GHA
Well-Known Member
Excellent idea - so obvious, Doh! Not complicated at all on this boat, no real difference in deploying than a single line. :cool
Anchor snubber design.
- Thread starter GHA
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Excellent idea - so obvious, Doh! Not complicated at all on this boat, no real difference in deploying than a single line. :cool
Neeves
Well-Known Member
Looks good to me!
In the Vendee Globe short chain, 10m-15m of chain has been used with longer lengths of nylon and with Fortress as the primary (in conditions most of us will never experience) at Auckland Island. Mixed rodes offer another choice.
thinwater
Well-Known Member
In reading Thinwater's reply (excerpted below), I noted the reference to size in relation to snubber breakage. He suggests one size smaller than the recommended rope rode for the boat. Given my boat is 12.5 metres and cruising all up weight of c. 14 tonnes I reckon around 20mm (3/4ish) rode would be about right. That suggests I should be looking at snubbers in the 16-18mm range, the 11mm leader rope Ive been trying certainly looks on the thin side. So, this is where the OPs link to the stretchy Liros comes in - another job for the winter will be to get some of that in an appropriate size and sort the ends out ready for next season.
I guess the minimalist wallet would blag as much line as they could get to make up several spares if climbing rope were to be on the thin side
I gave very conservative advice, based magazine requirement. There is little question that a smaller snubber can work well, so long as it has some length. Also, climbing rope is a special case. It's energy absorption per foot in a given size is 40-60% greater than other nylon rope, due to differences in constitutions. The down sides are that only a few sizes are available (7-11mm) and that it is more sensitive to chafe. But it is not stronger, so it needs length.
I would be comfortable with 11 mm climbing rope on a 12M boat. Many use that rope on that size boat. But it needs to be 35-45 feet long with good cafe gear (either a pulley, or run it inside tubular climbing webbing, the most proven chafe gear for climbing rope.
lw395
Well-Known Member
It does all seem rather complex.
TBH, the thought of having a snubber, which might potentially snap, on the side deck seems plain wrong. If a loaded length of nylon snaps that is quite likely to whip around and take out a shroud, your head, anything that's in the way.
I'd rather it was over the bow where it belongs.
Also I'd like to see the maths that says heating of the rope is not a problem, climbing rope is designed to absorb energy as it stretches. There is a lot of energy to be absorbed.
Neeves
Well-Known Member
LW395,
I'm not sure where the idea comes from that snubbers must be deployed from the bow. It might be common but that does not mean its the only way.
Climbing rope was used for years by Starzinger on Hawk and they had no issues. I've been using it for 4 or 5 years and had no issues. Others have used climbing rope, no-one has ever remarked on there being any issues - and if they snapped with the impact you suggest I'd guarantee posts would be all over everywhere - with people saying 'I told you so'. I do route mine through the bases of the stanchions (as you would furling lines) so if a rope were to break it is partially contained (but that is how we do it - I know other route simply along the deck..
The tension is hardly great - we are talking of 10% stretch, maybe 15% max, with a product whose limit is 40% at break. Now if you are talking of allowing 20% stretch (the Liros suggestion) and possibly some will allow this to creep to 25% (because their snubbers are too short) with cordage that might only have a max of 35% at break - I'd have to agree with you - this is pushing the limits.
If a snubber failed as you suggest for a snubber from the bow (uncontained by being routed through the stanchion bases etc) then I'd have to worry about the forestay and working on the bow - it never crosses my mind. I'm not sure why having the snubber from the bow makes it any safer.
Our system is dead simple - it is permanently in place, deploy anchor, attach hook, deploy length of snubber if required longer than 12m, attach back up chain hook - finish. It is no more obtrusive than headsail furling lines (on the side decks), or headsail sheets (in the cockpit). It does take time to set up - but you do it once.
To be of any use to the effectiveness of your anchor - they must be long, they must have elasticity - short snubbers 2-3m are no better than a chain lock.
But to support what you suggest - the US Navy have banned the use of nylon in some applications as a result of a number of serious accidents.
Jonathan
I'm not sure where the idea comes from that snubbers must be deployed from the bow. It might be common but that does not mean its the only way.
Climbing rope was used for years by Starzinger on Hawk and they had no issues. I've been using it for 4 or 5 years and had no issues. Others have used climbing rope, no-one has ever remarked on there being any issues - and if they snapped with the impact you suggest I'd guarantee posts would be all over everywhere - with people saying 'I told you so'. I do route mine through the bases of the stanchions (as you would furling lines) so if a rope were to break it is partially contained (but that is how we do it - I know other route simply along the deck..
The tension is hardly great - we are talking of 10% stretch, maybe 15% max, with a product whose limit is 40% at break. Now if you are talking of allowing 20% stretch (the Liros suggestion) and possibly some will allow this to creep to 25% (because their snubbers are too short) with cordage that might only have a max of 35% at break - I'd have to agree with you - this is pushing the limits.
If a snubber failed as you suggest for a snubber from the bow (uncontained by being routed through the stanchion bases etc) then I'd have to worry about the forestay and working on the bow - it never crosses my mind. I'm not sure why having the snubber from the bow makes it any safer.
Our system is dead simple - it is permanently in place, deploy anchor, attach hook, deploy length of snubber if required longer than 12m, attach back up chain hook - finish. It is no more obtrusive than headsail furling lines (on the side decks), or headsail sheets (in the cockpit). It does take time to set up - but you do it once.
To be of any use to the effectiveness of your anchor - they must be long, they must have elasticity - short snubbers 2-3m are no better than a chain lock.
But to support what you suggest - the US Navy have banned the use of nylon in some applications as a result of a number of serious accidents.
Jonathan
thinwater
Well-Known Member
There are calculations and there is math. Is "maths" a Britishism?
The calculations are here, simplified for easy discussion. Cycle one all you want, within the SWL, and then check it with an IR thermometer. It won't be warm.
http://sail-delmarva.blogspot.com/2016/09/can-nylon-rope-melt-due-to-load-cycling.html
The climbing ropes I have tested are more like 80% elongation to break on a slow pull. Drop impact is more like 40%.
As for recoil, I've broken climbing rope intentionally. While I would not want to be there, if it breaks any were near WLL due to chafe, you are wiledy exagerating the force is involved. It will only hurt, not cut a shroud. Like heating, it is a matter of scale. A 1-inch line is 6 times a 10mm yacht-sized line.
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Neeves
Well-Known Member
Thinwater,
Maths, to me, incorporates algebra, calculus, arithmetic, geometry, sets, logarithms (do people still learn about Naperian Logs?) etc calculations has a more limited application - it might be a complicated formula but in is basic its X x Y.
Whether its 'British' or not - never crossed my consciousness (but from your query alien to Americans). Which begs the questions what do Americans call that group of ideas that I describe as Maths?
I've not done a slow pull on climbing rope, only fairly rapid increases in load.
Jonathan
Maths, to me, incorporates algebra, calculus, arithmetic, geometry, sets, logarithms (do people still learn about Naperian Logs?) etc calculations has a more limited application - it might be a complicated formula but in is basic its X x Y.
Whether its 'British' or not - never crossed my consciousness (but from your query alien to Americans). Which begs the questions what do Americans call that group of ideas that I describe as Maths?
I've not done a slow pull on climbing rope, only fairly rapid increases in load.
Jonathan
thinwater
Well-Known Member
Math, like data, is both singular and plural for Americans. There is no "maths" or "datas."
From a gramar web site:
"Math and maths are equally acceptable abbreviations of mathematics. The only difference is that math is preferred in the U.S. and Canada, and maths is preferred in the U.K., Australia, and most other English-speaking areas of the world.
Neither abbreviation is correct or incorrect. You may hear arguments for one being superior to the other, and there are logical cases for both sides. One could argue maths is better because mathematics ends in s, and one could argue math is better because mathematics is just a mass noun that happens to end in s. In any case, English usage is rarely guided by logic, and these usage idiosyncrasies are often arbitrary. If you were raised in a part of the world where people say maths, then maths is correct for you, and the same is of course true of math. Don’t listen to anyone who says otherwise."
I think usage is somewhat different to, a least for engineers. Engineers would refer to doing calculations of immense complexity, and would only refer to studying the math if they were truly challenged by the concepts involved, and not just algebra, trig, or basic calculus. Something new to their understanding.
---
Two countries, separated by a common language.
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temptress
Well-Known Member
Seems overly complicated.
I spend 90% of my time at anchor and IMO you need to keep it simple. I use a hook in a bridal back to 2 cleets. Using 3 strand nylon i get all the stretch i need then i keep the anchor chain wrapped around a strong point in case the snubber breaks.
It takes less than a minute to setup or take off and has served me well over many years and in very strong winds. Use thick nylon rope through your bow fairleads and chafe should not be a problem.
Neeves
Well-Known Member
If you have a heavy long keeled yacht that is relatively docile and well behaved at anchor the need for snubbers is reduced. The docility might change in really heavy weather - so keeping some decent snubbers might still be advantageous.
There is no one size (solution) fits all but the majority of new yachts being bought today (and for the last few years) tend to be lighter and more flighty.
There is no one size (solution) fits all but the majority of new yachts being bought today (and for the last few years) tend to be lighter and more flighty.
Neeves
Well-Known Member
Again, personally, Maths is plural. Calculations can be of immense complexity or simple - its still a calculation.
In order to complete the calculation having some knowledge of arithmetic is invaluable and arithmetic is part of what I refer to as maths. If the calculation is more complex you might need to understand algebra or calculus - but its still a calculation.
No wonder we sometimes xmisundersant each other
GHA
Well-Known Member
Sounds complicated
living on the hook and moving anchorage often a dedicated setup helps.I've been running nylon down the side decks already, 2 soft shackles, takes moments and helps with having more length to stretch without lots of line rubbing through the oyster shells and mud on the seabed every wind / tide shift. With some dyneema through the bow roller there's no chance at all of chafe plus when some more line turns up splices will be much stronger than knots.
lw395
Well-Known Member
Dyneema is better than most ropes for chafe resistance, but to say 'no chance of chafe' is a bit optimistic.
There are lines on my Laser dinghy looking sordid after perhaps 50 or 100 races, probably not adding up to a week's continuous use.
GHA
Well-Known Member
How can nylon chafe without physically touching anything?
No way you ever chafe through 12mm D12 through a bow roller, I won't live that long
Neeves
Well-Known Member
GHA,
I think your ideas are sound (except for the idea of 20% elasticity!). I might have tried dyneema sleeves (hollow tape) for abrasion resistance rather than splicing (but maybe I missed that in the thread). But my motivation is partially laziness.
But still looks good to me.
Jonathan
I think your ideas are sound (except for the idea of 20% elasticity!). I might have tried dyneema sleeves (hollow tape) for abrasion resistance rather than splicing (but maybe I missed that in the thread). But my motivation is partially laziness.
But still looks good to me.
Jonathan
GHA
Well-Known Member
Think 20% is extremely unlikely, given that a snubber is rarely used anyway, in that once every few years blow I suspect I'd chicken out and fit something a bit bigger..
Splicing takes a few minutes and is free if some kind company donated a load of used once dyneema
Then for the nylon no going round a bending radius or chance of chafe. Big long soft shackle the the chains keeps the snubber clear and makes it easier to attach without having to bend down. Most of this has been used already and been fine so far, just getting refined.
Just thought, bending radius at the cockpit where it diverts back to the bow.. Oh well, pretty sure there's a large diameter rescue pulley stashed in a locker somewhere. Oh for a cheap waterproof load cell
Neeves
Well-Known Member
Why do you want the waterproof load cell (I understand the cheap ).
Jonathan
).Jonathan
GHA
Well-Known Member
Log a few months of real world loads with/without snubber, bucket off the bow, riding sail...... See what actually helps back in the real world. Probably be easy enough to rig up some sort of diverter system to get the cell dry but ain't gonna have happen though, load cells cost loads..Why do you want the waterproof load cell (I understand the cheap
Jonathan
Though next big blow it would be interesting to log sog/cog/heading once a second to see what it looks like, that would be easy with the Pi.
Neeves
Well-Known Member
To get actual tensions I've used a dyneema line from the chain and had the load cell at the bow roller. I've also measured loads at the end, transom, of the snubber. What I have not done is measure loads at the snubber/chain interface - I have your problem, my load cell is not water proof. I could measure tensions along the snubbers before it goes outboard, but have not done so yet. I was only looking for maximum loads vs windspeed. Sometime max load coincides with a gust but sometimes the yacht is moving resulting from a previous gust and it negates the next gust, other times (when you get maximum snatch) one gust reinforces the next. A gust hitting a veering yacht is intensified if the yacht is at an angle to the gust (greater cross windage) which is why reducing veering should be a focus, see below.
My load cell readings of scope vs tension are all documented in PS, without snubbers.
Tension of the snubber are unremarkable, tensions without snubbers (and at short scope) can be catastrophic.
The US Navy have done lots of work (at a larger scale!) and they have measured loads at the anchor, as well.
I've also measured veer but this is more difficult, or its easy to measure but analysing the results is more difficult. Its difficult to know what is an effect caused by a change in the snubber, or lack of, and a change in the wind. Wind varies in both direction and intensity but does, for example, a cold front vary in itself (do all cold fronts have the same amount of variation). Does a front have the same variability as a seabreeze? Veering depends on the anchorage as well as the wind itself - and I don't know enough about wind. Ideally you want to measure bearings of yacht/chain and wind simultaneously.
There are 2 measures of veer, the angle, or bearing, of the chain and the bearing of the yacht and then yacht vs chain.
With our very long snubbers veering was much less marked - as if the longer elasticity made the cat more stable - but that might have been because the wind was more stable. Bridles in themselves reduce veering (which is why they are used on multis) and the alternative for a yacht is to anchor in a 'V' as the 'inverted bridle' reduces veering and veering appears to be a major cause of anchor instability - hence our preference to 2 anchors rather than one in a big blow.) but I would not want to start another useless argument - so ignore the idea of the 'V'. There seems very little thought that intransigence will be reduced.
You can buy cheaper load cells (stg50??), I think they might be called crane cells, or crane scales. They measure upto about 500kg, they are not waterproof and you would need to manually log the tensions. But they are quite common place, I have a 350kg crane scale and 2t load cell (neither waterproof). 500kg will be more than enough for snubber tensions and for rode tensions at scopes over about 5:1.
Jonathan
My load cell readings of scope vs tension are all documented in PS, without snubbers.
Tension of the snubber are unremarkable, tensions without snubbers (and at short scope) can be catastrophic.
The US Navy have done lots of work (at a larger scale!) and they have measured loads at the anchor, as well.
I've also measured veer but this is more difficult, or its easy to measure but analysing the results is more difficult. Its difficult to know what is an effect caused by a change in the snubber, or lack of, and a change in the wind. Wind varies in both direction and intensity but does, for example, a cold front vary in itself (do all cold fronts have the same amount of variation). Does a front have the same variability as a seabreeze? Veering depends on the anchorage as well as the wind itself - and I don't know enough about wind. Ideally you want to measure bearings of yacht/chain and wind simultaneously.
There are 2 measures of veer, the angle, or bearing, of the chain and the bearing of the yacht and then yacht vs chain.
With our very long snubbers veering was much less marked - as if the longer elasticity made the cat more stable - but that might have been because the wind was more stable. Bridles in themselves reduce veering (which is why they are used on multis) and the alternative for a yacht is to anchor in a 'V' as the 'inverted bridle' reduces veering and veering appears to be a major cause of anchor instability - hence our preference to 2 anchors rather than one in a big blow.) but I would not want to start another useless argument - so ignore the idea of the 'V'. There seems very little thought that intransigence will be reduced.
You can buy cheaper load cells (stg50??), I think they might be called crane cells, or crane scales. They measure upto about 500kg, they are not waterproof and you would need to manually log the tensions. But they are quite common place, I have a 350kg crane scale and 2t load cell (neither waterproof). 500kg will be more than enough for snubber tensions and for rode tensions at scopes over about 5:1.
Jonathan
GHA
Well-Known Member
Back when I actually had a job it was industrial/entertainment rigging so lots time spent playing with calibrated load cells & test rigs. One job, waiting for the proper calibrated load cells to clear customs on a theatre build in China we got a few crane scales down the market cheap which were actually quite accurate, with something like 5% from memory. You can can absolutely anything down the side streets in an industrial city in China
These days most people on site use wifi load cells based around crosby bow shackles, which is handy for logging data with something like up to 200Hz sampling frequency. This is fast enough to show up the ripple in the load on a chain hoist as the gypsy isn't round , the velocity varies and can set up oscillation when lifting. Almost certainly would never be noticed on a boat though. But the fun of measuring things is enough on its' own
Lots of very cheap sensors available now but unfortunately load monitoring isn't one, or specific gravity. Oh well. There does seem to be a bit of a selection on ebay but the capacity is low, you'd need to rig up some multiple fall block & tackle but then with friction the errors would probably be through the roof.
2.5T on a soft shackle, diamond knot is well set now
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