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.
Kirk, perhaps I am using viscosity incorrectly, the proper term might just be drag.
The problem I have with F = ma is that both the m and the a involved are horrendously complex, unlike with solids. Water is being accelerated backwards, and upwards and in all sorts of directions around the arm and the acceleration is highly variable between bits of the total mass. If you can't nail down the mass involved, or the acceleration involved, how useful is the equation?
Drag on the other hand is a simpler concept to deal with, it is just the force necessary to drive the arm through the water at a given speed, including all factors. You can predict that an arm moved through water that is already flowing in the same direction will have reduced drag and transfer less force.
Sorry for belaboring the point. :duel:
Kevin, those animations are very cool, even if I can't grasp what information they convey!
Sculling the hand at 14,000 RPM provides the same effect as does a propeller, but it may cause other problems.
Yes, like maybe some serious carpal tunnel syndrome. :D
It is a myth that the Shkval travels faster than the speed of sound. It exceeds 200 mph, but gets nowhere near 700 mph. The Popular Science article only says that the US Navy has tested a prototype, but it never says that prototype approached the speed of sound. Geochuck, the military.com article you linked to dispels the myth that this weapon approaches the speed of sound! Yes the Shkval is a very slow 253 mph underwater. Irans torpedo maybe a fabriction??? Do you really think this.
The word is there have been US tests at near the 770mph but this could also be a fabrication.
Is it revelant to how fast we swim. NO
I don't shave my body and I can see little bubbles all over my body where hair is growing when I take underwater pictures. Do you think these bubbles are similar to the bubbles made by these newer type torpedos.
The word is there have been US tests at near the 770mph but this could also be a fabrication.And the WORD is also that the technology used to build these super sonic Thorpedos was stolen from aliens that crash landed in the 50’s in New Mexico.:shakeshead:
Do you think these bubbles are similar to the bubbles made my these newer type torpedos.NO.:doh:
Sound of speed in Water is something like 3000 Mph or is it 3000 knots per HR??
In fresh water, sound waves travel at 1482 meters per second (about 3315 mph). ... The exact speed of sound in steel is 5960 meters per second (13332 mph)
Iwanafly said it very well - “The bottom line is that the swimmer must minimize drag along his/her body, but maximize drag on the pulling surfaces (forearms and hands).” A definition of eddie current is ; “a current, as of water or air, moving in a direction that is different from that of the main current. Eddies generally involve circular motion; unstable patterns of eddies are often called turbulence.” The turbulence created as a swimmer moves forward and surrounds the body is an eddy current, the turbulence behind the hand is called a vortex which creates a drag force not conducive to propulsion. It’s also important for swimmers to clean/clear their hand of air because it also decreases drag or the ability of a swimmer to hold or leverage water effectively.
In order to maximize drag, like Iwanafly says, your hand must stay away from turbulent water. It’s not a freakish or weird theory. Ernest W. Maglischo, spends three pages on the Vortex theory. In the first chapter “Increasing Propulsion” from his book “Swimming Fastest – The Essential reference on technique, training, and program design” Ernie devotes over 40 pages on this fascinating topic (propulsion). Dr. James Councilman’s and his timeless book “The Science of Swimming” also spends a lot of time helping swimmers and coaches understand the importance of fluid dynamics and how it relates to competitive swimmers. If swimmers and coaches would read these two books the complex world of fluid dynamics becomes more clear. It is indeed complicated but not incomprehensible, even to guys like me.
As swimmers we would all like to become more efficient and faster. All coaches should have a solid understanding of stroke mechanics and how physics plays a role in swimming faster. Teaching swimmers how to reduce resistive forces by streamlining the best they can, and getting them increase propulsion by pulling and kicking with the best possible technique should be the mission of every swim coach.
So, how you pull your hand and position it as it travels through the water is important for fast swimming. Don’t over-exaggerate the “S” pattern, avoid stopping the propulsive mechanisms by gliding, clear the hand of air as you enter it into the water, set-up your forearm and get it vertical early, find a pulling pattern that is the most effective for you (improve your DPS), improve ankle flexibility and core strength, and train smarter not just harder. Good luck, Coach T.
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.
Still it all boils down to F = ma. If you aren't accelerating a mass, you aren't creating force.
As I said, drag your arm through the water at a constant speed, this will require force even if your arm is not accelerating.
Yes, because you are accelerating the water surrounding your arm due to the viscous shear. I still think it's F=ma whether we're talking about viscosity or not.
The pitch of the hand is ineffective unless it's moving toward or away from the mid-line (sculling).
Huh? Please explain.
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. However, your hand is already describing more or less an arc when viewed in a sagittal (i.e., "side") plane. So aren't we already getting that effect even without the "S" pull?
I just looked at Cecil Colwin's Breakthrough Swimming to see what he says about it. Not to say his view is definitive, but here's a quote:
Although the swimmer tries to pull in a direct backward plane, the rotation of the body on its long axis causes the hand and forearm to move laterally inward and outward under the torso. This action produces a natural sculling effect as the hand pitches inward across the body and then outward to round out the stroke at the side of the body...
