Which mooring spring?

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Deleted User YDKXO

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We are currently moored in a Sardinian marina where there is a fair amount of movement from ferries and wind induced swell. I have asked the marina to supply some mooring springs and they have offered me a set of springs with a breaking load of 20t or a set with a breaking load of 40t (at more than twice the price). The boat is 63ft long and weighs about 40t

Any advice on which set I should go for?
 
What is the material and lay ?

I would go for polyester three stand?

Nylon stretches too much and gives too much range hence more snatching.

Nylon returns to its normal length only when removed and in the locker.
 
Bandit said:
What is the material and lay ?

I would go for polyester three stand?

Nylon stretches too much and gives too much range hence more snatching.

Nylon returns to its normal length only when removed and in the locker.
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I think Deleted User means actual springs (commonly found in med moorings), rather than spring lines as used on pontoon berths.

Deleted User - how much movement is a 'fair amount'? What size lines are you using?
 
jimmy_the_builder said:
I think Deleted User means actual springs (commonly found in med moorings), rather than spring lines as used on pontoon berths.

Deleted User - how much movement is a 'fair amount'? What size lines are you using?
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Yup apologies for any confusion. I mean one of these things

test.jpg


The movement is not excessive but its uncomfortable at times. I use 20mm ropes for the stern lines
 
I'm not much help whit which ones to buy but the fisherman's co-op here in Spain supply good priced ones that I use in my home berth's bow lines.
I could get a couple for you and bring them out with me.
We wouldn't be there until late May though.
 
I bought some in palms the other day. Similar sized boat. The chandler recommended "10s" which was the biggest they had. Not sure if 10 is an official size measure or not. I bought inox as opposed to galvanised.
 
jimmy_the_builder said:
Well, according to this page, the strongest 20mm rope has a breaking strain of just over 8T. So surely the smaller springs with a breaking load of 20T would be adequate, no?
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Thanks, Jimmy, good spot. I didn't think of that
 
Hurricane said:
I'm not much help whit which ones to buy but the fisherman's co-op here in Spain supply good priced ones that I use in my home berth's bow lines.
I could get a couple for you and bring them out with me.
We wouldn't be there until late May though.
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Thanks H but I think I better get them sooner rather than later
 
jrudge said:
I bought some in palms the other day. Similar sized boat. The chandler recommended "10s" which was the biggest they had. Not sure if 10 is an official size measure or not. I bought inox as opposed to galvanised.
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I'm not sure about inox. They're a bit shiny and attractive to thieving scum. I lost a set of inox springs in Italy a few years ago
 
M, fwiw I've always had (and still have) inox springs, and never "lost" them... :)
Besides, I'm afraid that the 20T/40T they mentioned to you can't be referred to the breaking load.
More than likely, they are referred to the recommended max boat weight for each model.
In fact, on one hand a steel spring capable to withstand a 40T load is bound to be a thing requiring a crane to be handled...
...and otoh, it would take a huge tsunami to create a 40T load on the mooring lines of a 45T boat!

On a slightly different note, I would be interested to hear the panel view on this topic considering also the following: in my experience, which btw is mostly based on the very same marina that Deleted User is referring to, the need for "big/strong" springs doesn't actually depend so much from the breaking load.
Trouble is, in order to reduce the boat movements, the most important thing is to tighten the mooring lines as much as possible.
This way, any boat movement is bound to be more limited than with slack lines, and as a consequence, the snatch load (which is the most dangerous) is reduced.
Now, all the "traditional" steel springs I've seen don't have a very high initial resistance to load, to the point that when tightening the mooring lines with the winch, it's easy to compress, at least to some extent, the springs.
And this obviously is bad, because reduces the spring excursion and its capacity to absorb the movements whenever necessary.
In this respect, the best mooring device I've seen is the following, because it has a high initial resistance to load, but still maintaining a good compression capacity:
http://www.douglasmarine.com/engl/mooring.htm
Sadly, as often with boating stuff, the thing is priced beyond a rip off - which is the reason why I always refused to buy it.

But if anyone has other thoughts/suggestions/experiences on this matter, I'm all ears!
 
I lost my inox springs when I moored my boat in Monfalcone for the winter a few years ago which is why I'm reticent to pay out a lot of money for inox springs now! With regard to the 'breaking load' of the springs, I'm only repeating what Giuseppe at Marine Sifredi has offered me. He has referred to breaking load in his email rather than boat weight. Btw, the breaking load of the spring might be 40t but if it was used in a crane lifting application, it could have a safety factor of upto 5 so it couldn't be used for lifting very much!

Actually for me, the best way of reducing snatch loads is using crossed lines at the stern because usually a swell causes the boat to move sideways as well as up and down. Agree that mooring springs don't have a big initial resistance but they do have some resistance so they do reduce snatching. The other thing of course is that they are generally used with chains around the mooring bollards on shore which stops your mooring lines from chafing, at least at one end

Yes the Douglas springs look like an excellent piece of kit but as you say they are stupidly expensive and I couldn't justify buying them either. Also I would be surprised if those didn't 'disappear' quicker even than inox springs;)
 
MapisM said:
M, fwiw I've always had (and still have) inox springs, and never "lost" them... :)
Besides, I'm afraid that the 20T/40T they mentioned to you can't be referred to the breaking load.
More than likely, they are referred to the recommended max boat weight for each model.
In fact, on one hand a steel spring capable to withstand a 40T load is bound to be a thing requiring a crane to be handled...
...and otoh, it would take a huge tsunami to create a 40T load on the mooring lines of a 45T boat!

On a slightly different note, I would be interested to hear the panel view on this topic considering also the following: in my experience, which btw is mostly based on the very same marina that Deleted User is referring to, the need for "big/strong" springs doesn't actually depend so much from the breaking load.
Trouble is, in order to reduce the boat movements, the most important thing is to tighten the mooring lines as much as possible.
This way, any boat movement is bound to be more limited than with slack lines, and as a consequence, the snatch load (which is the most dangerous) is reduced.
Now, all the "traditional" steel springs I've seen don't have a very high initial resistance to load, to the point that when tightening the mooring lines with the winch, it's easy to compress, at least to some extent, the springs.
And this obviously is bad, because reduces the spring excursion and its capacity to absorb the movements whenever necessary.
In this respect, the best mooring device I've seen is the following, because it has a high initial resistance to load, but still maintaining a good compression capacity:
http://www.douglasmarine.com/engl/mooring.htm
Sadly, as often with boating stuff, the thing is priced beyond a rip off - which is the reason why I always refused to buy it.

But if anyone has other thoughts/suggestions/experiences on this matter, I'm all ears!
Click to expand...

agree on all points

the weight of the boat for speccing the spring (40T for Mike) has nothing to do with the max breaking load of the rope

no experience with the "softer" metal springs myself, never found one strong enough for BA (while searching for the make of my springs)
I actually do have the Douglas marine springs , at the time delivered together with the boat,
two year ago I bought the "chain boy" from Douglas Marina.

they have indeed high initial resistance,
but I have seen them working until maximum displacement in extremely rough conditions (ones in Cassis and ones in Porte Montenegro)
there might have been many more occasions in winter when we were not onboard.

I also think that tightening strong the mooring lines is key

during a night in Cavtat, we had extremely strong snatching on the ropes, so much that it made some damage around the fairleads,
we never take the springs with us onboard, they stay on our home berth. (unless we go away for a very long period )
 
Deleted User said:
With regard to the 'breaking load' of the springs, I'm only repeating...
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Well, I'm not saying that he surely mixed up breaking load with boat weight, but it definitely sounds like he did.

In these two webpages (albeit only in IT, I'm afraid) of Douglas Marine website, you can see that their bigger traditional s/steel spring, with a 12mm steel wire, has a breaking load ("carico di rottura") of only 6.2T:
http://www.douglasmarine.com/mollesilenziate.htm
Otoh, the bigger of those blxxdy expensive elastomer things, recommended for boats up to 150T, has a breaking load of 30T:
http://www.douglasmarine.com/mastermooring giga.htm

Bottom line, I can't rule out completely that G found some 40t breaking load springs, but I surely would be curious to see them and their specs.

With regard to your mooring technique, I agree with everything you (and also BartW) said, and I do exactly the same. Btw, B, if you check out the second of the previous links, I'm sure that would be more than adequate also for BA, if you don't mind being ripped off a bit... :)

Unfortunately though, when the bigger ferries steer hard over inside the harbour faster than they should (and it does happen, sometimes), the wash push the boats longitudinally, towards the dock and back, hence creating a snatch load on both the bow lines and the stern lines.
And crossed lines astern are useless in this case, for obvious geometric reasons.
Otoh, in this respect you have an advantage in being moored along the N wall, because this effect is much worse on the main dock, I suppose due to the steering direction of the ferries.
 
Well I'm very glad that Giuseppe didn't put me on the main quay then where the celebrities like you go! I have ordered the 2 x 20t springs on the basis that if 20t is the breaking load, then 20t is plenty and if its the max weight of the boat then 2 x 20t = the weight of my boat! But mainly its because I'm cheap
 
Shirley the breaking load of the "spring" will actually be the breaking load of the bit that runs through the middle of the gadget? It's the spring rate, load rate and damping that matter I'd have thought.
 
I would pick the 20 Ton ones too. If you go too big then the springs are so strong that they don't compress at all and you end up with the ropes and cleats taking all the shock. Its hard to judge exactly as no-one provides sufficient information. Worst case if you have gone too small they might totally compress occaisionally but they wil have slowed down the impact.
 
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