I have been studying videos of swimmers and find what was once called the "S" stroke has almost disappeard.
I have noticed that flyers use it. But crawl swimmers have modified it so much that it is almost gone.
Has it been replaced completely or was it an optical illusion? Did underwater film show us it did not exist.
We can talk physics, hydrodynamics, insertion without bubbles, low pressure , highpressure, etc. But when it comes down to swimming you have to have a true feeling for the water. We are not a boat with one drive force. We have many moving parts and it still is going to be trial and error.
We are definitely in a situation where fluid mechanics has not caught up with human propulsion in the water. I think coaches throwing around half-cocked theories of propulsion tends to slow down the effort to explain what is going on. In all the hoorah about lift forces for propulsion I saw exactly one study with numbers on it referenced. For shed vortices, none.
Ernie Maglischo in swimming fastest references some computational fluid dynamics studies showing that a slight side to side motion creates more propulsion, but not because of lift, it actually improves the drag forces on the hand as you pull.
If we are to get anywhere, for now it looks like the computational fluid dynamics will help us. But these things are fiendishly difficult to solve and take real horsepower. The ones listed here (projects.seas.gwu.edu/.../MAIN.htm) take 20 days or so to solve.
So I think we are left trying to feel the water and get a better purchase on it, we are also left having to discuss with no real science to back us up.
Tom - sound travels faster underwater depends on temperature of the water and whether it is fresh or salt water.
Make a noise underwater it travels at over 3000 mph.
Above water on land sound travels at 770 mph.
Really it has nothing to do with swimming unless your coach is yelling at you.
I understand what you're saying with the "quiet water" thing. When you start pulling, you accelerate the water behind your hand. To create additional propulsive force you need to find additional quiet water to accelerate. If you just continue to push on the already accelerated water you don't produce any additional force.
It has always seemed to me that many people in the swimming world use a rather simplistic if not misguided model of swimming physics. It seems like viscosity and drag are more appropriate tools for thinking about swimming than acceleration of mass. I think you will find that if you move your arm through water there will be plenty of force due to drag even after you have supposedly accelerated the water behind it. Another way to experiment with this is to put your arm in a horizontal position under the water and lift it up out of the water, observe how much of the water rolls off your arm instead of moving with it. Or stick you hand just under the surface and then throw some water up in the air, compare the force needed to accelerate the handful of water to the force needed to move your flat hand through the water at anything like an equivalent speed. I am open to being proven wrong but I don't think acceleration of mass is the dominant force to be thinking about, and certainly the idea that force goes to zero after you have accelerated the water behind your hand is just plain wrong and easy to disprove with a simple experiment.
I was at a Masters clinic yesterday at the University of Washington. One of the coaches (Thomas Hannan) said that the S-shaped stroke still occurs when you look at your hand position relative to your torso, when you take body rotation into account, which is similar to the quote that Kirk referenced.
Right - the "S" Stroke is still there but is hidden by the fact that most swimmers of to day are rotating the shoulders and it no longer looks like an "S" Stroke. Now does this fool us into believing we are doing an "I" Stroke??? I happened to see George Breen doing the big cross over stroke that Coucilman called an "S" stroke and was it ever a cross over with George Breen's almost scissor kick.
Do we have any quite water?
When the body moves through the water where does the water go. Some goes forward then it goes out, then it comes back and fills the void made by the body.
Once the shoulders pass through the water its starts roaring in to fill the void. We are not built like a boat pointed at the front end and wide at the middle and back end. The arms are our paddles and are not the pointed end of our vessel. Our width is from the head to the stomach where it is narrow again, wide again at the hips and then narrow at the back end. Then what some call the second wave really pours in to fill the void made at the middle and the back end. Now that water is moving towards the front. Now this is where the stroke starts to press on water going in the opposite direction. Firby always talked about this second wave with me we differred on what it was doing and how we could use it to our benifit. The so called second wave is the reason most sprint swimmers kick hard to use the second wave.
I think I like to use the water that is moving in the oppsite direction. This is why I mention the bow wave water. This is not the water that sets up that pretty "V" going out to the sides. I am talking about the water that is moving forward.
I don't need to listen to biomechanics. I can feel that water.
I don't need to listen to biomechanics. I can feel that water.
I would definitely trade my limited knowledge of hydrodynamics for better feel and kinesthetic awareness.
I only comment on physics when it seems to me that people are explaining swimming things using physics that seem to me not to be valid. I find the physics of swimming to be interesting but probably quite difficult to actually usefully apply to actually swimming.
We can talk physics, hydrodynamics, insertion without bubbles, low pressure , highpressure, etc. But when it comes down to swimming you have to have a true feeling for the water. We are not a boat with one drive force. We have many moving parts and it still is going to be trial and error.
I once read an article about the dolphins and how their skin movement helped them swim. It talked about the ripple effect of the skin. This may be our next great breakthrough. I have read articles about shark skin and it's effects on movement through the water.
The US Navy and there new torpedos that will move through water at the speed of sound.
Still lots to come to make humans faster in the water.
Still it all boils down to F = ma. If you aren't accelerating a mass, you aren't creating force.
Not all forces are the result of the acceleration of a mass. I think you are overlooking viscosity.
If you are pushing, the water is pushing back with an exact equal force.
Even working just with F=ma, any water you have accelerated is in turn running into further water that has not yet been accelerated.
As I said, drag your arm through the water at a constant speed, this will require force even if your arm is not accelerating.
