Deep anchoring

[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 removed and have been replaced by buoys marking the anchoring points for the dock.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

[aqfishing]

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 removed and have been replaced by buoys marking the anchoring points for the dock.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

Is your depth in feet or meters, either way I would not consider that deep.

[Muaddib1116]

How much chain do you have? 10 meters (33ft) isn't overly deep.

[AiniA]

Doesn't seem all that deep. Main difference is the length of rode needed. You mention 1/4" chain, seems light for a 37' boat. Also remember that there are different grades of chain with very different working loads - G43 is much stronger than BBB or Proof chain. Very importantly is how much chain you will have.

[hpeer]

Floating docks? They may be planning on putting them back in and are keeping the lines to the mooring blocks.

I have a quaint way if thinging about anchoring: the anchor hooks to the bottom, the chain hooks to the boat. You can calculate the stress on the chain/boat connection. It is far more difficult to calculate the anchor/bottom connection pull out point.

Moorings use a big, heavy block and rely upon mass and a very short scope. The bigger your anchor the less required scope to achieve Xkg pull out.

Frankly, and excepting a direct hit by a nasty storm (happened before) you are in a well protected anchorage, almost a pond in a lake, you should he fine with your set up as is.

I prefer a Mantus because 1: it is cheaper to by and cheaper to ship because it knocks down. 23 it uas by far the biggest roll bar and is then less susceptible to plugging.

Good luck.

[thinwater]

Long term or overnight? Overnight, no worries.

• What is the bottom type? That is the starting point for all anchoring.
• Try to avoid steep slopes, which rules out a few areas.
• Avoid the jetty opening and the area west of it. They put the jetty in for a reason. Note that the schooner is north of the opening.
• You still need to avoid the dock because of the floats, just not the traffic.

This leaves a few areas northeast and northwest of the schooner. Assuming the depth is in meters, you are going to need to locate carefully, and in certain wind directions you won't have a lot of drag space (if the boat drags you could be on the jetty in a few minutes). I'd anchor northwest of the schooner in 6 meters; my rode will be shorter and if I drag it's more likely to be a soft grounding than rocks... but I don't know the shoreline.


This is fairly standard anchoring. Chain and a standard, conservative anchor will be fine (assuming a good bottom).

[longjonsilver]

Originally Posted by aqfishing

Is your depth in feet or meters, either way I would not consider that deep.

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?

Originally Posted by hpeer

Floating docks? They may be planning on putting them back in and are keeping the lines to the mooring blocks.

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.

Originally Posted by hpeer

Frankly, and excepting a direct hit by a nasty storm (happened before) you are in a well protected anchorage, you should he fine with your set up as is.

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

Originally Posted by hpeer

I prefer a Mantus because 1: it is cheaper to by and cheaper to ship because it knocks down.

So do i.

Originally Posted by AiniA

Doesn't seem all that deep. Main difference is the length of rode needed.

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

Originally Posted by AiniA

You mention 1/4" chain, seems light for a 37' boat.

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.

Originally Posted by thinwater

Long term or overnight? Overnight, no worries.

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.

Originally Posted by thinwater

What is the bottom type?
You still need to avoid the dock because of the floats, just not the traffic.

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.

Originally Posted by thinwater

This leaves a few areas northeast and northwest of the schooner. Assuming the depth is in meters, you are going to need to locate carefully, and in certain wind directions you won't have a lot of drag space (if the boat drags you could be on the jetty in a few minutes). I'd anchor northwest of the schooner in 6 meters; my rode will be shorter and if I drag it's more likely to be a soft grounding than rocks... but I don't know the shoreline.

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

[donradcliffe]

It does look like a pretty short scope situation--less than 5:1, depending on tide. I would think about setting two anchors to limit swinging radius.

[longjonsilver]

Originally Posted by donradcliffe

It does look like a pretty short scope situation--less than 5:1, depending on tide. I would think about setting two anchors to limit swinging radius.

Spring tide about 6'

[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?

[Nord Sal]

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?

Yes. NOAA charts for the west coast USA show depth in fathoms.

[cal40john]

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?

Maybe something has changed, but fathoms doesn't make sense to me.

There is a depth marked 9 sub 8.

Fathoms can be fathoms and feet or fathoms and fractions.

If the soundings are in fathoms then that depth is 9 fathoms and 8 feet, which is 10 fathoms and 2 feet. No chart I have seen has feet more the 5 as a sub to fathoms. Making you add a fathom and subtract 6 from the feet number doesn't make any sense.

[aqfishing]

Originally Posted by cal40john

Maybe something has changed, but fathoms doesn't make sense to me.

There is a depth marked 9 sub 8.

Fathoms can be fathoms and feet or fathoms and fractions.

If the soundings are in fathoms then that depth is 9 fathoms and 8 feet, which is 10 fathoms and 2 feet. No chart I have seen has feet more the 5 as a sub to fathoms. Making you add a fathom and subtract 6 from the feet number doesn't make any sense.

That seems like a screenshot from Navionics Boating app. I just checked. You can choose to display depth in meters, feet or fathoms. All of them display in the same number format, i.e. big number with small decimal. So back to the OP’s post, it could easily be any one of the three.

[cal40john]

Originally Posted by aqfishing

That seems like a screenshot from Navionics Boating app. I just checked. You can choose to display depth in meters, feet or fathoms. All of them display in the same number format, i.e. big number with small decimal. So back to the OP’s post, it could easily be any one of the three.

You're missing the point.

If the 9 sub 8, is 9 fathoms 8 feet, while the app is in fathoms mode, it could just as easily have a sounding 1 sub 48. 1 fathom 48 feet. Both are dumb.

[cal40john]

Originally Posted by cal40john

You're missing the point.

If the 9 sub 8, is 9 fathoms 8 feet, while the app is in fathoms mode, it could just as easily have a sounding 1 sub 48. 1 fathom 48 feet. Both are dumb.

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.