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After a Professional Major Tune: Should a Really Thin Piece of Paper Fit in the Gap?

post #1 of 12
Thread Starter 

A well-known ski store in the SF Bay area just completed a "major tune" on my 2008/09 AC30's.  These skis had not been tuned before.  Back at home, I got out a straight-edge and a flashlight to shine from behind just to see how the the job turned out.  I observed that the plastic bottom has a very slight concave shape vis-a-vis the steel edges.   A sheet of normal copy paper won't fit into the gap between the straight-edge and the base, but real thin paper such as heat imaging cash register receipt paper just fits. 

 

Is this small amount of concave likely to affect the performance of the skis as compared to completely flat?   

 

The shop said the bottom edge bevel was done at 1 deg and the side edge at 2 deg.  Shining the light behind the straight-edge on the bottom shows the bottom edge does have a very slight bevel.  And for the side, my 2 deg side edge tuning tool does match up.

 

Overall, the tune looks good with wonderful burr-free sharp edges and a structured base.  But as above, I am not sure if the slight concave bottom shape is significant enough to challenge the shop for a re-do.

 

Many thanks for your comments.

 

p.s. The tune was a $0 comp which I got as a sweetener to close the deal when I bought something else of significance from the store.   So I probably am not on strong grounds to complain too much!

 

 

 

 

 

 

post #2 of 12

I can't imagine it affecting performance at any place you're likely to be skiing living in SF.

post #3 of 12
Quote:
Originally Posted by rardi View Post

 

Is this small amount of concave likely to affect the performance of the skis as compared to completely flat?   

 

 

You'll be fine. It is not a big deal.

post #4 of 12

How reliable is your "straight" edge.

post #5 of 12

If your skis seem a little bit squirrely on your first time out, you know where the problem is. Then take them back and complain.

 

Rick H

post #6 of 12

You seem to have taken a lot of time to analyze and measure the results of the tune on paper so to speak.  How much time did you spend checking the base before said tune?  It seems really unlikely that anything a typical much less a "well known" shop would do in the process of tuning that would INCREASE the amount of concavity.  I'm laying odds that they were more concave when you dropped them off than they are now.

post #7 of 12
Thread Starter 
Quote:
Originally Posted by skier219 View Post

How reliable is your "straight" edge.


Its a stainless steel precision ruler of which I have several.  Checking is straightness was also my first reaction when I observed the concave ski bottom.  Putting it against the others rulers and also against the bottom of a high quality 10" block plane, there are no high or low points.   ... So its pretty straight.

post #8 of 12
Thread Starter 
Quote:
Originally Posted by crgildart View Post

You seem to have taken a lot of time to analyze and measure the results of the tune on paper so to speak.  How much time did you spend checking the base before said tune?  It seems really unlikely that anything a typical much less a "well known" shop would do in the process of tuning that would INCREASE the amount of concavity.  I'm laying odds that they were more concave when you dropped them off than they are now.


Very possible!   The AC30's had edge burrs and some scrapes on the base, but I hadn't checked anything more before I dropped the skis off at the shop.  It was only after that I began to educate myself to learn more about ski tuning from this forum and from the forum's suggested links.   This interest because I had several other skis that hadn't been looked after since new, other than waxing and the occasional hand-honing of the edges.   Being the type that has a garage full of tools, a DIY personality and (only recently) the time, I wanted to do them myself.   I've purchased edge bevel tools and scrapers and such and started first with my oldest most beat-up pair before progressing to the others.   Upon return of the AC30's from the shop (they were there for about 10 days -- I wasn't in a particular hurry to pick them up), I was curious to observe the differences between their and my outcomes. 

 

All my other skis had high bases compared to the edge level.  I discovered its quite a job to remove the excess base material with hand tools.   

post #9 of 12

You are being a bit too critical. A sheet of copy paper is only .0035". That is the equivalent of one brown human hair. Ski 'em. You'll never notice.

 

Karl

post #10 of 12
Thread Starter 

Thanks all!

 

Yes, I will ski them first before any more concern.  At the worst, I can get them re-tuned.  Either I'll do it; with the next pro tune ... being more specific that I want the edges and the base next to them ground down enough so that the base is flat all the way across.

 

 

post #11 of 12

Ski them till you need another tune then get it done.  No point in grinding more life out of them.  Unless you're a racer you should be so worried about your bases.

post #12 of 12

Concavity is not a problem as long as..........................................

 

Concavity is not a problem if the skis are flat Approx. 10-15MM in from each edge

Concavity is a problem (not in and of itself)  if  your skis are underbeveled in the tip and tail due to the tuning tool creating less then a 1 degree base bevel adjacent to the concave areas. This is caused by the foot or glide of the tuning tool sitting down in the concave area raising the file guide and file up too high over the edge and cutting the steel edge less then the designated bevel guide. . If the skis are under beveled in the tip and tail (The most common concave areas) they will ski similarly to to having a hanging burr or being railed.For example a .75 in the tips and tail and a 1 degree underfoot, is not a complimentary combo.

 

Someone described the skis as possibly being squirrely, which to me means slippery or loose,  The skis would not be squirrely from concavity or being under beveled. Actually, they would act just the opposite. They would be difficult to roll onto edge and once there they would not want to come off edge and would be unpredictable and grabby.

 

If the skis are under-beveled in the tip or tail or concave from edge to edge they would ski poorly because it is as though the edge is sitting  the base whne the skis are base down.

 

You need to check the flatness of the base adjacent to the edge specifically and then use a true bar and check the consistency of the base bevel.

 

DO NOT HAVE THE CONCAVITY COMPLETELY GROUND OUT OF YOUR SKIS. IT IS NOT NECESSARY AND WILL ONLY DRASTICALLY SHORTEN OR COMPLETELY RUIN YOUR SKIS ANDS MAY NOT EVEN SOLVE THE PROBLEM.

 

Do the true bar check, but you before you do anything to the skis you must ski them first and determine what symptoms (if any exist) that you don't like.

 

Then you can inteligently tell a tuner what the skis are doing that is bothering you and any tuner worth a his salt will know how to fix them without ruining or shortening the life of your skis.


Edited by Atomicman - 11/24/10 at 8:17pm
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