A Local Knowledge Report from Vero Beach

[Captain Smollett]

Here's an excerpt from a posting to the A-30 mailing list that I thought might be of interest.

...

We had one scare that almost finished our trip.  We had just crossed the St.
Johns River and were approaching the McCormick Bridge when we saw standing
waves at the bridge.  It was too late to try and turn since the waterway is
rather narrow.  Sandy was driving and I was at the throttle when we went
under the bridge with RPM's that give us 7.5+ knots.  The turbulence was
unbelievable and the current actually stalled forward motion for an instant.
Our bowsprit almost hit the bridge which could have dismasted us.  A trawler
behind us put out a warning about the current, then complimented our
seamanship for being able to maintain control.  He also said that was the
worst current he had ever seen or experienced (I fully agree with his
assessment).  He later passed us and reported the conditions at the next
three bridges.

...

Jim Davis
Privateer Isa Lei

Another user responded that they had passed through that area without that issue, and he wondered if something had changed (specifically, the bottom).

[CapnK]

Not sure when it happened, but here a bit up the SE coast, we have had unusually, remarkably* high tides lately. Combination of lunar cycles and easterlies.



*"remarkably" in that they are unusual enough to have been a topic of discussion on the docks and such...

[CharlieJ]

Probably not John. I once caught my two youngest out in a skiff, surfing the standing waves under the Atlantic Blvd bridge, just south of where they were. They were throttling just enough to stay on the forward face of a wave, and stay in the same place. Having a ball, scared the bejeezus outta me when I saw it.

5-7 feet of tide, and a narrow channel makes for some impressive standing waves. Used to have a picture of some around 4 feet under that same bridge (Atl Blvd)

That's roughly where I built my trimaran.

[Captain Smollett]

Not sure when it happened,

Don't know when it actually happened, but it was posted 27 Nov.  I'd say within a day or two of that, so fits with the larger-than-normal tides you are talking about.

Charlie, that's very interesting.  I guess the dude that posted that he did not see anything like that there was just lucky on his timing.

When we grounded the A-30 just north of Ben Sawyer bridge, we hit a shoal that never existed before.  At low tide, we were surrounded by dry ground, and one local told me he'd never seen a shoal there at all.  It was probably gone in a few days, too.

The guessed cause?  An unusually high tide had eroded some nearby low, sandy islands and I guess we hit where the sediment was deposited (temporarily).

It happens.   ::)

I believe we are better to work with the tides.  too often, we get engines and think that gives us the "power" to bully nature around.  I contend that on a 30 ft full keel boat, that ain't gonna happen with any horsepower we can reasonably carry. 

I prefer slack water for certain inlets and cuts.  So what if I have to wait a few hours?

[CharlieJ]

"I contend that on a 30 ft full keel boat, that ain't gonna happen with any horsepower we can reasonably carry. "

Got that right- and when you are bucking stuff like this all you can do is go along with it, or against it, in this case.

I was WITH that current, went through a land cut from one river to another, and then was AGAINST the same tide. This was in the Carolinas, and sometimes you simply CANNOT time it better. I expect I was making about 1.5 when this was taken- had been making about 9.

[Captain Smollett]

Topsail Inlet buoy?

I hear ya.  The NC coast from the NC-SC state line all the way to where the ICW heads "inland" at Adam's Creek is a pretty near constant battle of ever-changing currents.  I call all the little cuts along that stretch "mini-inlets."  We cannot really boat through them, but they let the water in/out and as such, a switch of current in passing.

From Snow's Cut to Swansboro one trip was a constant change from 3 knots to over 6 knots...up and down every couple of miles.

It really helps to think in terms of "average SOG" over the course of a day and not get too married to the knot log's instantaneous readouts.   ;D

[CharlieJ]

Absolutely. And it often averages out. But if you're gonna move in that area, just get used to it.

And not telling you anything, but for others- a bigger engine won't help :D

And no- that was way up some river, where you go UP one, cut through a land cut, then DOWN the next. And the tide was coming IN :(

I can't say which, because the log book stayed with Tehani.

[Captain Smollett]

Absolutely. And it often averages out.

Well, it DOES average out to SOMETHING.   ;D

I'm wondering about what he wrote: rpm's for 7.5 knots.

(A) Does that mean he's pushing the A-30 to 7.5 knots in slack water?  I don't think so.  I THINK he's on an A-30 (since he's posting to the A-30 list).  Hull speed is a bit over 6 on the 22 ft LWL, and I doubt he's getting an 18% improvement over the bow wave.

(B) Does that mean he thinks the current was 7.5 knots?  I don't think so.  That'd be some sort of record for that area and BIG news.  Wouldn't it?

It could be that he was in a standing wave and could not push through that, even with HP that ostensibly  delivers 7.5 knots.  

Either way, no matter, really...just musing.  It's scary stuff to lose control of the boat like that, and not unlike driving a car on ice.  Physics still works, but it's not the physics one is used to or expects.

Edit:  Just another thought to add.

I think, and please correct this if I'm wrong, that full keelers like A-30 'feel' turbulent currents more than flat bottomed boats do.  I've noticed this with my boats, that the swirls seem to pass under the flat bottomed boat with less effect.  My A-30 gets knocked around pretty good from eddies.  I've yawed 30-45 degrees before I could even react in a case where I did not "pre-react" (?) just to see how the boat handled.

Something to think about for those of us coming from flat bottomed (such as power) boats to keeled sailboats.

[CharlieJ]

Read to me as if he was doing 7.5 knots. I'm with you- probably not gonna happen.

As I said- I built my trimaran on an island in the ICW, directly under the Atlantic Blvd bridge. The reason it is an island is that they dredged a cut through to make it one, because the currents there on full tide flows were so severe that the tow boats couldn't get through safely. This was years ago. Making it an island let the current divide, and cut the force significantly. But you still, even now, see tows working hard getting under the bridge, against a full bore tide.

Fully comparable to say- Snow's Cut, coming south into the Cape Fear River, or under the Wapoo Creek bridge, south of Charleston. In fact, they used to have a sign telling you that if you could not maintain a 6.5 knot speed, DON'T enter on  a full tide flow. Last I came through, I did it with the tide, and was logging 9 knots or better til it spit me out :o

Once coming through the Bayou Beouf Lock at Morgan City, La, we logged 11.5!!!! Those lock walls were FLASHING by!!

And yes, I definitely feel a full keeler feels current more. At anchor, Tehani will lay to the current, pretty much in spite of any wind. Gets annoying sometimes ;)

[marujo_sortudo]

What resource do you all use for local current predictions down south?  I used my copy of Eldridge extensively from Maine through here (Elizabeth City, NC) but it gets sparse after the Chesapeake and it seems like more detail should be available.

[Captain Smollett]

To be totally candid, I don't use anything for current predictions.  I use tide tables to estimate WHEN a current will flow and (probably, in most locations) which direction.

Beyond that, I don't usually worry about trying to predict what the strength is.  I usually find that out on the fly.   ;D

[CharlieJ]

I have an free app on my Iphone called Ayetides. Let's you find the nearest tide station, and shows in either graphic or tabular form, the rate and height of the tide, along with times.

Also, many GPS have tide info for nearby places. My Garmin 76 Cx does.

As for current strength? Captain Smollet is pretty much right, although the AyeTides app can approximate it. Around here, tidal current can be so much influenced by winds, that you really have to just 'figure it out' for your self.

[marujo_sortudo]

Thanks for the tips.  Guess I'll have to learn to be a better current predictor, because I do love using them to my advantage so.  I can certainly swear by the lovely current charts in Eldridge if anyone's sailing north of the Chesapeake.