Planning for current Chesapeake and Delaware Bays

[sailingharry]

I know how to use tide and current tables, but this is a specific question.


A thousand years ago, on our family's dugout canoe (a Garden designed 40' ketch, actually), my father used some sort of a graphical calculator to determine when and what speed to run up and down the Chesapeake and Delaware Bays to "ride a tide" -- in other words, to progress along the bay in keeping with the fact that the tide does not change at the same time the entire way.


I seem to recall some sort of a graph, and you'd lay a ruler along it, and connect two points or something. From that, you'd learn that, for example, leaving one hour before high tide at Chesapeake City and maintaining 5 knts would give you a fair current all the way to Cape May.



Anyone ever seen this? Anyone know where something like this exists? I've been trying to search, but I can't even come up with decent set of search terms...LOL.


Thanks!


Harry

[thomm225]

The tide changes in the bay every 6 hours or so.

At 5 knots, you're not going to get too far even with the tide.

You really don't need a graph for that.

Most of us just work it out in our head IF the tide is right.

Otherwise, we sail anyway and just deal with it.

I crossed the 20 miles of lower bay the fasted last September (3 hours) against the tide ........winds were gusting to near 34 knots though! (and it was very rough. Wind against tide)

[sailingharry]

Originally Posted by thomm225

The tide changes in the bay every 6 hours or so.

At 5 knots, you're not going to get too far even with the tide.

You really don't need a graph for that.

Most of us just work it out in our head IF the tide is right.

Otherwise, we sail anyway and just deal with it.

I crossed the 20 miles of lower bay the fasted last September (3 hours) against the tide ........winds were gusting to near 34 knots though! (and it was very rough. Wind against tide)

Yes, the tide changes every 6 hours at a single location. However, the tide changes at different times along the Bay - so in theory, depending on which direction you go and how fast you go, you can ride one tide for the entire length of the Bay, over much more than 6 hours.


5 kts was an example. I motor at 7, and can sail well above that. But if you can ride a fair tide the entire Bay at 5 kts, I might seriously consider throttling back.


Late Spring or early Summer (COVID depending), we are sailing from Annapolis to the C&D, and then down the Delaware and onward to New England. I'd like to suss out the ideal times to run it.


Just pulled up a some data for today, and it doesn't look good going down the DE. High tide at C&D is 1043 (so start then), low tide at Cape May is 1643, so that gives you 4 hours to run 100 miles, so it looks like you might get a full cycle (full ebb, plus full flood) in the tirp. Much better the other way -- Low to High is 8 hours, still not possible in a sailboat, but with 2 kts of current you might get most of they way.


Still, I'd love to find whatever that tool my father had. Perhaps in the Coast Pilot?


Your trip in Sept -- we may have had that same day. We were surfing up the Bay from Solomons to Annapolis at speeds in the 12's, dead downwind under double reefed main and no jib, with current behind us.

[thomm225]

Originally Posted by sailingharry

Your trip in Sept -- we may have had that same day. We were surfing up the Bay from Solomons to Annapolis at speeds in the 12's, dead downwind under double reefed main and no jib, with current behind us.

I was headed South. Wind was NNW.

I was taking waves over the side after I cleared the Eastern Shore coming out of Kiptopeke heading SW at that time before turning DDW

Video was taken near the end of the crossing............

I had only the one reef in my main (after furling the jib).........it has no more at this time, and I was single handing. I wouldn't have had the main up if I'd known the wind was going to be that strong and not the 22 knots that was forecasted.

Boat is pushing a lot of water.

The wind is still whistling through the rigging, but at a much lower volume than earlier

https://www.youtube.com/watch?v=-nXfjcCuiPk

[sailingharry]

I just looked up our trip. November 15, so not the same day (and different wind direction!). But, fall on the Chesapeake often has fun winds! LOL


A friend has a Bristol 30, she often single hands it. Nice boats.

[BillKny]

Apparently nobody else remembers... which I guess offical makes me an OLD salt.

But yes, there used to be charts that were maps of the bay, with current flows at various times through the tide cycle present graphically, and the OP is right about one way to use them.

They haven't been published in many years, and I have never seen electronic versions. Lost to progress, which is a shame, they were very useful.

[Pandor]

Originally Posted by sailingharry

I know how to use tide and current tables, but this is a specific question.


A thousand years ago, on our family's dugout canoe (a Garden designed 40' ketch, actually), my father used some sort of a graphical calculator to determine when and what speed to run up and down the Chesapeake and Delaware Bays to "ride a tide" -- in other words, to progress along the bay in keeping with the fact that the tide does not change at the same time the entire way.


I seem to recall some sort of a graph, and you'd lay a ruler along it, and connect two points or something. From that, you'd learn that, for example, leaving one hour before high tide at Chesapeake City and maintaining 5 knts would give you a fair current all the way to Cape May.



Anyone ever seen this? Anyone know where something like this exists? I've been trying to search, but I can't even come up with decent set of search terms...LOL.


Thanks!


Harry

The diagrams were included in the NOAA tidal current pubs. I think they’ve discontinued but you can find it in the archived copy for 2020 or before.
https://tidesandcurrents.noaa.gov/tidetables/2020/acct_2020_full_book.pdf

[Pandor]

By the way, the diagrams are a great tool and I highly recommend. I use the Delaware bay one every time going up or down. There is no reason to fight the current. Learning to use this will save you tons of time.

[Scrimshaw4]

Check an Eldridge East Coast Tide book. They're published annually. It contains tide tables and charts.

[tstano]

Originally Posted by Scrimshaw4

Check an Eldridge East Coast Tide book. They're published annually. It contains tide tables and charts.

I’ve been a fan of the Eldridge book, buying a new one every year. I’ve never seen the NOAA chart in use, but it seems reasonable.

[tstano]

I found the ebook, page 284 had the method.

284
CURRENT DIAGRAMS
CHESAPEAKE BAY EXPLANATION OF CURRENT DIAGRAM
This current diagram represents average conditions of the surface currents along the middle of the channel from Cape Henry Light to Baltimore, the scale being too small to show details.
Northerly streams are designated “Flood” and southerly streams “Ebb.” The small figures in the diagram denote the speed of the current in knots and tenths. The times are referred to slack waters at Chesapeake Bay Entrance, daily predictions for which are given in Table 1 of these current tables.
The speed lines are directly related to the diagram. By transferring to the diagram the direction of the speed line which corresponds to the ship’s speed, the diagram will show the general direction and speed of the current encountered by the vessel in passing up or down the bay or the most favorable time, with respect to currents, for leaving any place shown in the left margin.
To determine speed and direction of current.—With parallel rulers transfer to the diagram the direction of the speed line corresponding to the normal speed of vessel, moving edge of ruler to the point where the horizontal line representing place of departure intersects the vertical line representing the time in question. If the ruler’s edge lies within the shaded portion of the diagram, a flood current will be encountered; if within the unshaded, an ebb current, and if along the boundary of both, slack water. The figures in the diagram along the edge of the ruler will show the speed of the current encountered at any place indicated in the left margin of the diagram.
Example.—A 12-knot vessel bound for Baltimore passes Cape Henry Light at 1430 of a given day, and it is desired to ascertain the speed and direction of the current which will be encountered. Assuming that on the given day flood begins at Chesapeake Bay entrance at 1256 and ebb begins at 1803, the time 1430 will be about 1 hours after flood begins. With parallel rulers transfer to the diagram the 12- knot speed line “Northbound,” placing edge of ruler so that it will cross the horizontal line opposite Cape Henry at a point “1 hours after flood begins at the entrance.” It will be found that the edge of the ruler passes through strength of current in the shaded portion of the diagram averaging about 0.7 knot. The vessel will, therefore, have a favorable current averaging about 0.7 knot all the way to Baltimore.
To determine the time of a favorable current for passing through the bay.—With parallel rulers transfer to the diagram the direction of the speed line corresponding to normal speed of vessel, moving the ruler over the diagram until its edge runs approximately through the general line of greatest current of unshaded portion if southbound and shaded portion if northbound. An average of the figures along edge of ruler will give average strength of current. The time (before or after ebb or flood begins at the entrance) for leaving any place in the left margin of diagram will be found vertically above the point where the parallel ruler cuts the horizontal line opposite the place in question.
Example.—A 12-knot vessel in Baltimore Harbor desires to leave for Cape Henry Light on the afternoon of a day when flood begins at Chesapeake Bay Entrance at 1148 and ebb begins at 1718. At what time should she get under way so as to carry the most favorable current?
Place parallel rulers along the 12-knot speed line “Southbound.” Transfer this direction to the diagram and move it along so as to include the greatest possible number of larger current speeds in the unshaded portion of the diagram. The most favorable time for leaving Baltimore thus found is about 1 hour after flood begins at the entrance, or about 1248. There will be an unfavorable current of about 0.2 knot as far as Seven Foot Knoll Light; after passing this light there will be an average favorable current of about 0.3 knot as far as Cove Point Light; from Cove Point Light to Bluff Point a contrary current averaging about 0.3 knot will be encountered; from Bluff Point to Tail of the Horseshoe there will be an average favorable current of about 0.9 knot; and from Tail of the Horseshoe to Cape Henry an average contrary current of about 0.2 knot will again be encountered

[joefults]

It's not 100 miles from the C&D to Cape May, more like 50. If you leave the C&D at high tide, you would have no problem getting to Cape May at low tide.

[tstano]

Originally Posted by joefults

It's not 100 miles from the C&D to Cape May, more like 50. If you leave the C&D at high tide, you would have no problem getting to Cape May at low tide.

At 6 kts speed about 8 hrs. You run into adverse currents halfway extending the trip to about 11 hrs. Been tried by many.

[joefults]

I have done the Delaware Bay from the C&D to Cape May both ways many times in three different boats. If you time the tide and you don’t have a crazy opposing wind, there is no problem doing that trip in 6 hours or less.
Regarding current on the Chesapeake, I personally have never seen more than two knots of current.

[sailingharry]

YES! Too many useful posts to thank each, but yes, this exactly what my age-addled brain remembered. I appreciate the old salts that understood the question, and recalled where it was!


To Joe's comment about the tides on the Chesapeake, that's a big part of why I couldn't recall this information. I sail the mid Chesapeake, and rarely go 50 miles in any direction. Short trips, relatively minor current, and work schedules means that planning around currents is sort of irrelevant -- it is what it is. But a full run of the Delaware Bay (and yes, it's not 100 miles -- that's what I get for not checking!) is a different story with both distance, currents, and time to plan/schedule.


Thanks again all! Now to dig into my newfound knowledge.


Hmm... but a cursory review of the diagram (still on screen, I need to print it out and play with parallel rules) leads me to believe that the diagram is not as smart as it seems, and is less functional for slower boats (ie sailboats) and higher currents (ie, the DE Bay). It seems that the input is NOT SOW, but rather SOG. If you plot a line up the Chesapeake at 12 kts (their example) and run in a flood, you will be in a flood all the way -- but if you run in an ebb, you will be in an ebb the entire way and it will take the same steaming time. I need to print it and play!