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Old 29-05-2018, 07:58   #16
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Re: Tidal Currents Can Be Strong in Bays and Inlets and Rivers

Most satisfying was a very calm and gentle passage from Brazil up to Ilse Du Salut , not a load of wind so the free 70Nm a day from the current was very welcome
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Old 29-05-2018, 08:11   #17
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Re: Tidal Currents Can Be Strong in Bays and Inlets and Rivers

I have done alot of boating on the Connecticut river. Most of the time not a big deal thou once north of Essex there is a current running most of the time except during the incoming tide which affects the river all the way to Hartford. The fun is in the spring when the melt and rains really raise the river. Once when bringing the family 30' down the river for the season on a flood time we ran the engine at 1700 RPM (A4) and average almost 8 knots all the way to Saybrook when it finally slowed down.

Another time while working in the boatyard after an abnormally rainy fall I took the work boat with it's 35HP outboard and low pitched prop (it would rev out before it would plane) and hooked up to a 36 spray (steel Bruce Roberts design) and found myself being dragged down river trying to go full throttle up river. I finally decided to pull closer to one bank where the current slowed and crawled back up to the docks.



The worst current I have seen would be when I lived in Eastport Maine. Cobscook Bay and Passamaquoddy bay have 20' tides and narrowish entrances. Running thru Lubec Narrows in a Lobster boat with it's huge Cummins and making 3 knots headway against the 10 knot out going tide is crazy. Once while up there my roomates and I took out a plywood row boat one of them had built. Luckily it had two rowing stations as the tide changed when we got bit close to the Old Sow whirlpool. It took two of us pulling as hard as we could to break free and make it to the nearest shore.



One more side note sometimes an other wise easy inlet can become troublesome. While visiting a friend in Kennebunkport Maine many years ago we encountered an outgoing tide and a offshore breeze created massive standing waves in an other wise easy to run inlet. made it fun in the small center console we were in.
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Old 29-05-2018, 08:12   #18
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Re: Tidal Currents Can Be Strong in Bays and Inlets and Rivers

Great thread idea, thank you. I used to deal with "The Race" a lot, and routinely saw sailors "penalized" for not taking it into account. One morning I was sailing east on the ebb, and saw a 50 foot cutter facing me and hove-to. When we neared, I saw that he wasn't hove-to, he was on a close reach and not making any way!

I'm docked now in a cove of the Boca Ciega that has a very narrow mouth with a four foot tidal range, and entering the cove in a tender during peak flood is like a ride down the rapids.
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Old 29-05-2018, 08:12   #19
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Re: Tidal Currents Can Be Strong in Bays and Inlets and Rivers

Quote:
Originally Posted by Steadman Uhlich View Post
Good points.
Thanks for adding your experience and local knowledge to the mix on this thread.

Your point about current differences from nearby or not so near local tide reporting stations is a good one.
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For sailors visiting the American East Coast:

When on the voyage I just finished, we used a book that has been published for 144 years to help mariners navigate the tides and currents on the American East Coast (from Maine to Key West).

It is a paperback book (about $15) called "ELDRIDGE TIDE AND PILOT BOOK 2018." It contains numerous graphics that show the tidal currents in popular locations (from what I remember most were in the North East or New England state areas) with arrows representing the current directions, and tide charts etc. Books like this are very useful info to have aboard.

Eldridge Tide and Pilot Book

ELDRIDGE Tide and Pilot Book

At least here in the Northeast Eldridge is must purchase every year.
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Old 29-05-2018, 08:16   #20
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Re: Tidal Currents Can Be Strong in Bays and Inlets and Rivers

The following is posted as a general introduction to a topic I think most navigators and ocean sailors should know or be aware of when sailing the tidal areas of any ocean. It should be taken as a "rule of thumb" and it is always preferable to use more accurate local tidal charts for navigation.

I hope CF Members and readers find this helpful. If you have additional info on this topic, feel free to add to the discussion. I don't claim to be an expert on this topic, but am simply sharing what I find useful to know.
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The Rule of Twelfths

Tides ranges (how high, how low) and how often they occur, vary around the world.

Local ocean bottom bathymetry (shape/contours) has an influence too, so the tides experienced in a small cove may be different from those seen in a large bay. Make sure you check to know the local conditions or what tidal range is expected for a specific location.

Some places have one high tide per day, other places have two high tides per day.

The following applies to the East Coast of the United States, which has two highs and two lows each day or in places with a semi-diurnal tide zone (i.e. A location that has two low tides and two high tides).
_____________

The Rule of Twelfths

Since the average interval between high and low tide is just over six hours, a sailor can divide the cycle into six segments of one hour each. On average the tide rises or falls approximately according to the following:
1st hour - 1⁄12
2nd hour - 2⁄12
3rd hour - 3⁄12
4th hour - 3⁄12
5th hour - 2⁄12
6th hour - 1⁄12

In places with only a single high and single low (a diurnal tide zone), you can double the time to 2 hours each segment.
____________

From Wikipedia:
"The rule states that over the first period the quantity increases by 1/12. Then in the second period by 2/12, in the third by 3/12, in the fourth by 3/12, fifth by 2/12 and at the end of the sixth period reaches its maximum with an increase of 1/12. The steps are 1:2:3:3:2:1 giving a total change of 12/12. Over the next six intervals the quantity reduces in a similar manner by 1, 2, 3, 3, 2, 1 twelfths."

The rule is a rough approximation only and should be applied with great caution when used for navigational purposes. Officially produced tide tables should be used in preference whenever possible.

The rule assumes that all tides behave in a regular manner, this is not true of some geographical locations, such as Poole Harbour[4] or the Solent[5] where there are "double" high waters or Weymouth Bay[4] where there is a double low water.

The rule assumes that the period between high and low tides is six hours but this is an underestimate and can vary anyway."

The illustration below is from Wikipedia (Creative Commons).
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Old 29-05-2018, 08:21   #21
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Re: Tidal Currents Can Be Strong in Bays and Inlets and Rivers

North Florida thru the Carolinas ICW is just a series of tidal currents and often challenging to time as they will change based on the inlet you are passing.

Snows Cut runs like 5-6kts. Get it wrong and you are waiting. Get it right and hope no one gets in the way because you are going fast.

St. Clair River under the Blue Water bridge, full throttle making 1.5kts while hanging as close to the Canadian shore as possible. (top speed around 7.8kts).

Delaware Bay, watch for the wind against the current or it can really mess with your day.

On the Mississippi south of St. Louis, docked at full throttle at Hoppies Marina (really just a few barges tied off on the side of the river where you parallel park).

If you don't want to wait for a day or more for favorable currents, sometimes it's more efficient to throttle up as your SOG can go up by 50-100% for 20-30% more fuel consumption.
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Old 29-05-2018, 08:27   #22
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Re: Tidal Currents Can Be Strong in Bays and Inlets and Rivers

One thing that was weird and new to me was the fact that our boat would move upstream when anchored in strong current.

We would drop anchor, and fall back in the current. We’d set the anchor against the current. But a short time after I’d find the anchor chain hanging aft, with our bow still pointing towards the upstream current.

This really screwed with my head for a while, but I finally figured out it was due to our full keel was acting as a big wing. It was generating lift in the strong current; enough to drive us forward.
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Old 29-05-2018, 09:04   #23
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Re: Tidal Currents Can Be Strong in Bays and Inlets and Rivers

Quote:
Originally Posted by valhalla360 View Post
North Florida thru the Carolinas ICW is just a series of tidal currents and often challenging to time as they will change based on the inlet you are passing.

Snows Cut runs like 5-6kts. Get it wrong and you are waiting. Get it right and hope no one gets in the way because you are going fast.

St. Clair River under the Blue Water bridge, full throttle making 1.5kts while hanging as close to the Canadian shore as possible. (top speed around 7.8kts).

Delaware Bay, watch for the wind against the current or it can really mess with your day.

On the Mississippi south of St. Louis, docked at full throttle at Hoppies Marina (really just a few barges tied off on the side of the river where you parallel park).

If you don't want to wait for a day or more for favorable currents, sometimes it's more efficient to throttle up as your SOG can go up by 50-100% for 20-30% more fuel consumption.
Thanks for adding to this discussion.

I was a few minutes ago reading one of your other comments in another thread, and I learned from your post. Your experience is appreciated.

Each time I read about the ICW inlets, I take note. I have not been in so many yet, but when I do go, I want to be prepared.
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Old 29-05-2018, 09:09   #24
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Re: Tidal Currents Can Be Strong in Bays and Inlets and Rivers

Quote:
Originally Posted by Mike OReilly View Post
One thing that was weird and new to me was the fact that our boat would move upstream when anchored in strong current.

We would drop anchor, and fall back in the current. We’d set the anchor against the current. But a short time after I’d find the anchor chain hanging aft, with our bow still pointing towards the upstream current.

This really screwed with my head for a while, but I finally figured out it was due to our full keel was acting as a big wing. It was generating lift in the strong current; enough to drive us forward.
Interesting!

That would be something to see.
_________

When going through the Cape Cod Canal recently, (in a large full keel boat) I remember passing a shallower point in the canal (which is as wide as a river) where I could see the surface of the water disturbed (upwelling) off our starboard bow, and as we came closer, the "side" current pushed against our keel, moving our boat to the side of the channel. We were motoring at about 2,000 RPMs at the time, as I recall, and I felt a very obvious "push" to the side (so did the captain), and I suspect we moved about 15-20 feet to the other side of the channel from that push. "More Throttle!..Starboard helm"
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Old 29-05-2018, 09:10   #25
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Re: Tidal Currents Can Be Strong in Bays and Inlets and Rivers

Earlier someone mentioned tide against wind. The first time I really experience that was pulling into Barnegat Bay on an outgoing tidal current and a southeast wind. It was not a large channel, perhaps 200 feet wide (61.5 meters) and I was rather surprised to find three to four foot waves at the entrance. They weren't an issue but it certainly woke me up!


The Hell Gate on the East River in NYC can, on occasion, be quite a ride. In addition to quite strong currents, if the winds are just right you can get some respectable standing waves. In the video below, if you move forward to around the 45 second mark you will see what I am talking about.



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Old 29-05-2018, 09:10   #26
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Re: Tidal Currents Can Be Strong in Bays and Inlets and Rivers

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My life is nothing but tides and currents here in the Salish Sea (Puget Sound and areas north).

A couple of times remembered -
I've been 10 minutes late for slack tide at Deception Pass and had the current already 1.5 knots against me.

The flood current coming in the Straits of Juan de Fuca split to go north to the San Juan islands and south to Puget Sound. I timed a return to Seattle from the San Juans where I never got below 8 knots until I was south of Admiralty Inlet.

I was trying to go through Hole in the Wall from Okisollo channel and I bailed out when it looked like I was going sideways nearly as fast as forward. The overfalls over the rocks in Okisollo are impressive.

Tacking upwind through Seymour narrows with the current with me watching the trees in front of us slide to leeward.



Even in open waters the current can be 1/4 - 1/2 knot against you and you head for back eddies in bays to significantly help your passage time.

Tacoma Narrows max about 5 knots
Deception Pass 7
Dodd narrows 7
Lots of places in Puget Sound hit 2 to 3 knots.
All through the Desolation Sound area in Canada has narrows
Seymour narrows 14
Okisollo
Hole in the Wall
Surge Narrows

Too many to remember what I've been through.

Just found this fun tool -

DeepZoom Nautical Charts Tides and Currents

How long is slack time ??
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Old 29-05-2018, 09:18   #27
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Re: Tidal Currents Can Be Strong in Bays and Inlets and Rivers

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Originally Posted by Steadman Uhlich View Post
Each time I read about the ICW inlets, I take note. I have not been in so many yet, but when I do go, I want to be prepared.
My comment wasn't so much about going in and out of inlets (though definitely an issue at times).

My point is the ICW channel often runs thru the backwaters and will be impacted by nearby inlets but which inlet changes as you cover distance and also changes over time (state of the tide). Not at all unusual to be surprised by a tidal current going a different way than you expected.
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Old 29-05-2018, 09:28   #28
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Re: Tidal Currents Can Be Strong in Bays and Inlets and Rivers

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Old 29-05-2018, 09:51   #29
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Re: Tidal Currents Can Be Strong in Bays and Inlets and Rivers

Wednesday, August 31, 2016 Day 23 Umpqua River (Winchester Bay) to Newport (Yaquina Bay)

We had agreed to let Morgan sleep in to make the day watches easier, since there was no reason for both of us to be up so early. I slipped the lines for our 0705 departure to make the current at the bar. There were two commercial fishing boats behind us as we left the harbor and turned left and then right to the jetties. As we made the right turn, I could see a wall of white water stretching all across the bar. I slowed to let the fishermen go ahead, to both avoid the standing waves and to see where they would go. They both headed for the south jetty. Within just minutes the standing waves completely disappeared, meaning the flood had taken over the river’s ebb and the bar became passable. It really is critical to do the research and homework to time the bar crossings properly.

That timing couldn’t actually work perfectly for our entrance to Newport, because the tides change every six hours and this was an eight hour trip. This meant we’d have to enter Newport on the beginning of an ebb. We passed Florence around noon and there was light drizzle, but not enough for weather gear">foul weather gear. We could still see the coast from three miles out under the high clouds.

I had called the Newport harbormaster at 0800, they hadn’t opened yet, although the recording said they were experiencing a high volume of calls and to use their website to register for a slip. So I did. Just as I finished the laborious (for me) task of not-so-good-at-thumb-typing yet, they did call back and were quite friendly and helpful, and assigned us slip J3. Yup, I forgot to ask about wifi again!

When we arrived at the Newport entrance buoy the fog closed down to deck level. The GPS guided us from buoy to buoy to the jetties. It was quite lumpy against the building ebb and we saw our boat speed over ground drop two knots compared to our speed through the water. The conditions were very similar to gong through some heavy tide rips off The Golden Gate.


************************


I sailed SF Bay from 1978 to 2016. This is our second summer season here in BC, where the currents have to be part of daily activities. Timing is everything.
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Old 29-05-2018, 10:29   #30
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Re: Tidal Currents Can Be Strong in Bays and Inlets and Rivers

I think it's important to point out that current is not necessarily directly correlated to tide (i.e. that the strongest current is not mid-tide). Geography and topography can alter the relationship significantly.

For example, in some areas of the Chesapeake the strongest current can occur earlier or later than mid-tide...in some areas it can be strongest at high tide as "the wave" pushes through (Fishermen on the Bay are well familiar with this as several species of fish will search out high current areas to feed). I suspect this is true in most long relatively narrow, or narrowing bays.

So it's wise to look at current charts as well as tide charts to fully understand the dynamics at a given location.

Most inlets obviously have strong currents, particularly if they empty a large bay or river, and it's worth pointing out another consideration related to current that's important to mariners; the effect of wind against current. Most of us are familiar with this in general but in areas of high current "funneled" through a narrow straight iit can have a dramatic impact.
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