Making Sense of Figure Skate Blade Profiles

Blade profiles is one of those subjects to which entire web sites could be dedicated and somebody would still find something that wasn’t covered adequately, or a case where something didn’t apply. Nonetheless, it’s useful to understand what’s being talked about when there’s a reference to blade profiles and rocker radius (sometimes written as Radius of Rocker, or RoR in a similar way to Radius of Hollow (ROH)). Hopefully I can make some sense of the topic without getting too dragged down into the many, many variables involved.

Blade Profiles

The phrase blade profile refers to the shape of the blade surface (that is, the bit that touches the ice) as viewed from the side. I’m only one sentence in, but I already have to add a caveat that some manufacturers have also created products which change the profile of the width of the blade along its length (for example, John Wilson Parabolic blades, or some of the tapered blades which are thicker at the front and narrower at the back). For the purposes of this page however, we will ignore this complication and concentrate on the side profile of the blade.

Unsurprisingly there is no “one size fits all” for blade shapes, and over the years manufacturers have experimented with different curves and toe pick designs with varying degrees of success. In the end, though, many current blades seem to try to emulate some classic John Wilson blade designs such as the Gold Seal and Pattern 99, which are ubiquitous competition-level blades.

Anatomy Of A Blade

Figure skate blades are made up of three main functional sections, and understanding what each part of the blade does will help with the further explanations below.

The diagram above shows the two parts of the blade which are used for movement; the third part are the toe picks on the front. I am, by the way, ignoring the lethal weapons (toe picks) on the front of the blade for the moment. While they—and their relationship to the blade—are important, they won’t help this discussion any.

It’s important to understand that the two labeled parts of the blade are used for different moves. When gliding or stroking on the ice, the skater uses the rear part of the skate (the rocker). When performing jumps and spins, however, the skater moves their weight forward to use the front part of the blade (sometimes called the “spin rocker”). This is why the tapered blades I mentioned above are thicker at the front; to support the jumps and spins.

Rocker Radius

The shape of the blade profile for figure skates is usually quoted in feet, and as with Radius of Hollow, the idea is that if one were to draw a circle with that radius, the shape of the bottom of the blade would follow an arc of that circle. If that’s confusing—and it probably is—let’s make it clearer by using my daughter’s Jackson skates as an example. Her skates have the Mirage blade on them, and Jackson’s website has this specification:

Jackson Mirage Blade Specification

Based on the information above, the Mirage has an 8′ rocker radius. To illustrate this, I took the skate image into a drawing program and scaled it to represent its actual measured size. I then created an 8′ radius (16′ diameter) circle and overlaid it so that the circle’s arc could be matched against the blade. This is the result, and the thin yellow line is a small arc from that huge circle:

What should be obvious here is that while much of the blade aligns with the stated rocker radius, not all of it does. The rocker radius really refers to the rear part of the blade that’s used for gliding and stroking. The section of the blade used for jumps and spins is clearly not using a circle of the same radius.

What difference does the rocker radius make? Well, a larger radius means a flatter blade, which means more of the blade will contact the ice at any one time. This may make the blades feel a little more stable, although they may be marginally less maneuverable on the ice. Conversely a smaller radius means a smaller contact area, and skaters seem to report more instability especially if they were used to a larger radius rocker previously. Choosing an appropriate rocker radius is definitely an area where talking to your skate tech and coach is important. However, as you’ll see below, the rocker radius alone does not define everything about the blade’s behavior.

Two and Three Radius Blades

Figure skating blades do not in fact use a single radius, despite that being what’s quoted on the literature; they typically use two or even three radiuses along the blade. The largest radius is reserved for the rear section, and the front jump/spin section will normally be cut either from one other radius, or split into cuts along two different radius arcs. Looking at the Jackson Mirage blade again, the front section appears to be cut using somewhere around a 17″ radius. I have overlaid a green circle on the previous image demonstrating this much sharper arc as seen at the front of the skate:

It’s interesting to me that the only radius quoted for almost every blade is the main rocker radius rather than the front radius (or radiuses), because it seems to me that for a figure skater the properties of the area on which they perform jumps and spins might be far more important to them, or at least might have more impact on the skating performance. Maybe I’m wrong. What do you think?

Accuracy of Sharpening

Given that the exact curvature of each make and model of blade are part of the blade’s characteristics, finding a skate tech / blade sharpener who can accurately and consistently grind the right profile on to the blades is really important. In fact, this will probably become a recurring theme on this blog when it comes to skate maintenance: find a great skate tech (word of mouth is usually a good way), make friends with them, grab hold of them and never let go! You need to be able to trust that when your skates are sharpened, they’re going to come back correctly sharpened, the same way, every time. The corollary to this is that taking your skates to be sharpened by a different person or at a different place each time is a bad idea.

Hopefully if this was previously a confusing topic, this helped shed some light on the subject.

January 2, 2017January 6, 2017

Blades: Radius Of Hollow (ROH)

Ice skating blade descriptions often feature a specification called Radius Of Hollow (ROH). Ever wondered what it is?

Radius Of Hollow

When blades are manufactured (or sharpened), part of the decision to be made is what ROH to cut into the blade. Typical values for ROH might be between ¼” and 1½”, but more commonly for figure skates you’ll see values from 5/8″ to 7/16″. But what does this all mean?

Somebody who has never looked closely at an ice skating blade might have assumed that the blade surface (the part that is skated on) is flat, so looking at the blade end-on (rather than side-on), one might assume it looks like this:

In an ideal world, a perfect skater could (would?) use flat blades. The disadvantages of the flat blade though are that unless the skater were always 100% perfect in their movements, they would likely fall regularly, especially after jumps. Using a non-flat blade surface helps us get better grip and control on the ice, and since we are all terribly imperfect, that’s the norm.

With that in mind, the blade is ground (sharpened) using a curve, creating a kind of arch shape over the ice. This means that the blade actually touches the ice on two rather sharp edges:

The arch creates an empty space between the blade and the ice, and this is what is being referred to as the hollow in Radius of Hollow. As for the radius part, you probably know that a radius is the length from the center of a circle to the outside (i.e. it’s half the diameter, or distance from side to side).

To create the hollow, take a circle with the desired radius, center it horizontally on the blade, then move it until the bottom corners of the blade just touch the circle at those two points. The arc between those points is the curve we want to cut into the blade:

A larger radius means a larger circle, so the hollow that is cut out will be shallower. Conversely a smaller radius means a smaller circle, which leads to a deeper hollow.

Radius of Hollow (ROH) therefore refers to how deep a hollow is cut into the blade surface, and the value given represents the radius of the imaginary circle from which the hollow’s arc (curve) is taken.

ROH Drawn To Scale

The images above show an exaggerated representation of the ROH on the blades in order that it’s more obvious what’s going on. Drawn at scale, here is a 3/16″ width blade (fairly typical) with four different ROH:

It’s a bit hard to see the difference, so here’s a close up of the same four ROH profiles:

The difference is hopefully visible now, but looking at a skate blade I suspect I would be hard pressed to identify which ROH had been used!

Edges

The two sharp parts of the blade touching the ice are the edges. I’m going to state what’s probably obvious here and confirm that the sharp part on the outside of each foot is known as the outer edge and the one on the inside of each foot is the inner edge.

Misalignment

One reason to use a reputable skate technician to sharpen your skates is to ensure that they are capable of aligning the cutting tools very precisely. If the tool is off-center even by a small amount, the results can be anywhere from irritating to disastrous:

Trying to skate on misaligned edges like those shown above would be virtually impossible.

What ROH Should I Use?

Choosing a ROH is a matter of personal preference and, sadly, trial and error. There’s not really a magic formula to determine which will be best for an individual, as a number of factors can influence that decision. A radius of hollow around 5/8″ is a fairly typical place to start, sitting roughly in the middle of the usual ROH range.

Typically, the better the skater, the larger ROH they will use. To that end, one way to determine the shallowest possible ROH for your skater would be to increase the ROH each time the skates are sharpened, and then when an ROH is reached where skating becomes too difficult, back off to the previous ROH. It’s not a hard and fast rule, but it’s a start.

Larger ROH (Shallower Hollow)

A larger Radius of Hollow (shallower / flatter hollow) gives slightly less control and less tight turns, because the edges cut into the ice less than a deeper hollow would do. On the up side, the flatter hollow glides well and can (subjectively) make the skater look a little more fluid on the ice as a result.

Smaller ROH (Deeper Hollow)

A smaller Radius of Hollow typically gives more control and tighter turns (because the deep hollow means that the edges cut into the ice more) and as a result the blades are more forgiving of the skater’s form, especially where landings are concerned. Small ROH means more bite, but also means the skates will glide less well, and it may take a bit more effort to skate as a result. One final point is that the marginally sharper edges with a deeper hollow mean that the blades can apparently be more prone to chipping.

Weight

Weight is a really important factor to take into account because it alters the effectiveness of the hollow quite significantly. Heavier skaters will need to use a larger ROH (i.e. a shallower hollow) because their additional weight will force the blades into the ice harder and allow them to cut in effectively despite a relatively shallow hollow. Cut a deep hollow on skates for a heavy skater and they may find that their weight pushes the edges into the ice so deeply that they can’t stop properly, trip over themselves or have difficulty turning. Too much ‘edge’ can be as bad as too little edge in this case.

A lighter skater in comparison will generally need a smaller ROH to get better control because they don’t push the skates down as hard and the extra depth creates more angular edges which will cut into the ice more effectively.

Ice Temperature

Believe it or not, the temperature of the ice also plays a part in the effectiveness of the ROH choice. Colder ice is firmer which prevents the edges from cutting in quite as much as they would on warmer ice; therefore a colder ice rink may require a deeper hollow on the blades (smaller ROH) to get similar bite to a larger ROH on a warmer rink. This is something a little more out of the skater’s control, unfortunately, but it’s worth knowing about nonetheless.

December 30, 2016May 14, 2017

Renting Skates versus Buying Skates

Once of the questions I struggled with when my children started ice skating was when was right to consider buying skates. If you’re new to ice skating, you’re likely wondering the same thing too, so here are my thoughts on the matter.

Renting Skates

The summary is that rental skates suck. That’s not to say that you can’t have terrific fun wearing them, but they’re designed for casual skating only. They are shaped fit as many different foot shapes as possible, to accommodate the thick, warm socks that casual skaters might choose to wear to the ice rink, and to last a long time. They’re generally what are described as ‘soft skates’, which means they don’t have an awful lot of support (and are thus not safely usable for any kind of jumps and spins). I also don’t see the skate blades being dried off when rentals are returned, and the results are inevitable:

In this case, the state of the blades is less than stellar as well:

None of these attributes make rentals skates great for serious skating. However, when you or your child are starting out with skating, they are perfectly adequate. After all, who wants to drop money on brand new ice skates when there’s a chance that the child may not enjoy ice skating after all and will change their mind?

My policy was that when my children started following the Learn To Skate USA Basic 1-6 courses, I would not buy them skates at first. They started somewhere around February this year, and I spoke to their coaches to as them to advise me as to when they thought it would be helpful for my children to have their own skates. I also reckoned that this would give me maybe 3-6 months to find out whether they were engaged and enthusiastic before I made an investment. The kids did well using rental skates, and they were in good company; most of the other children in the lower Basic levels were also skating in rentals.

Buying Your Own Skates

Around the time where my oldest skater at the time (12 years old) got to somewhere around Basic 4, their teacher approached me as promised and said that this would be a good time (if possible) to consider getting them skates. Being reasonably well built and getting heavier and taller by the day, it was particularly important to find skates that would have reasonably firm ankle support.

The subject of which skates to buy is such a huge one that I wouldn’t even dare to start advising to go for one brand over another because it’s a very personal choice both in terms of budget, features and options. I will comment that most of the skaters I see at this level end up with Jackson or Riedell skates, but that may be a regional thing as much as anything else.

For the purposes of transparency, I am happy to share that I ended up selecting Jackson Ultima Freestyle/Aspire figure skates for my son.

While I was emptying out my wallet for one child it seemed rude not to finish the job and also get younger sister (aged 9) her own skates as well, as she was in Basic 3 and learning quickly. She ended up with the slightly cheaper Jackson Ultimate Classique figure skates which are in many ways similar to the Freestyle.

There is nothing quite like seeing the pride with which my children look after their skates. They are keen to restore the beautiful high-shine finish on the blades after they finish skating, which is just great. More importantly, after a lesson of tripping (during which they discovered what it is like to have skates whose blades actually cut into the ice!), they found their ice feet again, so to speak, and started improving rapidly from there. The teachers immediately commented on the difference in their performance with the new skates, which was also reassuring.

To summarize, if the skaters are serious and plan to keep taking lessons, budget for their own skates sooner rather than later.

How Much Should I Spend?

This is the impossible question. The common wisdom appears to be as much as you are comfortable spending. With ice skates, you really do get what you pay for to a large extent. Cheaper (e.g. sub-$100) skates of the kind often found in large sporting goods retailers and department stores are usually considered to be a false economy; the skate will be functional for sure, but often lacks support and does not have a blade capable of handling the jumps and spins that will be asked of it down the line. No problem to use these for recreational skating, but I hear over and over again that they won’t cut it for a developing skater.

Are Used Skates Ok?

In theory, yes of course! Like buying a used car, it’s just a question of knowing what you’re buying, what to look out for, how much sharpening life is left in the blades, and whether the price is fair. It’s also worth considering though that when skates are purchased new, over time they stretch and shape themselves to the owner’s feet. When buying second hand, the skates are already shaped to somebody else’s feet; whether that’s a problem may depend how different your feet are to that person, and how much stretching took place. It might not matter, but it’s something to consider. Overall, I am not in a position to advise on these matters, so I would always use somebody who does know about buying used skates as your ally. Coaches at your local ice rink will likely know of people selling skates (perhaps their own students) and can often advise on what will work.

Why Buy?

Have you even been ten-pin bowling before? The house balls are generally pretty chipped, the finger holes never quite fit the fingers properly and are a bit more slippery than is helpful, and the weight is always too heavy or too light. Basically, they’re effective at hitting the pins and it’s possible to do well with them if you can work with their compromises, yet league bowlers typically do not use the house balls; they buy their own. Why? Because then they can get a ball with a more reactive surface; the finger holes are custom drilled to fit the hand size perfectly; finger inserts can be added to add more grip and improve comfort to the holes; the weight can be much more closely aligned with your needs.

It’s the same with ice skates. You can use the rental skates for a while without major issues, but eventually you’ll get to the point where they are holding back your progress on the ice. Eventually, you will have to buy skates or your child will be repeatedly frustrated with their inability to perform the moves requested of them by their coaches.

To coin a phrase, buying your child their own skates will—quite literally—give them the edge they need to keep getting better.