Maximum Weight On Buoy Is It A Problem?

[sailorman]

The orogin of the imperial ton was the tun the biggest sise of wine barrel which weighed arround 2240 lbs. and was about 100 cubic feet. vessels have been comonly desribed by tonnage in which uses the volume referance of 100 cubic ft per ton and is still in common use.
I thought the UK Including the IOM went metric for weights and mesurments about 44 years ago.
although many boats built back in the 60s or prior would be imperial.

I would have thought moorings laid in recent decades would be by tonnes.
If marked in tons I would wonder if they were refering to tonnage rather than displacement.

between the outboard ends of the boat not including rudders and bow sprits. Multiply that by the maximum beam outside to outside.
Multiply that by the distance from the sheer line not including bulwarks
or cap rails to the outside bottom of the hull not including the keel.
Add the volume of the deck house/cabin top. Multiply by .5 for sailboats and .67 for power boats.
Divide by 100.

A bit of trivia...

Tonnage has nothing to do with the weight of your boat. It is a measure
of how much wine a vessel can carry.

The word "tun" was originally a size of a cask used to ship wine from
Spain & Portugal to England. In 1347 a tax of 3 shillings per tun was
imposed and this was called "tonnage." A ship's size became known by the
number of casks it could carry, and the word tonnage started being used
to describe a ship's size.

It was found that if you took the length x the breadth x the depth of
the hold under the deck and divided by 100 it was close to the number of
casks. That is where we get the "Measurement ton" of 100 cubic feet per
ton.

There are several kinds of tonnage: The first two are used by the tax
collector. The next two are used by designers. The fifth and sixth are
used by freight salesmen and canal operators and the last one is used by
the USCG for documenting boats.

Gross Tonnage - is the internal volume in cubic feet of the vessel
minus certain spaces above the main or "tonnage" deck, like stacks and
ventilators, which are called "exemptions" .

Net Registered Tonnage - is obtained by deducting from the gross tonnage
the volume of space that can't be used for paying cargo or passengers,
that is to say the space occupied by the engines, the crew's quarter,
the stores, etc.

Displacement Tonnage - is the actual weight of the water "displaced" by
the ship and is usually quoted in long tons of 2240 lbs.

Light Displacement Tonnage - is the weight with nothing in it.

Loaded Displacement Tonnage - is the fully loaded weight to the maximum
and is on her summer draft in salt water.

Deadweight Tonnage - is the difference between Light and Loaded
Displacement Tonnage....the actual carrying capacity of the vessel.

Panama & Suez Canal Tonnages - these are different from the internationally
accepted definitions. There used to be a lot of variations between countries and the canal owners thought they were being conned, so they came up with their own definitions.

All that was just way too much for bureaucrats to deal with for yachts so they came up with their own formula as described at the beginning of this post. no longer has anything to do with anything real; it only exists in the minds of government bureaucrats.

Another word came from the same orgin: rummage. Rummage was the manner in which the wine casks were stored in the hold of the ship and came to refer to the whole ship's cargo. After a voyage any unclaimed and damaged cargo was stacked on the dock beside the boat and offered for sale - a rummage sale.

 

[Daydream believer]

It depends on the depth and the general set-up, but in a perfect world a sinker will be lowered into a dug hole, not simply plonked on the seabed; if it is just plonked, I'd certainly rather anchor in strong winds.

Who is going to dig a hole in 5 m of water

 

[Seajet]

I said ' depending on the depth '.

If not dug in a sinker will need to be huge or linked on the bottom to others, as they are ( or certainly were ) at Itchenor for instance.

All our club drying moorings are well dug in, as my bad back can testify; we have used a chap with a mechanical digger on a raft this Spring though to get even deeper, into the chalk below the deep mud.

 

[NormanS]

I said ' depending on the depth '.

If not dug in a sinker will need to be huge or linked on the bottom to others, as they are ( or certainly were ) at Itchenor for instance.

All our club drying moorings are well dug in, as my bad back can testify; we have used a chap with a mechanical digger on a raft this Spring though to get even deeper, into the chalk below the deep mud.

Well, obviously drying mooring blocks have to be buried, otherwise the boats would sit on them. It would be highly unusual to attempt to bury deep water mooring blocks.

The blocks, sinkers, anchors, or whatever, are sized to suit the type of boat. If it says 5 Ton, or 5 Tonne, it doesn't mean 12 Ton, or 12 Tonne. Simple.

 

[Seajet]

Which is what I said to start with, but there's the complication of the 5 tonne moorings in question being visitors buoys which larger boats are directed onto.

With a private mooring, it's easy to say ' stick to the numbers '.

As I also said, deep water mooring sinkers need to be huge, and some are linked with chains along the bottom; another very good reason not to anchor among moorings, I found the bottom chains at Itchenor when diving to free the anchor for a berk who'd done just that.

These moorings at itchenor are for visitors, and can often have rafts of 4 or more large boats in a strong tide.

 

[Daydream believer]

I said ' depending on the depth '.

In other words-- no depth
Actually we use sinkers up to about 2.5tonne for a boat up to 30 ft but the sea bed is fairly thick mud so they do sink in a bit
However, ocassionally scouring by the current means they can loose their grip. Why we object to larger craft using the moorings is that they have a tendancy to break them free. Then the first gale that comes along causes them to drag

 

[dewent]

Well if people raft up on moorings they are most likely to be putting too much weight and windage on the buoy.However my observations is that this happens all of the time everywhere. The answer must be in calm weather on a public mooring there won't be a problem - just be sensible.

 

[Seajet]

Well if people raft up on moorings they are most likely to be putting too much weight and windage on the buoy.However my observations is that this happens all of the time everywhere. The answer must be in calm weather on a public mooring there won't be a problem - just be sensible.

Quite so; Itchenor is sheltered with plenty of options to clear off and go somewhere else if the weather turns bad.

The visitors moorings at Salcombe are a bit more serious, in the summer they are heavily rafted on as well, I've had to rig a spinnaker pole between the pole eyes of our and neighbouring boats to synchronise rolling and prevent masts clashing but that was mainly due to wash; I've been through a F9 in a 30' boat on one of the Salcombe moorings - don't remember any tonnage marks, long time ago - but if there was a boat alongside I would have cleared off pronto, there are still other options to go to.

The big problem is when there's nowhere else to go, say Braye, Alderney; I don't remember any tonnage marks on their visitors buoys either, must be massive, the place gets horrendous weather and the buoys are often rafted on, nowhere else to go apart from to sea, which I wouldn't fancy around there even with a strong crew.

When I was investigating Environmentally Friendly Moorings for BORG- used to be a member - I was very unimpressed, these things are basically a big corkscrew into the seabed !

I rang my insurers to ask their views on using a vistors' mooring consisting of one of these things; " what value boat do you think might use these ? "--- ' Oh it's right where Sunseekers are built, so say a few £ million ' --- " Err, we'll get back to you ! " Click BRRR. Needless to say that was the last I heard.

 

[nathanlee]

In the middle of Preston dock there is one of the original mooring buoys from when it was a working dock. It's seriously rusty, and as far as I know, not maintained. No idea what the rating it. In the summer months, there's often a few of us that will raft up to it, with perhaps 40 tonnes or more hanging off it. I think the most I've seen was getting on for 60t. Anyway, it's all fine, but nobody, and I mean nobody, would be daft enough to use it if there was anything more than a zephyr.