Understanding Tides and Current

Wow. If I read that right, the numbers that matter are:

Start - Low 5:19; High 11:16
Mid - Low 8:37; High 14:04 (2:04 pm)
End - Low 11:26; High 17:05 (5:05 pm)

These are perfect! Disclaimer - I am not trained in tidal navigation.

You could leave the dock anywhere between 5 and 11. Take your time. Get there before 5 pm.

Optimum efficiency: Leave dock at 8 am. Cruise at MAX RANGE cruise speed (6 or 7 knots). Check your ground speed. You need to know if the current is pushing you or slowing you down. If it's slowing you down by more than a few knots, cruise at your optimum cruise speed (25mph or so). If it's pushing you (river flow versus tide), cruise at your optimum hull speed (6 or 7).

You said it's 2.5 hours. I'm guessing 25 mph, or about 62 miles (55 NM). At 6 knots, you'll ride the wave of the max tidal flow (1/2 way between high and low, generally - think of a sine wave. The top and bottom are slack tides. The steepest portion is the fastest current, about 1/2 way between high and low.)

What would I do? I would start out between 7 and 8 am. I would start the morning with a cup of coffee and cruise at 7 knots for a while, enjoying the scenery and the morning air. After I got bored, I'd push it up to optimum cruise speed and drive to a point 1/2 way to my destination or so. Stop at a restaurant. Get out, eat, walk around, enjoy the concept of traveling by boat.

By about noon (no later than 1), start back up river. Check for ground speed again. My guess is that the further up river you get, the less the tides have an influence and the more the flow of the river does (if it's really a river). Get to your destination by 3 or 4 to take max advantage of the tides (or minimize your disadvantage of the river flow).

On your way home, leave an hour or so after high tide, cruise slowly out to the middle, shut the engine down, and ride the river and tide all the way home. Or, just cruise like you did to get there.
 
See... I'm just different...

I'd leave after about 10 am because it's just the freekin' James River and the tidal flow is minimal and I would want to sleep in.

Just remember this Greg... Your boat will depreciate $800 during the time you are trying to save $5.42.
 
I was thinking leave around 8 AM too. Stop along the way, anchor, eat some lunch, get going again. Looks like this will give us the optimal 'current behind us'.

This is a trip back to her home slip so there will be no trip back until next year.
 
Four Suns said:
See... I'm just different...

I'd leave after about 10 am because it's just the freekin' James River and the tidal flow is minimal and I would want to sleep in.

Just remember this Greg... Your boat will depreciate $800 during the time you are trying to save $5.42.
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It's a feel good mental savings. Knowing we are not fighting the current just feels good.

Having spoken with a broker at Bluewater about selling our boat, $800 depreciation over 4-5 hours is a conservative number. Yikes, what a horrible time to try to sell a boat.
 
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good point, Gary
 
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Now that Gary has been on the ocean his home James River is just a creek. Snob ;-)

On the trip down 2+ months ago we planned the trip around the tides. It was the first time we had ever done this. We definitely felt and saw a difference. She used less fuel and did not 'work as hard'. On a hull speed cruise then she picked up 3-4 knots without increasing RPMs.
 
If you picked up 3 or 4 knots, something else is going on... like your anti-gravity trim tabs are kicking in. The tidal flow on the lower James (down past the ghost fleet) is on the order of 1.5 knots. More north up by the Chick, it can get up to about 2 knots but that is at max ebb or flow... not for hours on end. My average impact of going up and down that river is only about 1 knot in either direction over the course of several hours.

I'm not trying to be a snob but the tides/currents up here are something you could probably get a real benefit if you tracked them... but they run like 6+ knots in some areas... we just don't see that in Virginia.
 
fwebster said:
And, since nav aids and charts are based on mean low water, what difference does it make?
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Hehe.... when I read this, it made me think...If we all boat more, we burn more fuel, which increases our carbon output, which melts the iceburgs, which means more water to boat in. :thumbsup:

If we melt the iceburgs enough, we might be able to boat right up to the pumps at some of the nearby gas stations and get fuel cheap enough to melt 'em some more. :wow:

Pardon my interruption. Let the tidal discussion resume. It is a fascinating topic for someone who never gave it much thought before.

Michael
 
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At low tide is there still enough water to "float the boat?" soo to speak.

Being from the north this is an interesting topic of discussion.

I do have a "jet" boat in which I run "skinny" water, but in the northern part of Cook Inlet you have to approch the rivers on the high tide due to sand bars.
 
Four Suns said:
If you picked up 3 or 4 knots, something else is going on... like your anti-gravity trim tabs are kicking in. The tidal flow on the lower James (down past the ghost fleet) is on the order of 1.5 knots. More north up by the Chick, it can get up to about 2 knots but that is at max ebb or flow... not for hours on end. My average impact of going up and down that river is only about 1 knot in either direction over the course of several hours.

I'm not trying to be a snob but the tides/currents up here are something you could probably get a real benefit if you tracked them... but they run like 6+ knots in some areas... we just don't see that in Virginia.
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OK, so there was a 30mph wind behind us.

My guess is we probably did have some wind behind us, plus it was probably one of those things where I was looking for a good result and "saw it". I did not capture any hard data.

I did not realize the current on the James was that low. At spots just east of Jordan Point if you jump in the water without a line you will float away rather quickly, like in seconds.
 
I've really been paying attention to tides and wind this year. Not just for fuel economy, but water conditions. a couple of weekends ago I was on the water where the tide and wind was in opposite directions and the waves where steep and brutal on our little boat.
 
TurtleTone said:
I've really been paying attention to tides and wind this year. Not just for fuel economy, but water conditions. a couple of weekends ago I was on the water where the tide and wind was in opposite directions and the waves where steep and brutal on our little boat.
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We experience this all of the time at our pass. We usually have only one high tide and one low tide per day, though they have 2 tides per day down the beach a hundred miles or so. We have a HUGE bay system the fills and dumps through a single pass daily. Our normal winds are West, and the jetty's are oriented NE-SW, so when the water is running out to the SW and winds are in from the West, we get some huge swells and violent chop. Add to that a bunch of boats and it'll sink a small boat.

Guys actually surf the area inside the pass against the East jetties. The waves roll in and curl/break over the sand that has built up there. I've windsurfed it in the past and kitesurf it whenever a named storm is in the area. It's a real rush.
 
Here's something I've done on my last three boats. It's not perfect and won't win any emy awards, but it's a good barometer for real time currents. It won't predict a current, but it sort of let's you know what you are 'in'. It works on boats with a gps and a Raymarine st-60. It would probably work with other brands of electronics, but I have no experience to talk with that regard. You must also maintain the cleanliness of the st-60 wheel under hull.

Make a few runs in at least two directions and calbrate the st-60 as close as possible to the gps speed. Directions for the calibration are in the manual. This MUST be done at slack current and on a day with minimal winds.

Then, when you are out running, look at the speed on your st-60 and compare it to the speed on your gps. The difference will be the speed of the current. If the st-60 is reading a higher speed than your gps, you are going against the current. If the st-60 is reading a lower speed than your gps, you are going with the current.
 
osd9 said:
Here's something I've done on my last three boats. It's not perfect and won't win any emy awards, but it's a good barometer for real time currents. It won't predict a current, but it sort of let's you know what you are 'in'. It works on boats with a gps and a Raymarine st-60. It would probably work with other brands of electronics, but I have no experience to talk with that regard. You must also maintain the cleanliness of the st-60 wheel under hull.

Make a few runs in at least two directions and calbrate the st-60 as close as possible to the gps speed. Directions for the calibration are in the manual. This MUST be done at slack current and on a day with minimal winds.

Then, when you are out running, look at the speed on your st-60 and compare it to the speed on your gps. The difference will be the speed of the current. If the st-60 is reading a higher speed than your gps, you are going against the current. If the st-60 is reading a lower speed than your gps, you are going with the current.
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Too much math for me

I am still trying to figure out if one train leaves New York City headed to Chicago at 2 PM going 100mph and another train.......
 
I just spit in the water as see what way it goes.
 
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