The Low down of Mooring lines?

Well, it depends on the tides mostly. When you tie up the boat, you have to have the lines adjusted to allow for the hight change in the tide without making the lines too loose or too tight. This is dependent on many things, including the length of the lines between points were they're secured, the height of the dock/cleats relative to the waterline (and the deck), the amount of tidal change, etc. So, most of the time they are (should be) tied with enough slack to allow room for tidal increases. At high tide, you would generally want to tie the vessel tighter so when the tide goes out, the lines are not excessively loose. There are certain situations where this can be difficult, and the best way to keep things in place is frequent adjustment. Most of the time, however, if done correctly, you can have enough line for the tide, but not more than necessary.

Also, over time, especially when wet and tight (or have tension put on them), the lines will stretch on their own. They should be adjusted as necessary if this occurs to keep things in place properly.

On the other hand... I have often seen boats large and small tied up with poorly adjusted lines where it seems to me they just didn't know what they were doing. This is far too common from what I've seen...

No problem.

While I'm not cruse ship expert, here's what I suspect. The tides certainly affect them as well, but it doesn't play as big of a role because of the extreme length of the lines. When the tidal change is 3-4 feet, and the lines are tied onto the boat 50 feet from the pier, the tidal change has a relatively smaller affect on the line tension. In addition, I suspect the difference can just be stretched out of those lines because of their length (although I don't know if that's what they do).

It would be important to keep the ship carefully in place relative to normal boats largely because of the importance of it sitting still. Think of the passengers coming on and off, and cranes (or whatever) loading and unloading cargo, etc. If a slight breeze were to come along and it wasn't tied tight, someone or something could get hurt/damaged... There's also a lot more momentum that can be created when those suckers move around and could cause more damage.

This is what I suspect. In addition, because of the man power on these ships, perhaps they adjust the lines frequently enough to keep them tight, but not too tight (not forcing them to stretch).

Hi Yachtluver,

modern cruiseships are normally equipped with automatic mooring winches. You can set the (range of ) required tension and they will pull in or let out the mooring lines to have the correct tension in the lines at all times.

Bruno

Yeah, sorry about that yachtluver. Sometimes we just get tired of answering questions for certain individuals.

You are correct that one of the most popular materials for lines is nylon. I honestly don't know if that's what the big ships use, but I would assume as much. The two main variations are three-strand nylon and braided nylon lines. Three-strand generally will stretch more and isn't quite as strong as the braided, which tends to stretch less than three strand. Three-strand is cheaper, however, and is often used for anchor line on smaller boats because it stretches more, and can be easily spliced.

Some other materials are polypropylene (normally yellow), which serves its purpose, although you wouldn't want to use it to tie up your yacht. This kind of line floats. Dacron line will not stretch, but I don't know much about its other properties. Then there's the good ol' natural fiber, which I suspect is what the large 7-8" lines you mentioned were made of. This is not as strong as nylon and will rot much more easily.

Hope this answers your questions. I was, of course, kidding about getting tired of answering your questions. Time for bed now, have a good night!

Many but not all large ships use wire cable especially if they have a self adjusting system.

Well the lines going directly from the tacht to the dock hold the vessel in and the crossed lines, springs restrain the vessel from surging along the dock.

The second "crossing" stern line is a back-up line and therefore does not need to be taunt. If you were tying up a 20 million dollar yacht, you would put out a few extra lines as well.

Hi,

These are commonly known as Fairleads

Hi,

I am pretty sure this term is used on any type of vessel.

Chocks and Fairleads

chock (n)
Definition: 1) Fairlead. A fitting mounted securely to the deck or cabin top through which lines are led. 2) A deck fitting used to secure moveable gear.

fairlead (n)
Definition: A block, padeye, ring or any other kind of gear which controls the path of a ship’s running rigging, and keeps it from fouling or chafing. Such as a turning block on a sailboat's sheet.

A chock is a fairlead, but a fairlead is not a chock, unless of course it's chockablock.

That photo is typical of the philosophy that "the more lines you have out, the happier you'll feel..."?! You can't see what's going on with the lines leading out from the bow in the photo, but anyway, let's remind ourselves what a mooring line is supposed to do:

1) Limit forward movements of the yacht (ie. stern lines)
2) Limit astern movements of the yacht (ie. bow lines)
3) Limit sideways movements of the yacht (ie. breastlines)
4) Limit forward, astern or sideways movements of the yacht (ie. spring lines)

When alongside, ideally, you'd have mooring lines to limit movements in all directions leading out from both the bow and stern of the yacht. In yachtluver's photo, that Amels appears to have just 1 spring line (to limit astern movement) plus 3 breast lines (1 of which is so slack as to not be doing anything at all except to catch fishhooks from nearby fishermen...). If I were the skipper, I might have preferred:

1) a stern line to limit forward movement from the innermost fairlead (ie. the 3rd or closest fairlead to the centre of the yacht on the port side) leading out to the mooring bollard farthest from the yacht's stern
2) a spring line to limit astern movement from the fairlead on the extreme corner on the port side leading out to the bollard on the quay / pier closest to the yacht's mid-section
3) a breast line to limit sideways movement from the fairlead on the extreme corner on the starboard side leading out to the same bollard as in 1)

In this particular situation, the extremely short breast line leading out from the middle fairlead on the port side may as well be a steel bar welded onto both the yacht and the quay...

By all means, "double-up on lines" if weather or tidal conditions demand, but at least ensure you arrange whatever lines you have out purposefully...?!

Obviously, a mooring line is just one part of a complete mooring system...whose components consist of the mooring bollards / bitts / cleats, fairleads and rollers or whatever on the yacht, the mooring line itself and the bollards / bitts / cleats or rings on the quay etc.

Severe injuries and even fatalities have occurred to passengers / crew or those on the quay due to the failure of one or more components, on yachts as well as in commercial shipping...

Before moving on, I'd just like to address another observation / question from yachtluver

The whole point of having these buoys at marinas like they do at the IYCA is so that yachts do not have to drop their anchors...! Actually, the problem is not actually dropping the anchors, it's about security and convenience, whilst other yachts "over whom you've dropped your anchors and chains" attempt to leave their berths, possibly dislodging your anchors and then when you yourself wish to leave your berth, and have to call in a diver "to untangle the mess lying on the seabed"...?! As for which particular fairlead the mooring lines lead out from the yacht to the buoys, well, it's all about purpose...?!

Back to mooring lines in general, for superyachts...

They're made of polyamide (nylon is the registered trademark of DuPont) or polyester, are of either double-braided or squareline (8 or 12 strand) construction and are usually spliced with a soft eye at one end. Rarely does one see 3 braided ropes used on yachts over about 25m (80ft).

Let's take a typical 50m (180ft) motoryacht's set of mooring lines:

Ø40mm double-braided or squareline, polyamide, with Ø75cm soft leather-protected eyes,

1) 4 x 20m
2) 2 x 30m
3) 2 x 40m

Depending on the classification society, you might also be required to carry a suitable tow-rope (a humongous coil of rope upto 200m. long and usually floating polypropylene squareline usually stowed (and forgotten) in the forepeak...which I'd recommend being cut down into say 2 x 100m lengths and used as the bow lines for when you go into somewhere like the IYCA and are allocated a 100m berth (and charged for it)...

Why polyamide (nylon), polyester or polypropylene? Here's some typical comparisons:

(all Ø40mm - just over 1 1/2")

Polyamide double-braided or squareline construction: breaking load: 40,000 daN (40,000kg to you and me); weight: 99kg per 100m; elongation (stretch) about 15-20% at 50% load; "a finished 30m mooring line weighs about 33kg".

Polyester double-braided or squareline construction: breaking load: 32,600 daN (32,600kg to you and me); weight: 121kg per 100m; elongation (stretch) about 10% at 50% load; "a finished 30m mooring line weighs about 40kg" . Granted, polyester has superior abrasion characteristics compared with polyamide, but is it really worth the additional initial cost for this and the fact that it has a lower breaking load...? I don't really think so all things considered, especially when your average superyacht owner likes to have "good-looking lines", replaced every 3-5 years...

Polypropylene squareline construction: breaking load: 26,500 daN (26,500kg to you and me); weight: 72kg per 100m; elongation (stretch) between 20-30% at 50% load; "a finished 30m mooring line weighs about 24kg". It also floats, compared to polyamide and polyester, which do not...!

So why polyamide?! Its' strength and weight advantages easily outweigh the wear characteristics of polyester lines. Provided the eyes and other chaffing points are suitably protected, I'd plump for polyamide (nylon) lines all the time. However, polypropylene lines will float, which makes them a lot easier to handle in some situations like when you're trying to get a long line out onto a dead tree (?!) in a secluded anchorage without swinging room somewhere in Turkey for example. Or tying up to the buoys at the IYCA...?!

But what do you do if you own a 86m yacht?!

Well, it's worth bearing in mind that unless you have multiple "California governors as deckies", it becomes impossible to correctly manually handle anything over Ø44mm mooring lines. A 30m Ø48mm polyamide mooring line weighs about 47kg, a polyester one about 58kg. The lines would probably not go around the mooring bollards / bitts / cleats, fairleads and rollers or whatever on the yacht, let alone the mooring capstans...?! So ensure that your new yacht has multiple over-engineered mooring bollards / bitts / cleats, fairleads and rollers so that you can satisfactorily double-up smaller lines...!

A short aside: commercial shipping nowadays is increasingly converting from use of steel-wire mooring lines to the use of synthetic alternatives like Spectra, Dyneema etc. which offer far greater breaking resistances for the same diameter. In fact, double-braided synthetic mooring lines are these days the preferred method when tying up your average 250,000 ton oil-tanker to its' offshore berth.

Another aside: a few ex. sailboat skippers who've moved onto (better-paying with bigger cabins etc.) jobs on motoryachts have brought along a new phenomenon which entails using very small (but extremely strong though not stretchy) Spectra and Dyneema type lines when first tying up, to be replaced by the more traditional (and bigger) polyamide mooring lines afterwards because they're so easy to handle (even by Nicole Kidman-lookalike stewardesses)...?!

Lastly, all the "traditional-looking" ropes one comes across these days (ie. the ones that look like hemp) are more likely to be of polypropylene construction: apparently it's because cultivating the plant that produces the original raw hemp material has inexplicably become illegal...

So you think I appear to be quite knowlegeable on the subject of mooring lines huh? Well, that's because once upon a time (a long time ago and in a far off galaxy), I was on the foredeck of a 40m yacht, had sent out the heaving line and was watching the mooring line being retrieved through the fairlead from the dock, until the end ran out as well...it was a bit short one decided afterwards?!