March 28th, 2009
The day after I made the spring break post, I got an e-mail from Chris Hall, director of nordic racing for Fischer Sports USA. I was very hopeful that I was finally about to be sponsored, but this was not the case. Chris had apparently been reading my blog, and was concerned that I’d been having some serious problems with Fischer skis (I’d complained that I noticed that Fischer bases sometimes don’t stay flat).
I explained my problem to Chris, and he wrote back with an informative e-mail that explains why this happens, and why it’s probably worth the minor inconvenience when waxing. I figure most people would be interested in reading it, so the relevant portion is below (don’t worry–I got his permission…).
“From your comments, it seems that this is not affecting the overall performance of the skis. I may be able to shed some light on to why this may occur occasionally in our skis. As you move out toward the tips and the tails of the ski, the height of the ski is smaller, as compared toward the middle section, where the height of the ski is larger. So, there is more core material in the center of the ski as opposed to the ends. Because of this, there is sometimes a tendency for the tips and tails to move out of “flat” and become slightly convex.
This can be considered a trade off for many reasons. One, it is important to use less material in the tip and tail so the swing weight of the ski can be as light as possible. Two, the camber of the ski is created by the carbon fibre layers and the core material in the center of the ski, so again, less or no core material is needed in the tips and tails. Three, the actual running surface of the ski, meaning the area of the base that is actually in contact with the snow and receiving the skiers body weight when gliding or kicking is typically further back from the ends of the tip and tail, so these extremities are rarely in contact with the snow, if at all. It would be possible to insure that the ski base remained perfectly flat throughout the ski for the life time of the ski, but would the trade off be worth it? It would probably mean increasing the weight of the ski and increasing the swing weight of the ski. In the end, this trade off would not increase the gliding characteristics of the ski.”
March 29th, 2009 at 10:49 am
It seems like over the last decade perfectly flat bases have gone from being a priority to something that is not seen as overly important. Stonegrinding was looked at as a way to “flatten” skis, and prior to stonegrinding taking off in the 90’s in the US, metal scraping and even sanding were used to get a flat base. I heard the saying “a flat ski is a fast ski” many times.
Now, stonegrinding is primarily about structure, and rehabilitating old bases. Rarely do you hear people talk about wanting to get their skis “flatter.” I have been told as well that hot boxing can cause skis to become “un-flat,” or at least speed up the process, yet this process is used extensively. Flatness just doesn’t seem to be a big deal. Though when it comes to scraping skis, there is nothing like a perfectly flat ski!
Obviously this is all anecdotal, and others may disagree.