"Question for you to ponder...Why is it that many of the most modern general-purpose canoe designs have slight rocker in the bow and less or none in the rear - but you never see one designed the opposite way. It isn't because inexperienced paddlers have trouble making a canoe turn... "
This has nothing to do with upstream or downstream travel, but everything to do with how the boat streams through the water while under power, and how easy it is to control as that is happening. Again, all the boat cares about is its interaction with the water that goes streaming by the hull. Which way that water might be moving is of no consequence in terms of boat-handling, for the same reason you can walk in any direction inside a large moving vehicle, such as a train or cruise ship, as long as its velocity is constant. You can even go bowling on a cruise ship, but you don't need to apply any special "English" to the ball. It's just like bowling on land. Same principle applies to paddling a boat on smooth, flowing water.
If more people had a rudimentary understanding of physics, fewer people would attempt to explain the movement of boats in ways that defy the laws of physics. Of course, none of this affects a person's ability to control a boat because they respond in ways that they have learned will work, but it does affect their way of interpreting what they see.
that’s what interesting about this site is you’ve got people from different paddling backgrounds interpreting scenarios from different view points. The amazon felt like a giant floating sheet cake. And that was intimidating to me. Its power was very deceptive. Flat but fast and totally out of my frame of reference. Each boating subgroup has its point of view. Of course the one that is right is the one that works within your own defined reality. For me that’s a dry hair day although Floating the currents in darkness does sound appealing.
Maybe not related to upstream… …but definitely related to efficiency and the ability to keep the boat on course, I think. Put one such boat on a flat lake, and paddle it backwards and forwards (from the middle). Which way will be best?
No one rockers the front and skegs the rear to facilitate turning.
The topic is not related to what I was talking about.
For what it's worth, Charlie Wilson has done a better job than I ever could of explaining the reason for this type of hull design. Some of these boats ARE designed to be paddled by amateurs (the Bell Yellowstone Solo might be the most extreme example), but for most of them, there's more to it than that (and in both cases I'm only parroting what Charlie and another person here have said about this).
Back to the “upstream” OP Everything that’s been said in this thread so far rings true. But what started this whole discussion was a post from someone who’s bow was getting pushed into a ferry when he tried to paddle upstream. It’s kind of silly for us to quibble over whether such a thing happens on a broad flat river or not (and I’m not sure that we really are quibbling about that) when the OP in the thread that started the whole discussion implies pretty strongly that is what was happening to him - indicating to me that his river isn’t all that broad.
No question in my mind that when going upstream on a smaller river the induced ferry happens if not corrected properly. And no question in my mind that even an intentional ferry requires some maintenance for as long as the current speed or direction changes as the channel is crossed - which can essentially be for the entire width of the river if that river isn’t very large.
Also no question to me that a heavy bow will amplify the effect of the turning forces on the bow. And it’s pretty clear to me that the most efficient attitude (sans wind issues) is trimmed evenly.
Right?
What I (and, I think - we) don’t know is why those Amazon paddlers seem to favor sitting in the bow when solo. I seriously doubt that it has much to do with anything related to recreational paddling in modern canoes.
"...how is it possible that a weighted bow in upstream current will result in an inability to go straight? I still don't get that. Its asserted that weight in the bow creates resistance and heightens turning. I find it difficult to turn the boat in that scenario."
The reason we are confused is that we are talking about different rivers. As GBG points out, if the river is broad enough, the boat will act is if it's on a (moving) lake soon after leaving the bank. In this case, bow heavy inhibits turning (if not exaggerated, as in the Knight demo).
If the river is small enough, the current is in flux as you cross it - sometimes all the way across the river. If the channel is arrow-straight, the current starts out weak at the bank, gets faster as you go towards the middle, and then grows weaker again as you approach the opposite bank. Throw in some bends, boulders, and other eddy-making devices, and it changes all over the place.
The OP in the "upstream" thread didn't hang around for further clarification - but I'm guessing from his description that he was suffering from a common problem with someone new to upstream travel on a small river. Either lacking eddies or lacking the knowledge to use them, the boater attempts to drive up near the middle of the channel (to have enough water to paddle, to avoid "suckwater", to avoid other obstacles near the bank, etc.).
Upon loosing control of the bow because of current differential, the boat is pushed into a ferry towards the opposite bank. Reaching the slower water, the boater easily corrects to head back upstream, but gets too close to the faster current again and ends up ferrying the other way.
The reason this happens (until he learns to control it and/or avoid it) is that the stern of the boat is in slower water than the bow as it crosses the faster current towards the middle of the river. As long as the length of the boat is crossing differential current (edit: with the bow leading into faster current), it will try to turn downstream.
If the bow is heavy, the boat in the latter situation will respond more rapidly and strongly to the current differential. If the bow is light, the boater can correct for the differential with less effort (edit: - or at least less skill). The differential and it's turning forces on the boat will always be there, regardless (in a small enough river).
In GBG's example of the broader river, the bow and stern are in water that is all going the same speed - so no turning force is applied.
Regarding the the fact that those Amazon paddlers seem to sit in all sorts of different parts of the boat when they paddle, here's something that occurred to me this morning. Siguard Olson was always perplexed as to why native Americans he encountered during his canoe trips in Canada would make camp for the night in the most God-awful locations imaginable. They'd camp where they had to walk around in the mud among thick undergrowth and hordes of mosquitoes, when 1/8 of a mile a way they could camp high and dry, in the open where a breeze would thin out the bugs, and they'd have a gorgeous view of their surroundings to boot. It turns out that these people would simply set up camp wherever they happened to be when the decision was made to camp, even if the campsite totally sucked (by white-man's standards) and a "good" campsite (again, by white-man's standards) could easily be seen just a short distance away. Well, MAYBE these Amazon paddlers have a similar approach to paddling their boats. MAYBE they put as much thought into choosing their paddle station as their northern counterparts put into choosing a one-night campsite. "I'm in the boat, sitting right here. Therefore I can paddle from right here. Why would I move to that other spot in this boat to paddle when I can simply stay where I am?" This is only a wild guess, but one which takes into account the possibility for a drastically different approach to life, as often occurs in different cultures.
On a similar note, ask any good archer if he thinks the shooting techniques of South American natives he's seen on TV documetaries would be considered "good form", similar to techniques known for contributing to high accuracy, or if using arrows that are three-times longer than the draw length of the bow makes any sense from the standpoint of accuracy. Techniques that are thousands of years old are not always examples of the best that can be thought of.