Tides and Currents

[Jim Hawkins]

*Spoiler Alert - I don't know if anyone else does this but I like the idea of ending a thread with giving the answer back at the beginning for those looking for info that would prefer not to read the whole thread. So, I believe the best answer was in post #16 if you care to fast forward. Post #2 alludes to the same without explaining why.

On a recent sail with my Macgregor 25 we were sailing fairly close hauled, making fair speed and having fun trying to keep up with a large sailboat. After we got well upwind from our starting point I wanted to practice sailing downwind. I tried wing and wing but it was not working and so furled the main and went downwind with Genoa only. We seemed to be just bobbing along at a very slow pace and getting bored I wanted to set a course for home. When the GPS showed me which direction to go I didn't believe it. It showed us much farther downwind then I thought our short slow sail could have possibly taken us but scanning the coast visually confirmed it. Only way to explain it I suppose is tide and currents. My knowledge of tides are limited to the rise and fall of the water but does that rise also come from a definable direction and where do I find that? I also suppose that tide and current can be two separate things. How in the world does one factor in these things? Are there tide and current maps that show present conditions?
Please forgive how novice this sounds, I just have a very limited understanding of how to allow for the direction of water under the boat.

 

[dzl]

Well I'm a newb, so this may be dumb... But surely you were checking your boat speed via gps? If not, I would suspect you were running downwind as fast or faster than you were beating upwind, it just didn't feel like it.

I hate to even mention something as duh as that, but sometimes you have to be reminded to check the gas tank first when the mower won't start....

 

[Jim Hawkins]

surely you were checking your boat speed via gps? ..

No, I surely was not. And don't call me Shirley.

 

[Stu Jackson]

Jim, any decent basic sailing/boating book will explain this in detail. Even Sailing for Dummies, which is quite a very great little book.

 

[JohnShannon]

Down in Florida you have this thing called the "Gulf Stream" flows at several knots, about the same speed as your boat on a not too windy day. Do you have a smart phone? Get Navionics or similar navigation ap, $10 and you will know where you are. Also have tide and current function. Tides I don't think result in much current where you are, but the Gulf Stream is a big factor.

 

[JohnShannon]

map http://oceancurrents.rsmas.miami.edu/atlantic/florida.html

 

[Joe]

Understand the terms "apparent wind" and "true wind".... going downwind never feels as fast as beating into the wind.... but you need to look at the speed on your gps (you really should have at least a basic handheld gps, btw) You might try googling "tides" and "tidal current" to help you understand this phenomenon. There are many types of current..... Tides are measure by height... but you have to understand the water just doesn't expand... or contract.... it's more like a world wide surge caused by the interaction between the moon and earth's gravity.
FYI.... you can quickly check for tidal current by looking at a bouy to see which way the seaweed is streaming.

 

[shemandr]

Are there tide and current maps that show present conditions?

There are many sources of tide and current information (And you are right in noting that they are different.) Local fishing stations, chandleries, hardware stores have paper tide tables. You often have to extrapolate for the specific time and place you sailing. Weather.gov has tide data - it takes a while to find it. Many marine GPS's have tide data. References such as Eldrige Almanac have tide data. Many websites have tide data and sailing sites for yacht clubs and regatta often have links for tides.
The main thing to remember is that these are all predictions. Many factors change the actual tide and current states. As Joe said one of he best ways to see what's going on when and where you are is to sail by a "Lobster pod" buoy or other fixed structure and observe the wake direction and speed.

 

[Jim Hawkins]

OK, thanks for all the responses but,
I'm not in or close to the gulf stream. Besides it goes the opposite direction.
I know there are plenty of websites for tide info and I have no trouble understanding the rise and fall of the tide.
I have GPS that shows speed, I just wasn't watching it. I was just watching the flow of water around the hull.
*I'm more trying to understand if there is a "current" associated with the rise and fall of the tide out in the open ocean.
Below is a chart where I was sailing, East and West about a mile South of the last channel markers.

 

[Anonymous 121765]

Jim,

I live on the left coast & we also have some strong tidal currents depending on the moon phases.
Here's some suggestions that may help.

1.) I assume you don't have an autopilot as one was not mentioned. An autopilot can be your best crewmember. And, they NEVER argue with you.

2.) You mentioned GPS but not if was a chartplotter. I myself do NOT like handhelds as the screen is too small & you usually have to use one hand to hold if not in a fixed holder. A chartplotter is the way to really go. This way, you can set your course accurately using both. If trying to sail a channel with an angled current, you may have to adjust your rudder angle to compensate for drift. This becomes much easier having both instruments working in tandem while visually seeing your course over ground made good.

2.) All of my area channel markers show in my chartplotter but as a backup, I also have them as waypoints. This way, I know exactly where I am with reference to the channel, as some charts might not as of yet been updated. Markers may move to different locations due to shoaling. It takes the positioning guesswork out of the equation. I can also turn on my Garmin NAV/MOB function where a line will show up from the bow to exactly where I am pointing.

3.) Sailing in channels. I don't know about your area but up here, we have alot of boat traffic man & some narrow channel areas with skinny water just outside, so many times you are in tight areas with passing boats throwing wakes. I used to double sail channels & have witnessed times on downward or wing-n-wing's with 60 footers passing from my rear throwing 2-3 ft. wakes. It can be a nightmare. I've witnessed other boats with ripped sails, swing/banging booms etc. It's just not worth it. Unless there is no traffic, I usually only use my main & my motor is running. Why sail hard when you can sail smart.

These are just my feelings pal, I hope this helps.

CR

 

[Jim Hawkins]

Thanks Cap Ron but,
I always seem to have trouble getting my question understood. I am not looking for an aid to navigation, I'm trying to understand the dynamics of currents as they relate to tides in open waters.
For example. I know a rising tide can cause a current to flow up into the mouth of an inlet and reverse as the tide goes down.
But down here in the islands of the Florida keys does the tide create a current through the islands? I always assumed (maybe incorrectly) that a rising tide created a current going from east to west or in the case of the lower keys, toward the Northwest. I thought that the pull of the moon pulled the water from the ocean through the keys and piled it into the Gulf of Mexico after which it would reverse and flow back out to the ocean. Is this the case?
Because of the rotation of Earth and Moon do tidal currents only move East and West?
What about 100 miles out, does the tide create a current?

 

[Jim Hawkins]

Would this be approximate of what a rising tide current would look like? (up is North)

 

[Anonymous 121765]

Jim,

In my area, we have a North/South current along the coast. However, the direction can & does reverse itself.
Also, current direction can be influenced by the shape of land mass. Think of water & air, if there is a deciding factor in angle of current, yes it can be mostly directional. You have a large Atlantic ocean interacting with a much smaller bay & also, the spinoffs from the Gulf Current. There are numerous factors that come into play. Planet rotation, prevailing weather, large vs. small bodies of water, landmass etc.

I've sailed the keys several times & there is I believe a unique set of current factors in your area especially passing East & West with tidal movement.

I am sure there are those in your area or online that can give you greater insight to you questions.
You only need seek them out. I am very interested in what you discover, as are the members in your thread.

We await your findings sir,

CR

 

[Jim Hawkins]

Thanks Cap Ron, and I loved your performance in the movie.

Joe, I took your advice and googled "tidal currents" I found this site which I'm still reading (lots of links)
http://oceanservice.noaa.gov/education/tutorial_currents/02tidal1.html

 

[Stu Jackson]

Jim,

You are asking a complicated question. WADR, in this case, Google can be your friend.

I typed in "currents in Florida Keys" and came up with a few hits, well more than just a few.

Here's the granddaddy of them all:

http://www.tidesandcurrents.noaa.gov/tide_predictions.html?gid=198

And many like this:

http://www.tidesandcurrents.noaa.gov/tide_predictions.html?gid=198

Please give Google a try yourself to learn lots more. As Ron says, it's a complicated subject.

Good luck.

PS I posted this just after your last post came through.

 

[Gunni]

K.I.S.S. Principle - You were fooled by the low apparent wind of your downwind sailing direction. True wind speed/direction - boat speed/direction = apparent wind speed. And the wind was conspiring in deceit by moving the wavelets in your direction of travel. This is how inexperienced sailors get caught with too much sail up going downwind. Doing so with the biggest sail on your boat, deployed in an unbalanced configuration - not prudent.

 

[Jim Hawkins]

Gunni, that has to be the gist of it.
I already understood when moving in the direction of the wind that the wind would seem to drop, I get that. Apparent wind, I get it.
However I was not considering that visually watching the progress of the boat I was deceived by the direction the wind was moving the ripples.
Thank you, that makes sense.
Heck, it more than makes sense, I think you just moved me up a wrung in my sailing studies.

 

[Ron20324]

Some chart books have the tidal flow diagrammed . Mine is "Maryland Cruising Guide" www.whmap.com. Maybe look at others on the shelves of your boat store?

 

[Gunni]

Jim;
I know your cruising ground well, used to be a favorite diving playground. The only current I would be concerned with would be the near-in edge of the Florida current/ Gulf Stream, there is sometimes a southward eddy. You can often see it off American Shoals - ripping north like the legendary ocean river it is.

A few years ago some visiting fishing pilgrims got themselves tangled up in the GS out there when their single engine mobo died. They drifted north for 3 days surviving off rancid cooler water and a bottle of Gin, witnessed the lights of Miami, then drifted south on an eddy to near Sugarloaf where they were rescued, at day 7. Always wondered why the locals would rent a bareboat to people, given the potential danger.

 

[Head Sail]

Thanks Cap Ron but,
I always seem to have trouble getting my question understood. I am not looking for an aid to navigation, I'm trying to understand the dynamics of currents as they relate to tides in open waters.
For example. I know a rising tide can cause a current to flow up into the mouth of an inlet and reverse as the tide goes down.
But down here in the islands of the Florida keys does the tide create a current through the islands? I always assumed (maybe incorrectly) that a rising tide created a current going from east to west or in the case of the lower keys, toward the Northwest. I thought that the pull of the moon pulled the water from the ocean through the keys and piled it into the Gulf of Mexico after which it would reverse and flow back out to the ocean. Is this the case?
Because of the rotation of Earth and Moon do tidal currents only move East and West?
What about 100 miles out, does the tide create a current?

The answer is yes, but not necessarily east to west. 100 miles out the answer is yes but usually not monitored because of insignificance.