Kuzmin Ski Technology AB
FP Drum
Demonstration (WMV)
Fluoropolymeric coating of the ski running surface
Kuzmin Ski Technology AB is proud to present a completely novel approach to improve ski glide – Fluoropolymeric Coating (FPC) and an innovative tool to perform the FPC – Fluoropolymeric Drum (FPD).
Someone, probably, thinks: They betray their own principles – “steel scraped ski base outperforms all today’s glide waxes”, “ski preparation have to be simple”. Please, wait, below we are going to present, that FPC outperforms all today’s glide waxes, and that the method is very simple and quick.
Introduction
Our own (Kuzmin and Tinnsten, 2007) and others’ (Palosuo et al., 1979) test results show a lower friction on the ski running surfaces with a higher water repellence. Thus, we have to employ a material with the highest possible hydrophobicity. In connection to this, such range of substances, as fluoropolymers, is a first-priority candidate. For a long time ago (in 1953) (Bowden, 1953, Bowden, 1955, Outwater, 1970) fluoropolymer was found to be a very promising ski base material. Even the biggest ski wax producer Swix® affirms it (Karlöf et al., 2005): “In fact, PE is one of the polymeric materials having the lowest surface energy (more hydrophobic). Only fluorpolymers have lower surface energy”.
However, all ski manufacturers avoid producing skis with fluoropolymeric ski base. We do not know why, and our thorough literature study did not bring any good explanation of this phenomena. Probably, because the UHMW kinds of fluoropolymers are less suitable for stone grinding in comparison with usual ski base material – UHMWPE. The fluoropolymers have about 2.5 – 3.0 times lower tensile strength at yield and the similar elongation at break. That means stone grinding will produce a very “hairy” surface.
The fluoropolymeric ski base is advantageous even from the health point of view (Strøm and Alexandersen, 1990, Bracco and Favre, 1998). There is no need to use health hazard perfluoroalkanes to improve water repellents of the ski running surface. For detail, please, see Summa Summarum of health-improving (?) skiing and IBU Warning.
Approach
Because it not possible to get skis with fluoropolymeric ski base, we can try to coat the ski running surface with some suitable fluoropolymeric compound. But the usual way to apply glide waxes (hot waxing – melting with iron) would not work; UHMW fluoropolymers melting point is around 330 °C, whereas melting point of ski base material UHMWPE is around 135 °C.
However, if we compare wear resistance of UHMWPE with wear resistance of UHMW fluoropolymers, we found, that fluoropolymers are about five times less wear resistant (Stein, 1999, Khedkar et al., 2002). Thereby, we can try to employ another method – rubbing in. Thus, if we rub powerful enough the fluoropolymeric compound in, we can get a fluoropolymeric film on the ski running surface.
Solution
We developed and made fluoropolymeric compound rod, which has M14 tool interface for coupling to angle grinder (FP Drum). See Figure 1 .
Figure 1 Angle Grinder with FP Drum
We use angle grinder with variable rotation velocity to get 11000 rpm when we brushing and about 5000 rpm to do FPC treatment.
Result
We got a very thin fluoropolymeric coating with excellent hydrophobicity and very good wear resistance. Our glide tests demonstrate glide improvement with about 2.5% (shorter descent time) in comparison with proper steel-scraped skis. After 3 hours of skiing on cold (-12 °C) dry snow, virtually we cannot see any wear out of the FPC.
The method can be used even for stone ground ski running surface. We tested it on new ground dry ski base. After FPC treatment the surface looks very shining, skis have good glide, and after 5 hours of skiing on cold (-8 °C) dry snow, virtually we cannot see any wear out of the FPC (Figure 2 ).
Figure 2 Shining FPC ski running surface
Comparative analysis (today’s ski base material UHMWPE in comparison with FPC)
- Hardness is very similar;
- Lower hydrophobicity;
- Higher wear resistance;
- Lower dirt repellence;
Comparative analysis (today’s glide waxes in comparison with FPC)
Hydrocarbon glide waxes
- Softer (dirt attraction);
- Much lower hydrophobicity;
- Much lower wear resistance;
- Application is hazardous to health;
Hydrofluorocarbon glide waxes
- Softer (dirt attraction);
- Lower hydrophobicity;
- Much lower wear resistance;
- Application is hazardous to health;
- Environment unfriendly;
Pure perfluoroalkanes (fluorocarbons, perfluorocarbons)
- Softer (dirt attraction);
- Similar hydrophobicity;
- Much lower wear resistance;
- Application is very hazardous to health;
- Very environment unfriendly;
- By far more pricey. 30 g of conventional fluorocarbon powder (about $180) is enough only for 3-5 ski pairs, Fluoropolymeric Drum (FPD) is sufficient for tens (may be hundreds) of ski pairs;
Mechanical impact of Fluoropolymeric Drum (FPD) on the ski running surface
- Flattening (burnishing) of structures (topography) on the ski running surface. It is advantageous for very cold weather and for wet snow conditions in combination with coarse riller;
- Filling of shallow and deep valleys (even scratches) on the ski running surface with FPC (leveling of the surface);
Concluding remark
FPC and FPD are a good stuff. However, if you do not like any increase of complicity, use just “+” and “U” scrapers and enjoy very good glide on very short time of preparation.
References
Bowden, F. P. 1953. Friction on Snow and Ice. Proceedings of the Royal Society of London. Series A, Mathematical and Physical Sciences, 217, 462-478.
Bowden, F. P. 1955. Friction on Snow and Ice and the Development of some Fast-Running Skis. Nature, 176, 946-947.
Bracco, D. & Favre, J.-B. 1998. Pulmonary Injury After Ski Wax Inhalation Exposure. Annals of Emergency Medicine, 32, 616-619.
Karlöf, L., Axell, L. T. & Slotfeldt-Ellingsen, D. 2005. Why is ice and snow slippery? The Tribo-physics of skiing. Technical Note. Lillehammer, Norway: Swix Sport AS.
Khedkar, J., Negulescu, I. & Meletis, E. I. 2002. Sliding wear behavior of PTFE composites. Wear, 252, 361-369.
Kuzmin, L. & Tinnsten, M. 2007. The contamination, wettability and gliding ability of ski running surfaces. In: LINNAMO, V., KOMI, P. V. & MÜLLER, E. (eds.) Science and Nordic Skiing. London, UK: Meyer & Meyer Sport.
Outwater, J. O. 1970. On the friction of skis. Medicine and Science in Sports, 2, 231-234.
Palosuo, E., Keinonen, J., Suominen, H. & Riitta, J. 1979. Lumen ja suksenpohjamuovien välisen kitkan mittauksia = Measurements of friction between snow and ski running surfaces (in Finnish), Helsinki, University of Helsinki.
Stein, H. L. 1999. Ultra High Molecular Weight Polyethylene (UHMWPE), Ohio 44073, USA, ASMInternational®.
Strøm, E. & Alexandersen, O. 1990. Lungeskade i forbindelse med smøring av ski = Polymer-fume fever and pulmonary oedema due to ski wax (in Norwegian). Tidsskr Nor Laegeforen, 110, 3614-3616.
NOTE: We recommend an angle grinder with variable speed. Eg Bosch GWS 6-115E, Bosch GWS 7-115 E, Metabo WE 14-125 VS.
Always use safety goggles!
