PERFECT ANCHORING
When it comes to anchor snubbers, everyone has been doing it wrong for years, says Jonathan Neeves, who has a very different approach to ensuring a secure night on the hook
Jonathan Neeves shares his very different approach to ensuring a secure night on the hook
Every skipper who has spent a night at anchor will be familiar with the niggling worry about whether they are truly secure. A jolt or rattle in the small hours is enough to wrench the sleeping sailor from his or her bunk and into the cockpit to reassure themselves all is well. I believe that cruising sailors would all enjoy quieter, comfier and more sleep-filled nights on board if they changed the way they used snubbers when at anchor.
A subjective survey of the average anchorage shows that many boats use no snubber at all, and those that do use a short one of 2m-4m, with almost no-one using anything longer. Multihulls have generally always used snubbers in the form of a bridle, which serves the same purpose as well as helping to quell yawing from side to side.
There is a problem with all of these, however. Virtually all snubbers and bridles are simply too beefy to offer any genuinely useful elasticity, making them somewhat redundant for the purpose they were intended for; that is, to dampen snatching at the anchor and reducing the forces that would break out an anchor and cause it to drag across the seabed or riverbed.
The situation has been exacerbated by the understandable popularity of the all-chain rode, driven by access to reliable, relatively cheap and efficient electric windlasses. At the touch of a button, whether at the helm or on the bow, we can handle ground tackle of considerable weight. While it might add weight in the bow, most sailors will accept this for the greater holding power, resistance to chafe and the increased damping of a heavier chain’s catenary.
Some sailors use a mixed rode, commonly nylon rope, either octoplait or three-strand, and chain. The disadvantage of this is that the rope must be of a similar strength to the chain to secure the yacht but the stronger the rope the lower its elasticity, as a thick rope stretches less than a thinner nylon rope for a given tension. The other dilemma of the mixed rode is deciding on the proportions. How much chain and how much rope? If you use a short length of chain your rope may be dragged across the seabed causing abrasion. You also lose most of the benefits of catenary and because the rope is beefy, it offers little elasticity. If you carry a decent length of chain then in shallow anchorages you might not deploy any rope at all, as the proportions you chose are fixed.
Chain has a number of obvious advantages. It is abrasion resistant, it does not rot, it is easier to clean than rope, it self stores into the anchor locker and it offers that fundamental characteristic – catenary, the damping effect of lifting the curving sag of a heavy chain. Sadly catenary has a limited range within which it works effectively before the chain is pulled into a straight line, unless you have a limitless supply of heavy chain. Nylon’s elasticity
range is limited only by strength and the tension applied; it will continue to stretch, approximately linearly, until it breaks.
There is another way, however. We have been using long snubbers of 10m or so for a number of years and, encouraged by the success of our practice, we have recently extended our snubbers to 30m.
Using such a long snubber alongside an all-chain rode offers the best of both worlds, with both elasticity and catenary, with none of the downside of either. What is more, by taking the snubber over the bow roller and aft to the cockpit, you can avoid increasing your swinging circle too dramatically, while allowing the rope on deck to stretch and snub to its heart’s content.
Our ultimate fall back is the chain. If the rope of the snubber fails, the yacht is directly connected to the anchor with chain, and the chain is of the appropriate strength for the yacht, secured to a strong point other than the windlass to avoid stressing it. Because the snubber is ‘auxiliary’ we can size it for its elasticity characteristics rather than ultimate strength. The only caveat to this philosophy is that we accept snubbers are a consumable, such as sheets or sails.
THE SCIENCE OF SNUBBERS
So why use a snubber at all? A bungy jumper uses an elastic tether because the elasticity of the bungy cord removes all of the shock load, and a long snubber can do the same thing for the loads of a boat snatching at its anchor chain through yawing, swinging or pitching. The table (above right) shows that 10m of 10mm nylon has the ability to accept the same energy, measured in joules, as 30m of 10mm chain up to a tension of about 250kg (roughly 25/30 knots for a 40ft yacht).
If the wind builds further to 35 knots, the simple answer would be to deploy another 30m of chain, if you carry that much, but you are then that much closer to yachts or lee-shores astern of you. If you don’t feel comfortable with moving and re-anchoring, the alternative is simply to deploy a further 10m (roughly one boat length) of snubber.
A snubber does not replace your use of available catenary. By using both nylon and chain, the two components share the load, dramatically increasingthe rode’s loadabsorbing capability.
We actually use a high tensile (HT) small link 6mm chain, which only weighs 0.8kg per metre rather than the 1.45kg per metre of standard 8mm chain. We have sacrificed catenary offered by the weight of 8mm chain, but have more room in our chain locker, less weight in the bow, and require less power to run our windlass, but we still have some catenary as well as the elasticity from our snubbers. We have not sacrificed any strength; our 6mm chain has the same strength as the 8mm chain it replaced. Our 8mm chain needed to be replaced and we could have regalvanised, or bought new. As it turned out, the 6mm HT chain cost less than new 8mm G30 chain would have.
SOURCING YOUR SNUBBER
Rock climbing gyms retire their ropes on a regular basis, so ask a local one if you can help ‘recycle’ their ropes – you’ll be keeping the rope out of landfill, and you can also use the line for mooring once it’s no longer good as a snubber. Most climbing gyms don’t have very high walls so only use 15m ropes, but find a taller climbing wall to source 30m ropes. A simple 10m, 12mm snubber will be unobtrusive on board, and it will be cheap second hand, although at 12mm, this is a bit too big for yachts under 40ft.
Once you’re happy with the setup, we would replace with 10mm rope for a 35-40ft yacht, and even 8mm rope for a 30ft yacht. For a 50ft yacht we would suggest 14mm rope, though this may need to be made to order from the rope manufacturer, unless you go back to three-strand or anchor-plait and accept that you’ll need to keep a closer eye on chafe, without the abrasionresistant cover.
RIGGING A LONG SNUBBER
Using a 10m snubber is relatively simple, and is a good way to start if you want to experiment and develop a system that works for the layout of your boat.
We route our snubber from a cockpit winch to a spinnaker block at the stern, along the side decks to the bow and over the bow roller, where a chain hook connects it to the chain. To keep the side decks clear we route the snubber through the stanchion bases, though you could use furling lines fairleads.
In order to get a clear run of the snubber from the line of stanchions and straight over the bow roller we have used low-friction rings, spliced onto strops that are long enough to adjust once tied off, to adjust the lead. A piece of plastic hose over the bow roller will also avoid chafe on the roller’s side plates.
We have added dedicated clutches at the stern to hold the line, but you could take it straight to a stern mooring cleat. On a 10m (33ft) yacht, a 15m rope will be long enough to run down the side decks from the transom, have 2-3m outboard beyond the bow and leave a 2-3m tail aft.
Much like a furling line or preventer, we leave our snubbers permanently rigged, hooked on to itself around the pulpit, locked off at the stern, and the excess coiled onto the guardrail or a cockpit rope bin.
CHAIN HOOKS
It’s worth giving some thought to how to connect the snubber to the chain, as it needs to be secure. Soft shackles are increasingly popular, but we found them difficult to thread through our 6mm chain. Some sailors, including Skip Novak, use painted steel hooks from the lifting industry. As they are not galvanised they have a limited lifespan, but are cheap to replace. Chain claws have to fit precisely to work well, and we found them difficult to remove if under any tension or not carefully aligned. Hooks with retainer pins are good in theory, but if you bend the pin, as we did with our Wichard hook, it can be almost impossible to remove and potentially dangerous. Claws and hooks using bent rather than forged metal also have a tendency to bend under load. In the end we settled on lifting hooks and had them galvanised.
MONOHULL BRIDLES
Developing a bridle system to suit your monohull means you have a horizontal
‘V’ which will help to control yawing. If you can devise a way to also incorporate a pad eye at the waterline (from a bob stay or even through the anchor locker drain holes) you will develop a vertical ‘V’ which will help to manage pitching caused by chop or swell. We have noticed, subjectively, that our comfort on board our boat has improved substantially with our arrangement. The other benefit is that bridle plate or chain hook will sit closer to the water, improving its angle to the seabed and the scope ratio of your ground tackle.
CATAMARAN BRIDLES
We currently sail a catamaran and use a custom-made bridle plate to secure the bridle to the chain. Our bridle plate is a simple design, similar to the one by Viking Anchors, made using duplex stainless with 316 threaded low-friction rings.
The bridle itself has a line on each side, attached to the bobstay pad eye (reinforced internally) just above the waterline. The line then runs through the bridle plate and back to a turning block on the bow and from there to the stern.
This means we have 30m of rope on each side, with the bridle plate attached to the chain just 10m ahead of the bow. We use 10mm kernmantle for this.
OUR ANCHORING SETUP
Our anchoring practice is cautious. If we are to anchor in a location with possible severe weather, we will locate a spare anchor and chain on the foredeck. This second anchor is not because we doubt the integrity of our primary anchor but because two anchors
deployed in a ‘V’ reduce swinging, which is a major cause of dragging anchors. Our spare anchor is made of a rode of 15m of 6mm HT chain and 40m of 12mm 3-strand nylon. Our primary rode, 75m x 6mm HT chain, is backed up with a short snubber in case our bridle fails to ensure we keep shock loads off the windlass.
Prior to using climbing ropes we had two bridles fail. The short snubber is secured to a strong point as part of our bow roller. We use the same short snubber to secure our anchor on the bow roller when on passage.