Are Underwater Snubbers A Thing?

[Dockhead]

You have covered a yacht that has a natural propensity to veer but veering can occur in an anchorage where in strong winds the wind is fuelled dow valleys, through gaps in the trees. Read people's experiences in, say, Skye and they will talk of williwaws - bullets of winds from varying directiona.

Adding a ride sail will only make the effects worse.

Shore lines come to mind

Jonathan

I don't need to read about williwaws, because I've had enough of my own painful experiences with katabatic winds. My worst night ever at anchor was on a charter boat in Croatia, decades ago, in Hvar harbour, when a storm hit bringing bombs of wind down out of the mountains. Not a single anchor on a single boat in the ancient harbor held that night -- it was madness. And no chart plotters, and zero visibility. It's a miracle I didn't go onto the rocks, or collide with another boat.

I've also experienced them in Norwegian fjords, and in Greenland.

We weren't talking about katabatic winds, which is a completely different problem from veering at anchor in an ordinary gradient wind. I disagree that a riding sail makes it worse -- in fact that was what I settled on as the best solution for katabatic winds. You get hit from different directions, and in bursts, and if the boat lies stably head to the wind, you minimize the forces on the boat, and on the ground tackle. If the boat veers off, you present a lot more area to the wind, and I've seen boats even knocked down or nearly knocked down, under bare poles. You really want to prevent this.

Shore ties are the choice of most Arctic sailors -- you can see the big drums of green polypropylene on the foredecks of proper expedition boats. I took appropriate ropes for shore ties to Greenland with me, but never used them. Katabatic winds come from different directions, and a shore tie holds the boat in a specific direction, irrespective of the wind direction. It would be awful to be held broadside to a wind burst. But Arctic sailors don't use shore ties for that purpose -- they use them in order to anchor in steeply sloping bottoms typical in mountainous parts of the Arctic. To keep the boat aligned to pull on the anchor uphill.

I didn't like that because of the risk of getting hit broadside by a wind burst. Then all your calculation of pulling the anchor uphill is out the window. I don't like anchoring on sloping bottoms, full stop.

So my technique was different -- I looked for coves where it was possible to anchor in the very middle, in the deepest part. That way the anchor can't be pulled off downhill. Inspired by Dashew's technique in Antarctica, I would do this even on very short scope, in very deep water. With a riding sail to keep the boat head to wind. It worked great.

 

[NormanS]

Adding a ride sail will only make the effects worse.

Shore lines come to mind

Jonathan

I wonder how much experience you actually have of riding sails. I use one, when needed, and it has a huge effect on diminishing the boat's yawing at anchor. Mine is a double sail, so when rigged, presents a "V" to the wind.
I have, on occasion rigged a shore line, but rigged it in the fashion of a Bahamian Moor, so that the boat would always swing head to the wind. I don't like the idea of having an anchor from the bow, and a shore line from the stern. There is then the likelihood of having the wind on the beam, which I certainly wouldn't want.

 

[Neeves]

I wonder how much experience you actually have of riding sails. I use one, when needed, and it has a huge effect on diminishing the boat's yawing at anchor. Mine is a double sail, so when rigged, presents a "V" to the wind.
I have, on occasion rigged a shore line, but rigged it in the fashion of a Bahamian Moor, so that the boat would always swing head to the wind. I don't like the idea of having an anchor from the bow, and a shore line from the stern. There is then the likelihood of having the wind on the beam, which I certainly wouldn't want.

I have no experience of riding sails as you well know, or I would have mentioned it. Multihulls do not lend themselves to the concept, we have no backstay.

But the idea of a cyclically yawing wind, say gusts, bullets 90 degrees apart - which we experienced in an anchorage in Bass Strait seems to allow the riding sail to be turned also through 90 degrees.

Our solution, the forecast was a Storm warning. was to deploy 1 anchors off the bow and take 2 shore lines, of the transom. The monohull in the same anchorage was to deploy two anchors and have 1 lines off the transom to shore. The wind direction did not matter - our orientation was dectated by the lack of room. If Blaze had used a riding sail this solution would not work.

One interesting facet - though we were being blown from pillar to post you could hold a single stern shore line in your hands - a simply stop the yacht(s) sailing at anchor and causing snatch loads.

The following day it was a lot calmer and I took this picture, you can just see the shore lines. The water is 5m deep and we both had a scope of about 5:1. The couple who owned Blaze had taken part in the first ARC then spent time in America and were circumnavigating. He was from the UK she, Oz.

Part of the arrangement was the thought other yachts might crave shelter and we needed to maximise the available space - in case (and as it turned out unnecessary).

Jonathan

 

[NormanS]

I have no experience of riding sails as you well know, or I would have mentioned it. Multihulls do not lend themselves to the concept, we have no backstay.

But the idea of a cyclically yawing wind, say gusts, bullets 90 degrees apart - which we experienced in an anchorage in Bass Strait seems to allow the riding sail to be turned also through 90 degrees.

Our solution, the forecast was a Storm warning. was to deploy 1 anchors off the bow and take 2 shore lines, of the transom. The monohull in the same anchorage was to deploy two anchors and have 1 lines off the transom to shore. The wind direction did not matter - our orientation was dectated by the lack of room. If Blaze had used a riding sail this solution would not work.

One interesting facet - though we were being blown from pillar to post you could hold a single stern shore line in your hands - a simply stop the yacht(s) sailing at anchor and causing snatch loads.

The following day it was a lot calmer and I took this picture, you can just see the shore lines. The water is 5m deep and we both had a scope of about 5:1. The couple who owned Blaze had taken part in the first ARC then spent time in America and were circumnavigating. He was from the UK she, Oz.

Part of the arrangement was the thought other yachts might crave shelter and we needed to maximise the available space - in case (and as it turned out unnecessary).

Jonathan

View attachment 197862

Well, obviously a riding sail won't work if the boat is tied fore and aft. I don't understand your saying that you could hold the shore line on your hand. Either the wind was from a head, or there wasn't much of it.
If/when faced with gusty winds in a very tight for space anchorage, yes I would rig a shore line, but I would make it fast to the anchor chain, well below keel level, so that we would lie head to wind. What's not to like?

 

[thinwater]

Many riding sails do not require a back stay. Just sayin. Cat hard tops are pretty much their own riding sail anyway.

 

[thinwater]

Why would you put a drogue on the transom rather than off the bow or even rode? You want the CLR to move forward and the bow moves more than the stern?

Yes, I have tested both. For me, setting the drogue (weighted) off the rode, about 15 feet forward of the bow, worked best. It reduced pitching and yawing.

 

[Dockhead]

. . . I have, on occasion rigged a shore line, but rigged it in the fashion of a Bahamian Moor, so that the boat would always swing head to the wind. I don't like the idea of having an anchor from the bow, and a shore line from the stern. There is then the likelihood of having the wind on the beam, which I certainly wouldn't want.

What a broody great idea. Why did I never think of that myself?? Why have I never seen that done?

This would fulfill the main task of shore ties -- preventing you from pulling the anchor off downhill. WITHOUT the fatal (in my opinion) drawback of being unable to swing to the wind.

My hat is off to you, sir.

 

[Dockhead]

I have no experience of riding sails as you well know, or I would have mentioned it. Multihulls do not lend themselves to the concept, we have no backstay . . .

You can belay a spare mainsail halyard to a quarter, or somewhere as aftward as possible, and bend the riding sail onto that.

I've seen cats using riding sails many times.

 

[ducked]

If you over size a snubber it will not offer elasticity.

You need a snubber that works for you up to, say, 30 knots of wind and a storm snubber for stronger wind. But you also need to decide how you are going to replace or augment the 30 knot snubber, with your 50 knot snubber. Saying is easy - doing it more difficult.

Working on the bow in 30 knots, at night, in the rain with a rapidly developing chop is no laughing matter. Read the article.

Jonathan

For now I'm personally trying to stick to very slowly beating my original question to death rather than getting into all the issues that have been raised, though the discussion and references will be very useful for me to review before doing any real anchoring.

However, since I'm taking a break from that paper...er... a relatively simple question (I THINK)

What is the difficulty yáll anticipate with multiple snubbers?

Given a loop of chain slack, cant you just install them in parallel either with different snubber lengths/degrees of slack (simplest) or attached at different points in the chain loop, so that they successively come on load as the chain straightens?

Of course "tuning" it might require some sums +/or experiment, but the basic approach seems simple enough. in principle.

 

[NormanS]

What a broody great idea. Why did I never think of that myself?? Why have I never seen that done?

This would fulfill the main task of shore ties -- preventing you from pulling the anchor off downhill. WITHOUT the fatal (in my opinion) drawback of being unable to swing to the wind.

My hat is off to you, sir.

You are very welcome.

 

[noelex]

What is the difficulty yáll anticipate with multiple snubbers?

Given a loop of chain slack, cant you just install them in parallel either with different snubber lengths/degrees of slack (simplest) or attached at different points in the chain loop, so that they successively come on load as the chain straightens?

I think you are making this way too complicated. Anchoring should be simple. I am not sure what you would achieve with multiple snubbers that "successively come on load as the chain straightens”.

Some boats benefit from a bridal arrangement, but the stretch from a single snubber is fine. In heavy weather, it is sometimes sensible to rig a second snubber, but this just acts as a back up in the event the primary line breaks.

 

[thinwater]

A potential problem with swinging to face the wind when using shore ties is snagging the keel. The lines are not running down to the bottom with a catenary. They are typically rope, no chain, and run right on the surface. In fact, keeping people from running into them is a concern. Obviously, this depends on the wind direction and geometry. Also tide changes.

 

[noelex]

Duplicate post removed.

 

[RunAgroundHard]

Many riding sails do not require a back stay. …

Probably not a coincidence since tech listens and logs personal interests. However, this riding sail, rigged on a mono, not using the backstay, popped up on my FB feed.

1.5K reactions · 28 shares | Peaceful moments like this… A still morning in a quiet little cove, just a stone’s throw from Kristiansand. The sea is calm, the air is crisp – and the coffee tastes even better out here. ️ Breakfast first. Then we set sail for another day along Norway’s stunning coast. Southern Norway ️ Sailing Ingrid-Marie No rush. Just rhythm. 58°08’29”N 8°02’43”E# ⸻ #sailing_ingridmarie #hallbergrassy #peacefulmorning #sailinglife #norwaycoast #boatlife #liveaboardlife #sailingadventure #oceanmood #anchored #lifeafloat #scandinaviansummer #sailingingridmarie #explorenorway #cruisinglife #slowtravel #morningslikethese | Ingrid-Marie

 

[NormanS]

A potential problem with swinging to face the wind when using shore ties is snagging the keel. The lines are not running down to the bottom with a catenary. They are typically rope, no chain, and run right on the surface. In fact, keeping people from running into them is a concern. Obviously, this depends on the wind direction and geometry. Also tide changes.

If/when I rig a shore line, it's made fast to the anchor chain, well below keel level, so nowhere near the surface. I don't use floating rope. We seldom anchor in as shallow water as you do.

 

[thinwater]

If/when I rig a shore line, it's made fast to the anchor chain, well below keel level, so nowhere near the surface. I don't use floating rope. We seldom anchor in as shallow water as you do.

There you go! Not the way most do it.

 

[Dockhead]

I think you are making this way too complicated. Anchoring should be simple. I am not sure what you would achieve with multiple snubbers that "successively come on load as the chain straightens”.

Some boats benefit from a bridal arrangement, but the stretch from a single snubber is fine. In heavy weather, it is sometimes sensible to rig a second snubber, but this just acts as a back up in the event the primary line breaks.

I've used multiple snubbers in really bad weather so that if one breaks, the other catches the chain. I leave one slightly slack. Works fine.

 

[ducked]

I think you are making this way too complicated. Anchoring should be simple. I am not sure what you would achieve with multiple snubbers that "successively come on load as the chain straightens”.

Some boats benefit from a bridal arrangement, but the stretch from a single snubber is fine. In heavy weather, it is sometimes sensible to rig a second snubber, but this just acts as a back up in the event the primary line breaks.

Re "anchoring should be simple", sure, but unfortunately, and evidently, it isn't, since there are Masters Dissertations about very small aspects of it, and much contention.

Re "what you would achieve "You would achieve a second (more if wanted) snubber, which has already been recommended by people who know a lot more about this than I do, so wasn't (previously) at issue. The question was about how to achieve it.

"Successively coming on load as the chain straightens" would reduce shock loading, which seems to be the overall objective, and could load share, reducing the probability of failure, while still giving redundancy.

It gives you something like a tunable variable rate spring. Many motorcycles have these, and probably a lot of people never tune them, but they could if they wanted or needed to

It just seems the obvious way of doing it, so I'm probably missing something.

 

[noelex]

Re "what you would achieve "You would achieve a second (more if wanted) snubber, which has already been recommended by people who know a lot more about this than I do, so wasn't (previously) at issue. The question was about how to achieve it.

The idea of rigging two snubbers in heavy weather is so that one acts as a back-up. If the primary snubber breaks, the second one takes over. As Dockhead has indicated, this is normally accomplished by rigging two identical snubbers, but leaving some slack in the back-up snubber so it does not take any load unless the primary snubber breaks.

Thus, the amount of stretch stays the same even if the primary snubber snaps.

If you rig two snubbers in series along the chain and one snubber breaks, half the stretch is lost.

 

[ducked]

The idea of rigging two snubbers in heavy weather is so that one acts as a back-up. If the primary snubber breaks, the second one takes over. As Dockhead has indicated, this is normally accomplished by rigging two identical snubbers, but leaving some slack in the back-up snubber so it does not take any load unless the primary snubber breaks.

Thus, the amount of stretch stays the same even if the primary snubber snaps.

If you rig two snubbers in series along the chain and one snubber breaks, half the stretch is lost.

OK, true. (except I didn't describe snubbers in series, I descibed them in parallel. This could be done load sharing or not. Load sharing is unavoidable and non-adjustable in series)

Dockhead has said that his objective with two snubbers is redundancy "leaving one slightly slack" (my bolding). This does not seem to preclude load sharing, perhaps happening while Dockhead is asleep, nor does the "works fine" operational summary. "so it does not take any load unless the primary snubber breaks" seems to be your editorial interpretation.

OTOH if you rig two identical non-load sharing snubbers and the first one breaks, then, unless it failed from an intrinsic weakness, the second one is likely to follow it if those conditions persist.

It seems a bit like an argument I've heard somewhere for rigging multiple masts independently, to which the (an) answer was, better not to lose any

I'd also think I might not want the stretch to say the same even if the primary snubber snaps, I might want it to decrease, and the restoring force to increase, in response to the worsening conditions.

This could be achieved by a beefier second snubber, or a third snubber should pretty much get around the dilemma.