Deep anchoring

[GordMay]

Didn’t U.S. charts begin switching [mid nineties?] from feet and/or fathoms, to soundings in meters, using the international standard for measuring depth? Has that trend been discontinued?

[aqfishing]

Originally Posted by cal40john

Or are you saying that ENCs can display decimal fathoms? 9 sub 8 would be 9.8 fathoms. 0.8 x 6 = 4.8 feet, plus 54 gives 58.8 feet.

I could see programmers thinking this was a good idea.

Sorry. Your are correct. It cannot be fathoms, was not paying that much attention. I merely asked if it was feet or meters in the first place. Fathoms did not even enter my mind to be honest, I think someone else brought that up.

So its either feet.decimal feet or meter.decimal meter as that is how the boating app displays it. Either way, and back to the original point, its not very deep.

[aqfishing]

Originally Posted by GordMay

Didn’t U.S. charts begin switching [mid nineties?] from feet and/or fathoms, to soundings in meters, using the international standard for measuring depth? Has that trend been discontinued?

Not sure. We referring more to the Navionics app as this is the screenshot the OP posted. It allows the user to choose the units.

What units do they use on official US paper charts? If it is indeed meters I can imagine this causing a few headaches for those used to imperial units.

[hpeer]

FEET.
Very roughly 3’ to 4’ of tide.

[thinwater]

Originally Posted by longjonsilver

i don't know. It is a Navionics screenshot from when i got the free trial. Locals say that the anchorage is about 60' deep. If so it might be in fathoms?


Rumor has it that the docks will never be put back in cuz the city of Halifax plans on using Mill Cove for the ferry terminal, altho that is still undecided, cuz, to me, there in not enuf parking nearby.


We took a look at this anchorage when the hurricane hit Halifax. It is WELL protected

So do i.

The question in my mind is "Wud there be enuf swinging room"?

Roy M on this forum, has an SR 40 and uses 1/4" HT chain, other trimaraners also use 1/4" in this size range.

Long term. This is close to my house, and under utilized. In the winter relatively ice free cuz of the inflow of fresh water from Moirs Pond. Big boats are tied to the breakwater in the winter.

The floats are the soft rubber/plastic ones. Why shud i avoid hitting them as i swing?

No idea what the bottom is, but Moirs Pond drains into it so i assume mud? Note the M in the Southwest part of the anchorage.

Note the pipeline into the anchorage, in the winter there is NO ice near the pipeline.



Like NO drag space, hence the question. Rocks all around and the jetty. No room for error.

If long term, put in a proper mooring. Any anchor has some risk of tripping, anchor chain is sized differently for long-term, and your swing will be less (more room for other boats). More reasons. You may need a permit.



If you swing over floats they will snag you rudder and prop, requiring a dive to clear, replacing the markers (you damaged them and they are not yours) and potentially doing damamge to your prop or rudder.

[rslifkin]

Originally Posted by GordMay

Didn’t U.S. charts begin switching [mid nineties?] from feet and/or fathoms, to soundings in meters, using the international standard for measuring depth? Has that trend been discontinued?

For ENCs my understanding is that the depth data can be displayed in feet, fathoms, or meters depending on user preference (as it's just data and can be converted as needed by the display software).



The raster charts I'm familiar with are all in feet or fathoms. A quick search indicates that the 1990s attempt to convert was abandoned very quickly and very few charts were ever converted. Some documentation from 2017 mentions assessing another attempt to convert now that all the data has been digitized, but with raster charts being discontinued (which I personally am very disappointed by), I doubt it'll ever happen.

[Breaking Waves]

two thoughts:

(1) you are a multi-hull, I presume with a shallow draft. Can you anchor in that shallow area in the upper left (or another shallow area) of your chartlet? This keeps you out of traffic zones and makes the anchoring depth/scope issue much less. As Thinwater will tell you, you will need a good snubber.

(2) when the swinging room is an issue in tight spots, one solution is using a stern short tie. This is means you will always be pulling the anchor upslope (which is vastly better than downslope). You presumably have mostly westerly winds - I would think to do this in the NW corner to provide shore protection from two sides. It is not always the best solution, but it is a useful one often.

I'm puzzled by whatever you are doing with charts. The two chart snips you posed have different numbers and even different contour shapes. You are obviously toggling something different between the two. You should sort that out and (1) get the most accurate contours and (2) know what units the depths are in.

Bedford bay is in fact quite protected, except against a very strong southerly wind and big swell - a large southerly swell can roll right up and potentially cause issues. But Mill's is pretty protected from that.

[longjonsilver]

Originally Posted by mako

Let me ask something. Except for the word “fathom” sounding all nautically and whatnot, is there any real practice reason to ever use it as a unit of measure?

i cannot fathom why anyone would need to use it....

Originally Posted by hpeer

FEET.
Very roughly 3’ to 4’ of tide.

Today, near the full moon, 5.9 feet

Originally Posted by thinwater

If long term, put in a proper mooring. Any anchor has some risk of tripping, anchor chain is sized differently for long-term, and your swing will be less (more room for other boats). More reasons. You may need a permit.

i will have to talk to the harbour authority at the Halifax Waterfront.....

Originally Posted by Breaking Waves

you are a multi-hull, I presume with a shallow draft. Can you anchor in that shallow area in the upper left (or another shallow area) of your chartlet? This keeps you out of traffic zones and makes the anchoring depth/scope issue much less. As Thinwater will tell you, you will need a good snubber.

3 foot draft with centerboard up. A year ago winter, the local yacht club towed their docks and tied them up in that area. This last winter there were no docks there. Many tris use a bridle to the floats and that limits yawing and serves as a snubber.

Originally Posted by Breaking Waves

when the swinging room is an issue in tight spots, one solution is using a stern short tie. This is means you will always be pulling the anchor upslope (which is vastly better than downslope). You presumably have mostly westerly winds - I would think to do this in the NW corner to provide shore protection from two sides. It is not always the best solution, but it is a useful one often.

Someone has placed anchors into the rocks on shore (like the power company uses for its poles) and sometimes a rowboat is tied to them. Prevailing wind is SW.

Originally Posted by Breaking Waves

Bedford bay is in fact quite protected, except against a very strong southerly wind and big swell - a large southerly swell can roll right up and potentially cause issues. But Mill's is pretty protected from that.

i have never seen swell in Bedford Basin, even during the hurricane.

[Dieseldude]

Originally Posted by mako

Let me ask something. Except for the word “fathom” sounding all nautically and whatnot, is there any real practice reason to ever use it as a unit of measure?

A fathom is a very practical unit, being that it is the average or nominal span of a man's outstretched arms. Your measuring instrument is your arms. So for measuring line when there is no need for a high degree of accuracy, this is an expedient method and unit. For measuring most ordinary working lengths of rope or other line, it is generally good enough. For better accuracy, a line's length can be determined by simple arithmetic by summing the number of arm spans counted. For mentally comprehending a depth in fathoms, the number of average height (6 foot) men standing atop each other foot on head can be mentally visualized. By legacy, the unit remains in use.

[Auklet]

Originally Posted by aqfishing

Sorry. Your are correct. It cannot be fathoms, was not paying that much attention. I merely asked if it was feet or meters in the first place. Fathoms did not even enter my mind to be honest, I think someone else brought that up.

So its either feet.decimal feet or meter.decimal meter as that is how the boating app displays it. Either way, and back to the original point, its not very deep.

I can’t see cruisers looking for a spot to anchor and being interested in fractions of a foot of depth. That would be ridiculous to have to mull about 7 tenths of a foot when your draft is 6 1/2 ft; whereas, 7 tenths of a meter is something to notice if your draft is basically 2 meters. That boat might go into 2.7 meters, but certainly not 6.7 ft, etc.

[Shrew]

I believe that the depth notation in subscript can be multiple things based on the settings:

Number = Fathoms
Subscript = feet

9[sub]3[/sub] = (9 fathoms; 3 Ft)

----------------------
Number = Meters
Subscript = tenths of meters

9[sub]3[/sub] = (9.3 meters)

----------------------

Since a fathom is 6 ft. Having a notation of 9[sub]8[/sub] makes no sense in fathoms, but it does in meters. 9.8 meters would only be 32 feet.

Reported depths in feet sound like this is denoting fathoms.

Is there a chance the notation of 9[sub]8[/sub] is 9.8 fathoms (58.8 feet)??

[MJH]

Originally Posted by longjonsilver

What are the requirements/differences for deep anchoring? i am looking at anchoring medium term a 37' trimaran in Mill Cove NS. Most people i read advocate a 45 lb new generation anchor and 1/4" chain for general anchoring purposes. How would this deep anchoring differ?



Green line is about 300'. An 80' schooner is moored or anchored near red circle. The docks have been permanently (?) removed and have been replaced by buoys marking the anchoring points for the dock.

All advice is welcome. jon

What is medium term? Are you leaving the boat or staying aboard? What anchor do you have?

First, I Googled Mill Cove, Nova Scotia and don't see anything like your posted diagram. The only facility I see is the Mill Cove Government Wharf. Is there possibly another Mill Cove in NS?

That aside, deep anchoring is the norm in the Pacific NW and standard anchoring rules normally apply; 7:1 ratio is ideal, 5:1 is common, 3:1 the minimum. However, I have had to anchor at 2:1 due to limits of chain & rope on a previous boat but weather forecast was light & variable for the night...I did not experience any problem.

I agree with a previous post that 1/4" chain is too light; I would go to 5/16".

Good Luck.

~ ~ _/) ~ ~ MJH

[Dieseldude]

Originally Posted by MJH

What is medium term? Are you leaving the boat or staying aboard? What anchor do you have?

First, I Googled Mill Cove, Nova Scotia and don't see anything like your posted diagram. The only facility I see is the Mill Cove Government Wharf. Is there possibly another Mill Cove in NS?

That aside, deep anchoring is the norm in the Pacific NW and standard anchoring rules normally apply; 7:1 ratio is ideal, 5:1 is common, 3:1 the minimum. However, I have had to anchor at 2:1 due to limits of chain & rope on a previous boat but weather forecast was light & variable for the night...I did not experience any problem.

I agree with a previous post that 1/4" chain is too light; I would go to 5/16".

Good Luck.

~ ~ _/) ~ ~ MJH

I know of two places in NS called "Mill Cove". One is at Bedford Basin, which is actually the inner portion of Halifax Harbour. The other is a fishing port on the west side of St. Margaret's Bay. The posted chart section does not look like either. So perhaps there is another "Mill Cove".

[Chrisatlantic]

The original Navionics chart snip appears depth in decimal meters, the subsequent chart snip looks to be depth in feet.

Contours are not precisely the same but close enugh to make those assumptions.

[pbmaise]

It is easy to find on Google Earth

https://earth.google.com/web/search/...1AId8BtsWIA11A

When I was confined to a small area and worried, I first dropped anchor with a relative short scope of chain. I then attached a heavy kellet to the anchor chain and then dropped that down to the bottom. When I left I pulled up the kellet. I was using a 55 gallon drum and would fill it with sand and gravel. The trick was tipping the drum upside down and I had to have a line on the bottom of the drum and pull that upside down from the ama. I had a much bigger trimaran and a strong windlass to pull it up. In your case weaving a Dyneema line into the chain and then dropping like a about 4 five gallon pails should add enough weight. Don't depend upon the wire loop of the five gallon pail to hold the weight. I drilled the plastic of the 55 gallon drum edges to weave the line there.