Low friction rings are a robust and cost-effective addition to your boat. Using HMPE (high modulus polyethylene) rope such as Dyneema or Spectra makes them incredibly strong, but you'll need to use a Brummel Lock Splice to attach them properly. Graham Snook explains how to do it
The equipment you’ll need for the splice is:
- D12 Dyneema
- A tape measure
- A low-friction ring
- A marker pen
- A sharp knife
- A fid – we’re using the outside of a pen
Low friction rings
We often hear about trickle-down technology from the top echelons of yacht racing, but it’s not often you’ll find a modern take on an ancient idea on board a carbon-fibre race boat, let alone a cruising yacht. Yet the concept of a low-friction ring goes back hundreds of years; the humble deadeye has been brought up to date for good reason. Cheap, light, stong and effective; if you haven’t come across a low-friction ring, or have discounted them as a new-fangled gadget, think again.
The traditional lignum-vitae wooden deadeye and bullseye, and the later metal thimble, are now a lightweight hard-anodised aluminium ring available for line sizes from 3mm to 26mm (with external diameters from 12mm upwards). Around the outside is a smooth groove for one line; used to secure the ring and in the centre is a hole that’s been rounded in all directions to allow one or more lines to pass through as fairly and freely as possible.
When rings are better
Low-friction rings can be used to replace blocks, but should you? A roller-bearing block can cost over 10 times as much as a ring with less than half the safe working load but are these low-friction rings as efficient? In a word, no; they can be used to replace blocks in certain applications, but not all. Knowing how best to use them, and where they can and can’t be used is important.
The rings can be used with any suitable line material, but given the rings’ size and strength when used with HMPE (high modulus polyethylene) ropes such as Dyneema and Spectra that have the strength of steel, rings are incredibly strong and versatile.
It’s possible to buy pre-made loops, but knowing how to do a simple lock splice in 12-strand Dyneema (D12) will enable you to use a low-friction ring as a thimble with the strongest attachment point. Having a couple of rings and a few metres of HMPE cordage in your spares box could well get you out of trouble.
Low-friction rings are not, however, a panacea to replace all your sheaved blocks. Low-friction rings can replace many blocks, but doing so may increase the friction within the system – they are not ‘no’ friction. If you want the most efficient system, blocks with bearings will offer the least friction and therefore the best solution.
If, however, you’re happy to add a little friction and save both money and weight or add control lines that would have been prohibitive in cost, then rings are the way forward.
Rings work best in static or semi-static applications and they are particularly good when used to deflect loads less than 90°; if you have a line that chafes, adding a ring to make the lead fair can work wonders and protect your boat too.
They work less well as turning blocks used to reverse the line’s direction when lots of line will be passing through the ring, as Andy Ash-Vie, managing director at Harken UK, explains: ‘On high line speed applications, like spinnaker or mainsheets, the friction and heat can build up fast. It is harder on the trimmer and on the sheet itself.’ Even on a 40ft club racer, a roller block will be a better option and your trimmer will thank you.
Ideally, you should keep the number of rings in a purchase system to a minimum; the more you have the more the friction builds up. Ash-Vie won’t use more than one, preferring to use a pulley system to get the mechanical advantage from a cascade purchase, but other manufacturers are less concerned.
You should also consider what you’re hoping to achieve by adding rings or replacing blocks. Rings are lighter and smaller and can often take higher loads than blocks, so can also be used on sails without increasing the weight you have to lift when hoisting the sail, for example.