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Selecting Control Lines

Updated August 2021 following Olympics! Polytech now standard Technora line.

The main factors involved in selecting control line are useability (rope diameter, feel, grip in the hands, and colour differentiation), durability (basically how long will it last), and suitability (strength/elongation/stretch). In this article I will explain how these factors apply to each system, and what I believe are the best lines that we offer to use.

We should point out that there are many rope manufacturers, each offering a wide range of control line, so it is impractical, and would be very confusing, to offer every rope available. What we do is to continually review what is available from the ten or so manufacturers that we track, if we think it is interesting test it, and decide what we think is most appropriate to offer to our customers. The range of control lines that we offer to our customers from leading rope manufacturers Robline, Marlow and Gottifredi Maffioli, reflects this. If you think that we are missing a key control line please let us know.



I will start with the kicker/vang as this is probably the most critical and will also help explain most of the factors that apply to other systems.
The kicker/vang is the only highly loaded system on the Laser where there are many small sheave size blocks in the lower unit and in the floating double block creating multiple turning points. The resistance in a system like this is a factor of the number of turning points, the block sheave size, rope diameter and rope construction. When a rope passes around a block, no matter how perfect the block is, the rope is distorted and there is internal friction in the rope. To explain this another way if you were to rig a standard kicker using a very very thin control line you would find that it runs amazingly well and without it attached to the boom you would be able to pull the top block and all the control line through the system easily. That is because the ratio of the line diameter to the block sheave diameter is much smaller and the line isn’t being distorted as much. If you rig it with a typical 4mm line you won’t be able to pull the top block by hand as there is just too much friction caused by the distortion of the rope and extra surface area contact.


The high loads and frequent cleating/uncleating mean that the kicker/vang line has a hard time so, unless we are happy to replace our lines frequently, we want a line that is durable. The durability of control lines is a complex combination of the line diameter, construction and above all materials. The smaller the diameter the less material there is in the rope which results in it wearing quicker than larger diameter ropes. For ropes with a cover and a core (like the majority of secondary lines) the movement of the cover over the core causes friction which in turn causes internal wear. The materials that the rope is made of influence both the durability and suitability. From a durability perspective the use of Technora® in the cover makes the rope last far longer, which on the highly loaded kicker where the cleat is used a lot is a definite advantage over normal Polyester covered rope. Technora in the cover also results in a rope that has more grip in the hands.

We sell two secondary lines that have Technora in the cover: Marlow Excel Racing GP78  and Robline Dinghy Polytech. The Marlow GP78 rope is incredibly durable as a result of the materials used to make it and the tightness of the core to cover, but this tightness does result in a rope that is quite stiff. This stiffness of the rope seems to increase the friction in a kicker system in comparison to a normal 4mm polyester covered secondary line such as Dinghy Control. The 4mm Dinghy Polytech has Technora in the outer which gives greater longevity than a normal polyester covered line of the same diameter. This Polytech rope is also slightly more supple as the cover to core is not as tight as the Marlow GP78 rope. This means that the Polytech runs better but we feel it won’t last quite as long as the Marlow GP78.

All the control lines that we sell have Dyneema cores and either Polyester or Technora/Polyester covers. The Dyneema cores give all the ropes the suitability that we need as they are very strong and have very low stretch/elongation.

So, in summary the best rope for the kicker is a compromise between durability and ease of use in terms of flexibility and grip. If you are sailing a lot and want a line that is durable we recommend Robline Polytech or Marlow GP78. If you are a more occasional sailor the more economical Polyester covered lines such as Robline Dinghy Control or Gottifredi Maffioli EVO Race 78 are suitable.


For the downhaul things are much simpler. There are fewer blocks and they are normally larger in sheave size (29mm or 30mm) so the effects of rope friction are far less than for the kicker/vang. Like the kicker, the downhaul has a lot of pressure on the system and is adjusted frequently. Therefore, wear through the cleating area is the main factor to be considered so we need a very durable rope. Robline Polytech or Marlow GP78 are the recommended ropes.

“On your bottom section, try and make sure your gooseneck bolt has the head of the bolt on the same side as the secondary line. This should help prevent the thread/nut end of the bolt constantly catching your blocks as you release them. Especially with the MkII sail (a much stiffer cloth than Radial and 4.7) I’ve found that deck cleats will promptly chew through any soft ropes on windy days, so the Marlow GP78 is a good rope here – fit it and forget about it for a while and go sailing!” – Team GBR sailor Michael Beckett


The outhaul system poses its own challenges. Unlike the kicker/vang and cunningham/downhaul, the outhaul is a lightly loaded system, and in very light winds the main load on the system is actually just the inhaul shockcord/bungee. The system typically has four small sheave size turning points, and another major source of rope friction in the system is the deck cleat fairlead area. When we uncleat the rope we want the pressure in the sail and bungee to pull the rope out as the sail is released. So, the key factor here is useability rather than durability. A year ago I rigged my Laser using the Marlow GP78 line but I found that it was just too stiff and I actually had to help the rope through the cleat/fairlead to help it release in light winds – even with our double puller inhaul bungee. As a result of this I moved to the slightly more supple Robline Polytech line which is perfect for the outhaul system. The slightly thinner diameter and suppleness means that it runs very smoothly. The Technora in the cover provides excellent grip in the hands. A lower cost solution for the outhaul is to use a Polyester covered line such as Robline Dinghy Control or Gottifredi Maffioli EVO Race 78. In summary we recommend Polytech for the outhaul– it will work and last exceptionally well.


We want colourways that easily distinguishable between the three control line systems. Certain colour combinations should be avoided as there isn’t enough colour separation between them – an example is to avoid using pink/black with orange/black as in bright sunlight I found that I couldn’t see the difference between them. We asked Marlow to produce their GP78 in blue/black to give us another colourway.

“Please don’t underestimate this consideration! It doesn’t matter if you’re reaching in for your vang at the windward mark of a club race or at the Worlds, picking up the wrong line by accident because the colours are too analogous is like selecting the wrong gear in your driving test, just a nightmare. So give it 30 seconds of thought before you put your order in – what colours do you already have, and when your brain says ‘downhaul’ what colour does your hand reach for? Bear in mind that these colours also have to stand out on your deck, which is probably a light shade of grey, ice blue or purple white.” – Team GBR sailor Michael Beckett

Other Considerations

For all our systems we seal the ends of the control lines to ensure that they don’t fray, and to keep the core/cover together. If you are ordering our pre-cut secondary lines or rope by the metre we offer a cost effective rope sealing service. This is more important for the Technora covered ropes as heat sealing itself is not sufficient to stop the ends from fraying in use.


The table below shows a full summary of the control lines that we offer. The lines that I use myself are:
Kicker/Vang – Robline Dinghy Polytech
Downhaul – Robline Dinghy Polytech
Outhaul – Robline Dinghy Polytech