Page 200 - J. C. Turner "History and Science of Knots"

190 History and Science of Knots

of each other. For any one kind of rope, the basic fibres are always the same
size, whatever the size of the rope. Laid rope and simple braids tend to have
yarns of the same size, so that the main differences in different size ropes is in
the number of yarns per strand. Sheath and core ropes are more complex; the
yarns forming the sheath change in size, but the core may change in several
ways, depending on the details of the design. When a rope passes round a
curve, as in a knot, the curvature of the rope as a whole, expressed relative
to the diameter of the rope, is more or less constant whatever that diameter,
but the curvature of the individual fibres, expressed relative to the diameter
of the fibre, is much less for large sizes of rope (containing many fibres) than
for small (containing few). The effects of all these differences in structure are
unknown. Barnes [7, p. 861 found that knot efficiencies were lower in lighter
nylon monofilament lines.

Table 4. INFLUENCE OF ROPE SIZE AND TYPE
ON KNOT STRENGTH EFFICIENCY
Laid and plaited Polypropylene and double-braided nylon ropes [19]

Polypropylene Nylon
Three-strand laid Plaited Double-
braided
Knot and Ashley number [5] % inch 'h inch % inch • inch 1 inch Mean (to ' inch 1/2 inch
diem diem diem diem diem Table 2) diem diem
Bends
Reef Knot #1402 36% 44% 44% 43% 41% 42% 37% slipped
Sheetbend #1418 40% 52% 48% 51% 48% 48% 40% 48%
Double Sheetbend #1434 41% 49% 51% 49% 48% 48% 49% 61%
Overhand lend #1410 36% 44% 38% 46% 47% 42% 43% slipped
Loops
Bowline #1010 52% 61% 62% 55% 56% 57% 53% 88%
Hitches
Clove Hitch #1671 43% 67% 60% slipped 45% 54% 61% 73%
Timber Hitch #1665 64% 67% 66% 70% 67% 67% 70% 86%