02 October 2010

Go With The Flow

I've mentioned before that I have been reading Arthur Ransome's "Amazon and Swallows" books. What I didn't mention was how much I've been learning from them.

Any Brit reading this blog will have read all of them, but they are relatively unknown in the US. I’ve read dozens of sailing books, but did not discover these until recently. I’ve got the entire set with me (bought second-hand from Amazon), and I am savoring my way through them, as slowly as possible.

My favorite, so far, is called “Coot Club”. In this story, 5 children and an old lady go on a cruise through England’s Norfolk Broads. They have all sorts of adventures, but the heart of the book is an epic dawn-to-dark sail down to the treacherous water’s of Yarmouth, and beyond.

Of course, their small, gaff-rigged sailboat has no engine, and the tidal currents on these river’s are significant, so the crew -- commanded by the oldest boy, Tom Dudgeon -- have to play the wind and current’s for all they are worth. And they do.

They ride the ebb tide down one river to the North Sea inlet of Yarmouth, hitting Yarmouth at slack water, then ride the flood tide back up another river.

In my years of sailing on Long Island Sound, I’ve never given tidal current’s much thought. Maybe that’s because I always sailed in boats with big diesel engines, or because the currents in my part of the world aren’t very fast. Or maybe because no one I sailed with in my formative years ever mentioned them.

But the fierce currents in Florida’s rivers and inlets are a major bother. They sometimes run 3 or even 4 knots. Since the Blue Moon’s hull speed is about 5 1/2 knots, that makes a difference! When you’re sailing with the current, the current’s speed is added to your boat speed. But when you’re sailing against it... well, you might as well drop anchor and crack open a Blue Moon beer. 

Not that I was smart enough to do that. I have to confess that the whole current thing just didn’t ‘click’ in my head. For hundreds of miles, I made no effort to catch favorable tides, or avoid unfavorable ones. As a result, I spent a lot of time gnashing my teeth over my lack of progress and the all-too-common GPS reading of 2 knots SOG (speed over ground.)

I was sailing, as John Walker would say, like a duffer.

But no more! Reading the “Coot Club” opened my eyes to the problems and opportunities of tidal currents.

A Coot, in case you were wondering...
wikimedia commons

In fact, the next leg of my voyage posed a similar problem to that faced by Tom. Right outside the marina in Jacksonville Beach is the Pablo Creek (also known as the ICW), which flows 8 miles north to the broad St. John’s River -- a major inlet to the Atlantic Ocean, and thus a major driver of local tidal currents. I needed to cross this river and then head up Sister’s Creek. See chart 11489 for details.

I’d already experienced the current on the Pablo Creek (and not in a good way), so I was ready to put the “Coot Club” lesson’s to work.

Heading out at last
photo jalmberg
First, I had to estimate the time of slack water, where the ICW crossed the St. John’s River. According to the tables, low tide at the Pablo Creek entrance -- where it intersected the St. Johns -- was at 3:00 pm. But that didn't mean it would be slack water at 3 pm. Far from it. According to my 1947 copy of the American Practical Navigator, slack water wouldn’t occur until later. How much later was an open question, but given the length of the St. Johns, I figured at least 2 hours. Maybe 2 1/2 hour. I didn't know for sure, but after dithering a bit, I decided 5:30 would be 'close enough'.

I also wasn’t sure how much of a tail wind I’d catch going down the Tolomato, at that stage of the ebb. One knot extra? Two? I wasn’t sure, and none of the dock watchers had a clue, either. If it was one or more knots, I could regulate my speed at around 6 knots, so it should take me about 1 hour and 20 minutes to get to the St. John’s River. Add 10 minutes to cross it. Call it 1.5 hours. I’d leave at 4pm.

After a day of stocking up on food and ice, I finally headed out of the marina at 4 pm on the nose. Once on the Pablo Creek, I eagerly checked the first buoy I passed, and, sure enough, saw the current swirling around the north side of the buoy. At least that part of my theory was right. The current was flowing north, adding to my speed. I set my speed to 6 knots SOG, as measured by my handheld GPS.

Goodbye Florida!
photo jalmberg
As I flowed down the creek, towards the St. John’s, I kept checking the buoys. Gradually, the current slowed down. As I approached the crossing, my SOG dipped under 6, down to 5.5 knots. No current. Slack water! It was almost exactly 5:30.

Once across the St. John’s, and up into Sister’s Creek, the current gradually reversed and started pushing me up the Creek. It worked! I had duplicated the Coot Club trick, and taken advantage of the currents, rather than ignoring them, and being their unwitting victim.

This strategy would come in handy in Georgia, where the currents were said to be even worse.

Who says you can’t teach an new Coot old tricks?

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  1. Hi John,
    Tried to send this earlier but it disappeared. Glad to hear you talking about Arthur Ransome again (I wrote to you about Peter Duck).
    If you ever get the chance to visit the Norfolk Broads there is a fleet of original 1930's sailing boats for hire at Hunters Yard (www.huntersyard.co.uk). No engines (just a long pole for 'quanting') and oil lamps in the cabins. It's like stepping back in time.
    On the subject of AR books, I recommend 'The big six' also set in Norfolk or may be 'We didn't mean to go to sea' would be more appropriate for you at the moment.
    Finally, as I have been talking about you blog such a lot, my wife has started one of her own 'My brilliant mother'
    Best wishes from the UK,

  2. Hi Edward,

    I'd love to hire one of those boats and sail the Norfolk Broads. They sound great. I think those kids (or should I say Arthur) were pretty good sailors, though.

    I've been all over the south of England, from Ramsgate, to Tintagle, but the only time I've been a bit north was to Oxford to visit a friend. One of these days...

    I've already read "We didn't go to sea". Wow... exciting! I've got "The Big Six" with me. Reading "Swallowdale" at the moment.

    Tell your wife to have fun with it.

    -- John


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