bondage rope on the market.
Through these connections, we’ve learned there’s no such thing as a “standard” jute ply and lay ratio, since “tight lay” and “loose lay” are subjective.
Instead, the ratio varies based on a number-of-factors.
Determining Jute Ply and Lay
The first step is determining the quality of the raw fibers, including the length- and finesse-of-the-filaments.
(Read more about jute yarn grading)
More fine filaments can be twisted together into a tighter yarn of equal count, than that of a lower-quality, course jute. The relationship between coherence and obliquity makes this possible.
Don't Get It Twisted...
As filaments are twisted, their strength increases up to the “optimum twist”. Batching oil is critical for this step, in order to help the filaments coalesce
Any twisting past that optimal point, decreases obliquity because fibers tend to lay more perpendicular than parallel to the length-of-the-yarn. This is called losing linear orientation.
A lower-grade jute has a lower optimum twist. Therefore, there’s a direct correlation between grade and overall longitudinal strength.
When you wind strands together, the yarn determines the optimum counter-twist.
If the twist dynamics counter each other, the strand will hang straight. However, if they're not properly balanced, they won't be correctly oriented.
Once all strands have the correct dynamics, they must be twisted together to physically make the rope.
The twist dynamics of the yarn pulling in one direction, the strands in the opposite direction, and the rope in the original direction must align, in order to prevent the rope from corkscrewing into itself.
These three dynamics balance against each other, and determine the lay-ratio of the rope.
While not as detrimental as over-twisting the yarn, when strands or rope are tightened too much, it passes the optimum point-of-strength. In turn, making filaments more prone to breakage.
The tighter a rope is wound, the more difficult it becomes to manipulate. On the other hand, when it’s still within a ratio for structural integrity, a looser lay will feel super soft. But it is easier to damage.
Lay is commonly measured with a simple system. On one end there's a retention; the other, a wheel.
Measuring Jute Ply and Lay
A rope runs over the wheel, pulled by a weight, then stretched using a ø (mm) x ø (mm) ÷ 8 (kg) load, so a clear 1-meter-length can be measured.
For example, for a ø6.0mm rope the equation would look like this:
6 mm x 6 mm = 36 mm
36 mm ÷ 8 kg = 4.5 kg
Jute rope manufacturers lay paper over-the-top-of-the-rope and rub a crayon, or other writing utensil, to mark the indentations.
This makes it easy to calculate the twist of the rope. The ratio is determined by taking the distance the strand has rotated, and dividing it by the rope’s diameter.
However, this method only calculates the lay-ratio-of-the-rope; the repeated winding of the strands.
Owing to the aforementioned rope dynamics, a ratio of 4.5 can feel very-loose-to-slightly-tight. On the other hand, a 3 can feel super-tight-to-slightly-loose.
Measuring a rope’s diameter in a compressible, pliant manner is complicated—especially when it contains a spiral of 3-strands. That’s why manufacturers measure the uncompressed-diameter-of-a-circle which encloses all-strands.
It’s extremely difficult to measure with a typical 2-dimensional gauge, like a caliper, if the surface is flat.
The Trickiness of Multiple-Ply
To complicate matters further, multiple-ply yarns add in a fourth twist dynamic. Semi-loose 2- and 3-ply yarns can feel soft, which impacts the twist dynamics, and in turn, the lay.
If multiple yarns are tightly wound, they may become too hard, resulting in an uncomfortable, knobby feeling.
(A similar feeling may occur if you store your bondage gear incorrectly. Learn how to organize your jute rope to maintain its integrity for the life of the rope.)
Jute Ply and Lay at AmatsunawaUSA
AmatsunawaUSA no longer specifies jute ply and lay-ratio, instead, opting to focus on education of how natural bondage rope is used.
We teach our machine operators and students to really get a feel for the rope, and keep a keen eye out for top-notch quality control.
That's why our jute ply and lay paves the way for a rope that is hands-down the highest quality on the market!