WHAT IS THE IMPORTANCE OF ANTI-TORSION ROPE OR CABLE ?
An anti torsion cable is by definition a bond of technical fibers such as Kevlar, ensuring the link between point A and point B with minimum loss of torsion.
It is frequently composed of an aramid core compacted into several parallel strands, then an anti-torsion sheath also made of aramid and finally covered with a protective polyester sheath.
Terminations or ferrules are made by crimping, splicing and or stitching directly onto thimbles. This is usually done by a rigger or a sailboat. We speak of anti torsion rope when it is composed only of fibers and cable when the fibers are covered with a plastic protection (usually thermoformable).
The anti torsion ropes or cables are integrated into the headsail luffs which are intended to be used with a furler. They are also used as a winding support for spinnaker furlers which is a subject that concerns us more particularly.
The characteristics of a good anti torsion cable are :
- Very low weight
- Significant torsional stiffness
- Real flexibility and therefore easy handling and storage once the sail is furled
- Sufficient load capacity
- The largest possible external diameter (for a spinnaker furler)
- A length adapted to its use
Weight : Historically, the anti torsion rope or cable has replaced stainless steel cables. A 30 meter stainless steel prop of 12 mm and resistance of 10 tons weighs around 20 kg when a cable of equivalent resistance in textile weighs only 1.5 kg !
Stiffness : The importance of this cable is directly linked to its anti torsion quality because it is it which will transmit the furling movement to the swivel. A turn of the continuous line wheel on the deck must turn into a turn of a swivel at the head of the sail. The longer the luff is, the greater are the anti torsion properties.
Flexibility : The goal is to be able to store your sail and its anti torsion in the smallest possible space. The sailmakers have adapted their sail bags for longer and shorter models to facilitate handling.
Charge capacity : Anti-torsion is also defined by its load bearing capacity. The more the guide is taut, the better the connection between the drum and the swivel. (Also to read : Why use a reeving optional 2:1 block ?). The load capacity is ultimately less essential than the anti-torsion characteristics but as one does not usually go without the other, this criteria must be verified. In any case, the load capacity must be at least slightly greater than the one of your furler.
Diameter : Prefer the maximum diameter that the thimbles of your furler can accommodate. Beyond 5T of working load, we recommend the use of anti torsion cable instead of ropes.
A large diameter ensures better torque, and therefore effortless winding of the spinnaker.
Length : It is extremely important that the cable is not too long. The length will be to the detriment of the tensioning. You will have to remove the obstructions from your furling system at the measured rope distance. For some suppliers it will also be necessary to subtract a
coefficient of elongation.
ROPE OR CABLE ?
An anti torsion rope is sold by winding and is then detailed by the meter. The length is adjusted by seams or clamps. It is a very relevant solution for the majority of sails used for pleasure on sailboats up to approximately 14 meters, working loads of up to 5 or 6 tons or lengths less than 20 meters.
An anti torsion cable is always a cable made custom for a project. It is a more technical solution, more expensive but much more efficient. The cable is systematically chosen for technical sails and offshore racing. This solution becomes an obligation when the working loads are high or the lengths exceed 20 meters.
WHAT ARE THE DANGERS AND SYMPTOMS OF POOR QUALITY CABLE ?
As explained previously a poor quality cable will not or very badly lead the swivel. The furling will be greatly affected, will require more effort on the furling line and can therefore sometimes prevent the complete functioning of the furler.
After making sure that the halyard tension is sufficient, here are the main symptoms that are easy to spot :
- Many furling turns before seeing the sail roll up.
- The cable rolls up on itself (pigtail).
- Elastic returns.
- Cable elongation visible to the naked eye
- Diameter too small (see our recommendations)
- You manage to twist the rope between your hands (30 to 40 cm)
- The swivel touches the mast and therefore prevents more tension in the halyard
KARVER AND ANTI TORSION :
The development of Karver in its early years is explained by the support of its clientele of racers and professionals (Super Yachts). At their level, the choice of anti-torsion is a strategic element for which we leave them full responsibility.
Karver’s more recent turn towards boaters, however, prompted us to offer anti torsion rope. This remains optional out of respect for the convictions and working habits of each sailboat or rigger.
We have chosen to offer our customers the Pro Drive 2 string from Marlow which seemed to us to be very good value for money and which had been used by our English distributor for many years.
However, there are many other quality ropes of which here are
some examples :
· Armare / Soft Rig
· Future Fibers
· Gottifredi Maffioli
· Smart rigging
· Cousin Trestec (FR)
· FSE Robline (AT)
· Gleistein (DE)
· Gottifredi Maffioli (IT)
· Hampidjan (IS)
· Lancelin (FR)
· Liros (DE)
· Marlow ropes (UK)
· New England ropes (US)
· Southern Ropes (ZA)
We will be happy to complete this list with elements you send us.
Karverpedia article written by Alois Kerduel (Update April 2021)