This article mostly wrote itself after I posted this video of Katarina (Turčinović) Zubčić's turns during her 218 meter DYN. There was a lot of good feedback and some good questions. Certainly, many will be trying to learn this turn now. Ordinarily, I would just throw the information about this into my article on monofin turns, but we got into so much detail after the post that it justifies a separate article, I think. Thanks first, to Katarina, for allowing the use of her DYN video in this way. She could very easily have said no.
You will probably have to watch the video a number of times to completely get what is going on. I stopped it many times to take a closer look at the positions she gets into and how she does it. I will use pictures of some of those points later to elaborate on what she is doing.
As she approaches the wall, she starts rotating longitudinally. When she hits the wall, she is rotated, the fin is almost vertical, and her lower legs are parallel with the bottom still, helping the fin follow her feet through the turn. This reduces drag and prevents any unwanted warping of the fin.
Her feet are probably a half a meter above her head, with her torso angled down toward the bottom. This reduces the lateral component of the turn, thereby reducing the correction required later to line her up with the pool.
Notice that as she pushes off the wall with her hand, she allows her knees to bend more, bringing the fin up behind her back. This is in cooperation with the water rather than resistance to it, so drag is reduced and momentum is conserved. This also puts the fin in a perfect position to execute the stroke off the wall.
The stroke actually begins as her lower body starts dropping before she is even lined up completely. She uses her left arm to get lined up, but also to help propel herself through the turn. She drops her knees only a little as she makes the stroke, further reducing drag. As her lower body finishes its downward movement, her body is angled slightly up, so that when she is done with the stroke, she does not send herself to the bottom, but rather straight, giving her a nice glide after the turn.
She recovers her arms after the turn is done and when she is firing off a stroke. That is one of the keys to the effectiveness of her stroke off the wall. The later arm recovery does not seem to slow her down at all.
The first part of any turn is preparation to hit the wall. This involves rotation. This would seem easy, but some people tend to think in only two dimensions when they turn. You can tell by how they do it, so this kind of rotation can be difficult for them. The rotation is longitudinal, like turning a screw driver. It is important in every type of turn except maybe the flat-spin turn, which is only useful for solid winged monofins such as the DOL-Fin class of fins, or perhaps the Lunocet.
The reason this is important is that it sets up the fin to follow the feet through the turn. In this way, unwanted warping of the fin is prevented, reducing drag, and preserving angular momentum. To get this right, you just have to practice it. It helps a lot to have someone watching you to make sure you are doing it correctly.
Take a look at her position when she first touches the wall:
This is the position you want. Her back is arched. Her lower legs are parallel with the bottom. Her torso is angled down. Her whole body is rotating longitudinally to vertical. Her fin is following that rotation.
You can see that with the fin traveling this way, it is impossible for it to warp. Fin warping is a killer in turns. It kills angular momentum and can cause you to have to waste the stroke off the wall to get straightened out.
Also, with her body angled down, she almost goes inverted. This reduces the lateral component of the turn and speeds the turn up. You will see how this plays out through the rest of the turn.
As she pushes off the wall, her back is still arched, and she is bending her knees more, while bringing, or perhaps allowing, the fin up behind her back. She is cooperating with the water, rather than fighting it. This reduces drag and helps to conserve angular momentum. Now her fin will be in a perfect position to make a stroke off the wall. This also helps her get away from the wall, so that she will not whack her fin on the side. Momentum and fin are both conserved.
In fact the stroke begins right about now, before she is even completely lined up, as her lower body starts to drop to follow her upper body, and her left arm starts to move backward to help propel her through the turn. To use an aeronautical term, she is in a coordinated turn, so that all of the forces are balanced and the thrust she produces will push her only in the direction she wants to go.
Her fin continues to follow her feet, with absolutely no warping of the fin. The rotation she does before she hits the wall makes this easy.
Her lower body continues to drop, and you can see the stroke progessing. She is still not completely in line, but she is getting there.
Now she is fully in line to finish the stroke. Her left arm has completed its motion. As her lower body stops its downward movement and she continues the stroke, her knees drop, but only a little. Too much knee drop also kills momentum. Her body is angled up slightly so that her stroke will not send her to the bottom, but straight, and into a nice glide.
And off she goes. The last thing she has to do is to recover her arms. This may be the ultimate secret to the effectiveness of Katarina's stroke off the wall. During the turn, her arms are used only to aid the turn in some way. The drag from the recovery is delayed until after the turn is done and the glide is complete. The arms are recovered to a streamlined position immediately before or during the first stroke after the turn, when the stroke can easily compensate for the drag caused by the recovery.
All of this combines to give her a very fast turn and awesome distance off the wall.
Here is some interesting data based on estimates from watching the entire video, and assuming that the red floats started about the 5 meter point on both ends of the pool:
Her split times for the middle 40 meters of each lap were 31.11, 31.5, 29.9, and 27.72 seconds (1.33 meters/second average). For the last and first 5 meters of each lap, including the turns, her splits were 9.01, 8.29, 8.29, and 7.47 seconds (1.21 meters/second average). The turns are therefore costing her about 1.2 seconds each - nothing wrong with that at all.
This is the Katarina turn. Good luck as you try this. May yours be as effortless as Katarina's appear to be.
First published December 7, 2015
Latest edit December 6, 2016