Fridtjof Nansen legacy
Best types of wood for skiing are homegrown
TRANSLATED BY M. MICHAEL BRADY
FRIDTJOF NANSEN AT THE INFANTRY WINTER SCHOOL
His last public lecture, on the gliding of types of wood on snow BY 1st LT. GUNNAR JUST
The Infantry Winter School, which reckons it began in 1923, has, as long as it has existed, considered questions of military winter technologies. Its work to develop military models of skis, bindings, sleds, winter clothing, etc., will be familiar from daily press reports.
The school thus far has been headed by Maj. Qvale, a well-known skier and winter gear professional. He has been able to attract experts on relevant topics to the school. Over the years, a number of professionals, expert in their areas, have visited the school for shorter or longer stays. These men motivated the school and contributed significantly to its further work.
The major’s ultimate achievement most likely was in persuading Fridtjof Nansen to explain his testing of and experience with the glide of wood types on snow, a matter that plays a crucial role in skiing, and hence, in military approaches to winter problems.
For we in the military, it’s essential to find a material for skis that grows within the country and meets the requirements of skiing. Nansen, through his work, tests, and theories, has unquestionably elevated the subject, which we can follow onward toward a final result.
The members of Skiforeningen are particularly interested in finding out about Nansen’s theories on this matter, so I’ve been asked to give an account of his lecture.
Nansen himself didn’t write the lecture. This was his intention, but he lamentably didn’t have time to expand upon the question.
Hence, the report here is only a stenographic transcript supplemented with some details that the stenographer didn’t record.
“The gliding of skis and sled runners on snow under various conditions is an extremely difficult subject. The matter has been inadequately studied scientifically and has not been subjected to thorough studies and experiments. Thus, I can merely convey my impression of the matter.
“Various conditions are involved in the movement and glide of skis and sled runners on snow. First and foremost, friction between the surface of a ski or runner and the underlying snow surface, resistance due to shape, suction due to air under a ski or runner, and various other effects.“First, let us look at the friction between the surface of a ski, specifically its sole, and a snow surface. You know that a ski glides easily in dry snow under ordinary conditions. This happens because heat due to friction between the wood surface and the snow crystals melts them slightly and the ski glides on a surface of water. Naturally, the amount of water is only microscopic. I can envision the peaks of snow crystals being broken to bits that become water.
“We all know that moving about under some conditions isn’t easy. When the temperature is extremely low, it’s like skiing on sand. In such cases, there is so little friction that little of the snow crystal peaks melt to water and we move on solid bodies, ice bits that don’t melt. This explains why the material in a ski plays a key role. In days of old, elm was considered a slippery wood for skis; hence, King Christian V’s law (of Denmark and Norway, 1687) forbade elm as a ski material.
“Finding good hickory or ash—solid and heavy materials—ensures easy glide. Impregnating the woods with tar or tallow improves their glide, because adhesion is less than with a raw wood surface. This holds in normal temperature conditions. Many skiers have found that as temperature drops, hickory skis glide less well, while birch skis, for example, begin to glide relatively better than other skis. The reason is easily explained. Birch is more porous than denser ash or hickory. It conducts heat poorly. So, less heat is led away from the ski sole. Hence, more heat remains to melt snow crystals, so birch skis glide more easily than skis of denser woods.
“The situation is more obvious with metals. A metal runner squeaks at minus-10°C or less and glides slowly. Metal conducts heat well, so less heat remains to convert a snow surface to water. Metal runners are all right at the melting point of snow but progressively worsen with falling temperature, and the thicker they are, the slower they glide. They lead heat more rapidly away. There also are differences between metals. Steel glides less well than copper, and German silver glides better, but runners must then be thinner. I have tried an extremely thin (¼ mm) overlay of German silver and have used it at extremely low temperatures.
“I believe that this is a general principal to consider in assessing the suitability of skis and sled runners at differing temperatures. On our polar expeditions, we used a thin German silver overlay, but we used good wood materials at lower temperatures. In my experience, the metal overlays we used worked at minus-15° to minus-20°C. Their surfaces are smooth, and resistance is considerably diminished, and in a way, that offsets their higher thermal conductivity. As mentioned, certainly at very low temperatures, the porous woods—for example, pines are better than dense hickory or another heavy solid material. I believe this is an obvious explanation of that phenomenon.
“Other matters also are brought into play. Why is glide so slow in drifting snow? Temperature then has no influence. This is a new matter that’s difficult to explain. I believe that suction under a ski matters here. Rim or hoarfrost is porous and doesn’t adhere; drifting snow, however, is made up of tightly packed, rounded snow crystals. Skis will cling to snow because there’s less air between their soles and the snow. It’s more like skiing on cloth.
“Adhesion between wood and snow plays a significant role. This is also why we set skis more firmly when we go uphill. This forms a harder surface that helps ski grip. One might object that glide improves as snow is more easily converted to water and should be excellent in wet snow. However, adhesion again enters the picture. There’s so much water that a ski and the underlying snow stick together; a ski collects clumps of snow, and resistance increases considerably.
“Lubricating with a fat lessens adhesion. Skis glide more easily, and we avoid clumping and excessive resistance. I believe that these are the essentials, but many other conditions of which we’re not yet aware play a role. We know little about the microscopic composition of snow. Rime is among the best surfaces to glide on. Its crystals are so loose that their peaks are easily altered because friction is distributed over several of them. But as mentioned, wet snow adheres and slows movement.
“Of course, other matters also come into play in the movement of sled runners. Friction is a decisive influence, and it’s also obvious that resistance increases as one sinks deeper into snow. The shapes of skis and runners also play a significant role. As a matter of fact, the influences of shapes are difficult to understand fully. Many other factors play their roles, such as quality of skis. Skis with sharp edges glide less well than those with rounded edges. Skis with rounded edges follow tracks better. I tried using steel strips under sled runners when I
found that steel runners had better glide on hard snows. However, I’ve not tried anything worse. Even when we turned a sled only slightly, we had to shove snow aside; its runners were useless. Our experience indicated that runners with rounded edges were best, as their glide was so much better. Of course, they easily glide to the side when going diagonally downhill, but I nonetheless believe they are reliable in use.
“Other factors also are important. If a ski is broader in front, the rest of its sides are clear of snow in gliding, though one must then consider the increase of resistance due to other factors. In my opinion, cross-country skis have attained an efficient shape. But then other difficulties become apparent. Unfortunately, we seldom make our own tracks and consequently have less experience in the performance of skis in plowing our way ahead alone. Members of the military have the same problem.
“One skier breaks a track, and others follow after. Nonetheless, I still believe that cross-country skis have attained an efficient form. Finnish skis apparently have a successful shape. They are slender up front, so the skis meet resistance on their sides and also under their soles. My impression is that the most efficient shape is an increase in width, but not abrupt, as several matters must be taken into consideration. Forests and mountains. In a forest, snow cover as a rule is loose; a skier sinks down, and the support surface must be larger. Snow in the mountains may be hard packed, with draft edges, and so on. So, the need is for two completely different shapes of skis.
“Hence, no one shape is absolutely the correct one. Friction is the same in both cases, so materials are decisive for glide. At very low temperatures, as mentioned, I believe that a runner or ski should be of light, porous material. I also believe that in such conditions, tarred, greased skis glide less well than dry skis, which conduct less heat. Skis with rough soles often glide better than those with soles of hard, dense material. Pine skis without tracking groove, but worn to expose the fibers in its sole, will always glide well in some conditions.
“This is a topic that has seen little research, but I’m pleased in having the opportunity to draw attention to it. There’s sufficient material here for anyone who seeks to research it further. I assume that a thorough examination of the topic in a variety of temperature and snow conditions will, as often happens, bring to light matters not considered in advance. One more thing: I’ll not take a closer look at ski waxing. Avoiding thermal conduction, minimizing friction, and other considerations, play roles about which we know so little that only experience can determine what’s best.”
This article originally appeared in the Dec. 11, 2020, issue of The Norwegian American. To subscribe, visit SUBSCRIBE or call us at (206) 784-4617.