KETTU- PART 2
CONTINUED FROM PART 1
7. Knot (unit)
The knot is a unit of speed equal to one nautical mile(1.852 km) per hour The
ISO Standard symbol for the knot is kn. Worldwide, the knot is used in
meteorology,and in maritime and air navigation—for example, a vessel travelling
at 1knot along a meridian travels approximately one minute of geographic
latitudein one hour.
Etymologically, the term derives fromcounting the number of knots in the line
that unspooled from the reel of a chiplog in a specific time.
The speeds of vessels relative to the fluids in whichthey travel (boat speeds
and air speeds) are measured in knots.For consistency, the speeds of
navigational fluids (tidal streams, rivercurrents and wind speeds) are also
measured in knots. Thus, speed over theground (SOG) (ground speed (GS) in
aircraft) and rate of progress towards adistant point ("velocity made good",
VMG) are also given in knots.
8. What is knot in general talk?
A knot is a method of fastening or securing linearmaterial such as rope by
tying or interweaving. It mayconsist of a length of one or several segments of
rope, string, webbing, twine,strap, or even chain interwoven such that the line
can bind to itself or tosome other object (the "load"). Knots have been the
subject of interest for their ancientorigins, their common uses, and the area
of mathematics known as knot theory.
There is a largevariety of knots, each with properties that make it suitable
for a range oftasks. Some knots are used toattach the rope (or other knotting
material) to other objects such asanother rope, cleat, ring, or stake. Some
knots are used to bind or constrict objects.
Decorative knots usually bind to themselves toproduce attractive patterns.
9. Learning
While some people canlook at diagrams or photos and tie the illustrated knots,
others learn best bywatching how a knot is tied. Knottying skills are often
transmitted by sailors, scouts, climbers, cavers,arborists,
rescueprofessionals, fishermen, linemen and surgeons.
9a. Most familiar knots
The male knot is one which can beeasily removed by pulling one of the strings.
The female knot is one tie with gripand untie both strings. In brooms, joints
etc we use female knot. While packing paperbundles we put male knot just for
holding with out damage. Cartons for transport are tied only with female knots.
Aya(Koti) (clothesline) is timed either with male or female knots depend on
whether temporary orpermanent. Dhobi put male knots in the river bed. In the
house we put femaleknot, since it is permanent.
The bucketto fetch water is tied to rope with female knot. But the other end of
the ropewill be tied to the beam supporting pully mostly with a male knot.
A loop with female knot end is thrown to a smaller pillarto tie the boat. Other
end connected with femaleknot is adjusted in the boat for getting in and
getting out from the boat to the embarking area.
10 Strength
Knots weaken the ropein which they are made. Whenknotted rope is strained to
its breaking point, it almost always fails at theknot or close to it, unless it
is defective or damaged elsewhere. Thebending, crushing, and chafing forces
that hold a knot in place also unevenlystress rope fibres and ultimately lead
to a reduction in strength. The exact mechanisms that cause theweakening and
failure are complex and are the subject of continued study.
Relative knotstrength, also called knotefficiency, is the breaking strength of
a knotted rope in proportion tothe breaking strength of the rope without the
knot.
Determining aprecise value for a particular knot is difficult because many
factors can affect aknot efficiency test: the type of fiber, the style of rope,
the size of rope,whether it is wet or dry, how the knot is dressed before
loading, how rapidlyit is loaded, whether the knot is repeatedly loaded, and so
on. The efficiency of common knots ranges between 40—80% of the rope'soriginal
strength.
In most situations forming loops and bends with conventional knots is far more
practicalthan using rope splices, even though the latter can maintain nearly
the rope'sfull strength. The working load limit of a rope is generally
specifiedwith a significant safety factor, up to 15:1 for critical applications.
While putting adhothi the load on the rope is different from when putting a
shirt or putting abed sheet for drying. When more objects or objects withweight
are put chances of dhum is more with ropes.
11.Security
Even if the rope doesnot break, a knot may still fail to hold. ***Knots that
hold firm under a variety of adverse conditions are said tobe more secure than
those that do not. The main ways knots fail tohold are:
My note- ***This I am not able to grasp
Slipping-The load creates tension thatpulls the rope back through the knot in
the direction of the load. If thiscontinues far enough, the working end passes
into the knot and the knotunravels and fails. This behaviour can worsen when
the knot is repeatedlystrained and let slack, dragged over rough terrain, or
repeatedly struckagainst hard objects such as a masts and flagpoles.
12 Components
A bight is any curved section, slackpart, or loop between the ends of a rope,
string, or yarn.
Bitter end- More a rope worker's term thana knot term, it refers to the end of
a rope that is tied off, hence theexpression "hanging on to the bitter end". A
bitt is a metal blockwith a cross pin used for tying lines to, found on piers.
Loop-A full circle formed by passing theworking end over itself.
Elbow-Two crossing points created by anextra twist in a loop.
Standing end-The standing end isthe longer end of the rope not involved in the
knot, often shown as unfinished.It is often (but not always) the end of the
rope under load after the knot iscomplete.
My note- Inplastic wires the end is slightly heated and twisted so that threads
of thewire would not split in the end.
Standing part-Section of linebetween knot and the standing end .
Turn-A turn or single turn is a singlepass behind or through an object.
Working end-The active end of aline used in making the knot. May also be called
the 'running end', 'live end',or 'tag end'.
Working part-Section of linebetween knot and the working end.
13 Categories
Decorative knot -A complex knotexhibiting repeating patterns often constructed
around and enhancing an object.List of decorative knots.
Hitch -A knot tied to a post, cable,ring, or spar. List of hitch knots.
Buntline hitch for tying a rope to a pole.
Diamond hitch for packing trailanimals. Rolling hitch for securing a rope to a
pole, or one rope to the middleof another
Plait (or braid)-A number of linesinterwoven in a simple regular pattern.
On those days beforeour beauty parlour had so much popularity women used to
plait their hair and tied at end. Sometimes twoplaits, which added beauty for
young women. Hairs of Small female children going to school were plaited
splitting to two parts and tiedwhich added their beauty. Naughtyfemale kids
with such plaits were/are called- Rettival rukkudu. Nowhair is cut to such
a length not able to even to tie the ends. Even aged women above
shashtipoorthi are not exception.
14 Trick knots
Trick knots are knots that are used as part of a magictrick, a joke, or a
puzzle. They are useful for thesepurposes because they have a deceptive
appearance, being easier or more difficult to tie or untiethan their appearance
would suggest.
15 Knot theory
Knot theory is abranch of topology. It deals with the mathematical analysis of
knots, theirstructure and properties, and with the relationships between
different knots.In topology, a knot is a figure consisting of a single loop,
abstracted fromany physical rope or line, with any number of crossing or
"knotted"elements. As such, it has no proper ends, and cannot be undone or
untied.Various mathematical techniques are used to classify and distinguish
knots.
16.The Ashley Book of Knots
The Ashley Book ofKnots is considered the definitive work on the topic. Knot
tying consists ofthe techniques and skills employed in tying a knot in rope,
nylon webbing, orother articles. The proper tying of a knot can be the
difference between anattractive knot and a messy one, and occasionally life and
death. It isimportant to understand the often subtle differences between what
works, andwhat doesn't. For example, many knots "spill" or pull
through,particularly if they are not "backed up," usually with a single
ordouble overhand knot to make sure the end of the rope doesn't make its
waythrough the main knot, causing all strength to be lost.
17 .Difficulty
The tying of aknot may be very straightforward (such as with an overhand knot),
or it may bemore complicated, such as a monkey's fist knot. Tying
knotscorrectly requires an understanding of the type of material being tied .
Forexample, cotton string may be very small and easy to tie with lots of
internalfriction to keep it from falling apart once tied.
18. Material
The form of thematerial will influence the tying of a knot as well. Rope is
round incross-section, and has little dependence upon the manner in which the
materialis tied. Nylon webbing, on the other hand, is flat, and
usually"tubular" in construction, meaning that it is spiral-woven, and has
ahollow core. In order to retain as much of the strength as possible
withwebbing, the material must be tied "flat" such that parallel sectionsdo not
cross, and that the sections of webbing are not twisted when they crosseach
other within a knot.
Chakku charatu could give more grip during tying ofbrooms than with thin
metallic rods called Kettukambi.For holding milk box / Post Box with grip this
kettukambi is used to hold withgrip. Post Box may not carry weight. But milk
box has to carry 4 packets ( 2lire weight). Hence there is a difference in
tying the two items to compoundgate.
The crossing ofstrands is important when dealing with round rope in other
knots; for example,the figure-eight loop loses strength when strands are
crossed while the knot isbeing "finished" and tightened. Moreover, the standing
end or the endfrom which the hauling will be done must have the greater radius
of curvaturein the finished knot to maximize the strength of the knot.
As the day goes, due to wear and tear the knot go looseas well as tying
material too loose quality. Effort is requiredto untie. If Nylon rope is used
for a Koti(Clothes line), reusing is leastadvised on break, since at breaking
point the strands could appear as grains and even may fall in eye whilecloths
are put for drying.
19. ToolsTools are employed in the finishing of a knotspecially during
operations. With the advent of wire rope, many othertools are used in the
tying of "knots."
My note- Stitching made on wounds and knots put at end. Afterjointing skin the
stitching is removed. While knots are removed, heavy painwould be left.
20 Meanings of knot
1. A fastening madeby tying together lengths of material, such as rope, in a
prescribed way.
2. A decorative bowof ribbon, fabric, or braid.
3. A unifying bond,especially a marriage bond.
4. A tight cluster ofpersons or things: a knot of onlookers.
5. A feeling of tightness: a knot of fear in my stomach.
6. A complexproblem.
7. A hard place orlump, especially on a tree, at a point from which a stem or
branch grows.
8. A protuberantgrowth or swelling in a tissue: a knot in a gland.
9. Nautical Adivision on a log line used to measure the speed of a ship.
Compiler- R.Gopala Krishnan, 77 retired AGM, Telecom, Trivandrum
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