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Anke and I are building our next boat, and writing about it at ABargeInTheMaking.blogspot.com. Access to the net comes and goes, so I'll be writing in fits and spurts.

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Fair winds!

Dave and Anke
triloboats swirl gmail daughter com

Sunday, February 19, 2012

At the Races: Running Narrows Without an Engine

EEEEEEE! ha?
Photo of Sergius Narrows  by Richard Nelson
(Check him out!)


I don't blame you for being scared -- not one bit. 
Nobody with good sense ain't scared of whitewater.
Humphrey Bogart in The African Queen


Archipelagos, by their nature, are full of islands. Islands, by theirs, break up tidal flow of water, and squeeze it into passages between islands. When water is squeezed down tightly, we get narrows.

Most narrows develop some current. Via a complex of factors, tide will be higher on one side than the other, and water will flow from high toward low until equilibrium is achieved. The greater the difference, the greater the current.

Water, by its nature, is chaotic. A chaotic system cannot be fully charted. Races and rapids are inconstant, surprising, changing from moment to moment, often for no apparent reason. They are wild and utterly magical places. I love 'em. But I respect 'em, too!

Dangers - At some, vague point, certain narrows develop races, or rapids. Really bad ones - those with complex course, edge or bottom - may develop eddies, rips, haystacks, standing waves, swirls, or whirlpools. And of course, rocks, shoals and cliffs.

Some narrows form passages between inner and outer waters. On the outside, onshore ocean swell, surge or seas can meet a strong, current outflow with spectacular and often deadly results. Avoid these conditions at all costs. Many's the seasoned fisherman has foundered in these conditions.

Yahoos present a significant danger. Traffic often backs up to wait for windows of lesser current (see TIMING, below). Our preferred time of transit can be crowded with traffic, all of us more or less hopped up on body chemistry. Most traffic is competently captained. But there's an ever increasing percentage of empowered morons.

Some of these may be generally reckless (planing boats have a high percentage of yahoos at the helm, and all are skipping across the water). Other while serious, may be in over their abilities. In restricted channels with limited and/or erratic maneuverablility, defensive seamanship on your part is essential. Communicate via clear signals, radio, and voice where possible. Don't rely on the comprehension of idiots, however.

One of the worst dangers is panic. Adrenaline flows in direct proportion to current. Even for experienced sailors, rapids can suddenly introduce new situations, never before encountered and threatening disaster. It is essential that you overcome panic. Breathe, assess and address. Seconds are precious.

Finally, no matter how calm it is outside the narrows, it can be wild within. Take all safety precautions you would in a full storm. Wear your life-jackets and Clip in! You may not have a moment or hand free to do it once inside. Consider going in reefed... you can always shake it out.

Information - Chart names often give a hint as to what lies ahead. Devil's Elbow, Race Point, Ford's Terror - these are subtle, red flags. Narrows are often charted with intimidating symbols and annotated with cautions, usually in close-up insets of their own. Coast Pilots and some cruising guides provide important information. Local knowledge, when available, is invaluable.

Good information will let you plan a transit course. All things being equal, this will let you know, in advance, which side of the channel to favor at any given point. Develop a clear understanding of where the known dangers lie, all along the route.

Don't forget weather. Squally weather is no time to be sailing through narrows. Narrows often funnel and intensify the wind, and even a light squall can develop storm force gusts. Entrances and exits can get tricky with opposing, wind driven waves.

Don't forget that all information regarding chaotic systems is incomplete, save as embodied by the system itself. Inform yourself, but stay open and flexible to conditions as they arise. Your eyes and ears will be providing the most pertinent info... look ahead (down current) to observe and assess dangers as they emerge.

Physics - Momentum is an important factor in running narrows.

As Isaac 'Fig' Newton pointed out, objects in motion continue in a straight line, unless acted on by a force. As a kid riding a bike, you probably attempted a sharp turn and skidded out. Our best and most ancient teacher - pain - patiently drove Mr. Newton's lesson home until we got it.

Our boat's gonna be moving fast in the races. If narrows take a sharp turn, water (following the same rule) piles up on the down-current shore in local and persistent chaos before sorting itself out and tearing off in the new direction. Left to our own devices, we'll do the same. Assuming there's anything left of us to continue.

Moral? Favor the inside, up-current side of any sharp turn, and control your speed.

Boats with keels and/or very hard chines need to be aware of sheer. This is the equivalent of a flat water broach. We come racing out of fast moving water into a patch of slow or counter moving water. Keel grabs and acts like a giant rudder, turned. Combined with momentum, this effect may take you a startlingly long way off course before you regain positive control. And they don't call these 'narrows' for nothing!

Timing - Current in narrows, like all things tidal, follows the Moon. Tidal ranges are greatest at spring tides and lowest at neaps. The greater the range, the greater the differential of height on either side of the narrows, the greater the volume of water rushing toward equilibrium and therefore, the faster the current. Whatever dangers lie in the narrows are made worse by this greater mass of water rushing through it. Waiting for lower tidal ranges, or even neaps, may be prudent.

Slack tide is all important for engineless sailors. This is a short period of (relatively) still water between foul current and fair. Near springs, it may be very short, and though water is not flowing, it may be jostling uneasily. Neaps allow longer, more tranquil pauses. We don't always transit near slack, depending on the narrows and conditions, but it's the safest course.

Our general method, for moderate to extreme narrows, is to wait for settled weather toward neaps, then work our way against the last of a foul current. As current eases off to slack, we force our way through. Once the new, fair current sets in, we're spit out the far end.

All our wild water experience and advice comes from pushing the envelope by choice or misjudgement. Timing is everything! The rest is dare-devilry.

It helps to have an anchorage - even a toe hold - in easy reach of the opening. Preferably where we can see and assess water movement (flotsam helps). Under some conditions, the route through the narrows can be scouted by foot or with a good tender, before committing the mothership.

When in doubt, patience is the rule. Wait for conditions in which you are confident.

Control - Staying in control is important. While water itself won't hurl you onto a rock (it takes a more sensible path around it... momentum, however has no such qualms), it can drag you over shoals or through reefy combs. The ability to maintain and/or change position within the current is vital.

That being said, there are limits to control. These need to be understood, accepted and worked within.

Once into a rapids, one is pretty much committed. Timing was your best bet on control, but now you've cast your lot. From here on out, your control consists of nuancing your position within the channel and current.

Steerageway is the standard method. One needs a certain speed relative to the water to maintain it. Probably more than your open water minimum, as the water is not likely to be homogeneously smooth. Remember that your momentum is based on speed over the bottom, not over the water. But don't worry... the shoreline flashing past will remind you.

To keep momentum down, hold your speed made good as low as possible while maintaining control. Reef, if necessary. Initiate evasive actions early, and have a good picture of your general transit route. Do your best to coordinate local ducking and weaving into that bigger picture.

An alternative is to make way against the current while transiting stern first. This allows more speed relative to the water, subtracting from your speed over the bottom and therefore momentum. The danger is that, if you get swept into relatively slow moving water, the momentum you do have can back you down abruptly on your rudder. Keep a sharp eye aft with this method!

In a light breeze, real or apparent, one can luff and tack to maintain position within the current despite near zero steerageway. It helps to have a crewmember standing by to back a foresail, and an oar out to assist tacking.

With zero wind and lesser currents, one can relax and let the boat drift sideways. An oar out the side can be given a push or pull as necessary to adjust position.

Techniques - Use a push pole to fend off shore or shallows, and assist tacks near the edges. It can double as an oar (fat end as 'blade') in support of the main sweep(s). We carry a pole at all times, but one can be cut for the transit.

Take care not to get in line with the pole, as it is like a current powered lance... only push at near right-angles to the boat. Take care not to wedge the tip in a crack... the fixed pole will then sweep the decks as the boat rushes by. In very heavy current, skip the pole entirely.

Dredging is an old sailing barge technique. Big barges used to drag iron sleds to keep their bows up-current. A shot of chain is more practical for smaller boats, and you can control your drift by the length of chain let overboard. Tie the end to the boat, and be ready to slip if there's a hang-up, and have a Plan B ready to hand. Don't use chain you can't afford to lose!

Play the eddies. Especially while the main current is foul, one can work into it by exploiting eddies (counter currents) and slower moving patches. Both tend to form along the edges. Keep a sharp eye on your motion, both relative to water and the shore.

If necessary, break a long transit into smaller legs, anchoring up in a quiet stretch clear of the main rapids. Be aware that a quiet spot with the current running one direction may not be at all quiet in the other!

Use ranges (aka relative bearings) to determine whether or not you're clearing an obstacle or point. I'll talk about this generally important skill in another post. In this case, they help you determine your critical progress in relation to an object... whether you'd pass ahead, behind or collide, given your present course and speed. They will let you know when and by how much to alter position, course and speed in order to clear the object.

*****

So that's what I know on the subject. I'm sure there's still a LOT to learn.

Races are exhilarating and sometimes terrifying. I still suffer cotton-mouth every time we go through. Forces involved are awesome and humbling. Drain the macho right out of you! They demand multi-tasking; not my forte. They're some of the best education available in reading water, written, as it is, in a bold hand and gripping narrative.

Narrows are some of the most beautiful and dynamic places on Earth. Their currents stir nutrients that attract a broad swathe of the food chain. Predator and prey - most often one and the same animal - leap and flash in the tumult. Seabirds dive in raucous glee. Whales number among the traffic transiting between bodies of water, their numbers concentrated by the enclosing shorelines.

So we do our homework, steel our nerves, hedge our bets, take a deep breath... and take the plunge!


Nav Buoy in Sergius Narrows... they can go completely under!
Photo by Richard Nelson
RN hosts a most excellent radio show, ENCOUNTERS

PS. These skills, like all of them, are best acquired through practice. Start small, in low current situations through straightforward narrows. You can make four passes a day, if you like. Work up in difficulty as you're abilities increase. Don't let other priorities push you through before you're ready for them! Assess, address, debrief.

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