Ski Base (Glide) Structure

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General

This Tech Page discusses creating or adjusting the glide zone structure of your ski base.

Why Structure the Ski Base?

Structuring the ski base is simply about improving the glide of your ski. The better the glide the less effort you need to go the same distance and perhaps even go faster. This sounds good, you say. But can't the ski manufacturers do this for me? These days most ski manufacturers do in fact structure the ski base. The most care for this structuring is applied to the more expensive skis.

If you are purely a recreational skier then it is unlikely that you will really need to structure your ski bases different from their current state. The effort is non-trivial in terms of time and possibly cost (more on that later).

If you are a fitness skier, a "weekend ski warrior" or a racer then this may interest you enough that you want to do some structuring. Please note that there is a good chance that the structure on your skis is just fine for the skiing you do. Don't start until you are sure.

So what is about the structure of the ski base that will help the ski glide better? It depends on the conditions that you are skiing. A structure that works well at -15C does not work well at 0C and the reverse holds true too. In general terms the colder the snow the "finer" the structure and the warmer the snow the "rougher" the structure. For a given temperature with certain humidity and snow structure there are near-optimal structures. Glide wax is still needed of course.

This page is not going to discuss how a ski glides. The topic of why a ski glides is worthy of an entire web page itself. Once that web page is written a link to it will be placed here and on the Tech Page listing.

Preparing to Structure the Base

Each section below, on the different types of structuring, describes most of the prepartion needed before starting. It is simply easier to deal with it specifically for each case.

Rilling

The Rilling Section applies mostly to Nordic/Cross-country skis. This is something not regularly done with Alpine/Downhill skis.

Rilling is the process of pressing, not cutting, small grooves into the base of the ski. The grooves can be wide or thin, go the length of the ski or be produced in short dashes and be parallel to or angled to the direction of movement. The benefit of rilling is to provide a macro-structure to the base to help the ski glide better in wet and humid snow conditions. Rilling can be done in both warm and cold conditions when appropriate. Rilling done in inappropriate conditions can make the ski slower.

Generally speaking rilling is used when the snow pack is very humid or wet. This usually means the snow has aged from fresh, well-defined crystals to old snow or ice crystals. Rilling done when the temperature is very cold and the snow is well defined will result in the snow crystals literally getting stuck in the rills. This is a physical drag to your glide. A typical condition when rilling is of benefit is a day that is above 0°C on old snow with lots of sunshine and no wind. Here there will be lots of water/humidity in the snow pack. The rills will help this water flow off of the ski and break the surface tension between the ski and the water/humidity.

There are different sizes of rills and different patterns of rills. Some of the rill patterns match or mimic what a stone grinding can do to the bases. The benefit of rilling, when you don't own a lot of skis, is that the rilling tools are easy to carry in your wax kit. Small, thin or fine rills are used at colder temperatures while big, wide or thick rills are used at the warmest temperatures. At the in-between temperatures there are in-between rill sizes. At temperatures that are very warm you can go all out and put all of the different rill sizes onto the base of the ski.

Note: once the rills are on the base you should do a practice ski. The rills act just like the big groove in the ski base: they keep the ski moving in a straight line. You will find it harder to "carve" a turn in a parallel or telemark style. A step turn may be easier depending on the rill job. Because of this control some people, for training purposes, put light rills on the base to help them improve their technique. For people who are over-pressing their skis and are experiencing their skis twisting, light rills in the center of the ski can aid in the control -- it won't necessarily make you faster.

There are a number of different tools that can be used for rilling. Over the years people have used tools such a files/rasps and stiff wire brushes. These have fallen out of favour for several reasons: they tend to remove base material, they leave a lot of p-tex strings and hairies dangling, and there are more effective rilling tools. The price range for a good riller is from about $100 up to several thousand dollars (we jest not). A good riller will not cut into the base or remove material. A good riller will add macro-structure to the ski base.

Preparing for Rilling

Wax your skis with the wax of the day. Doing this on a ski profile will make the rilling job easier. Of course the ski profile should be attached to a solid table that will not move when you press down on the ski. The best ski profiles for rilling clamp the ski down by the ski binding. Ski profiles that hold onto the ski from the side can make it awkward to rill the length of the ski in one pass as rill guides often run along the sidewalls of the ski to help you maintain control.

You should remove any excess wax from the glide zones of the ski with a scraper. But do not brush yet. The scraping will remove excess wax that could clog the riller mechanisms and/or not allow the riller to press the ski base. By not brushing a thin layer of wax will remain that can shield the ski base from getting accidentally cut by a riller, and if the riller does remove wax it removes wax that is not needed. If the bases are brushed first some rillers have a tendancy to remove a thin layer of wax. This can be especially telling with pure fluorocarbon powders. If the ski is brushed and then wax removed, you'll have to wax the ski again or accept the sub-optimal glide job.

Doing the Rilling

Most rillers come with instructions. You should read these instructions. Don't throw the instructions away. Place the instructions in a small ziploc plastic bag and then place the bag in your wax kit or wax box. The bag will keep water, wax and klister from damaging the instructions. The instructions should tell you which rill should be used for which condition.

Many rillers are uni-directional. That is they are designed to work from the tip of the ski to the tail of the ski. Using the riller in the opposite direction can result in the glide being not as good as it can be.

Try and run the riller the length of the ski, tip to tail, in one smooth, even pass. The "smooth" means no stopping or stuttering; the same deliberate pace the whole ski length. The "even" means the downward pressure on the riller should be consistent the entire lenght of the ski. An stuttering and/or uneven pass of the riller will make for a poor rill job. Of course if you are rilling a ski for classical skiing you will want to skip the kick zone with the riller.

Now brush the skis as you would normally. You may want to make one or two very light passes with fibertex to remove any of the base material that may have been raised by the riller. If you have used a large rill then more base material may be raised than is good for the ski's glide. In this situation use a sharp plastic scraper lightly along the base before brushing and using fibertex.

Sanding

This section is written about sanding the glide zone(s) of skis. For sanding the kick zone refer to Sanding the Kick Zone.

Sanding is a structuring method that you can do at home without a high cost. It does involve a time investment, but it is an investment that should reward you with better glide. Another bonus is that you can easily carry all of the equipment for sanding in your wax kit no matter where you go. (Ski base stone grinders are a little heavier to carry around ;-) ).

The coarseness or fineness of the structure that you will place into the ski base will be determine by the grit number (roughness) of the sandpaper you choose. A coarser structure is better for very wet and/or humid snow while a finer structure is better for colder and/or drier snow. You may start your sanding with a coarser grade of sandpaper to remove base material more quickly. You must finish with the grit value that matches the snow condition you are aiming to optimize for. The structure placed into the base by sanding can be enhanced with the rilling technique. The two techniques can complement each other.

A special note about the type of sandpaper we recommend you use, and the type of sandpaper you should not use. Do NOT use garnet sandpaper. Garnet sandpaper is cheap sandpaper; the grit always comes off the paper. This can leave grit on the base. The garnet grip isn't the smoothest cutting either. We recommend using a waterproof, silcon carbide sandpaper. It keeps the grit on the paper, it can be made wet for cleaning, it can be wet while in use, and the cutting action is very clean. We recommend this sandpaper be used for these technical reasons.

Below is a recommendation for grit values matching snow temperatures and snow structure. It is a guideline only that you can adjust with experience.

  Temperature     Snow Type     Grit Value  
 0°C..warmer All #80
 0°..-5°C All #120
 -4°..-12°C All #220
 -10°C..colder All #400

Preparing for Sanding

If you have any base repair it should be done now too.

The tools you will need are: waterproof sandpaper, a rounded sanding block, a plant mister, slightly soapy water and a ski profile/bench to hold the ski. The grade, or roughness, or sandpaper will be your choice as described earlier. The plant mister will be filled with the slightly soapy water. Standard liquid (non-chlorinated) dish soap mixed with water will be sprayed onto the ski bases. This will help keep the movement of the sanding block even, suspend base particulate to help keep the cutting clean and help keep the sandpaper clear of base material so it can cut effectively.

The sandpaper should be placed on the rounded side of the sanding block. You will be moving the sanding block with the sandpaper on it in a rolling or rocking motion as it progresses along the ski. This will expose new sandpaper to the base for a cleaner, more even cut. It will also create an interrupted structure that is beneficial to glide.

Put the soapy water mixture in the mister. Spray the ski base with the soapy water. As you sand the base regularly re-spray to maintain the liquid on the base. Occationally you will want to wipe the base with your hand or a squeegie to remove the base material suspended in the liquid.

Starting the sanding block at the tip of the ski and drag it lightly towards the tail. The downward pressure should be about the same as the weight of the sanding block. The pressure along the base should be even and constant. Each pass along the length of the base should take only 2 to 4 seconds. Remember to maintain the soapy water layer on the ski base. After about a dozen passes take the sanding block to a sink and under running water rinse the waterproof sandpaper clean of base material.

The start of each pass, at the tip, will begin with the leading edge of the sanding block touching the base. The end of each pass will finish with the trailing edge of the sanding block, at the tail, touching the base. This is achieved with a single rolling of the sanding block as it progresses along the ski from tip to tail.

When you have removed as much base material as you need to create the structure on the base wipe the soapy water off. With a wet cloth wipe the base clean to remove any soapy residue. Then either let the ski dry or wipe the ski dry. Once dry, with a steel scraper make 2 or 3 very light passes to remove any large bits or strings of base material. Now make several dozen passes over the base with green (coarse) fibertex. If you have used a finer sandpaper you may want to use the white (finer) fibertex. Using a roto-tool (the velcro with fibertex on it) makes this part of the job a lot faster, easier and enjoyable. The fibertext pass will remove any residual "hairies" from the base.

You should wax the ski as soon as possible (i.e. now). See the footnote on After Structuring.

Stone Grinding

Preparing for Stone Grinding

Preparing for stone grinding is not so much preparing yourself, your skis or your workshop, but researching who can do the job well. A shop that does stone grinding on alpine skis and hasn't ever done nordic skis should likely be avoided. A ski is not ski. There are specific grinders designed and built just for nordic skis. If the shop has a nordic grinder then you've likely found a good shop. Some grinders can use a bridge that is placed over the binding so that the ski will feed smoothly through the grinder. Without a bridge the bindings will have to be removed (it is a pain to remove and reattach binding). If the grinder can use a bridge you should ask that it be used.

If possible it is a good idea to ask people that you ski with for a recommendation of a good shop. If you belong to a ski club the coach of the ski team is a good resource to ask. There are a few shops that accept skis by mail or courier, grind them, and then ship them back. More information on these shops can be found through Internet search engines.

There are a couple of things to do before the grinding process with your skis. You should remove any wax (particularly grip wax or klister). Most shops will do this for you since they don't want their machine gummed up. But if you do the cleaning beforehand some shops will reduce the price. If you have any base repair it should be done now too. Minor scrapes will be removed by the grinder. But deep gouges should be repaired.

Doing the Stone Grinding

If you happen to own your own stone grinder then you've had detailed training on how to use it. If you are taking your skis to a shop to do the stone grinding for you then you must remember to ask if they are going to do the job while you wait. If you can wait for your skis then this means you can do a post-grinding basewaxing ASAP. If the shop is putting your skis in a rack until someone can get to them and you can't wait, be sure to check that the skis will be waxed immediately after grinding. The wax job should be a travel wax; wax on in a thick layer with no scraping and no brushing. Otherwise you risk the result of the structuring being less effective than it could be.

Most grinding shops offer a variety of different grinding patterns. If you have only one pair of skis or this is your first trial at using stone grinding you should pick the most generic grind pattern/structure. This should give you the best general purpose structure. Otherwise the staff at the shop can either verbally explain or give you a pamphlet explaining what different grind patterns they offer and which may best suit your needs.

Stone grinding machines are made by a few different manufacturers (mostly European). The variety available even from one manufacturer is truly amazing. Some machines will grind, hot wax and polish up to six pairs of skis at once! Most shops won't have something that fancy. Most shops will have a grinder that deals with one ski at a time. The key component to the grinder is, without surprise, the grinding stone. The stone is responsible for flattening the base as well as placing the structure on to the base. Over time the stone wheel wears down. The better machines automatically adjust the RPM of the wheel to have a consistent surface speed over time. This reduces the chances of a grind job sealing the base and improves the quality control for the structure placed on the base. The structure pattern placed on the base will be a result of the choice of stone or stones used plus how the grinder uses the stone. Some grinders can oscillate the stone different ways to produce different structure patterns. While the stone is grinding the ski water will spray to provide a lubrication for the stone on the ski and to help keep the ski base from heating due to friction.

In general, if your ski is fairly new, in good condition or recently stone ground then not as much preparation will need to be done by the technician. Regardless, the grinding process usually goes through the following stages: flattening, leveling/polishing, structuring, buffing/polishing and waxing. The flattening stage is needed so that the structure can be put on to the base. Without a flat base it's very difficult to add structure. The leveling/polishing stage is often combined with the flattening stage. This stage removes any existing base structure so the base will be a "clean slate" for the new structure. The structure stage add the structure to the base. The buffing/polishing stage removes any fine "hairies" from the base. Most stone grinds will be fairly clean so the buffing/polishing stage won't do too much, but it's part of the process for a good structuring. The final stage, waxing, is to cover the base to prevent oxidization of the base before you can start basewaxing.

After Structuring: Waxing!!

This section applies to the sanding and stone grinding types of structuring.

With base material removed to a significant depth fresh P-tex is now exposed. The sooner wax is impregnated into the base the better the glide of the ski will be. If the fresh base material is left exposed it will start to oxidize making it more difficult to wax to be placed in the ski base.

We recommend that you follow the instructions on glide basewaxing web page. Remember that you should do at least five (or more) basewaxes for the most optimal coverage and depth.



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