You may be surprised to learn there’s nothing new about the half-doughnut-half-sheave-shaped bits of aluminum known as low-friction rings. In fact, low-friction rings, in one form or another, go back thousands of years in the form of the traditional lignum vitae wooden single deadeye. They have more recently been brought up to date for the simple reasons that they’re cheap, lightweight— and they work.
If you haven’t come across a low-friction ring, or have discounted them as race-tech gadgetry, think again. Made of lightweight hard-anodized aluminum and available for line sizes from 1/8in to 1in (with external diameters from 1/2in upward), they can, in fact, serve a multitude of uses.
Around the outside is a rounded groove much like that of a traditional sheave. However, in the case of a low-friction ring, the running line feeds through the hole in the middle, which has been rounded in all directions to allow the line (or lines) to pass through as smoothly as possible. The outside groove, on the other hand, is used to secure the ring at the end of another piece of line with a loop.
Simple enough. However, this bit of kit can be used for everything from fairleads and through-deck fittings to snatch and foot blocks, thanks in part to the fact that, unlike traditional blocks, once in position they allow a line to exit in any direction.
Rings can be especially tempting for the cost-conscious sailor, since a comparable block can cost hundreds of dollars. However, in answer to the question, “Are they as efficient?” the answer is, no. Which means that while they can be used to replace blocks in many applications, they can’t be used in all of them.
That said, rings can be used with a wide range of lines material, and given their inherent strength when used with strong-as-steel UHMWPE materials like Spectra and Dyneema, they can be incredibly robust for their size. Better still, unlike a conventional block, which will disintegrate upon reaching break load, a ring supported by a piece of line will simply deform.
To get an idea of what kinds of loads we’re talking about here, figure a 3in/75mm block for a 10mm line may weigh around 7-14 oz. and have a SWL (safe working load) of 1,100-1,900lb. A comparative low-friction ring will weigh less than half an ounce and have an SWL of 3,500lb.
Again, though, while low-friction rings can replace blocks in many situations, there’s a caveat: doing so will increase the friction within the system. These are, after all, “low” friction, not “no” friction rings we’re talking about here.
Also, unlike a block, where the amount of friction will be constant and fairly minimal no matter the entry and exit angle of the line or the type of cordage used or the load it’s under, the same cannot be said for low friction rings. Adjust any of the above variables and the friction between the line and a ring will also change.
As an example, take a block, pass some 1/4in Dyneema through under minimal load and deflect 30 degrees. The increase in friction will be barely noticeable. By contrast, a 1/2in line with a hard-wearing high-friction outer cover of Aramid/Technora passing through a ring and loaded up at 1,000lb or more will increase the coefficient of friction dramatically. Passing the line through the ring under load will also generate heat.
With this in mind, rings work especially well in settings where a line doesn’t move a lot: in other words, static or semi-static applications. They are also good when used to deflect loads less than 90 degrees. For example, as, say, headsail fairleads they can work wonders.
By contrast, they work less well as turning blocks where it’s necessary to reverse or deflect a line past 90 degrees, or when lots of line will be passing through. As Harken’s Andy Ash-Vie explains, “On high-line speed applications, like spinnaker sheets or mainsheets, the friction and heat can build up fast. It is harder on the trimmer and on the sheet itself.”
Along these same lines it’s also best to keep the number of rings in any purchase system to a minimum, since the friction buildup will be cumulative with every ring. Ash-Vie, for example, says he won’t use more than one at a time, preferring to use a pulley system to get the mechanical advantage from, say, a cascade purchase system. Others, however, are less concerned. The ultimate decision is up to you.
Finally, it’s always a good idea to consider what exactly it is you’re hoping to achieve by replacing a block, or blocks, with low-friction rings. Are you doing it just to save a little money or will there be a real benefit? This goes for cruisers and daysailers as well as hardcore racers. Which is not to say they don’t make sense on cruising boats. Weight savings, for example, may seem a moot point aboard a cruising boat. But try winching up a block-laden mainsail 60ft or more, and you’ll be happy to make things as light as you can get them.
What follows are some considerations to keep in mind when thinking about low-friction rings in a number of different applications.
While it might be tempting to try and save hundreds of dollars by spending $20 on a low-friction ring instead of a conventional block, doing so successfully depends on the size of your boat, the loads at work and the sailing you do. Because of their increased friction, rings don’t release smoothly, which means lines under load can “jump” when eased or trimmed.
Bottom line, with lines that are trimmed frequently under high load the best solution is still typically a conventional turning block. That said, if you’re a set-it-and-forget-type when flying a spinnaker, then the turning block could be replaced with rings attached to strong points (like cleats, toerails or padeyes) with a store-bought or homemade strop. Just keep in mind that potential friction buildup.
Mast Base Blocks
If the base of your mast is getting crowded with blocks, as is often the case with older boats in particular, replacing some of the lesser-used ones with rings is a great way to free up some extra space. Keep your good-old roller blocks for the main and spinnaker halyards. But if your genoa is on a furler, and you only raise and lower it at the start and end of the season, it might be a good candidate for a low-friction ring. Another good way to reduce the number of blocks is to run more than one reefing pennant from the boom back to the cockpit through a single ring, as you’ll only be using one of them at a time.
Where low-friction rings and fittings are truly in their element is deflecting semi-static lines (i.e., lines that don’t move a lot) under load. Low-friction deck organizers (close cousins to low-friction rings), for example, take up much less room than those with sheaves. You also don’t have to worry about them getting bunged up with salt.
There is no doubt a low-friction ring works better than a seized or twisted block, and few blocks on board get as salt-encrusted as those used to guide headsail furling lines aft. Several rings attached to an equal number of stanchions will typically work well, especially when there is little load. Again, though, as the load on the furling line increases so will the friction on each ring. This will all add up, so the fewer rings the better.
Vangs and backstay systems
Low-friction rings can also be used successfully in a semi-static purchase systems like those found on vangs and adjustable backstays, where loads can be high but the movements/size of the adjustments is small. Rings lend themselves especially well to cascade purchase systems, in which the load is roughly halved with each ring pulling down on the ring directly above, with the static ends all attached to a single point. As the loads decrease, thinner line and smaller rings can be used to further decrease weight and increase savings.
Using small rings with nice, thin lazy jack lines means less sail chafe than would result from using smaller, more expensive blocks. By running the lines through rings, the system will also be lighter and the airflow over the surface of the sail less disturbed.
In and out-Haulers
An area in which rings are especially popular is as barber haulers or other systems used to adjust headsail sheeting angles. Typically, a genoa sheet runs back to an adjustable genoa car on a track. Forward of the car, though, close to the clew, the sheet can also be run through a ring that is controlled from the cockpit and used to pull the clew closer to the boat’s centerline, narrowing the slot between the headsail and the main. An out-hauler, or barber hauler, does the opposite, pulling the sheet outboard to open up the slot when off the wind.
Genoa Sheet Twing
Sailors of older boats often cannot adjust the genoa sheet lead under load from the cockpit, since the pin in the genoa car has to be pulled up, and the genoa car physically moved along the track in order to do so. Of course, fully adjustable genoa cars can also be prohibitively expensive given the value of many older yachts; however, a much cheaper solution can be had using a ring as a downhaul in front of the car to bring the lead down closer to the deck. This will serve the same purpose as moving the genoa car forward, thereby tightening the leech and reducing twist—an especially handy tactic when going off the wind or when a furling headsail is reefed. To make the loads more manageable, friction rings can also be used to increase the mechanical advantage of the system on its way back to the safety of the cockpit
Friction is the enemy on any mainsail reefing system and if you want the most efficient single-line reefing system you’ll have to put your hand in your pocket and spend money on high-load blocks and sheaves with bearings. That said, you can also try going with a ring on the leech with little gain in friction. Be warned, though, if you have a single-line system don’t be tempted to replace the block at the luff, as a lot of line has to pass through at this point and shaking out a reef can become the devil’s work if you introduce more friction. Be happy that instead of buying four or six blocks you have, at least, halved the number.
Antal Marine antal.it
Barton Marine bartonmarine.com
Colligo Marine colligomarine.com
Harken Inc. harken.com
Photos courtesy of Graham Snook