Re: [Paddlewise] Tudes and Current Speed

On Wed, Oct 28, 2009 at 8:14 AM, <rcgibbert_at_aol.com> wrote:

> I usually avoid the rule of 3rds and stick with David Burch's 50/90 rule.
> That being at the end of the first hour after slack the current is 50%, the
> second 90% and the 3rd 100%. It reverses the same way. It is a pretty good
> guide, but not a tack driver for all places. Deception Pass has 2
> inlet/outlet features at Canoe Pass and Deception Pass proper. The time for
> slack varies all over the general area and in some places it still ebbs
> while others the flood begins. I wouldn't say it goes full on just after
> slack, all the times I've been there it seems to me to take on a noticeable
> ramp up period, but less than the 50/90 rule would imply, perhaps due to the
> features you've noted and others we both are overlooking.
>

I think that the rules work best for tides and current through a large bay
but fails at a really constricted entrance. I always thought the rule of
3rds was for tide height and the 50/90 for currents. As far as Deception
Pass goes I suspect current speeds reach 90% of full speed within 1 hour of
slack.  I agree that it seems to be flowing out in one place while flowing
in somewhere else. No way in a small boat to be all over the place.

I think I'll take the Zodiac and a GPS over there this summer as a project
and find out. This question has nagged at me for 20 years at least. Paddling
back and drifting through would be a pain in the butt in a kayak but a piece
of cake (and probably fun) in a Zodiac.

>
> There are 2 areas that I have been that have a noticeably similar current
> dissimilarity to published guides, the mouth of the Strait of Juan de Fuca
> and the mouth of Icy Strait. A yachtie who owns armchair Sailor in Seattle,
> informed me that closer to shore in JDF on the US side the water *usually*
> ebbs longer than it floods.


That doesn't surprise me either. Tidal flow is calculated and represented as
linear but, like all hydraulics, it's more chaotic. The linear
representations work fine as an over all view and most clients of tidal data
don't much care about anything more granular. Most of them not being
kayakers.

The sheer volume of water from Puget Sound and the southern Georgia Strait
> collides with the flood that usually sets against Vancouver Island. Most
> times I've been out the mouth of JDF it was this way. The ebb was still
> going strong while the flood was starting, albeit in mid channel. The one
> time I've been through the mouth of Icy Strait, we planned on the flood not
> helping us for 90 minutes prior to published flood. Sure enough, the rips in
> the Inian Islands were still going off. That's one time, though, hard to
> make a claim based on that, however looking at the chart for Icy Strait,
> there was no way all that water in there was going to come out nice and
> uniform.
>

No but 90 minutes seems a bit long. I always give myself 30 minutes for
slack water at any pass in a slow boat (like a sailboat or a fishing boat)
and that seems to work. I bet the tugboat drivers could add a lot to this
discussion. All the guys I knew have long since retired so I might have to
chat one up some day given the chance.

>
> Cattle Pass between San Juan and Lopez islands is another tight opening,
> relatively speaking, that seems to have a quicker max, but it still develops
> over time.
>

Yes, they all develop over time (of course) but I think that the time is a
lot smaller than any of the rules would make us believe. Bob Burnett has
been doing a lot of playtime in Cattle Pass lately with newbies so I would
expect him to be pretty aware of how current speeds develop. I'll try to ask
him.

There is a PhD in here somewhere. :P


Craig Jungers
Moses Lake, WA
www.nwkayaking.net
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