I was thinking about this yesterday when running a twisty creek where the current was so slow it didn’t matter.
But after all these years I realized I really don’t know the answer to this question:
What is the fastest way to run (race) down a river with good current and lots of bends – staying in the faster current on the outside of the bends, cutting through the shorter route in the slow water on the inside of the bends, or some sort of “split the baby” compromise route?
Dunno
on the outside, sweepers can ruin your time…
on the inside, around every curve can be an eddy…or a gravel bar…that can ruin your time too.
depends on each bend
– Last Updated: Jun-03-13 10:05 AM EST –
How much distance is saved by going inside vs. the lack of current or strength of eddy on the inside?; if there's an eddy on the inside, is there a line you can take to miss it?, EDITED to add: What is the strength of the current (inside or outside) in this particular spot vs. my strength to muscle through on the inside -- can I gain an advantage by staying inside?, etc. Gotta read the river as you go. (I ain't no racer, so I offer this as 'discussion" vs. answer). Most often, I do stay in the current. Perhaps enter the bend just a bit toward the inside so you can read and make a quick move either way (perhaps to avoid that strainer on the outside!) Answer: no pat answer -- skills and experience reading the river. (my 2 cents or less)
Forget dangers and obstructions
My question only relates to the fastest way to run the current over the course of the entire twisty race.
I assume downriver racers have doped this out long ago.
My own general instinct is to run more in the middle, sometimes a little closer to the outside, sometimes a little closer to the inside, depending on the sharpness of the bend. But this isn’t based on any data or theory.
Theoretical rivers my have no dangers
– Last Updated: Jun-03-13 10:13 AM EST –
but in real life I can't and don't want to forget dangers and obstuctions. And my take on it was: there ain't no theoretical answer that could be doped out; you have to read the real river (which must include potential dangers and obstructions) in every moment. (I guess in race courses where all dangers and obstructions have ben removed, it's different, but there still is the point that every bend is different and the speed to be gained inside or outside can't be a pat answer).
I should just shut up now and let racers answer.
Rule of Thirds
– Last Updated: Jun-03-13 11:06 AM EST –
Depends a lot on the river of course. I race "flat" but moving small and large waters, including the Yukon, which is a completely different beast from the others.
For relatively small narrow rivers (creeks) with current, such as Brown's Tract (my personal favorite stretch on the "90") on the Adirondack 90-miler, it is all about maintaining speed and timing of anticipated track line, especially when overtaking another racer. The outside current can just as easily plaster you to a dead stop bow first into a mud bank as it is to help you, if you are not adept at heeling your boat into a turn at speed. You have to plan ahead a turn or two to put yourself in the best position to pass, and to be good enough to out maneuver them on the curves. Living on the edge, a single misplaced stroke at speed can make all the difference in a smooth turn, or in planting you in a mud bank or mud shallows. The inside cut may put you into a shallows of mud, or it may not, it just depends. Even with current, eddies are not really a factor in fast turning narrow Brown's.
For slightly larger rivers, an experienced racer once told me about the "rule of thirds" as the primary rule of thumb. Start with that thought and adjust from there. This works well on rivers such as the Raquette or somewhat larger rivers with slow to moderate current. If you stay about a third of the distance from either inside or outside bank, you end up making the same time for fastest transition around a bend. Faster current on the outside but greater distance equals slower current with shorter distance around the inside of the bend. Adjusting of course with experience, degree of bend, and knowledge of that particular river's characteristics. Seems to work pretty well.
For Yukon class rivers, read the current, read the current, read the current. The river literally "boils" with upwelling colliding currents. Moving over left or right just a couple of boat lengths may gain you 2+ mph, but you can't waste efficiency by needlessly hunting for where that might be. Look and read the surface. Viewing how the convoluted surface flow constantly changes, and looking ahead to see what shoals and islands will do to the current direction is all important. Current tends to be faster on the side of the river with steep mountainsides to the river's edge, shallow slower current is on the gradual landscape side. And especially know about "helical currents". You can easily find yourself either in the wrong channel around an island or obstacle, or simply being swept an extra half-mile to the outside of a wide bend, and you may not be able to paddle hard enough to counter it if you act too late. You can easily lose a whole mile of distance and many minutes of hard fought time. Read the current and anticipate way ahead where to expect to see the current breaks as it splits into different directions, as much as a half mile ahead is not too far to choose your best current/time line. Helical currents, very important.
Racing upstream? There is a completely different set of considerations and techniques.
Understand current, deposition, sediment
– Last Updated: Jun-03-13 12:14 PM EST –
Cutting the corner could destroy your time,
depending on water levels and float of the boat.
http://redrundrain.files.wordpress.com/2011/12/helical-flow-in-river-bend.jpg
Helicoidal Flow : a corkscrew movement in a meander bend
of a creek, stream, river.
This is what moves material from the Outside of a bend
and deposits it on the Inside of the next bend.
Interested in learning more about streams, creeks, rivers, etc ?
Flip thru the technical stuff - see the pics
http://www.slideshare.net/maliadamit/river-channel-processes-landforms-1026801
Generic, easy to understand, simple explanations
Just did some racing on the Shiawassee River
this Sunday in Holly, Michigan.
Aerial Video of Shiawassee Races
http://youtu.be/yzugZmjQX-k
Speed in bends
There is a very complex set of variables involved here. And experience is still the most valuable asset.
Going inside is usually the route to pass others, but you may need to up your effort a lot to make up for the slower current and shallower water. Being passed you can often shake off the passer by forcing them way inside onto very shallow water, or on the wrong side of an eddyline in a deeper bend.
To save energy on a fast moving stream we will run the C-4 in the faster deeper outside current. Using the gradual bend means we can keep more energy going into forward motion and less into directional thrust.
A really tight stream like Brown’s tract that has only a boat wide channel flanked by shallow flats and floating vegetation is really tough with a long boat or a hull with a vertical bow to catch the vegetation.
Even boat displacement comes into play on bends. A heavy boat that really bogs in suckwater loses a lot of speed on the shallow inside track, and you put a tremendous amount of energy into maintaining speed. For a couple of turns its now problem, but for a stream with hundreds of such bends you wear yourself down.
We raced head to head from Axtons Landing to the Crusher in our Minnesota IV against an experienced team in a Minnesota III. They would go inside of us on every turn and we would come out with our bow on their stem. In the straights we would gain back the lead and enter the next bend with their bow on our stern. Only a boat length of separation at the finish. But next day they could hardly paddle. The price paid for all the effort expended in the shallow inside water by a team of 50+ paddlers. We made up 5 minutes on them the last day, they were just spent. Our ages were all 55+.
Sorry to not be able to give you a cut and dried answer, but there isn’t one for all streams and canoes. River by river maybe a guide of stay inside or stay outside, or follow the thirds rule above, it will give you time to go either way as you see what the water is like going thru the bend.
Bill
I tend to hang on the outside bends
– Last Updated: Jun-04-13 10:45 PM EST –
mostly because I'm lazy....errr I mean efficient. Here's a case for outside bends: 1)tends to be deeper (I paddle a lot of shallow places), 2) water tends to move quicker and thus it is often faster and 3)it requires less effort to move down a river if you stay in the current. I'm not very fast but I do try to maximize the use of whatever current exists. All that bein' said, I also found myself cuttin' corners on Brown's Tract because the turning radius was small. In other words, that's the way I could make the tandem canoe fit on that twisty creek. I used the inside eddy to help turn the boat. The primarily disadvantage of paddling on outside bends is that it tends to be the place where strainers collect because that's where the most shore erosion occurs. Paddling around wood can be inconvenient, slow you down, and even dangerous. All the above bein' said, the most efficient way to move down a river is by staying in the current. Ask any rafter. Tryin' to move one of those tubs ain't easy. If you got little or no current, flat bendy water, just go straight. It ain't gonna matter. Now shore eddies is a different topic, you don't want to hang that close to shore unless you're attainen'.
It’s all about the skill "River Reading"
Experienced paddlers can just look and see the channels of faster moving water. Ferrying and back paddling are essential skills to move into the faster channels. It takes several seasons of practice to get it down, even so, nobody can tell what’s around the next bend in the river.
Phyics answer for idealized river
– Last Updated: Jun-03-13 5:03 PM EST –
It may be that "it depends" is the best possible answer for a real river, but I think there has to be a physics answer for the idealized river.
Imagine an sinuous river channel made of stainless steel. There are no obstructions in the river or on the banks. No erosion. No sandbanks. No rocks. No trees. Just an empty sinuous stainless steel channel.
Imagine you are in a boat, with sufficient skill, such that you can pivot smartly around any bend and never be swept into the outside bank.
We KNOW the current is fastest on the outside of every bend. We KNOW the distance is shortest on the inside of every bend.
Assume you expend the same amount of power per stroke whether you go on the outside, the inside or in the middle.
How do you run the bends to run the entire river in the fastest time? It just seems there HAS to be a physics answer.
Why isn't the answer: a cork. Throw a cork in the river and see how it runs each bend. Wouldn't it tend to stay in the fastest line of current? Of course, the cork is not powering itself. However, if the paddlers are expending the same amount of power per stroke (X power) no matter what line they run, wouldn't they then be wise to follow the same line as the cork (under 0 power)?
If the cork hypothesis is true, what line does the cork run? I don't know.
Build it and we will all come to see it.
Glen,
When you get done with building your ideal Stainless Steel River of “ideal” gradient and with “ideal” radii, let us know and we will all show up with personalized corks and run many statistical repetitions to find out if corks predict canoe behavior.
Bill
Depends on the speed of the current
– Last Updated: Jun-03-13 5:37 PM EST –
It's a "simple" optimization problem :) If the current is sufficiently faster to compensate for the longer distance, then you go out. If not, stay in. Even the idealized river will have different optimum paths depending on the width of the river, how tight the bends are, and the speed of the current... So, no one answer, unless someone has figured out the mathematical model for this and you can plug-in your numbers in it, to get the definitive answer for a set of criteria that define your river.. Then add conditions for how hard you want to paddle, how fast and how efficient your boat is, etc. to get to the optimal answer for you paddling that ideal river....
That makes sense
On a really, really slow stream like the swamp I was in yesterday, it seems obvious to me that I can reduce my time by cutting corners. The current differential between the outside and inside currents is more negligible than the distance differential.
Conversely, if a very fast current is really ripping around the outside of the bend and is virtually stopped on the inside, it would seem that staying outside would be faster.
But I think the width of the river plays a role, too. If we have a huge river that is a mile wide, it’s probably faster to go around the inside of a big bend even if the outside/inside current differential is pretty large.
Catch the Eddie Line
It’s that fine line between the outside current and the eddie. That is what I do. Always successful? No but many time yes.
dougd
My experience
I don’t race,but have tryed many methods on the Osswagochie for making the sharp turns the easiest. I found that with a boat that will carve a turn well(flashfire,Echo),going upstream ,I could steer around corners mostly by heeling the boat,staying app in the middle. I needed little paddle correction. After making that great “discovery”,my joy was shattered by finding it didn’t work at all going downstream. I still havn’t found an easy way to do that and keep much speed.
Turtle
Cork experiment
Out of curiosity, why would you expect the cork to follow the fastest line of the river?
On a typically narrow twisty river. …
the way we do it is to cut the corner, but before you get around it follow the current out toward the middle and then try to stay in the center of the “V”.
If you keep cutting and don’t do that you’ll end up getting pulled into the eddy, and hopelessly watch the other boats go by you on the outside.
Our favorite is the Edistoe in SC where we have that down to a science.
Another good one is the North River up in Mass.
Someone above mentioned Browns tract in the ADK 90. We pass a half dozen boats there just by doing what I describe above.
I love racing narrow twisty rivers, especially with my bow paddlers expertise on cross bow rudders, draws and posts.
Jack L
A corking good question
I don’t know that all corks would follow the line of fastest current. That may depend on where they were initially dropped in the river.
Here’s what I had in mind. Place the cork in the exact center of the river on a straight section. This should be where the fastest thread of current is. Will this cork stay in the fastest current thread as it goes into, around, and out of a bend?
I don’t know, as I said, but for some reason it sounds plausible to me.
Corks might be smarter than sticks
– Last Updated: Jun-04-13 8:35 AM EST –
I commonly see sticks laying in eddies, but they may not have the same down-river speed goals as corks.
You are right of course. If the water takes multiple routes at a variety of different speeds, anything supported by that water will go where "its" water happens to take it. Then throw in spiral currents which at the surface cut diagonally across the "average" flow direction and the opposite diagonal direction along the bottom, and when a particular stream of spiraling water dives to the bottom, whatever small object (like a cork) that was floating along that line is now stranded, unable to follow the main flow. I think that usually means getting stuffed into the reduced-flow zone that's right against the vegetation or roots along the outer bank, based on what the current in deep-channel bends tends to do to small boats. This would be easy to look up though. I've seen a bunch of diagrams of this spiral flow - I just can't remember if the flow at the surface is diagonally toward the outer bank or diagonally away from it. I THINK it's toward. Maybe I'll check later. Anyway, the point is, a small floating object can't actually remain within a main stream of current on account of that spiral flow around bends, but your boat can stay in the main stream because it's being steered and not blindly following off-angle currents.
Okay I checked, and spiral currents on bends are directed toward the outer bank at the surface, and toward the inner bank along the bottom. In fact, it turns out that the deposition on point bars comes in part via erosion of material from the outer bank, carried diagonally across the river bottom to the inner bank (the material within point bars doesn't only come from farther upstream). There's one river near here where spiral currents on the bends are particularly apparent, but on most rivers I usually only notice it when I pay really close attention, and sometimes not even then.