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First String
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So I'm as some of you know in the process of moving to the next step in my training. I'm in the planing stages of my first over-night near shore passage. I will leave early am: 4:00 with a full moon to help and head out to the "R 4" F1 R4s @ 32-05,901"N 080-35,099W this is the channel into Port Royal sound Beaufort SC.
I intend to sail out with the tide its a 19 mile ride I figure 5.5 knots of speed? That will put me there at Day break or just after 3.45 hrs.
Then run straight east for 5nm to 32-029'899N 080-29'988 W That will take a nother 90 min,
Here, I will turn south to 32-03,997W 080-29'167W 1.92 miles = 34min
Here i will turn back west to 32-03'984W 080-34'965w this 4.92 leg take .89 min
Then I will turn North to will bring me the 4.92 nm back to to the "R 4" F1 R4s @ 32-05,901"N 080-35,099W the bell marker at the mouth of the channel. Then my hope will be to take the the Tide back in.
So here is the question." If I do this near shore how much will the tide effect my timing in the course: I plugged in the 5.5 based off motor speed.
All together time from the dock and back to the dock. 10.956 hours to cover 60.26nm
How much time will the tide cost me off shore? I know a bought the tide in and out of the river. Just need help with the offshore expectation?
Thanks again. let me know if you need more information.
Cheers, LT
Near-shore tide what to expect. "Need some Guidance"
 

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Simple rule for tides when offshore: the tides go 'up' and 6 hours later (on the East Coast w/ diurnal tides) the tides go 'down'. When offshore you dont get the FLOW (current) of tides as you do in shallow estuaries / onshore .... and their 'hydraulic anomalies' due to land 'differences'. Once youre in more than 50-100 ft. deep water and well offshore, tides are 'inconsequential'.
The only place you need to be concerned with tides and their resultant generated CURRENTS is in Rivers, Bays, Inlets, etc. as in the 'ocean' the tide only go 'up' and they go 'down'.
 

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The only place you need to be concerned with tides and their resultant generated CURRENTS is in Rivers, Bays, Inlets, etc. as in the 'ocean' the tide only go 'up' and they go 'down'.

Except for thing called "The Gulf Stream"

I bought a place on Ladies Island and haven't had the chance to explore much beyond Port Royal Sound. The currents in the rivers and sound are significant. The distances you are talking about are pretty close to shore. I'm sure currents would be effected by the volume of water going in and out of the sound. Looking for some charting.
Jim
 

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Itgoshen. Have you spent time at the inlet around posted high and low tide and observed the current? The current often lags behind the posted time for high and low. If for example you plan to be back at the inlet at posted low hoping to catch the slack and then flood up river to Beaufort you will probable be way to early and will be running against the current. I have no notes on Port Royal but that is what I have seen at other east coast inlets.
FWIW. Dan S/V Marian Claire
 

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Itgoshen
Be flexible, research the inlet tidal current and near shore currents, but be ready for the wind and near shore breeze to not cooperate. Have an alternate plan ready if needed.
 
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Something else to be aware of is that tide tables are based on algorithms (not direct observations), and are frequently off. The current will vary significantly on where you are (shallow vs deeper water) throwing another big variable in your calculations. Add to that, the surface water doesn't really start going back the other way after a tidal change for more than 1/2 an hour (in Charleston harbor, at least). Offshore, I would be willing to bet that current is downright unpredictable once you get away from a channel entrance. Sorry-- I hate to rain on your parade, but this stuff is full of all kinds of pitfalls...

Man, I hope you're not going anytime in the next few days... brrrrrr!
 

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Consult Eldridge's Tide and Pilot book
www dot landfallnavigation dot com/-bp002 dot html

I am not familliar with that section of the coast (mostly I sail in New England) but Eldridge covers the entire East coast.

Also learn how to add the current vector to your course vector and plot it on a chart.

From your use of Lat Long coordinates it appears that you may be planning on relying on a GPS. That's OK, but use the marine chart, course vector and current correction as well so you have a back up. Don't rely entirely on GPS, it can go wrong for many reasons.
 

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I also see a bigger issue. Maybe I'm just dead wrong, but if you've got a good headwind on any leg, you can expect to NOT make the 5.5 kts you're using as your rule of thumb. Sure, you might get ahead of schedule on some of the legs because of the strong wind, but once you're pushing hull speed... What kind of boat, and what kind of engine do you have again? Also, since you're assuming day break is 7:30 AM, that sounds to me like you're expecting to do this some time in the next several weeks. What time will the sun set? Are you OK getting back in the dark if something happens? If you wait a month, you might have more daylight to play with as a safety factor.
 

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First String
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Discussion Starter #11
From your use of Lat Long coordinates it appears that you may be planning on relying on a GPS. That's OK, but use the marine chart, course vector and current correction as well so you have a back up. Don't rely entirely on GPS, it can go wrong for many reasons.
I have 3
1) brand new for christmas a Garmin echo50s
2) Working Garmin 215 backup unit
3) Garmin 72 hand held.
I have been studing the charts for



Thanks for the great advise
 

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First String
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Discussion Starter #12
I bought a place on Ladies Island and haven't had the chance to explore much beyond Port Royal Sound. The currents in the rivers and sound are significant. The distances you are talking about are pretty close to shore. I'm sure currents would be effected by the volume of water going in and out of the sound. Looking for some charting.
Jim
Hey and thanks Jim, We live with 10 miles of each other we should sail sometime. I have been sailing the Morgan river Beaufort River, and the Port Royal sound for a couple of years now. Light air most of the time. a lot of Shoaling. Great place to sail.

My question, Where the Port Royal Sound dumps into the Atlantic Ocean is in a south easterly direction. How far north or south would I have to run north or south of that current on a out going tide for the effects to calm down?
Thanks Curtis
S/V East Coast Lady
 

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First String
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Discussion Starter #13
Itgoshen. Have you spent time at the inlet around posted high and low tide and observed the current? The current often lags behind the posted time for high and low. If for example you plan to be back at the inlet at posted low hoping to catch the slack and then flood up river to Beaufort you will probable be way to early and will be running against the current. I have no notes on Port Royal but that is what I have seen at other east coast inlets.
FWIW. Dan S/V Marian Claire
Yes I have and I have thought something was wrong with where I get the tide information from?
Error Message Page
 

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First String
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Discussion Starter #14
I also see a bigger issue. Maybe I'm just dead wrong, but if you've got a good headwind on any leg, you can expect to NOT make the 5.5 kts you're using as your rule of thumb. Sure, you might get ahead of schedule on some of the legs because of the strong wind, but once you're pushing hull speed... What kind of boat, and what kind of engine do you have again? Also, since you're assuming day break is 7:30 AM, that sounds to me like you're expecting to do this some time in the next several weeks. What time will the sun set? Are you OK getting back in the dark if something happens? If you wait a month, you might have more daylight to play with as a safety factor.
Its a 1981 C&C30 MK1 with a newly installed Yanmar 2gm20D
S/V East Coast Lady
 

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Have you been out with 15-20 kts on the bow? What's your speed with the engine then? My boat has a fair bit of freeboard and other "windage" so we're probably not a good comparison, but our first day out of our "migration" north we had a headwind of 15-20, and we only saw 3.5-4 kts with the engine at essentially full throttle. When the wind wasn't on our nose, we were able to reach a little over 6 with the engine alone, and a little over 7 with the sails and engine employed at the same time. Of course, your boat is more performance-oriented than mine, so you will probably do better, but still...if it were me, my luck would be that the winds would be on my head on the way out, and then change to be on my head on the way in, too.
 

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You may also want to read the following article
www dot ritchienavigation dot com/docs/ESRitchieLR dot pdf

It illustrates well the problem with GPS units when your speed over the ground is low (resulting from sailing at a speed close to the speed of the current). A GPS unit determines direction from position measurements. The GPS also determines the direction of movement of the boat, not it's heading, so if the current is carrying you sideways then the difference becomes obvious.

Keep a good compass on board ($50 - $80 is quite enough), cross check your heading taken from the GPS against the compass from time to time, and plot your GPS position on the chart. Any difference between compass heading and GPS will show up.

Are you single handing ? Do you have some sort of self-steering gear rigged up ? There will be times when you need, want, to take a break from helming.
 

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Here is another article which may help. It explains how GPS finds direction. Because sail boats move at a slow speed (unless you are on an America's Cup team!) and because the current can be significant compared with boat speed then your movement over the ground (which is what GPS measures) can be low enough to confuse a GPS.
www dot gpsreview dot net/electronic-compass/
 

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First String
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Discussion Starter #19
You may also want to read the following article
www dot ritchienavigation dot com/docs/ESRitchieLR dot pdf

It illustrates well the problem with GPS units when your speed over the ground is low (resulting from sailing at a speed close to the speed of the current). A GPS unit determines direction from position measurements. The GPS also determines the direction of movement of the boat, not it's heading, so if the current is carrying you sideways then the difference becomes obvious.

Keep a good compass on board ($50 - $80 is quite enough), cross check your heading taken from the GPS against the compass from time to time, and plot your GPS position on the chart. Any difference between compass heading and GPS will show up.

Are you single handing ? Do you have some sort of self-steering gear rigged up ? There will be times when you need, want, to take a break from helming.
I have 3 GPs's and a binnacle compas.
I also have a auto-helm 4000 self steering that works from my GPS or from the the ST50 wind vane.
I will be single handed, however there will be a experienced sailor on board in case I need support.
 

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First String
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Discussion Starter #20
Start of Route 32.391848 -80.677071 0
Waypoint 32.377352 -80.672951 0.9
Waypoint 32.36434 -80.677199 0.81
Waypoint 32.34324 -80.661364 1.5
Waypoint 32.315354 -80.650635 1.76
Waypoint 32.260826 -80.656857 3.29
Waypoint 32.169001 -80.592828 6.41
End of Route 32.097991 -80.584931 4.29

One way =18.96 nautical miles
Total Distance: 37.92 nautical miles
37.92 / 4.5 = 8.42 hours.
do-able yes?
 
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