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Zenturtle 09-20-2018 11:24 AM

Sculling traction
here is some elite doing a 6 stroke 25 m.
He uses a big scull in his pull to get extra traction.
Hand basically does not move back while body glides forward during his scull.
At higher strokerates there is no time for these tricks and wiggling the arm around much.
When doing doggy paddle the urge to scull becomes greatest i think. You almost start to wiggle your hand automatically under the body then.

scull start point

scull inward

Zenturtle 09-20-2018 11:25 AM

scull outward
image uploaden

upload photo

so his hand leaves at the same place where it started the scull at the red line, while his head moved from 2.5 tiles to 4.5 tiles, so 2 tiles forward.

from this video>

Zenturtle 09-20-2018 11:44 AM

So, whats his slippfactor then?

6stroke 1

6 stroke 2

6 stroke 3

his hand moves 2.4 tiles back, while his head moves 3 tiles forward.Slipfactor = 2.4/3= 0.8. So not super for an elite, but very good taking the 6 stroke in account.
There has to be relative much deceleration between strokes, so at every stroke he also has to accelerate his body again, which takes extra force = extra slippage.

Sclim, there is 1 component I forgot: the kick propulsion. More kickpropulsion at the back, means less propulsion at the front, means less slip.
This guy has opened my eyes for the possible propulsion of the legs , even from a 2 BK. Never thought you could get so much propulsion from a 2BK.
Still hate the kneebend it needs to set the big kick up, making it a nono for higher speeds I think. Have to take a look how much Sun Yang bends his knee.

Zenturtle 09-20-2018 01:04 PM

If we compare the elite guys with an adult onset swimmer, we can see the ellite are doing pretty well, and the adult onset swimmer has some work to do to keep up technically.
Coach Stuart also has a slipfactor of about 2 for example.
stuart 1

stuart 2

stuart 3

from this footage

if anybody can supply some info about the last swimmer, Rachel Vanscoy...I love here stroke.. very nice.

WFEGb 09-20-2018 01:26 PM

3 Attachment(s)
Hello ZT,

Terry's SF has been around 0.79 with 1.02-SR (I'd call that competition SR). Interesting for me the SF in his first phase from just starting the hand's hook to nearly vertical is 0.8 and the second part 0.78, just oppsosite to Shinji's.

Best regards,

Zenturtle 09-20-2018 05:37 PM

So, we now have another abbreviation in the swimming jargon: SF :-) ?

Again, you didnt pick the right start point. The start point is not where the hand is still gliding forward, but the point where it starts pressing water back. Thats where the slipping starts.
The slipfactor is only about the backward pressing phase of the underwater armstroke. It gives an indication how much hold you have on the water. How much the arm is slipping.
If you pick a point where the arm is still moving forward you get a much lower slipping factor, because then you add up negative slip (hand moving forward in the water) and positive slip (hand moving backwards in the water).
With a stationairy background you can determine pretty precise when the hand starts to move backwards.

But, its fun that someone else is also interested in this stuff.

Zenturtle 09-20-2018 06:28 PM

shinji gracefull freestyle

Shinji 1

Shinji 2

Shinji 3

Hand 11-4 =7 units
head 15 -8.5= 6.5 units.
Slipfactor is 7/ 6.5 = 1.08, not exceptional.

I think Shinji gets very little propulsion from his kick. Thats a big difference with the elite 6 stroke swimmer. He always looks like a pullbuoy swimmer to me. But his streamline can hardly be improved.

WFEGb 09-20-2018 08:18 PM

Hello ZT,


So, we now have another abbreviation in the swimming jargon: SF :-) ?

Again, you didnt pick the right start point. The start point is not where the hand is still gliding forward, but the point where it starts pressing water back. Thats where the slipping starts....
:-) It's already in the list...

But then you'll "never" find a starting point, that can't hold for further discussion. In Terry's and in Shinji's example I started with the point where their hands hooked to move backward (related to their body) to the point where the same hand exited the water... same as you did with your straight-arm-example. So "my" SF is more or less the relationship from arm/hand-movement under water (related to a fixed point) to the movement of the head (related to fixed point). That's indirect the connection to my estimation realted to SPL. Every other points seems (to me) much more subjective, as you stated, how to include the amoutn of kick? With an extreme kick you might get a SF=0.


But, its fun that someone else is also interested in this stuff.
Hmm... not sure what could be taken from it for own swimming and coaching. SPL and SR seem to be the "harder" and more reproducable reference numbers.

Best regards,

Zenturtle 09-20-2018 09:55 PM

The point where the hand starts to move backwards in the water is a pretty definite point in my view.
It will never be super accurate, but you get a reasonable idea where you are.
You can compare 2BK swimmers for starters, like the straight arm girl.
DPS is also a rough number to judge stroke quality from.
You can have hard slipping pulls with a lot of glide in between and smooth fluient non slipping strokes with less glide giving the same DPS.
The same problem with kickpropulsion exisst in DPS efficiency marker. Big propulsive kick gives high DPS, but do you want it that way?
In the end , the good coach sees in 3 strokes if its good or not, so its all extra numbers to check first impression.

Had a look at the straight arm girl again, and I took the starting point also too early. hand was still moving forward.
New picture 1 and slipfactor will follow.
Slipfactor increases to 0.72 ( plus 0.15) with new starting point. Still very good.

What i find remarkable, is that the TI swimmers start pushing water back at a shallower arm angle than the competetive swimmers.
The competetive swimmers have a slightly more patient catch than the TI swimmers! (depending on the definition of patient)
You know my explanation for this difference by now I guess? .-)

Its also clear that everybody is pushing water down.
The arm is under 45 degrees or shallower when the backward pushing starts, so a lot of water is pushed downwards.
The Sun Yangs have their forearm and hand almost vertical when they start pushing back, so thats a big advantage.
Better for balance, better for propulsion.

Zenturtle 09-21-2018 12:00 AM

Terry at brisk pace
Slipfactor about 1.3.
Starts pushing back at a shallow angle here. probably can get to lower SF at lower speed.
Terry 1

Terry 2

Terry 3


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