At 10:00 a.m. on February 8, 2022, China's Gu Ailing won the championship in the final of the Beijing 2022 Winter Olympics Freestyle Ski Women's Big Jump held at the Beijing Shougang Ski Jump.
Standing at the starting point of 48 meters high, Gu Ailing's hands drooped, sliding down the snow slope, the snowboard advanced at high speed, and the big jumping platform threw her into focus, flipping, flipping, flipping, flipping... The rotation of her body dragged her gaze to the cloudless sky, 4 and a half weeks, 1620 degrees, before that, no girl in history had ever challenged an action, including Gu Ailing herself.
Before competitive sports, freestyle skiing is first and foremost an extreme sport, the competitor rides the snowboard under his feet into the air, may draw a graceful arc, or may not be able to fall uncontrollably to a corner of the snow field, highlight moments and painful experiences are often between the minute, the tension of the movement is magnified to the extreme.
Gu Ailing, who is only 19 years old, set a record and refreshed our cognition again. Swiss ski brand FACT has customized its "dragon among men" skis, adding a strong Chinese style to the champions.
△ 2022 Beijing Winter Olympics Chinese skiers customized snowboard Source: FACTION
● The core design requirements of skis
While technical prowess, physical strength, endurance and agility are what any athlete, whether pro or amateur, snowboarding, which helps athletes achieve better results, also plays an immeasurable role. High-performance skis first and foremost guarantee weight and strength. It must be light enough to float better in the snow, but strong enough to absorb the impact of the landing when a skier suddenly stops. This requires extremely high stability for the board.
The core design of the ski is important because the core layer determines the amount of vibration that the skier will feel. The speed at which the skis go downhill or across terrain can cause vibrations that can affect skiers. Too much vibration can make skiers tired and difficult to control their skis. To eliminate this, ski engineers tried to design an internal structure that absorbs as much vibration as possible without sacrificing the life of the ski. Although skis appear to be a fairly simple, lightweight synthetic material, the factors involved in their design are based on complex physical, engineering, and materials science principles.
The Faction Prodigy 0.0 snowboard is lightweight, tolerant and flexible, and is a new model for emerging freestyle skiers. Featuring softer elasticity and a mix of wood and foam cores, the Prodigy 0.0 features a versatile directional dual shape for easy regular or switch riding
● Ski materials for the mass market
The way each manufacturer makes skis is slightly different, but the basic structure is very similar.
Skis designed for entry-level capable or budget-conscious users tend to be made of softer, gentler, and more tolerant polyurethane foam cores with less elastic rebound properties to keep riding smooth and controllable. These cheaper cores are generally less dense than metals and denser wood, and tend to load with less energy when the curvature is compressed by your body weight during the turn.
Compared to stiffer skis, foam skis release energy at the corner exit and bounce less. These characteristics translate well into beginner or intermediate users to develop their strengths, forms, and techniques. Foam skis are pleasant to operate at low to medium speeds, as their easy bending also results in reduced responsiveness at higher speeds.
△ Image source: lib-tech
Snowboard manufacturers produce cores with different weights, torsional stiffness and longitudinal bending combinations, offering a wide range of skis for skiers of different styles and capability levels. Most manufacturers designed skis for the mass market are still built with wood cores, and the wood-based core has multiple price points to choose from and offers popular cornering popular mixes and straights stability, which makes people who are used to skiing happy. However, in the eyes of people in the foam material industry, this may be the smugness of the snowboard mass market that is difficult to go to the high-end.
To accommodate the aggressive, fast-riding style of experienced professional skiers, a small number of manufacturers have produced stiffer skis by reinforcing the wood core by blending the composite layer with exotic materials such as Titanal, triaxial fiberglass, and carbon fiber with a high-strength foam combination.
● Core material for professional-grade skis
For professional-grade ski cores, you can't be a winner if you don't use the right materials.
The core of cross-country skiing is considered the most important part of skiing, as it is responsible for the intensity and flexibility of skiing. This core, which used to be made of wood, is now built with a variety of materials. With the introduction of metal in cross-country skiing, the material of the skis is now becoming crucial. Ski manufacturers and enthusiasts are divided into two camps, one prefers wood, such as many cross-country snowboard manufacturers still prefer wood as an inner core, and the other faction chooses foam materials, such as XC snowboard manufacturers firmly support foam.
△Ski structure: 1) ultra-high polymer polyethylene 2) tall manganese steel steel side strip 3) rubber strip 4) glass fiber 5) polyurethane foam core 6) ABS shock absorption side strip 7) carbon fiber 8) anti-slip, waterproof and scratch-resistant panel. The core of the ski is located under the fiberglass and is the part wrapped around the rest of the board. The core makes up most of the thickness of the skis. This is usually made from a combination of composite foam, wood, honeycomb panels, or other composite materials with a set of metal inserts required to install the bindings.
With wood as the core, cross-country skiboard manufacturers need extreme precision while matching the amount, type, style and cut of wood used in each pair of skis. This allows the left and right skis to move in the same way at high speeds. The wood core is made of laminated hardwood strips that extend along the length of the board. Ash willow, beech, poplar and ash trees are the most common woods in skis. However, the wood core is also not completely independent of use, and sometimes foam support is required. This is done to give different areas of the ski different strengths, bends and weights, resulting in different properties and characteristics.
△ Many manufacturers inject PU foam into the shape of a core
Foam was first introduced as a core material in the 1970s, and some of the wood cores of modern skis are also being replaced by foam cores. The foam-based core makes the ski lighter than comparable products. In addition, the construction of foam-based cross-country skis is relatively easy because it can absorb different vibrations and helps manufacturers design curves. As mentioned earlier, most foam cores are made of polyurethane, and the core made of honeycomb is lightweight and very strong. Foam cores are easier to control during the manufacturing process and absorb vibrations better than wood. It also has the added bonus of being cheaper than wood. So these cross-country skis end up costing less than skis with wooden cores.
Despite the lightweight advantages of foam, as more materials emerge and are replaced, some manufacturers no longer use foam as the primary material because they worry that the board will soon lose its arch and be a bit soft, and the foam core will sometimes lose its elasticity. The use of a wood core ensures a smooth response and a lively bend from the board. While foams can still appear in some low-stress areas of the core to reduce weight, however, they may have underestimated the invincible evolution of foams.
Many ski companies still advertise the essence of wood for their skis. The foam was developed for core materials, but it took a long time to obtain a high-performance foam that was durable and strong enough. It needs to be acknowledged that the traditional foam strength and durability is a big issue, and the injectable snowboarding technology that is still used today for very low-end skis, has brought the foam a very bad reputation as a whole family. However, high-performance foam and excellent design overcome this technical challenge.
Foams need to be reinforced or made into very high densities to achieve high enough strength and durability. High-performance foam, it's time to show off its true stunts!
●PMI foam: Adds value to high-performance skis
In professional-grade skateboarding, where foam is under pressure that some manufacturers perceive as marginal, DPS has done the opposite, introducing aerospace-grade foam into the core layer of its new product, the Pagoda Tour series. The foam has incredible strength, energy and lighter weight as well as excellent downhill performance. When sandwiched between two pre-immersed carbon laminates and combined with plenty of paulownia and some ash, the result is that the foam skis are very lightweight, allowing you to be both strong and confident when you descend, but relatively light for a more pleasant ascent.
△ The wood and foam of the Pagoda Tour are laminated and layered into blanks. This creates a vertical laminated core of ash, paulownia and foam, rather than a separate horizontal layer of each material. The vertical orientation adds more labor and precision to building the core, but increases stiffness under the same amount of material. Image source: wildsnow
This aerospace-grade foam is a carefully designed closed-cell rigid polymethacrylimide (PMI) foam. It has impeccable high mechanical properties: it has high specific strength and high specific modulus; its tensile, compressive, bending and shear strength and modulus are far superior to other foam or balsa cores such as PVC, PU, PET, and are isotropic.
PMI foam sandwich composites have a higher strength-to-weight ratio compared to solid composite laminates alone, and when they have to be delivered quickly, this is a huge advantage that PMI foam sandwich panels have over solid composite panels. PMI foam ultimately makes snowboards have to withstand the high dynamic pressure of this top competitive sport.
△ PMI foam with skin, carbon fiber and foam sandwich panels for extremely lightweight applications Source: Rock West Composites
△ Cross-country skiboard PMI core Source: Evonik
Many winter sports enthusiasts have rediscovered cross-country skiing, thus driving a new trend in winter sports. Over the years, cross-country skiing has become increasingly popular, especially inspired by the success of Germany's top athletes, Norwegian snowboard manufacturer Madshus has been using Evonik's ROHACELL high-performance PMI rigid foam as an integral part of its ski core.
● Let the composite materials win-win
While high-performance foams are often very expensive, they have a very unique combination of properties. When combined with wood, the best of both worlds can be achieved: the skis are lightweight, but still retain damping and innovative design, which in turn makes wood core skis popular.
The combination of sandwich design overlays made up of fiber plastic composites and high-performance foams is increasingly important for modern sports equipment. Through heating and pressure applications, high-strength PMI foam can be combined with all conventional plastics to form an extremely durable composite.
Composites with overlays made of materials such as CFRP enable a high-strength, rigid design and extremely low weight. These materials are ideal for lightweight but durable sports equipment such as cross-country skiing and downhill snowboards, racing wheels, rackets, hockey bats, skis and surfboards.
△ Image source: Mtbachelor
Keywords: # Interfoam Foamers Alliance # Polyurethane Foam # PMI Foam # Sports & Leisure # Skis # 2022 Beijing Winter Olympics # Carbon Fiber #