Ovako to radi SKYWALK!
RANGE 2 kasni sa izlaskom na tržište i dobra je prilika da se uz razloge kašnjenja vidi kako se testiraju sjedala u Skywalku i što utječe na finesu ukupno.
Aerodynamic Research on the skywalk RANGE2The Formula1 teams work around the clock in the wind tunnel in order to optimize their race cars. Every detail is checked and rechecked, and the casual observer has to ask the question: Why does it take so long, does one really have to work night and day in the wind tunnel in order to make something better?
Well, paragliding is not exactly Formula 1, but it also very helpful for us, in order to test ideas and make simulations in real air flow and subsequently collect the technical measurements.
For this purpose, skywalk decided to gather our harnesses and visit the huge Daimler Wind Tunnel in Stuttgart.
The Daimler Wind Tunnel has impressive dimensions:
125m long, cross section of the jets: 32 square meters, 5000kw (6800PS) drive power, maximum wind speed 250km/h, 9000m³ air quantity.
Photo 1 Turbine in the Daimler Wind Tunnel
All of the other equipment is of the same impressive quality:
Airspeed can be exactly controlled to one-tenth of a Km/h. Smoke trails make it possible to ideally observe the air current and development of turbulence in front of a black photo background, which can be pulled down from the ceiling, as needed.
Walk-in platforms allow photo-shootings from above.
The harnesses were mounted via a harness stand and all strengths were transferred to the data center, where computer-assisted data storage and analysis takes place.
The current rate is extraordinarily good in this canal. This means that only seldom does turbulence occur, which can make it very difficult to take comparison measurements.
In order to avoid the oscillation of the harness in the air current, adjustable fixation lines were attached, which limited the sideways motion of the harness.
The support frame was measured alone, including risers and fixation lines, at the start, and then, after the actual measurement with harness, subtracted from this value. The result is exclusively the resistance value of the harness including pilot.
Many different parameters play a part in harness design. A high significance is placed on aerodynamics, especially with regard to prone harnesses like the RANGE2.
Along with a comfortable sitting-lying position, the weight of the harness should remain low, the accelerator should operate efficiently, the safety must remain guaranteed, but above all, the pilot should be nestled aerodynamically, so that he/she can take full advantage of wing performance.
The design calculations show that performance can be significantly influenced by the harness factor.
With an assumed launch weight of 90kg on a CAYENNE3, ca. 96N account for the total drag at an assumed glide ratio of 9,3 ca. 96N .
From that, the canopy contributes the largest share, at ca. 60N, the lines have significantly less, at ca. 18N, and a good prone harness like the Range1, according to wind tunnel measurements also ca. 18N, including the pilot with hands in flying position on the brake lines.
Photo 2 Range1, hands in flying position, drag 18N
When we position the pilot in a conventional seated harness in an upright position, the drag of the pilot-harness system increases to ca. 34N. The result: a glide ratio of ca. 8, with the very same paraglider!!!
It also applies the other way round. If we put the pilot, in this case the cross country pro Oliver Teubert, in an aerodynamically optimized harness like the RANGE2 and optimally adjust his position,
then the result is a sensational drag value of only 12N! The good flow ratio was made visible with the smoke trails and confirms the harness design.
Photo 3 RANGE2 Flow visualisation with smoke trails
Our measurements show that it is clearly better to correct the position so that the legs are positioned relatively high, and then the top side of the harness is therefore almost parallel to the approach flow.
Photo 4 side view RANGE2, Top side of the harness aligned nearly parallel to air flow. Drag 12N!
In this case, the improvement of drag compared with the RANGE1 amounts to an unbelievable 33%! The aerodynamically formed back part, including the 17cm foam protector, contributes just as much as the integrated cockpit, to the very good results of the RANGE2, which diverts the air flow very well from the pilot’s upper body.
Additional fittings such as, e.g. the ramair tail-end extension built by Oliver, contributed no further significant improvement to drag values. There is still room to play with optimisation; the wind tunnel testing has considerably widened the horizons.
Photo 5 Tail Fairing
Back to the performance analysis:
Still flying with the CAYENNE3 and the same pilot, now flying an aerodynamically optimized harness, like the RANGE2, at a glide ratio of almost 10, compared with a conventional prone harness, achieved an improvement of ca. 0,5 glide ratio.
The difference between a conventional seated harness and an upright position amounts to almost 2 drag ratio points and therefore contributes more than glider class to glider ratio differential.
The measured values at a glance with the effects on glide ratio:
At this point, it must be admitted that prone harnesses also have a disadvantage: there is an increased danger of getting twisted after stall, because the prone position leads to a significantly higher moment of inertia. However, the RANGE2 gets points here, too, because it also permits a relaxed upright seated position.
Weight and pack dimensions of pod harnesses are normally higher and one must get used to the ground handling. But prone harnesses can take getting used to as well, especially when it comes to accessing the rescue.
On the other hand, the pilot can enjoy flying even at colder temperatures in a pod harness and has, e.g. with the RANGE2, a comfortable integrated cockpit, in which the instruments can be ideally mounted.
At any rate, Formula 1 would be overjoyed if they could achieve 30% more performance from a single spoiler or another crucial part!
With the RANGE2, skywalk was able to make this enormous improvement of more than 30% a reality, in combination with optimal pilot position.
Anyway, the skywalk windtunnel tests have shown again how much potential remains in the sport of paragliding!
Our thanks to the team at the Daimler Windtunnel and our team pilots Reiner Braun and Oliver Teubert, who helped to make these measurements possible.
Manfred Kistler, skywalk Development
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