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Edge Bevel Diagram: Need Instruction

post #1 of 17
Thread Starter 
I just did some research on the net regarding how to tune skis. I would appreciate it if those of you with experience could answer a few questions. I could use some help and I know others who are learning probably could too. I just purchased a Video Tutorial on tuning along with a wax kit and some basic files and stones with a beveling tool.

I am trying to understand the process of base and edge beveling and the resulting mechanical effects on the ski. I made a little diagram in Photoshop as it will probably make my questions and the answers more clear.

In the diagram below(obviously not to scale) the edges are represented in red. The bevel angles are exaggerated for the purpose of visualization. On the left the edges are shown without any bevel.


On the right the bevels are shown with the edge material(in red) filed away and the area within the yellow triangles represents the removed edge. The base bevel is pretty straightforward. Regarding the edge bevel do I have the diagram correct or should the angle be reversed from the vertical as shown in the 2nd diagram?



Diagram 2:



From reading the info on ski dynamics and beveling I take it there are 2 reasons for beveling:

1) The bevel on the base lifts the edges off the snow and the result is the ptex makes most of the contact with the snow and there is less drag due to the metal edges making contact with the snow when running flat. This results in less drag and more performance.

2) Edge bevel increases the edge grip slicing into hardpacked snow and makes carving the ski smoother and more efficient with much better edge-hold.

What other performance modifications does beveling produce?

What would the performance be like if you used the ski without edge beveling as shown by the edges on the left?

Regarding tuning:

How often do you file your edges to sharpen them?

Also do you need to use a bevel tool to deburr the edges using a soft stone or soft diamond stone? Is it soft enough that it will not grind away the bevel angle if you just rub it lightly against the edge to remove any burs?

Thanks for any input you can give.
post #2 of 17
Top diagram is correct.

A 1/2 degree base bevel does make it a little easier to skid, and not have to be constantly on guard against your skis taking you off on a tangent as well. Some people prefere more, but 1/2 is all you need imho. The side angle is to make the edge pointer and give yo better ice grip.
post #3 of 17
Ghost, you're a very accomplished, east-coast skier, hence the preference for 1/2 degree. Out here, most folks I know ski 1 and 3 degrees unless they are slalom skis (which are more like 1/2 or less).

FWIW.
post #4 of 17
Also, always worth a bump is dipstik's tuning guide: http://www.tetongravity.com/forums/s...&threadid=5528
post #5 of 17
I was quite happy skiing the shaped demos at 1 degree base and 3 side. If my skis came with 1 and 3 or 1 and 2 I would leave them that way.
post #6 of 17
My skis have a 1-1.5 base bevel along with a 3 degree side bevel and I am sure the base bevel has helped me "save it" on a number of occasions when I've caught an edge.
post #7 of 17
.5 to 1 is a good range to aim in, knowing you'll never be that exact and consistent over the entire length of all 4 edeges anyway.

I have a friend, master skier and tuner, in Vail who swears by 3 degree base and 3 degree side. I tried that for a while. I don't like it, particularly in the east, because it has very little quick bite when you need it. When the base bevel gets too large you need to roll the skis over more to get to your edges. It works for him because he skis soft snow and angulates SO much that his edges are there for him even with that extreme base bevel.

As to your other questions, there are many threads here on tuning, so you should see if the search function can help you find them. Most of us do very little to our base edges, just using diamond stones on them. For the sides some file more than others, but all of us use stones on the side edges.

A coarse diamond is good to use before filing to remove case hardened burrs that the file wouldn't handle well.
post #8 of 17
Continuing.... no bevel on the base would create a ski that is "railed" like riding on two rails, when your skis were flat not only would you not be as fast as on the base, but by having both edges engaged unpredictable things can happen. As to the side edge, 90 degrees or more acute are needed to bite, so a 1 degree base bevel would need at least a 1 degree side bevel so the resultant angle would be 90. A 3 degree side bevel (very common) gives an even more acute (sharper) angle.

As to whether you need a guide for stones, you'll hear both sides of this one. I certainly don't use a guide on a gummi stone, so on the soft diamonds usually don't. On the other diamonds sometimes I do, sometimes I don't. On the coarse one I probably should, but don't always and just freehand it. Interesting to hear what some of the other bear-tuners have to say about this.
post #9 of 17
Like the original poster I would like to hear the pros and cons of different angles (both base and edge) and the tech behind why poeple use such bevels. As opposed to just stating that you use a 1 degree base and 3 degree side bevel, state why you use those angles and what was your experience with other angles.

I Have found lots of other threads on bevels but not anything getting into the whats and whys of various bevels. For us newbies that are getting into the tuning game it would go a long way to understanding what you experienced Bears are doing and why. Thanks in advance for your insight .

Skimangojazz thanks for reply and explanation.
post #10 of 17
Quote:
Originally Posted by team ftb
Like the original poster I would like to hear the pros and cons of different angles (both base and edge) and the tech behind why poeple use such bevels. As opposed to just stating that you use a 1 degree base and 3 degree side bevel, state why you use those angles and what was your experience with other angles.
Well, I'll throw my $0.02 in.

I tune my skis to .5/3

Base bevel determines how quickly the ski will hook up after transition. A flat ski will hook up abrupty ...before I want it in most cases. .5 feels good to me. I tune my wife and daughter's skis to 1 or they'll complain that they're grabby and twitchy.

Edge bevel determines the purchase of the edge as it pushes into the surface. You want an acute angle (as shown in the initial diagram), this leaves a void between the side of the edge and the ice you're carving on as the edge pushes into the ice. Without this void, the side of the edge could (will) be deflected, causing the platform you're riding on to be destroyed ...you're sliding sideways now! Everything leaves my bench at 3 deg. Seems to be enough for my purposes, and anymore just makes the edge more vulnerable to damage. I'd probably look at this differently if I raced, but I'd likely have dedicated race skis as well.

Edge Angle is the combination of base bevel and edge bevel. .5/3=87.5

You can certainly play with these after you get the next base grind. You have to start at the smallest angles first then increment up. Going back means you have to use up the skis with a file or grinder and I hate to think of that ...I'd rather wear them out skiing!

To sorta disagree with SkiMangoJazz, I wouldn't characterize a flat ski as railed, although I'd agree it could feel pretty darn twitchy. I understand a railed ski to be when the metal edges are higher than the bases and/or the bases are concave.

Chris
post #11 of 17
i ski a 1/2

a high side bevel makes a sharper edge.....which also becomes dull more quickly.

i use a "moonstone" daily with a guide. if i do so on a daily basis with a liquid cutting solution i rarely need to have major work done.

i think folks fail to realize how critical "structure" is on the base of a ski
post #12 of 17
Quote:
Originally Posted by cgeib
To sorta disagree with SkiMangoJazz, I wouldn't characterize a flat ski as railed, although I'd agree it could feel pretty darn twitchy. I understand a railed ski to be when the metal edges are higher than the bases and/or the bases are concave.

Chris
I guess that is a better description and the more common use of the word "railed." If the base is concave you're really railed, but I'd think that the base edge would still have to be 0 to get the full railing effect.

Good description cgeib.
post #13 of 17
Quote:
Originally Posted by SkiMangoJazz
If the base is concave you're really railed, but I'd think that the base edge would still have to be 0 to get the full railing effect.
.
At that point, you have to ask 0 with respect to what?

Most would think it's with respect to the base immediately next the edge

- which would give you a railed ski even at angles >0 because the edges are tilted inwards relative to the middle of the base.

- Would be highly dependent on the tuning tool

- Would be relying on the (quite dubious) assumption that the concavity is uniform tip to tail to achieve repeatable results.
post #14 of 17
Quote:
Originally Posted by comprex
At that point, you have to ask 0 with respect to what?

Most would think it's with respect to the base immediately next the edge

- which would give you a railed ski even at angles >0 because the edges are tilted inwards relative to the middle of the base.

- Would be highly dependent on the tuning tool

- Would be relying on the (quite dubious) assumption that the concavity is uniform tip to tail to achieve repeatable results.
I was actually thinking about my post later and thought, well if the base is concave and the base and side edges were 1 and 3 you probably would still be railed as the ski would be pressing straight down into the snow until those two lips of the inverted half pipe that a concave ski looks like press into the snow and eventually engage those beveled edges.

Now on to convex bases If your skis are base high you'll have trouble edging and will be very unstable. Similar to too much base bevel, but worse.
post #15 of 17
When talking about beveling base/edges, one of the fundamentals is to have the proper tools as I found out. I know it's just another expense but I think it's money well spent given all the money we spend to ski, plus it's a one time outlay.
I use to do the bases with a taped file and an adjustable edge bevel tool. I recently bought some svst tools from one of the bears. What a difference. Not only in the ease of doing the tuning but in the precision of the bevel. A dedicated tool for each degree of bevel.
post #16 of 17
Quote:
Originally Posted by SkiMangoJazz
Now on to convex bases If your skis are base high you'll have trouble edging and will be very unstable. Similar to too much base bevel, but worse.
I haven't seen many base high bases since my old Atomic ATC1s. (eeew).

I find them pretty easy to reduce to flat with hand tools (Sears shaper plane and one of those base planers from Tognar).

I'd agree with your assessment of 'worse' only if you include base high that's created by sloppy/inaccurate/overzealous base beveling.
post #17 of 17
So included.
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EpicSki › The Barking Bear Forums › On the Snow (Skiing Forums) › Tuning, Maintenance and Repairs › Edge Bevel Diagram: Need Instruction