Where is the greatest resistance?

RE: Where is the greatest resistance?

Former Member — Fri, 29 Jan 2010 17:11:19 GMT

Thank you Allen for the good points. Your square vs. cube comparison prompted me to an observation (maybe?) that beginners usually work on the form drag, while advanced swimmers work more on the wave drag? One reason I do head-up breaststroke is to avoid the unknown stuffs in the pool :cool: Edit: Thanks scassady--just saw your reply. Thanks for the article--going to read it.

RE: Where is the greatest resistance?

Former Member — Fri, 29 Jan 2010 17:05:07 GMT

I agree with the discussion on hydrodynamic resistance for swimming primarily being made up of form resistance and wave drag. Another interesting article can be found at: www.swimalberta.ca/.../morphology_and_hydrodynamic_resistance_in_young_swimmers.pdf One other thing to consider might be for all the physiological power your body is capable to put out, what is the most efficient. I see the challenge as trying to tune the insweep/recovery/breath to minimize the up motion and get momentum energy moving forward.

RE: Where is the greatest resistance?

Former Member — Fri, 29 Jan 2010 15:50:45 GMT

As Matt Mann told me many years ago, Swim Down Hill is to get the body up on top of the bow wave and swimdownhill. This was his theory of popping out of the water after a turn or dive and get on top of the bow wave. Others have a different idea of what swimming down hill is.

RE: Where is the greatest resistance?

Former Member — Fri, 29 Jan 2010 15:41:07 GMT

Here's an interesting tidbit. If the body of a swimmer doubles the depth (sinks) as they swim, it would take eight times the power or effort to maintain their speed (peak). So when you body sinks (even a little bit) and as you increase your speed, frontal resistance is killing your speed.

RE: Where is the greatest resistance?

Former Member — Fri, 29 Jan 2010 15:33:43 GMT

One way to think about wave drag is in terms of the force needed to lift all the water in the wave that is above the normal surface level. Water is heavy and it takes a lot of energy to lift all the water in a large bow wave.

RE: Where is the greatest resistance?

Former Member — Thu, 28 Jan 2010 14:46:07 GMT

Now I have a question: why, then, in freestyle, one should not have the head completely immersed in water, but keep the water level at about the hairline? Is it because it would be hard to turn to surface to breathe? So if one doesn't breathe, would it be faster to bury the head underwater? When doing head-up breaststroke, I feel I'm faster than the regular breaststroke (head popping up and down)--never timed, so I don't know, though I spend more strokes in head-up. Maybe it's just because I can see the scenes passing by? :rolleyes: Or maybe I wasn't swimming the regular breaststroke right (my feet tend to be out of water) :(

RE: Where is the greatest resistance?

Former Member — Thu, 28 Jan 2010 14:44:07 GMT

Cutting down resistance. I have been experimenting with my breakout from a dive or turn on freestyle. The first stroke being a two arm butterfly stroke. Then leaving the one arm at my side to get back into regular crawl. I have noticed a 0.5 time improvement in my times per length. Now maybe this is because I am overweight. It makes me pop out of the water like I used to in the old days when I did my deep dive. After I pop out I seem to have a better body position for swimming. Two things Matt Mann told me in 1952. He said "You must learn to swim down hill, and when you dive in or when you exit a turn you must pop up out of the water."

RE: Where is the greatest resistance?

Former Member — Thu, 28 Jan 2010 13:29:37 GMT

Thanks all for the comments, and thanks to Steve for the great article (just starting to read, but at first look at the pictures of the marine mammals, I like to be the Florida manatee :D). Water surface tension and wave formation make a lot of sense. I wonder if the wave formation factor applies more to good swimmers than the bad ones, because a good swimmer can make "good" underwater waves for himself, while for someone who can't swim well, he can't move much anyway, whether on surface or underwater. Does this sound like a reasonable conjecture? :rolleyes:

RE: Where is the greatest resistance?

__steve__ — Thu, 28 Jan 2010 12:16:30 GMT

Something about wave formation on the surface that it creates extra drag. Moving about under water of course creates drag too but can be less resistant with shape and movement like with SDK where currents roll of the body's surface. I think most mammals go under water for acceleration, just watch Phelps.

RE: Where is the greatest resistance?

knelson — Thu, 28 Jan 2010 12:10:05 GMT

More resistance on the surface. That's why submarines go faster when submerged. Also consider that some people can kick significantly faster underwater than they can swim on the surface. Here's an experiment to prove it. Push off from the wall and streamline and see how far you go 1. while on the surface, and 2, while under water.

RE: Where is the greatest resistance?

Allen Stark — Thu, 28 Jan 2010 11:38:22 GMT

While hydrodynamics are very complicated a good rule of thumb is that form drag(pushing and pulling water by our body's shape) goes up as the square of velocity,where as wave drag goes up as the cube(these are not nearly exact but close enough at elite swimming velocities.)In all strokes you want your head in neutral position as much as possible as raising your head causes some other part to drop(usually hips.)Head up breaststroke is definitely slower,if you can avoid raising your head at all you will be faster(breath by raising your torso at the point where the insweep naturally causes it to rise.)

RE: Where is the greatest resistance?

fritznh — Thu, 28 Jan 2010 09:29:06 GMT

I'm pretty sure the greatest resistance is on the surface. Just from an energy balance, if you're right on the surface and you're making waves, it takes energy to do that. There is energy in the wake. If you're far enough under water where you don't interact with the free surface, all of your energy can go into forward motion. If you're not Michael Phelps and you don't have enough lung capacity to go four feet down for 15 meters every turn (wow!) dolphin kicking on your side is more efficient because you won't interact with the surface as much. Illegal in backstroke, you can't be past 90 degrees, so you'll need to go deep to get the most out of the kick. I've been working on SDK, though I still don't go deep enough. When I do hit the turn right, I can tell the difference and it feels faster, but it takes more lung capacity than I have to do it every turn, all the time.

RE: Where is the greatest resistance?

orca1946 — Thu, 28 Jan 2010 08:38:48 GMT

This is why we have the 17 yard rule in backstroke. They went faster under water, but no one knew a race was on !

RE: Where is the greatest resistance?

Former Member — Thu, 28 Jan 2010 06:32:29 GMT

during swimming? Completely underwater, or half underwater (water surface)? Ask breaststroke specialists. They are the one having to constantly face this dilemma. I'm far from being a breaststroke specialist, but as a well informed observer, I think that the depth prescription for breaststrokers have changed over years. Not sure where it stands right now (and I don't really care). Pushing off the walls and after the dive, we've known pretty much forever that you have to go little deeper than the surface in order to get more velocity. Phelps (among others) has pushed this principle to a new extent by literally diving deeper after each push off.

RE: Where is the greatest resistance?

__steve__ — Thu, 28 Jan 2010 05:30:35 GMT

Attached is a good article on the subject.

RE: Where is the greatest resistance?

Redbird Alum — Thu, 28 Jan 2010 04:17:55 GMT

In addition to the "wave" action noted above, another scientific reason for increased resistance at the surface boundary is the energy you expel in breaking the surface tension of the water at the surface boundary.

RE: Where is the greatest resistance?

ande — Thu, 28 Jan 2010 02:38:49 GMT

I've described the reason for deeper dives & push offs with: Tip 239 The Suit Surge from Swim Faster Faster Since the new permeable suits don't float was much as the rubber full body suits, I recommend taking in a big breath just before your turn and holding it while you streamline glide & SDK Pushing off the walls and after the dive, we've known pretty much forever that you have to go little deeper than the surface in order to get more velocity. Phelps (among others) has pushed this principle to a new extent by literally diving deeper after each push off.

RE: Where is the greatest resistance?

Former Member — Wed, 27 Jan 2010 15:32:45 GMT

I would think it's where each swimmer is the widest probably in the hips, shoulders, or abdomen Hmmm, what I meant is, when your body is completely underwater, or when the upper part is outside the water? I seem to have read different opinions but can't remember where. Some say the greatest resistance is on the water surface. However, if the air has less resistance, shouldn't half air and half water be less resistant than completely underwater? :confused:

RE: Where is the greatest resistance?

ande — Wed, 27 Jan 2010 10:26:05 GMT

I would think it's where each swimmer is the widest probably in the hips, shoulders, or abdomen