Since I've no experience and no one to paddle with, I've been very conservative about how and where I kayak. Today I paddled across a short channel in the Johor Straits from mainland Singapore to a tiny uninhabited island called Pulau Seletar (scarcely a sand bank). The total crossing time is no more than five minutes. The interesting thing was that I could see the waves/ripples moving southeast through the channel, however when I paddled through it, perpindicularly, the boat actually was drawn northwest unless I compensated. I scratched my head about this one. The effect was actually amplified when I paddled back on the second half of the trip. A Sumatra (summer afternoon storm) kicked up, winds picked up, seas got a bit higher, yet the pull was as strong or stronger. I ended up paddling only using my northwest-side paddle just in order to stay on straight course to my target. So my hypothesis is that the current was moving from southeast to northwest through this small channel. The wind happened to be blowing the opposite way, which generate a bit of chop, and apparent wave flow, but the overriding dynamic was the current or tidal flow through this channel. I suppose maybe this sounds like a "duh... no shit..." sort of thing, but this is my first experience through currents and I want to make sure I understand what was going on. I looked at the Hydrophic Department charts Singapore publishes of the area and they don't indicate any currents on the chart, but perhaps they're marginal enough here for most vessels to neither notice nor care. From my readings of Fundamentals of Kayak Navigation (David Burch) it seems that relation between current flow and the tidal pattern are not as obvious as you'd think. Any good advice on seeing/reading tides and currents beside from just knowing the tidal schedule? In my case, I have a relevant tide station very near my paddling area: http://www.mobilegeographics.com:81/locations/5729.html I was there in the early/mid afternoon, which based on this chart for today (one day later) it seems that is one of the steepest changes on the tidal chart, so I presume I was experiencing strong tidal flow. Regards *************************************************************************** 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/ ***************************************************************************
Black Coffee 2002"<black-coffee2002_at_karavshin.org> wrote: > I looked at the Hydrophic Department charts > Singapore publishes of the area and they don't indicate any currents on the > chart, but perhaps they're marginal enough here for most vessels to neither > notice nor care. From my readings of Fundamentals of Kayak Navigation > (David Burch) it seems that relation between current flow and the tidal > pattern are not as obvious as you'd think. > Any good advice on seeing/reading tides and currents beside from just > knowing the tidal schedule? In my case, I have a relevant tide station > very > near my paddling area: > http://www.mobilegeographics.com:81/locations/5729.html > I was there in the early/mid afternoon, which based on this chart for today > (one day later) it seems that is one of the steepest changes on the tidal > chart, so I presume I was experiencing strong tidal flow. BC, You are on the right track. Indeed, Burch identifies a couple of oddball current/tide relationships, but almost all the time the tide follows the current ... meaning flooding precedes a high tide, and ebbing precedes a low tide, more or less, unless there is a river estuary involved. The problem is that the "flood" current moves from a tide station which has a higher tide to one with a lower tide level, as a first approximation. So, in order to guess at the current in an open passage (as contrasted with a passage that has only one end open to the sea) from tide information, you need __two__ tide stations. If you don't have that in your area, then about all you can do is establish empirically which direction the flood usually runs, and then key it to the high tide at the one station you have. You can even construct your own rough empirical relationship between the difference between these two stations and the current velocity, if you can measure the velocity at times when you know the difference (see hint below). A couple caveats: 1. The layout of the passage where you experienced this current, so the geography (and bathymetry) will also play a role. 2. In passages where the maximum currents are less than a knot, there is often no note on the chart, because a current this weak is of little consequence to a freighter or larger powered vessel. But, a beam current of one knot will set a paddler of hull speed 3 knots about one sea mile every hour ... a pretty large error if you are crossing a 3 sea mile passage at right angles to the current. And one hint: if you read Burch carefully, he gives you some angle measurements you can make with your deck compass to get a quantitative indication of the current magnitude. Yes, you do need a deck compass! -- 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/ ***************************************************************************
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