Backing Down on a Mooring?

[Scotty Kiwi]

Marlborough Sounds NZ - all moorings incl privately owned ones need a Resource Consent from the District Council - the local authority. they check them periodically (every year or two), hold the owner responsible for maintaining them.

It's a very expensive system - I think (but are not sure) around $800 p.a. per mooring, which includes an element of rent for the public assets.

Here's a map of them published by the council https://maps.marlborough.govt.nz/sma...e2e99c58e84453

But you can trust them - you'd think no real need to back down.

That said, with all that process and cost, I've woken once in the middle of the night with the different movement on the boat - drifted a few miles. I never used to back down on them, but having now read this I will in future.

[Normanskier]

Staying overnight in Shrouds Cay in the Exumas I opted to set our anchor, a CQR, with 200 feet of chain. There were a number of moorings available as it is a Marine Park of sorts. Lots of squalls at that time. I was about 75 yards in front of another sailboat. My anchoring option was based primarily on the typical scope of the mooring versus anchor. We had three squalls come through with the last one about 5:30 AM. I got up every time it started to rip. The fellow at my stern was constantly monitoring the mooring rode as the seaway brought in 2-3 footers. That poor guy was jerked up and down incessantly. Not a great way to spend the night. The catenary gave us a fairly comfortable night. Highest mph was 65. Fifteen miles to the northeast a squall came through at 114. Set an anchor if you can.

[Bycrick]

Moorings are usually designed for 2:1 scope, or less if in protected areas. Several sources talk about one "maximum water depth" of heavy chain and one of lighter chain. Thus the heavy chain sits on the bottom most of the time and lifting it in heavy weather provides some shock absorption. If things get nasty enough, you’re dependent completely on the mooring anchor.

Lots of people use concrete for mooring anchors. It’s cheap. But it loses about half its effective weight in water. So, in very general terms, if the design tables indicate 1000# deadweight anchor, you can get away with a 600# mushroom anchor, or a 2000# concrete block. Four 500# concrete blocks are not equivalent and the hardware to tie them together creates more failure points. Like any parallel connected system, the load will never be quite evenly distributed. So the weaker link breaks first, putting increased strain on the rest, and so on until you’re drifting.

One can’t "trust" moorings unless you dive to inspect them completely AND have lab tests of the bottom characteristics. Even after all that, the insurance companies are unhappy with the lack of certainty.

And then something can just break.

Whenever you’re on a mooring, make sure your anchor is quickly and easily deployable.

[lituya1617]

I never use a mooring unless there are no other options. My rules: 1. that the mooring must be diver inspected. 2. the specifications of the mooring anchor and line/chain must be available to me prior to the dive inspection so I can verify that the equipment is as specified. 3. I pay out 50 feet of mooring line (3/4" nylon) from my bollard on the foredeck and back hard taking up the slack against the mooring attachment (I bounce the mass of the vessel against the mooring and generate several tons of strain, far more than the prop could generate with a steady pull.) before I am satisfied the thing will hold. I have seen moorings that specified they were 4,000 pound concrete blocks that were actually old engine blocks lucky to weigh 800 pounds; specified one-inch galvanized chain that was actually frayed one-inch polypropylene line; I have seen 3/8" shackles on moorings that attached large chains to heavy concrete blocks through 1/2" rusty re-bar hoops in the concrete. Apparently, no standards exist for moorings. Moorings are a hazard I like to avoid. A proper inspection requires light and about half an hour underwater. Then you have to rinse your suit and clean up your equipment. It is just too much time and effort to moor to an official mooring. I would rather pay to tie to the transient dock. Of course, some moorings are done properly but my anchor is always done properly.

[lestersails]

How much of this relatable to the entity who installs and maintains the mooring and how often it is used?
I am thinking here about the National Park Service moorings, in St. John, for example. First, you mostly have to use them. Second, I am naive but rather suspect that they install them properly and take decent care of them. Plus, they are in use nearly constantly, which means that someone is very likely to have been on that mooring very recently. And it is essentially certain that a boat of your size has been pulling on that tackle. Isn't that a decent stress test?
I would think a ball like that would be more likely to be reliable than a random privately installed mooring I might come across.
I understand there are no guarantees, so an anecdote that an NPS mooring might have failed once is not useful. But aren't the odds better in a location like this?

[Bycrick]

Lituia is right: There is no standard for moorings. There are marina design books, studies and papers by all kinds of people. But there are no "standards." Even if there were, there’s no way of knowing that the mooring you’re tying up to would ever have, much less right now, have met them. You might be able to tell from an underwater inspection that something is broken, or maybe about to, but a lot of failures won’t be visible. Even if someone gave you the description of the mooring components, you would know that it’s real. "We used 1/2” proof-tested shackles blessed by this testing organization." Would you know the difference after six months in the water. What’s the piece of 1” steel bar actually attached to with the big lump of concrete?


Moorings are a crap-shoot, unless you were there when they were built and installed and you supplied and checked all the pieces. "We inspected it last week." True or false.

Operating a mooring field properly is a big job and not easy. It’s tempting to cut corners. Private moorings are even more likely to be badly designed, poorly made and never inspected.

You use any mooring at your own risk. Keep your anchor handy.

[robertandanneke]

Hi,
In addition to what was discussed already.. we always put our anchor alarm on, also on a mooring, as especially in the dark it is hard to see whether you and the mooring are drifting.

In Palmerston they also knotted a line from the boat to the next mooring, just to be sure..