Eric--- I didn't credit FlyWright because I didn't see his post until just now. And he makes sense to me. It certainly explains why when we have the currents mostly with us on a run into the islands, the trip is really short (comparatively speaking), while when it is mostly against us the trips take forever even though the actual SOG differences are not that great. It's because of the extra time we are bogged down going slow.
This next is really long, even for me, but I'm waiting for a computer so have a bit of time. Please skip it if the length is too intimidating.
There is another aspect affecting why positive and negative current effects don't mirror themselves on a trip up (or down) the Inside Passage that I'm amazed nobody from here seems to know about since nobody's mentioned it (unless somebody does while I'm writing this.)
It's a very complex concept so I will attempt to break it down into its simplest components for those to whom the behavior of water continues to be a mystery. It may seem overly basic to some but apparently that's what's needed here for some folks.
The moon, gravity,earth's rotation, and a bunch of other stuff cause the water in the oceans to move around. When it gets pushed in our direction up here along the northwest coast the level of the water goes up. When it gets pushed in someone else's direction the level of the water level along our coast goes down.
When it's pushed in toward us the level of the water when it's as far up as it's going to go is called high tide. When the water is pushed away from us and it's reached the lowest point it going to go, that is called low tide.
The difference between the height of the water at high tide and low tide is called the tidal range.
So far, so good, right?
Now when the water is going out as it's pushed away from us, or is coming in as it's pushed towards us, that movement of water going in one direction or the other is called current.
Now it starts to get a little tricky so I'll write slower to make sure people can follow along.
The tidal range varies. Yes, I can tell from your reactions that it's hard to believe, but it does.
It varies day by day, week by week. Some days there might be a real big tidal range, the next day, not, or there could be big tidal range between low tide and high tide but a small range between that high tide and the next low tide.
Some parts of the month might see high tidal ranges, other parts of the month might see relatively low tidal ranges. And in this part of the world, with four tides a day, there can be high tidal ranges and medium or low tidal ranges within a single 24 hour period.
Now, because the tidal range is always varying, it follows that the current varies, too, since the current is created by the water action that's causing our high and low tides. So when the tidal range is large, the current is what we call, what do you think class? SomeSailor? That's right, strong.
When the tidal range is small, the current is what we call weak. Very good.
I'll give you a minute to wrap your head around this always varying tidal range business and how it affects the current.
Okay. Now this will seem unrelated but it will all come together in the end. It takes an eight-knot boat, running every day, all day, only in the daytime, in May (relevant only because of the length of the days) ten days to go between Bellingham and Ketchikan (or the other way if you prefer). This is assuming no weather or mechanical delays.
I know this because we know a fellow who used to run an eight knot charter tour boat between Bellingham and Ketchikan in May for a number of years for the summer season and then back again in October. He told us that on those occasions where he had decent weather the whole time and could run every day, it took ten days.
But most recreational boaters will take longer than that. They have weather delays, they visit places, and so on. So they may take two or three weeks or a month or even more to get up (or down) the Passage.
So now we're going to put all this together. It's a hard, complex thing to grasp but I'll do my best and write really, really slow.
We have tidal ranges that are varying all the time. This means that the currents are varying all the time. Some parts of the week or month might see stronger flood currents during the day than ebb currents. At other times, there might be stronger ebb currents during the day than flood currents.
So a person running a boat up (or down) the coast over a ten day or two week or even one month period of time is not going to see mirrored currents every day. If they did, what SomeSailor and others believe would be correct.
But depending on when our boaters goes, depending on where the tide cycle happens to be, depending on how much his plans are messed up by weather or other delays, our boater can spend more time bucking adverse currents than being pushed along by following currents.
Or it could be the other way around.
Which is one reason why, in taking a boat up (or down) the Inside Passage, you cannot count on, and most likely will not experience, the effects of currents going against you being balanced out by the currents going with you.
If you're lucky you might spend more time in following currents than adverse currents. But if the adverse currents are consideraby stronger than the following currents, which they can be, this can negate and even remove the advantage of the extra time in the following currents. And of course it could happen the other way.
Couple this varying current strength business with the geographic effects on local currents which I talked about before--- and the calculations that FlyWright did for us--- it becomes very obvious--- at least to me and the people I boat with--- that you can very easily spend more time going up (or down) the Passage than you throught you would and burn more fuel than you thought you would.
It's true you could spend God knows how long calculating every current in every channel at every time of the day for entire window of time you think you might be enroute so you can determine exactly how long it will take you and how much fuel you will use. Which would take forever since much of the local area current information is not in the books and may not even exist.
But I've never met anyone who does that and we won't if the day comes we take our boat up (and down).
Everyone we know or have talked to who has done the Passage does fairly basic calculations based on the distances and the rather skimpy current detail that's available for the Passage, particularly the middle part, arrives at "it will take us about this long and we'll use about this much fuel" figures, and goes. And in all the cases we know of personally, it always took longer and always required more fuel than the boater figured, which they all atributed to the effects of the currents they encountered along the way.
If you want to talk about a round tripto Alaska and back, it's possible that whole run could end up without, or with a very small, impact from the currents, assuming both runs were made under similar tide and tidal range schedules.
But I've been talking about a one-way run as it relates to the range of our boat and why we can't make it on one load of fuel even though we theoretically could (barely).
Our dog, a Little River Duck Dog aka Nova Scotia Duck Tolling Retreiver, the official dog of Nova Scotia, has a maritime heritage that goes back hundreds of generations. So this whole tide-current-variation business is in his genes and is part of his inherent instinct. Which is why he was able to explain it to my wife and I so succinctly. If you don't have a water dog but have something like a dachshund or a Scotty or something, he or she may not be of much value in this regard.
But prior to Albi spelling all this out for us, I spent a few years crewing on a co-worker's racing sloop here in Puget Sound. And in my opinion there is no better way to gain an appreciation, if not an understanding, of what the currents are like in this area, particularly how local currents can affect one's progress, than challenging them with a sailboat, particulalry in a point-to-point, long distance race when you are actually measuring the effects of the constantly changing currents against the shoreline and the other boats in the race.
The only other thing that will give one the same or better appreciation and eventually knowledge is, in my opinon, kayaking (which I have never done).
