XD Cunningham / downhaul system – Laser
Description
XD Cunningham / downhaul system – Laser
In the strict one design Laser class there is a degree of freedom with control systems.
The Cunningham / downhaul system is possibly the most difficult of the Laser control systems to get right because of the limited “travel” distance available & the differing requirements of the three sails.
The Harken XD (eXtra Dimension) Cunningham / downhaul system was first introduced in 2005 proving to be a big improvement over the previous system (which wasn’t difficult!). At that time it set a new bench mark by which other systems were judged. Originally it was supplied for an intended purchase of 6:1 with 16mm “Air” blocks. However with the introduction of the Standard Mk2 sail & composite top mast an increase in the power & efficiency of the Cunningham / downhaul was sort & later a mix of 29mm & 18mm “Carbo” blocks were supplied. With development the more usual purchase became 8:1 coupled with blocks of bigger sheave diameters & wider “throats” reducing friction & improving efficiency.
Today’s XD Cunningham/downhaul system is supplied as an 8:1 system with a choice of either Harken 29mm “Carbo” blocks or Ronstan 30mm “Orbit” blocks. The Harken blocks are slightly lighter & the Ronstan blocks more robust. The primary line is spliced whilst the secondary line is knotted to facilitate change of the secondary line (which will be needed from time to time during the life of the system in order to maintain its function, reliability & efficiency). In theory a “Fiddle” block has less rope on rope friction but larger dimeter blocks have inherently less friction so it is a “six & two three’s” situation with the bigger blocks having the slight advantage.
If looked after reasonably well (kept clean, occasionally lubricated but primarily free of sand & grit) these systems have proved to be exceptionally effective & durable.
The most widely used Cunningham / downhaul purchase arrangement is now 8:1 (6:1 is not enough for any Standard sailor & most Radial sailors prefer to apply Cummingham / downhaul progressively rather than “grunt” it on).
The system comprises:
1) Harken 29mm “Carbo” blocks (three single blocks) or Ronstan 30mm “Orbit” blocks (three single blocks).
3) Primary line: 5mm Dynema D12 (Anthracite)
5) Secondary line: 4mm (Neon/white, Black/white)
6) Quick rig nook (optional)
Over the years sailors have used a variety of other manufacturers blocks some of which have worked reasonably well. Essentially the Cunningham / downhaul blocks need to be robust in order to survive operating in proximity with the gooseneck, have smooth profiles to prevent catching & have wide “throats” to accommodate the fact that the secondary line does not always have a straight “lead-in” to the block. The Harken 29mm “Carbo” block & the Ronstan 30mm “Orbit” blocks nave both proved to be efficient, reliable & durable in these regards although there strengths are different.
Of course, by themselves control systems do not make you fast although they can prevent you being slow, which is nearly the same thing…
(If you are fighting your controls when others are not then the chance are that you are loosing distance to them.)
Sail & Sport offers the XD Cunningham / Outhaul system with either block rigged 6:1 with high quality lines & setting up instructions.
Should you wish for a custom system email us your requirements: info@sailandsport.co.uk
