# Ski Ogasaka Triun SL 17/18. Part 3, stiffness and deflection

In this note I will consider the stiffness of the slalom skis Ogasaka Triun SL 17/18. In addition, from the analysis of the shape of the deflection I will try to evaluate the “rails” in the arc of a carved turn.

About thirty years ago, mountain skis had two main characteristics, well “palpable” by hands. The first is softness and elasticity to the deflection. The ski had to bend well and resiliently “return back” the load. The second characteristic is the stiffness on the twisting of the tip and tail, should be as much as possible. The turn was basically like this: the ski was put on the edge and the tip was loaded simultaneously. At the same time the ski clung to the snow with a wide part of the tip and, if the rigidity on the twisting was sufficient, then the tip “bitten” with the edge into the snow. Therefore, loading the tip, for example move the knees or the body forward led to the bending of the skis. Sometimes pretty strong, “to the sausage”. The softness and elasticity of the ski was very important, too soft and the “sluggish” ski could “fail” with such loading, and too rigid simply did not bend. But if everything was good, then as a result of such a simple movement immediately got bent in the arc of the ski at the edge.

I wrote this in detail because this turn did not go away with the arrival of the “era of the carves”, it simply ceased to be the main one. For example, it is desirable to use it at each exit from the “hairpin”. This is advice from Alexander Mityakov, more in this article: Slalom skiing tips & tricks. Season 2017 (section: Dive forward (on a double pole) at the exit of vertical gates). Therefore, too rigid skiing, even if perfectly balanced with the ability of a carving turn, will have some limitations. Still back to this 🙂

### Deflection of the skis under load

To measure rigidity, I repeated the stand on which Ogasaka 2015, 2016, 2017 measured a year ago. More information: Ski Ogasaka Triun SL 16/17. Part 3, stiffness and deflection. The load on the ski changed from about 6 to 30 kg, not counting the weight of the bindings, the shape of the deflection was fixed by the camera, the digitization – through photoshop with an increase in the vertical scale. Recalculation to linear dimensions (centimeters and millimeters) was made using a separate “calibration” frame.

The results of measurements of the ski Ogasaka Triun SL 17/18 in comparison with the measurements of the ski of last year look like this:

#### The concept of deflection

It can be seen that the concept of the deflection of the ski has changed fundamentally, the arc of the deflection has become smooth. This could be expected, since the “stabilizer” was removed from the design of the ski, more details here: Ski Ogasaka Triun SL 17/18. Part 1, catalog.

In general, Ogasaka paid close attention to the correction of elasticity in the central part of the ski. In the Ogasaka slalom series from 2012 to 2017, one can see a change in technologies located in the central part of the skis: “Accumulator”, “Beam” (additional elements inside as beams to the tip and tail), ” Power Platform” (an additional plate in the middle of the “pie”), “stabilizer” (an additional plate of complex shape under the topsheet).

As far as I understood the idea of Ogasaka engineers, to improve stability in the arc, the ski was functionally divided into areas with different rigidity/elasticity: the fore and tail areas cut the arc, and the middle absorbed the unevenness. That is, since skiing doing on far from non-ideal coverage, it is necessary that all “high-frequency” impacts do not disrupt the arc, but just slightly lift the central part and at the same time “absorbs”. Although, of course, the ideas of Ogasaka engineers are unknown to me 🙂

In general, now, judging by the catalog, all technologies from the middle part are thrown out, on the sagging shape this led to a beautiful smooth curve indicating the uniformity of the design 🙂

#### Stiffness

The ski of 2018 became noticeably tougher than the previous one.
With small loads, it seems that it bends easier, but in fact in the ski of 2017 just taken over a back deflection (camber). Starting with medium loads, the ski of 2018 is tougher and with a camber. In the middle part of the ski, the difference in deflections of skis 2018 and 2017 with the minimum and maximum loads is 5 mm. Those the ski of 2018 became stiffer by about 5 units according to the “Atomic scale”.

Honestly, it worries me, but it can be in vain 🙂 The fact is that the ski of the last year of 2017 was already much stiffer than the skis of the previous model years. There were serious fears that it would be possible to bend it, especially on our Moscow hills. But due to the surprising balance of the shape of the deflection and the shape of the side cut, the skis were not perceived as rigid. Read more here: Ski Ogasaka Triun SL 16/17. Part 4, test on snow.

The reviews were mostly positive. But nevertheless there was also one “mark” review. Alexander Mistryukov tested the ski for three days. At the end of testing, he put the course with a very difficult way out of the vertical gates. On Ogasaka 2017, He could not pass this place in any way, but He was stable on his old Atomics. He stated that Ogasaka was still too stiff for him and did not consider them further. I note that this kind of turn corresponds to the case from the beginning of the note, when the softness rigidity of the skis play a big role.

Therefore, even greater strengthening of rigidity in the next year’s model from my point of view is rather risky. Even with the ideal “rail”. By the way, we will consider this indicator.

### Rails (balance of sidecut and free deflection)

In a note Ski Ogasaka Triun SL 17/18. Part 2, sidecut shape, side cutout defines the shape and length of the working section of the side cutout. There this sidecut was mathematically angled in order to get a trace on the snow. With this operation, the deflection of the ski corresponding to this trace is also determined. If the deflection calculated in this way more or less coincides with the natural deflection of a real ski, then when skiing, the ski will lie on the snow simultaneously with the whole edging. This is the “rails” in the context of this note. Read more here: Compliance ski sidecut shape to deflection. Part 2. An attempt to choose such a angle of the edging, so that the calculated and measured deflection would coincide look like so (two curves for each load):

It can be seen that the curves do not coincide: (Unless in the tail part of the skis, but as only there, this is not rails: (

I’ll try to go from the opposite side, as shown in the animation on the left. The ski is placed at the widest points of the edge, then is set an angle of, for example, 55 degrees, after which the load is applied to the ski. The calculated deflection of 55 degrees in the graph is shown by a solid black line. This is the deflection, which in the end will in any case, since the ski should lie on the slope. While the ski has not touched the snow, the deflection is determined by its own characteristics. On the graph, such areas are marked in blue. When in contact with snow, while the forms of free and calculated deflection coincide +- millimeter, there are no internal stresses. Such a section is marked in green. If part of the edge when applying the load is too strongly pressed against the snow, it is a red color.

On the ski of the past, in 2017, along the shovel and tail, there were significant areas of compliance (they would be marked on a similar chart in green). In the middle there remained a small almost horizontal section of “damping” (it would have been marked in blue). In the ski of this year there is no such correspondence. At small loads there is compliabce in the tip and tail, but the areas are too small to be able to talk about the arc. Then the ski is “pressed” into the slope by the shovel and tail with internal stresses over the entire working length (marked in red). This most likely means that the unevenness of the coating will initiate the ski to return to the state of free deflection by dropping it from the arc 🙁

### Conclusions

From the conclusions so far refrain, need to wait for the snow 🙂  I can only say for sure that the ski of 2018 has become even stiffer than the 2017th. About the rail on the basis of static measurements – it can all in the dynamics will not be so 🙂 And in general, whether the rail is needed with such a more radical radius of the sidecut (reduced by almost a meter, from 12.6 to 11.7 m) – is not known. After all, rail, in general have a minus – it is more difficult to “pull off” the ski from the arc. As was discussed in the note Ski sidecut radius and radius of a carved turn, the carved turn in the course is only “pieces”, a significant part of the turn is passed in a state of a small “drifting”, that is, the direction of the ski does not coincide with the direction of motion along the arc. But nevertheless, based on above mine personally like more skis of last year: Ogasaka Triun SL 16/17. Yes, and my own skis Ogasaka Triun SL 14/15 like no less than skis of last year 🙂 They are all different in characteristics, but not in character 🙂 Ogasaka’s character is very, very recognizable 🙂

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