I was asked on the SDK thread about my past posts on speed and height.Here is a more complete explanation.There are 2 main forms of drag affecting swimmers:form drag and wave drag.Wave drag only occurs at the surface so it is not a factor when swimming underwater.Lack of wave drag is why SDK can be so fast even though it is less propulsive than full stroke.
Form drag is from how much water you push in front of you and pull behind you. Improved streamlining decreases form drag.There are many things we can do to decrease form drag:good body position,shaving down,technical suits,losing weight,etc.For a given shape form drag resistance increases as the square of the velocity.
Wave drag comes primarily from pushing your bow wave. There is very little drag from this until you exceed your "hull speed" at which point you are climbing up on your bow wave.At this point resistance goes up as the cube of velocity so it rapidly becomes the primary resistance.
The formula for hull speed is:hull speed(in knots)=1.34times the square root of the length at the waterline(in feet)(for a swimmer that is the height)This is why longer boats(and taller swimmers) are faster.
For example I'm 5'8" (or 5.67 ft) so my hull speed is 3.19 Kt.A knot is 1 nautical mile per hr or about 1.67 fps so my hull speed is 5.32 fps.This is doing 50 yd in 28.19 sec.Going faster than that requires disproportionally more power than going slower than that(at the surface).
What can you do to decrease wave drag?You can be tall(or at least swim tall),you can stay underwater,or you can swim slower.Obviously swimming slower is no help in a sprint,but it does mean that even pacing will use less energy than going fast for part of the race.
Here is a table I calculated of height and hull speed
Height Hull Speed(feet per sec) Time for 50 yd
5' 5 fps 30 sec.
5'3" 5.12 fps :29.29
5'6" 5.24 fps :28.62
5'9" 5.36 fps :27.98
6' 5.47 fps :27.42
6'3" 5.59 fps :26.83
6'6" 5.71 fps :26.26
Former Member
A long vessel with an empty tank does not move well through the water. I also like front wheel drive and a full tank. (Full tank is conditioning) A thing I have not been able to accomplish for a long time.
It is a drag for sure. The old hull no longer speeds.
This always makes my head spin. Isn't drag always going to occur when you move forward. Opposite and equal and the "L" effect.
Yes, drag will always occur. If you are at a constant velocity (which, of course, you never are when swimming) then your drag is equal and opposite to the force you are creating to move you forward (your kick and pull).
The bottom line is the more you can minimize your drag the faster you will go.
This always makes my head spin. Isn't drag always going to occur when you move forward. Opposite and equal and the "L" effect.
also, I'm always so surprised to see how much peole actually do look like a hull of a ship when they are swimming.
This is getting boring. Learn to race and don't over complicate things. Enjoy!! Allen your getting to serious and I suggest you just let it go and race.
I agree this thread is getting boring and should just drift away to the second page.Streamlining is not boring though.Streamlining is "free" speed.I am always looking for the easiest way to go the fastest.:bouncing:
I agree this thread is getting boring and should just drift away to the second page.Streamlining is not boring though.Streamlining is "free" speed.I am always looking for the easiest way to go the fastest.:bouncing:
Not boring at all. Keep thinking and talking, please. :)
I came across this while searching for front quadrant. I was messing around during warm-down and tried swimming with no kick at all, to see how much my legs dragged with different stroke techniques. I tried front quadrant style and normal style, and my legs were dragging noticeably worse with normal stroke. The whole idea of front quadrant swimming is to move your center of buoyancy forward for a large part of your stroke cycle, right?
I haven't tried front quadrant in workout sets yet, but plan to, to get a feel for whether it works for me or not. It seems like the 'catch up' drill is probably a good way to develop technique.
Good point.
I think front quadrant swimming allows the weight of your arms to help balance out the weight of your legs and create a flatter streamline profile. This helps in distance when your kick is less activated. Thorpe was the master.
"Hull speed" is an issue for any object that is moving through the water, regardless of shape; all things being equal, the fastest ships tend to be the longest ships. The formula for 10-meter racing sailboats gives designers the flexibility to make trade offs between sail area (power) and hull length (reduction of resistence) - and you may have noticed that most 10-meter boats have roughly the same hull length because designers want to get the most from the benefits of faster hull speed. The analogy of boats to swimmers, however, does not apply to the "speed boats" - they exceed their hull speed by hydroplaning, and humans cannot attain such speeds because they cannot generate enough power or leverage on the water to drive themselves forward out of the water. The lesson for swimmers: swim low in the water (and ignore what the coaches taught me a long time ago, which is to keep your head high - instead, keep your hips high), pay attention to that "front quadrant stuff" (it's as valid in breaststroke as freestyle). A couple months ago I began to experiment with "front quadrant" ideas after looking over this book:
www.amazon.com/.../unitedstatesmast
I noticed I needed fewer strokes to get across the pool - I think that was because of lower resistance, not more power, as my underwater stroke changed little. That book encouraged that notion, as did this one:
www.amazon.com/.../unitedstatesmast
Meanwhile, someone noted the effects of the irregularities of shape in the human body. These, it appears, further heighten the resistance as a result of the eddy currents and boundry water. The purpose of a technical suit is to mitigate this resistance. The problem with "bobbing" is that this also heightens eddy currents. The "new" wave-style breastroke is designed, in large part, to reduce the resistance in the leg recovery that come from dropping the knees in the old "flat" style. Meanwhile, boat designers have been able to improve speed by altering hull and keel designs, for example, but those alternatives are less available to swimmers.
Here's one simple way of looking at this:
swimming.about.com/.../offsite.htm
