Cover Factor I & II
Relative cover
The fraction of the cloth area covered by the threads of one set is d / p — yarn diameter over thread spacing. If the diameter is derived from the count (Lecture FD-12: d in mm = √tex ÷ 26.7, assuming a packed specific volume of 1.1 cm³/g), relative cover can be written entirely in terms of count and density:
Example from the lecture: 25 tex at 267 threads/100 mm gives K = 1335, relative cover 0.50; 36 tex at 334/100 mm gives K = 2004, cover 0.75. Cloth cover combines the two sets: C = C₁ + C₂ − C₁C₂ = 0.50 + 0.75 − 0.375 = 0.875 ≈ 0.88.
The mill version: K(Ne) = EPI/√Ne + PPI/√Ne
With English counts the same idea becomes threads per inch divided by √Ne (the diameter in inches is about 1/(28√Ne)). The maximum for one set is about 28, so a plain fabric with warp cover 28 is “jammed” in the warp direction.
| A | B | C | |
|---|---|---|---|
| 1 | Warp | Weft | |
| 2 | Count Ne | ||
| 3 | Threads per inch | ||
| 4 | Weave | ||
| 5 | Cover factor (threads / √Ne) | 24.15 | 12.52 |
| 6 | Relative cover (K ÷ 28) | 86.2% | 44.7% |
| 7 | Total cover factor | 36.67 | |
| 8 | Weave divisor | 1.00 | |
| 9 | Plain-equivalent cover factor | 36.67 | |
| 10 | Cloth cover C₁+C₂−C₁C₂ | 92.4% |
Weavability limits (airjet) and weave factors
| Loom width | Standard total cover | Upper limit |
|---|---|---|
| 75" | 36 | 37.5 |
| 110" | 28 | 32 |
| 134" | 25 | 32 |
Wider looms insert the pick over a longer distance, so they tolerate less cover: a construction that weaves comfortably at 75" may be unweavable at 134".
| Weave | Divide K by |
|---|---|
| Filling rib 2/2 | 1.5 |
| Warp rib 2/2 | 1.26 |
| Panama (hopsack) 2/2 | 1.4 |
| Drill 2/1 | 1.22 |
| Drill 3/1 | 1.3 |
| Twill 2/2 | 1.34 |
| Drill 4/1 | 1.34 |
| 5/1 | 1.4 |
| 6/1 | 1.44 |
| 7/1 | 1.45 |
| Satin 1/4 | 1.41 |
| Satin 1/5 | 1.51 |
| Satin 1/6 | 1.59 |
| Satin 1/7 | 1.67 |
| Satin 1/8 | 1.73 |
Original lecture material
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