Tides and Current - I think I understand it :)

R

RobertV

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Sep 20, 2007
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28629
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Questions about the tides:
We want to run with the current if possible and I think I understand it now :)
If the low tide in Haverstraw is at 6:15 am on the 19th, I am heading north, I think I want to leave around 8:15 to flow with the current.
Is this correct?
When would the slack tide be?
I thought it might make sense to leave as early as we can - you know it will be a long day.
We plan to cruise around 20kts or so - is there a point that I will catch up to and pass the favorable current on the way up?
TIA
 
Robert
It depends on your speed, destination etc.. I have a plot from Bowline up to Kgn, but without knowing your speed and destination, it's pointless to run the numbers.
 
Robert, you will find that the more detailed the information that you give will result in more detailed answers.
 
Here is some more info:
We are leaving Viking Boat Yard in Verplank and heading to Alcove Marina in Schuylerville and plan to cruise around 20 kts.
I understand that we will be at the mercy of the lock operators and speed limits above Troy, but up till there, we should have clear cruising. We are doing this on the 19th.
TIA for the input.
Please let me know if I should provide more information.
 
At 20 knts. the tide won't really make a difference : )
Jon
 
Once you get above Kingston you are also subject to a lot of NO WAKE zones as the river narrows. Basically you can make time from Verplanck to Kingston, but after that point you will find yourself slowing down or at least coming off plane numerous times.

Are you picking up a new boat at Viking?
 
Ok, I'll post back when I get to the laptop on the boat again. I have a route from Kgn down to Croton and I can run it for 20 knots to give you some info. I suspect at 20 knots the affect the tide has on your overall time is less than it would be at 10 knots. At that speed the delta in time spent is around 45 minutes depending on the time of departure.

Ooops. Forgot I had all the software here. Anyway, as I thought running at 20 knots the delta is less than something to worry about. It's only ten minutes.
From a starting point off Croton Pt. in the channel, to Kgn and the Rondout Yacht Basin,
I came up with a best departure time of 5:20 AM and the trip takes 2:17. If you left at 11:21 PM the trip would take 2:27. Considering a burn rate of 20 gph that was 46 or 49 gallons. So you earn some extra beer money!

I found a route from Kgn to Troy that I tacked on to the above route, and over the course of 5 hours at 20 knots the delta is still only about 10 minutes.

And,

I had the route going the wrong way (above)! With the route going north, the best departure time is 11 AM! This is the complete route from Croton up to Troy. Again, it's still only a 10 minute delta at the speed you can carry. If you intend to go all the way to Schyl. Then merely leave as early as you are comfortable.
Look at it this way, the "tidal wave" isn't that fast and you will pass it by one way or the other.
 
That's interesting Dan - Isn't peak current on parts of the River around 4kt? I always figured that even at 20kt a 4kt current would cause some trouble - after all its 20 percent of your speed!!!

Perhaps it has to do with the length of time that such current is at its peak? The old "twelfths" rule surely applies, no?

Relative current speed per hour of tide (complete tide change in roughly 6 hours).

Hour 1 1/12
Hour 2 2/12
Hour 3 3/12
Hour 4 3/12
Hour 5 2/12
Hour 6 1/12

Based on that concept, the fastest moving water is about 3-4 hours after the tide change. So if it was in your face, using your example, you'd be making 16kts over ground, and if it was with you, you'd be making 24kt...

The other variable, I suppose, is that the current is not uniform all the way across the River (although it is strongest in mid-channel). And when the River bends, the current is at an angle to your boat's course so its effects are muted. So all these other factors likely make a difference in your progress as well...
 
quote:
Originally posted by mannmade

Once you get above Kingston you are also subject to a lot of NO WAKE zones as the river narrows. Basically you can make time from Verplanck to Kingston, but after that point you will find yourself slowing down or at least coming off plane numerous times.

Are you picking up a new boat at Viking?
Click to expand...


New to us 1988 Silverton 34X we got in West Islip LI and wintered her at Viking.
THX for the No Wake info.

quote:
Originally posted by boatbum

If you intend to go all the way to Schyl. Then merely leave as early as you are comfortable.
Click to expand...


So Dan, I can leave when I want since the delta is only about 10 mins? Is it OK to leave at 6am?
TIA
 
Ok guys you asked for it. Let me get a screen shot of the output. Then you can see what it looks like. This will pro'ly expand the width of the thread to get it clear enough. We're talking about a 100 mile trip from Croton up to the Troy lock.
I re-attached all the tide stations and the results are a little different.
Now it's about a 1/2 hr spread...

It's been our experience on long trips that at a constant speed over the long haul it still takes a while and that the amount of time doesn't vary that much, unless you are trawling speed.

hdsnrte.jpg


Here is one at 8 knots:

slwrte.jpg


Maybe in a "dream world" our trip and tides line up so we get the max velocity. But in reality, like it or not, our velocity never seems to quite line up with the max tide in any one direction over a long trip. And to make matters worse on the day we travel when we wind up at a spot that has a fast tidal current, it's probably not that great when we arrive.
I think the program shuffles things around to get the best time for all the legs of the trip.
 
Bruce this is part of Nobeltec's Visual Navigation Suite. I am not sure if Boatfix is a dealer but you can look them up on the web very easily. If you are looking for some "freeware" this is licensed software that we have to buy.
 
Good info if you have perfect weather conditions go along with your departure times :)
 
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