Over the years I have heard many theories about how to estimate the speed of current at a particular point in the tidal range. Several "rules" are out there but they all seem to me to depend upon a factor that may not exist. Tides and currents may not actually follow a rule of "thirds" (or any other rule). Especially not in narrow channels (like Deception Pass). My experience with Deception Pass (admittedly gathered only since 1963 when I first moved into a small cabin on Similk Bay just around the corner from Deception Pass) is that you have only a few minutes of "slack water" and then the current ramps up to virtually full speed within the next 15 or 20 minutes. Miss the "slack" and, for all practical purposes, you might just as well run through at full current. Current tables generally give you the slack water time and the time (and speed) of maximum current. Sometimes there are curves that accompany the tables which may correspond to speeds and times; or they may not. It just seems unlikely to me that the currents through a small aperture of rock would nicely follow along a curve. I'm guessing that most of the time these curves are simply artistic representations of the tidal stream velocity and little else Does anyone have any links to any data that actually correlates current speeds with tidal range in a channel? 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/ ***************************************************************************
Craig Jungers wrote: > Does anyone have any links to any data that actually correlates current > speeds with tidal range in a channel? No. Because you also need to consider the momentum associatedof the water mass as it moves toward the constriction ... and the bottom topography ahead of the constriction. In short, there are more variables than just tidal range, although it is certainly an important one. Think on how the flow through a shallow, narrow "overflow channel" will be massively affected by small changes in the height of a large area of deep water adjacent to the channel. If the channel is the only outlet (simplest case; multiple outlets just complicates the math but conceptually is the same game), then a small rise in the water level adjacent can give rise to a huge current in a short time in the shallow channel. But, if the adjacent body of water is small in area, the same rise in height will produce a smaller flow in the channel because a much smaller amount of water needs to get through in a given time. And, variations in channel depth (related to cross section) from location to location will also give different currents through the differing channels for a given rise in tide. Places like Nakwakto Rapids are very narrow and adjacent to large bodies of water ... and they experience helacious currents for a given rise in tide compared to channels not as narrow adjacent to same-area bodies of water. Nakwakto: http://www.mobilegeographics.com:81/locations/4028.html -- Dave Kruger Astoria, OR *************************************************************************** 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/ ***************************************************************************
On Tue, Oct 27, 2009 at 9:23 PM, Dave Kruger <kdruger_at_pacifier.com> wrote: > > No. Because you also need to consider the momentum associatedof the water > mass as it moves toward the constriction ... and the bottom topography ahead > of the constriction. In short, there are more variables than just tidal > range, although it is certainly an important one. > Well I'll go along with that. But I can think of a couple of ways to actually measure current speed to see how fast the current actually ramps up. I'm pretty sure that in constricted channels it gets to very nearly full speed quickly... nothing like the nice smooth curves you see in tidal tables or on the Internet web pages. I would have thought some geophysical science post-grad would be all gung ho about doing this sort of thing. 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/ ***************************************************************************
Craig Jungers wrote: > Well I'll go along with that. But I can think of a couple of ways to > actually measure current speed to see how fast the current actually ramps > up. I'm pretty sure that in constricted channels it gets to very nearly full > speed quickly... nothing like the nice smooth curves you see in tidal tables > or on the Internet web pages. > > I would have thought some geophysical science post-grad would be all gung ho > about doing this sort of thing. I believe NOAA set up current meters in selected channels and actually did the measurements for a few, generated the algorithm which seemed to fit best, and then extrapolated that to other areas where no actual measurements were taken and called it good. Given other variables which changed from day to day would throw the models off anyway, it probably was not going to improve things much if they set up current meters in every tidal channel. To be sure, the smooth curves are idealized results. But, the shape of the curves is not the same for all channels; some are asymmetric; others are symmetric. My experience on the Columbia using a modeling program (Tides and Currents from Nobeltec) suggests they are within a half a knot most of the time, except when in the input of fresh water from tributaries or through Bonneville Dam is very high or very low. In the big flood of 1996, they were off by 3 knots, everywhere! [More on that flood: http://www.cpc.noaa.gov/products/assessments/assess_96/pacnw.html ] Researchers, one a guy I have known for 30 years, are still gathering detailed current information on the lower Columbia River system and attempting to model the flow in more detail, under US Navy funding, I believe. I see their ships and their continuous long term CTD buoy arrays in the River regularly. For complex systems there is more effort required than a grad student in a cubbyhole somewhere can provide. More field data is needed. I can understand about half of what my buddy tells me about this stuff when he comes to visit, and will send you his email so you can put your challenge to him personally if you want. -- Dave Kruger Astoria, OR *************************************************************************** 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/ ***************************************************************************
On Wed, Oct 28, 2009 at 3:36 AM, Dave Kruger <kdruger_at_pacifier.com> wrote: > ...... For complex systems there is more effort required than a grad > student in a cubbyhole somewhere can provide. More field data is needed. > > I can understand about half of what my buddy tells me about this stuff when > he comes to visit, and will send you his email so you can put your challenge > to him personally if you want. > > I'm sure the lower Columbia is complex as anything out there what with separate inflows and such. All I am after is someone who has gathered data on a relatively simple tidal narrows indicating just how fast the current ramps up to full flow. I'm pretty sure it's closer to a rounded square wave than the nice clean sine wave shown on all the tables with graphical representation of current speed. If he's got funding to do that on the lower Columbia River system then he's pretty much got his career sewn up tight. :D Craig *************************************************************************** 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/ ***************************************************************************
Craig Jungers wrote: > All I am after is someone who has gathered data on a relatively simple > tidal narrows indicating just how fast the current ramps up to full > flow. I'm pretty sure it's closer to a rounded square wave than the nice > clean sine wave shown on all the tables with graphical representation > of current speed. The curves in my Tides and Currents program for locations on the lowetr Columbia River are clean sine waves for some locations and skewed sine waves for others, all drawn from NOAA data and modeling. I would not characterize any of them as rounded square waves, but they are not for spots like the ones of interest to you. I agree a rounded square wave is a better representation of reality than a sine wave for typical tidal narrows spots. Certainly folks who have waited around for "high slack" near Nakwakto Rapids and similar passes know that, know to compensate from the NOAA (etc.) graphs. I think all you need to do is broaden the centers of those plots a bit and you are good to go. I thought you said you wanted the max current as a function of the "tidal range." The max current will not be a simple prediction from tidal range, for the reasons I cited last post, principally area of the basin on the upstream side of the narrows. But you read the post, so you already know that, I expect. -- Dave Kruger Astoria, OR *************************************************************************** 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/ ***************************************************************************
On Wed, Oct 28, 2009 at 12:17 PM, Dave Kruger <kdruger_at_pacifier.com> wrote: > > I thought you said you wanted the max current as a function of the "tidal > range." The max current will not be a simple prediction from tidal range, > for the reasons I cited last post, principally area of the basin on the > upstream side of the narrows. But you read the post, so you already know > that, I expect. I probably didn't explicate that (as they'd say in Canadian) as well as I should have. What I'd like to see for paddlers in narrows is a way to explain how the current speed ramps up and stays up during the tidal cycle. I think a lot of people expect to find a nice comfortable period of 2 and 3 kts in a current cycle with a max of 7kts and that is just not gonna happen. I always plan on the maximum current very soon after slack. I'm almost never disappointed. But it is interesting that no one knows if anyone has studied this. I figured you'd know for sure. :P 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/ ***************************************************************************
Craig Jungers wrote: > But it is interesting that no one knows if anyone has studied this. I > figured you'd know for sure. :P Well, as I think I mentioned, the detailed, full-cycle long term data were gathered for selected narrows and used to develop the basic algorithm, which was then extended to other localities. Then what happened, pretty sure, was that the algorithm chosen was one selected for ease of use and accuracy at highest flows and slacks, at the sacrifice of detailed accuracy in the midrange of current. In short, they elected to cut and run, given the influence of other variables on the actual current at the surface. You probably know that fresh water inputs from other sources and stratification will result in differing currents at depth than occur at the surface. Of course, we care about the surface current. As to the possibility of a FUD thesis, you're not too past your prime for that, Craig -- go for it! -- Dave Kruger Astoria, OR *************************************************************************** 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/ ***************************************************************************
On Wed, Oct 28, 2009 at 2:58 PM, Dave Kruger <kdruger_at_pacifier.com> wrote: > > > As to the possibility of a FUD thesis, you're not too past your prime for > that, Craig -- go for it! > > If I lived closer to a university I think I would. There are a lot of things in geology and geophysics that interest me but I know little about. But I have no interest in on-line education; what I enjoyed about college was the interplay among students and faculty and learning from the really smart folks around me. That was where I think you get the real education... that tossing of ideas back and forth. Otherwise it's just a document. Craig *************************************************************************** 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/ ***************************************************************************
Why not consult a hydrologist or hydraulics engineer or even a physicist? There's probably one in your neighborhood. If all else fails, call Oprah. Brad > Craig Jungers wrote: > >> Well I'll go along with that. But I can think of a couple of ways to >> actually measure current speed to see how fast the current actually ramps >> up. I'm pretty sure that in constricted channels it gets to very nearly >> full >> speed quickly... nothing like the nice smooth curves you see in tidal >> tables >> or on the Internet web pages. >> >> I would have thought some geophysical science post-grad would be all gung >> ho >> about doing this sort of thing. > Dave Kruger wrote: > I believe NOAA set up current meters in selected channels and actually did > the measurements for a few, generated the algorithm which seemed to fit > best, and then extrapolated that to other areas where no actual > measurements were taken and called it good. Given other variables which > changed from day to day would throw the models off anyway, it probably was > not going to improve things much if they set up current meters in every > tidal channel. > > To be sure, the smooth curves are idealized results. But, the shape of > the curves is not the same for all channels; some are asymmetric; others > are symmetric. *************************************************************************** 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/ ***************************************************************************
On Wed, Oct 28, 2009 at 8:31 AM, Bradford R. Crain <crainb_at_pdx.edu> wrote: > Why not consult a hydrologist or hydraulics engineer or even a physicist? > There's probably one in your neighborhood. If all else fails, call Oprah. > > I'll bet there are more of them in your neighborhood than in mine. Ask around. I'll call Oprah. Craig *************************************************************************** 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/ ***************************************************************************
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 *************************************************************************** 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/ ***************************************************************************
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 *************************************************************************** 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/ ***************************************************************************
Craig: 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.B 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. Rob: There is also a rule of 3rds for current. 33% at the end of the first hour 66% at the end of the second and the rest at the end of the 3rd hour. Doesn't work well around here in most places I've been. Rob: 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. Craig: 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. Rob: All the shipping I've seen are out in the lanes in mid channel. It wouldn't surprise me to be more uniform out there where the West Entrance buoy is. My observations are based on numerous trips from Neah Bay to Cape Flattery and watching the ebb near shore continue for up to 90 minutes after the flood was supposed to begin. I've eddy hopped back several times until I asked the question to the Armchair Sailor guy. Craig: 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. Rob: Having padled there numerous times I wouldn't say it goes off full tilt very quickly, but I agree with your supposition that it develops more fully sooner than the rules of thumb would imply. I think you are right, that areas with tighter constrictions and more convoluted bathymetry can defy the *rules.* Rob: I have a new one for ya, Craig. The WA side of JDF from Port Angeles to Cape Flattery often experiences a double ebb; a very short and weak flood; or, sometimes more *normal* conditions. It makes surf prediction at Crescent Bay and other breaks difficult, for one thing. It ranges from diurnal to the more NW standard of semi-diurnal tides. In my opinion the anomalies there are are more PHD worthy than current differential in tight embayments. Next time you see a Captain Jack's Almanac, look it up. Cheers, Rob G -----Original Message----- From: Craig Jungers <crjungers_at_gmail.com> To: rcgibbert_at_aol.com Cc: paddlewise_at_paddlewise.net Sent: Wed, Oct 28, 2009 9:04 am Subject: 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.B 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 *************************************************************************** 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/ ***************************************************************************
I was once expecting to go into the Straits of Jaun de Fuca on the flood and paddled into an ebb all the way to Neah Bay. I went quite a ways out from shore (1/4 mile or more) to see if I we in a near shore back eddy. It I lost ground to the group by being further out. I thought maybe the trip leader just had gotten the currents wrong. The trip leader was taking a ribbing about this already but he knew he had checked the currents and he was an experienced sea kayaker. When we got back home and I checked the currents he had been correct. I think there is a huge back eddy that forms there and I'm not sure the current flows anyway but out near the South side of entrance to the straits. *************************************************************************** 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/ ***************************************************************************
This archive was generated by hypermail 2.4.0 : Thu Aug 21 2025 - 16:33:52 PDT