Re: [Paddlewise] Tudes and Current Speed

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.

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. 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.

If you go over to UKSKGB.co.uk they have a present tidal race 
discussion and more logged in the almanac. They find the 3rds rule 
appropriate for the Scottish Islands. Anyway, I don't have any links 
that provides any insight into the current speeds and tidal range 
factors. I have used the 50/90 rule in lots of places and it generally 
holds up well. 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.

Cheers,

Rob G
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