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Concave Atomic (and others) ski bases

post #1 of 10
Thread Starter 
Spinheli brought this subject up in a thread on ski bindings in this General Gear discussion when he was mentioned that in tuning skis for the season don't try to get the concave shovel area of an Atomic ski flat because too much material will be lost reducing the useful life of the ski.

As we start thnking about getting equipment ready for the upcoming season this question arises:

Are wide tip skis actually designed this way or is it that manufactuers simply cannot avoid a concave result when dealing with today's wider surface areas at the shovels of many of today's skis?

In the past a concave or convex condition or both often occurred in various places along the length of skis as a result of the skis being shippend from the factory after a base grind but before being fully cured.

Some manufacturers dealt with this problem by taking extra care to first let the skis cure completly. Then they would grind them more or less flat. Some suceeded better than others in this regard.

I wonder what the l tuning practice is with wide shoveled skis used on the World Cup? On my own skis the widest shovels I have are 103mm and concaveness was not a problem when I purchased them.

I raise this question out of intellectual curiousity but also because I lack the motivation at the moment to do something more productive with my time.

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[This message has been edited by Lostboy (edited September 09, 2001).]</FONT>
post #2 of 10
Not this one again. We beat this topic to death last season. Try to do an archive search for the related threads.
post #3 of 10
Thread Starter 
Thanks for responding. I did check out the threads I found on the subject.They contain a lot of discussion on whether the bases should be ground flat or not and whether the concavity was a uniform feature of all the skis that left the plant.

My question though is what is tuning practice on the World Cup in this regard. It is not only Atomics that have this concave feature. A lot of wide tipped ski do. I didn't find any answer to that in looking at past threads unless I missed something.<FONT size="1">

[This message has been edited by Lostboy (edited September 09, 2001).]</FONT>
post #4 of 10
My team stock Atomic Race 10.22 and 9.16 had concavity in the shovel area. These are the same skis that Maier or Raich would have used last season.
post #5 of 10
Thread Starter 
But how do they tune them on the World Cup? That is my question.

And not just Atomics. While the ski is highly edged it would not seem to make any difference but at high speeds during transitions or any time the skis are running straight it seems to me that it would. That's why I asked.

Looking at the prior threads It seems that some thought this might be a knock against Atomics. That is not my intent. I think that many if not all wide tiped skis probably have concavtivity at in the shovels out of the wrapper.

I'm just interested in how the top tuners deal with the issue where the longevity of the ski would not be an issue.
post #6 of 10
I noticed same thing on my K2 Mod X's last year when i got them. I skied them anyway and they seemed fine.
post #7 of 10
I asked someone who prepares a lot of atomics about this and got somewhat of a different answer. I'll quote/paraphrase here.

>> A concave base will not ski as well as a flat base. This is more pronounced
in firmer snow that is grippable than in soft snow where the ski does not
get a firm bite. Most manufacturers have difficulty delivering a finely
tuned product to the consumer for several reasons:
1 - Resins used in ski manufacturing tend to cure for some time after the
ski is produced which can cause a ski to take on an irregular shape. It is
simply not practical for the manufacturer to set unfinished skis aside for
several weeks for curing before doing the final grinding to flatten the
2 - Finishing processes at the factory level are entirely by machines which
change during production runs. Machines must be constantly "dialed in" as
their abrasive drums or discs wear away. Different sidecuts and sizes
(thickness and length) also require changing setting on the machines to
deliver some degree of uniformity.

Atomic tends to ship concave skis. This is probably because the Beta shape
with the higher humps tend to put more pressure in the center of the ski
when the ski is fed through a grinding machine with a pressure wheel on top
of the ski. Their base edge bevels also are quite erratic as they
consistently vary between 0°- 3°. I believe this is caused because the
automatic bevel machine cannot grind the edge where the ski base has any tip
curvature. Therefore, the skis usually have no bevel in the extreme forward
contact point and then tend to pick up a 3° "divot" immediately after the
bevel machine makes contact with the ski.

Our solutions:
1 - "If it ain't broke, don't fix it." Many "imperfect" skis perform quite
well depending on the skier and snow conditions.

2 - Make certain the base bevel is at least 1° by using a base bevel guide with
file and polishing stone. Don't worry about slight irregularities of
increased base bevel unless you feel performance is being compromised.

3 - Erratic behaving skis are ground to somewhat flatten the tip area. We
grind with only hand pressure on the ski to eliminate the concavity caused
by the feed wheel putting pressure on the center of the ski. We consider
the ski to be flat when it is flat about 25% in from each side. A slight
tunnel in the center does not have any adverse effect. We then use hand tools to establish 1° base and 3° side bevels. Edges are polished and deburred. If the ski is still hooky you might try a 1.5° base bevel in the forward 15-25cm to soften immediate edge contact in the extremity.

4 - Many erratic behaving skis are actually the result of improper boot
alignment or canting. <<

And finally this comment:

>> Atomic's World Cup results are not a result of skis that are concave in the
tips other than the slight tunnel as described. Race skis are meticulously
tuned to perfection by ski team techs and don't resemble what is on dealer
shelves. Speed skis are usually convex because bases glide faster than
edges and you don't need or desire immediate edge hook-up at high speeds. <<

hope this helps, though it may stir the pot...
post #8 of 10
I actually heard basically the same answer from Atomic guys at Mt. Hood this summer:
Concave base is the result of manufacturing process and is not a design feature.


Speed does not kill, the difference in it does...
post #9 of 10
Thread Starter 
BetaRacer, dc9mm,Tog, VK,

Thanks for your responses.

I had mixed feelings about getting back to the subject of skiing today in light of yesterday's terrible events.

But then I thought that we should not be cowed by those who committed yesterday's horrific acts so minimal a gesture as this response is.
post #10 of 10

Beta is cringing but it think it needs saying. I would check the bases with straight edge prior to purchasing any Atomic product.

Of the four pair of new Atomics that graced our race team this year (that I am aware of), one pair was severly cupped and a lot of base had to be taken off just to make them servicible. One (coaches pair) had a ski that was true and one horribly concave.

My son's skis had bottoms that showed very slight cupping and were OK.

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[This message has been edited by yuki (edited September 12, 2001).]</FONT>
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