Re: [Paddlewise] Eddy currents and down river racing

From: Craig Jungers <crjungers_at_gmail.com>
Date: Sat, 8 Aug 2009 07:48:55 -0700
On Sat, Aug 8, 2009 at 12:34 AM, rebyl_kayak <
rebyl_kayak_at_energysustained.com> wrote:

>  Question is are there some
> rules of thumb that can be used to predeict which side of the river an eddy
> is
> likely to be running counter to the tide? Would it always be the shallow
> side,
> or up stream or down stream of the concave or convex side of a bend ? Are
> their other parameters to consider?


A great question and a complicated one for an estuarial river where the
current can flow each way. Dave Kruger and others who paddle the big tidal
rivers on a regular basis probably will have more valuable input than I have
but I'm willing to get the ball rolling.

First of all, I think I'd try a "pre-race" run in conditions that duplicate
the tidal range as much as possible. Scope out the places where you discover
the major eddies and figure out how you want to deal with them beforehand.

In general I would hug the bank on the flood and seek the mid-channel on the
ebb. And when I say "hug the bank" I mean so close that you have to worry
about your paddle hitting the bank. The greater the current against you the
closer you want to be.

On the ebb I think I would gravitate to the outside of bends. On the flood I
would work the inside of the bends but always aware that greater current is
found at the cusp of a sharp bend. You might find it faster to move out
early and cross the river to avoid a very sharp bend.

Avoid shallow areas on the ebb and seek them out on the flood.

Avoid obstructions on the ebb and seek them out on the flood. Large eddies
can form behind the root balls of fallen trees, rocks, sand bars, etc. so on
the flood you can paddle up "behind" them and get some relief from the
current.

Paddle faster in adverse currents and husband your energy in advantageous
currents. The theory behind this is that when the current is against you
then you want move to get out of it as quickly as possible and back into a
favorable current stream.

I think I would take a GPS with me and keep it set to show speed in small
increments (something digitally rather than a "speedometer") and watch it
like a hawk. The nice thing about GPS is that it shows speed over the ground
so any variations in current will show up as long as you have a consistent
paddling style. One of the reasons racing coaches prefer paddlewheel speed
sensors over a GPS is that the GPS doesn't show how well an oarsman is
pulling because there is some lag. The GPS has to integrate forward movement
over time to come up with a speed... a paddlewheel simply counts
revolutions. The GPS offers an advantage for downstream racing since you
really don't want to see a lot of variation in speed caused by paddling but,
rather, by currents.

Glider pilots are always aware of which wing is rising when seeking out
thermals. The theory behind this is that a thermal to one's right will cause
the starboard wing to rise (and vice-versa) so you would always turn into
the rising wing to find the center of a thermal. You might find it
appropriate to adopt much the same tactic in current and watch how your bow
swings along with GPS speed.

So if your bow suddenly swings watch the GPS to determine if you're moving
into a favorable current or an adverse current and take appropriate action.

So there are my thoughts on this. I expect this thread to be an interesting
one.


Craig Jungers
Moses Lake, WA
www.nwkayaking.net
***************************************************************************
PaddleWise Paddling Mailing List - Any opinions or suggestions expressed
here are solely those of the writer(s). You must assume the entire
responsibility for reliance upon them. All postings copyright the author.
Submissions:     PaddleWise_at_PaddleWise.net
Subscriptions:   PaddleWise-request_at_PaddleWise.net
Website:         http://www.paddlewise.net/
***************************************************************************
Received on Sat Aug 08 2009 - 07:49:03 PDT

This archive was generated by hypermail 2.4.0 : Thu Aug 21 2025 - 16:31:37 PDT