Importing cars into Canada: 2018

This is email from Zach Caldwell at : http://www.caldwellsport.com/ who explained to me, why some of the XC skate skis I used in the past, have base deformation and it makes them hard to scrape. After several scrape passes wax was still left out on places across the base surface because concaved base surface ( mostly close to the tip and back of the ski )

Zach has years of experience in cross country ski waxing, base grinding at the advanced and competition level. He goes through hundreds of skis every winter, waxing and grinding them and knows all the aspects of glide waxing.

Here is what he wrote:

In general, all skis start out quite flat when they come off the factory finishing line. The factory equipment can’t make anything else. However, all skis are composite objects, and are subject to some level of deformation over time. Some of this can occur during a curing process between manufacturing and when the ski is sold. In general, that should be minimal. But a brand-new, never waxed, 2014 Fischer Carbonlite will for sure have a significant degree of convexity in the tip and tail region (for example).

With that as a starting point, it’s worth noting that about 95% of the deformation we see in skis that come in for grinding is caused but the owner of the ski during regular waxing. All of the propensity for deformation in every brand’s construction is accelerated and exacerbated by heat.

Now - a major point to keep in mind is that this is pretty much NEVER a problem with the BASE of the ski. The Madshus have very heat-sensitive core material and laminations. ALL of the serious deformation that we see is caused by over-ironing the ski during waxing. Multiple iron passes put heat into the core of the ski. The resins that hold the ski together are heat activated, and when the material BELOW the base reaches temperatures in excess of 100 degrees C, those resins soften, and the various composite parts of the ski construction can start to move in relation to each-other. Because these various parts have different levels of thermoplasticity, this almost always results in deformation of some kind. And it’s almost always what we would call “characteristic” deformation - it’s the same deformation that we frequently see in a given brand or model.

The waxing process is very widely misunderstood, and there is a huge amount of very bad information out there about how it works. The way it ACTUALLY works is very fast. Wax dissolves into solution in the amorphous material of the base as long as the base reaches a critical temperature of just over 100C. We want to keep the core of the ski well below 100C. So the temperature gradient through the base is very important. If you have a 140 degree iron, working with CH6 (or whatever), and a 20 degree (room temperature) base, then it’s easy to understand that there is a steep temperature gradient, and it will take some time for heat to penetrate from the iron, all the way through the base (which is about 1mm thick). However, after that first pass, the heat dissipates in the base, and now the whole base is much warmer, and the heat will penetrate through much more quickly because there is less thermal resistance. It doesn’t take too many passes with an iron - even when it’s set at a relatively low temp - to get the core up to 100C. And that’s when you start causing the deformation of the base.

And, most important - it’s not necessary. You need the wax to dissolve into the base near the surface, but you only ski on the surface. Really “soaking” the base does NOT make it faster. It just ruins skis.

I haven’t even mentioned actual base material damage, but this often occurs in the same way. If you’re seeing black wax shavings, or your bases turn white after a bit of skiing, then it’s due to one of two factors. 1 - high iron temp for the wax - each wax can tolerate a certain amount of heat without overheating. When the paraffin overheats it carries a lot of excess chemical energy, and when it goes into solution in the base it will destabilize the amorphous material. That is where the carbon-blacking live, is suspension. And if you destabilize it, then you pull carbon-blacking out of the base when you scrape wax, and the skis tend to slow down very quickly. 2 - “overcooking” - long-term exposure to low heat will cause the base to lose its structure - like overcooked pasta. It becomes “porridgy”. That frequently accompanies badly warped skis, because it’s caused by the same type of waxing behavior.

So - in short… no, ski manufacturers do not expect people to grind new skis. If you do grind your new skis, it should be because you’re looking for optimal performance from a better finish and structure pattern. Sometimes new skis that have been on the shelf for a long time are “pre-deformed”. This will happen, to a degree, depending on the construction. Generally, it’s not a deal breaker. Flatness isn’t actually that important for the performance of the skis.

Final note - when you’re seeing concavity in the base - low material in the center, along the groove - that’s concerning. Pretty much the only way that this occurs is when the ski has been subject to so much heat exposure that the core has collapsed. That is very, very rare, and usually only occurs on skis that are very old. It’s much, much more likely that you’re seeing wax remaining in the center of the ski because you’re flexing the plastic scraper, or perhaps using one of those Toko ceramic scraper sharpeners which, over time, but a nice curve into your scraper. It would be a good idea to get your skis cleaned up, and then examine them with a straight-edge or a true-bar. If you lay something that you KNOW is straight across the base, and then look at it with a light source behind the true-bar, you’ll be able to see whether the ski is actually deformed.

Almost all “normal” deformation causes the bases to go convex, not concave. The exception was a couple of production series of Fischer skis from about 2005 when they tried changing up some laminations to make their skis NOT go convex. It made them terrible slow, so they stopped! But those skis had normal deformation that actually made them concave. Beyond that, it’s pretty much only cores that have been obliterated by heat that go concave.

Cheers,

Zach
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Repair NESLAB RTE7 waterbath

Thermo Fischer Scientific RTE7 troubleshooting

Thermo Fischer RTE7

Issue: ERROR 25 , display shows current temperature -99degres
Potential problems: dual element RTE temperature probe faulty : Thermo Fischer part numer : 082393RTE -> Price $120USD OR analog to digital converter port ( pin 9 or pin 10 faulty : ) U5 on the main board
or any elements going from the probe all the way to microcontroller.

FOUND : resistor R81 ( value : 1.21kOhm ) opened - reads 3.3Mega ohms instead.