CONSTRUCTION OF LAID (with twisted strands) CORDAGES
is a summary from the fibres to the cable
so as to 'anchor' ideas in memory here is another
way to do the laying
HOW TO PROTECT CORDAGES : WORMING, PARCELLING, SERVING.
shows how to and with what you worm a cordage to make it
parcelling it (note the way each layer recover the other as the tiles
roof) and finishing by serving it and then tarring it.
Taken straight from The Seaman’s Friend : A Treatise on
Seamanship by Richard
Henry DANA Jr First published in 1879.
[Begin quote p 44]
a rope , is filling up the divisions between the strands, by passing
along them, to render the surface smooth for parcelling and
PARCELLING a rope is wrapping narrow strips of canvas about
it, well tarred, in order to
secure it from being injured by
rain-water lodging between theparts of the service when worn.
parcelling is put on with the lay of the rope.
SERVICE is the laying
on of spunyarn, or other small stuff in tourns round the rope, close
together, and hove taut by the use of a serving-board for small rope,
and serving-mallet for
Small ropes are sometimes served
without being wormed, as the crevices between the
strands are not large
enough to make the surface very uneven ; but a large rope is always
wormed and parcelled before being served.
The service is put on against
the lay of the rope.
HOW TO FIND THE ANGLE OF THE LAY
Here again a simple
should be enough to show how to find the angle
axis of the whole cordage and the axis of a part of a
This angle of lay is determined by the amount of twist applied to the
strands when laying the
The smaller the angle the softer the laying.
More twist, that is harder laying, open the angle.
Which leads to : the harder the lay the shorter the
in the helical course followed by
the yarns of a
and by the the strands of the rope.
For a given hardness of lay the greater the diameter of the rope the
greater the step of helices.
Same thing in a strand with the twist
applied to the spun yarns.
Note that in each strand a given amount of twist will result in an
angle that is more acute for
the inner fibres than for the outer
Identical remark for fibres in a yarn.
This is what makes that the angle of the lay of the whole rope a not
really sure indication of
the physical properties of the rope
considered as a whole.
In fact the hardness and stiffness of the rope is the
effect of twist of fibres and
yarns, twist of yarns and strands and
twist use for laying the strands into a rope.
Were you to input maximal twist to the strands when laying the rope
this rope will not be
hard laid if there is not already enough twist in
the strands themselves to maintain the laying
of the rope.
The twist in a strand is what make the the
the rope to elongation under load.
When under load the yarn tend to
the cost of a tremendous - a handful of weeks - work here is the
of the essential points
fabrique des manoeuvres pour les vaisseaux
de la CORDERIE PERFECTIONNÉ
Mon Sieur Duhamel du Monceau paru
en M. DCC. LXIX ( 1769 - seconde
édition ) à
Paris chez Desaint, Libraire, rue du Foin.
(alas in French and 18th French at that even if I did some 'cosmetics'
about that, most
French cannot even read it fluently !) of nearly 600
pages of this monumental work the best
ever done on the subject,
present days included! even the Encyclopaedists Diderot et
took from it and the only clear part in this Encyclopaedia is a direct
This I will not translate or not without many, really many, asking (in
number not in repetition)
Even this summary is really much work .
I will never cease to marvel at the very modern approach of Duhamel du
auditing the Royal Roperies.
Only tool that is
there is modern Statistics that were still to be found.
It is not yet finished but you are in for many hours of study
just with what is already done.
Fortunately images are international.
dessin montrant un quarré et un chantier
de corderie - Rope walk
de corderie en raccourci - Roprwalk shortened
et clavette - Top or topper
1 de l'art de la Corderie en petit format - Engraving from Art de la
2 de l'art de la Corderie en petit format - Engraving from Art de la
Diaporama grand format des planches de l'Art
de la Corderie ( big format , huge even )
Le même diaporama mais en 800
pixels de large pour une ouverture plus rapide
Diderot & d'Alembert Encyclopaedia engravings : une
FORCES , CORDAGES & KNOTS
These simplistic drawings should be enough to give an idea of
the forces inside a cordage in
service ( load )
a bending curve, knot or pulley.
a strand of a load bearing cordage
ADDED 2008 June
27th : recent documents from Brittany (
If those two drawings seem a bit obscure and abstract to you then here
is a modelization of
what is 'really' happening.
I used special threads found in a garden centre ( a thin wire
rubber foam around it ) and
plasticine clay to make some modelization.
There is no hidden sleight of hand.
- with these pictures
see forces N°1 et N°2 in their results :
under loading there is an elongation and the helix "step" become longer
and the cylinder it has
been put around see its diameter
lessening. The wire cut into the cylinder, just as yarn
situated at the
periphery of the
strand compact this same strand when said strand is
becoming thinner under a pulling force.
- Here is another illustration of the constriction
coming from the periphery and leading to a
-This makes clear the fact that when a tension is imposed following an
helix , there is a
lengthening of the "step"
the cylinder of revolution round which it is inscribed see
- Here you should see the 'cutting' , shearing effect imposed by
a tension following an helix.
- This is an illustration of three strands under tension : they lengthen,
the "step" of the helix followed by each strand elongate.
don't keep a perfectly circular cross section, but they
are compacting each other
- Helical distribution of tension
can be readily seen here.
-Here is a modelization of how 3 strands are pushing
against each other under tension.
I hope that these visuals will have make the phenomena clearer for you.
illustrate the compression zones and elongation zones in a
Analyse carefully these zones and where they
This slideshow should show what tensions can happen
during the building of knots.
There exist friction forces :
- between fibres
- between yarns
- between strands
Illustration done with springs which will give you some sort of
approach of the right idea.
This slideshow is about how tensions are born
in a knot
HOW TO COIL A CORDAGE SO
AS TO GET A SNARL FREE UNCOILING
(MARINE NATIONALE de FRANCE )
Just coil it as shown by this digital
created after a photography by Marine
HOW A LAID CORDAGE BEHAVE UNDER A LOAD
will not show it while it is in rotation on its axis. The end result of
rotation is that it somewhat
'un-twist' itself. Photo show the result : the 'step' of the helix
course of the strands lengthen, the angle of the lay lessen and the
cordage becomes thinner.
Experience is easy to do with 20" of 3S nylon 3 mm and a 400g weight.
Just take care to leave both extremity to rotate following the vertical
ROCHEFORT : THE ROYAL ROPE WALK ( SUN KING LOUIS THE 14th )
LA CORDERIE ROYALE
This covered rope walk was but a small part of
a huge naval
It was the longest rope walk of the known world
in its century : 374 metres ( 390 meters
outside size )
Twisting "to the third" it could give 374m * 0.66 = 246 metres long
cordage was the
That is over a French cable length.
[a cable -French- was 1 encablure = 120 brasses = 100 toises
= 195 metres
it was 1/10 of 'un mille marin'
-- 1 toise = 6 pieds = 1.95 metre -
1 brasse = 10/12 toise =
1/120 encablure = 1.62 metre.]
Some pictures there :
by VERNET, a famous French painter.
by some other artist.
-This is an
of La Corderie Royale taken from
Corderie Royale - ROCHEFORT (17) Juin 1995. (photo André LE
Copyright © 2001-2006 [BDC HENRI]. Tous droits
by kind authorization given by Dominique
HENRI whose personal pages
really worth to
be seen. ( http://perso.orange.fr/bdc.henri/ )
- my own slideshow
of the outside aspect
- what can be seen inside
in Le Centre de la Mer ( The Sea Centre )
This huge building was built on swamp ground.
Thousands of oak were used to stabilize the
" / a raft was built ;
Centuries later it is still there despite huge destruction by
Army Vandals in WW 2 !