Skiing – Pet Pixels

February 9, 2025February 12, 2025

Skis are not strong enough

“I break my skis because I ski too hard” is something of a humblebrag, but frankly it’s getting expensive and annoying! There are many ways that you can break skis, as I have documented in my ski equipment I have killed page, that are not specifically to do with skiing technique – delaminating tails for example is often caused by banging them on the ground to dislodge snow before you stick them in your car. What I’m talking about here though is definitely a consequence of how I ski. So let’s talk about cornering.

Modern “parabolic” skis have a sidecut, where the tip and tail are wider than the middle, and there’s a curve between them down the length of each side of the ski. If you tilt a ski to one side, it will rest on the edges at the tip and tail, and the middle will be lifted off the ground. If you then apply force to the middle of the ski (by standing on it), the ski will bend until the middle of the ski touches the ground. The ski will then be bent along its length, and where the edge meets the ground it will form a curve, which is roughly a segment of a circle, and when the edge runs along the ground along this curve, the ski will turn. The more sidecut, the more force, the more flex of the ski, the shorter the radius of the circle, and consequently the tighter the turn you can do. This happens particularly when you do a kind of skiing known as carving introduced in the early 1990s, which is in contrast to the technique that preceded it known as parallel, which is more or less skidding. A key difference between the two is that when carving a turn, the ski doesn’t move sideways (much) relative to the ground. This makes carving smooth, quiet, stable, and also preserves speed through the turns, but it puts a lot more force on the edges – I’ve measured myself (75kg + kit) pulling 3.5g in corners, and that makes for a lot of pressure on those edges. Skidding is still useful, especially for losing speed, stopping, performing very abrupt manoeuvres, or in confined spaces like couloirs or lift queues.

Here’s a pic of me carving on the exact skis I talk about below:

A ski is typically constructed from a sandwich of layers of different materials chosen for strength, stiffness, vibration absorbing, water resistance, and so on. It might look something like this in cross-section:

This is only a rough idea, and the structure varies widely, but however the ski is constructed, the edges (which provide grip on hard, icy surfaces) are usually the same: a square steel section with a flange that extends into the body of the ski – the little red bits in the diagram above. Steel is strong, hard, but not very flexible, so edges are thin, around 2-3mm square in section, with the flange extending perhaps 10mm into the ski. The flange is segmented so that it remains well-anchored within the ski structure without adversely affecting the flex of the ski. These are bare edges, before being built into skis:

When the ski turns, it’s put on its edge and force applied. This results in a strong torsional force on the edge:

I had a few goes at using AI chats to figure out exactly how much torque is applied, and it’s quite tricky, however, for a 75kg skier (me) exerting 3g of lateral acceleration (that’s pretty hard!), it apparently works out at around 5Nm of steady-state torque, which is about what you can do by hand with a screwdriver. It doesn’t sound much, but that edge is really quite small, that’s a fair amount of torque, and in reality, it will be changing very rapidly, with peaks well above that value. All that force, applied repeatedly over many ski days, leads to this:

Here the torque acting on the edge has caused it to rotate out of the structure of the ski, partly levering the base away from the ski core. Here’s what it looks like on a real ski (my beloved Elan Wingman 82 prototypes, just 2 years old):

You can just make out the segmented flanges inside the crack. If you look across the width of the ski, you can see that the base is raised on one side, and the base material sits proud of the steel edge, when it should be flush. The time you’re most likely to spot this is when waxing your skis, and before you see cracks forming, you might see the base developing bulges or ridges, usually just ahead of the bindings on the inside edges, where the most stress occurs during turns.

This condition is somewhat dangerous because the edge is no longer firmly attached to the structure of the ski, and a gap between edge and base can open up, making it more likely to catch on a rock and completely tear the edge out of the ski; not good if you’re going fast at the time. Water can also get into the crack and damage the ski core, by frost cracking, mould, rust, etc.

This is quite different to the kind of damage that can occur when you hit a rock, as I did on my Salomon Q105s a couple of years ago:

This cracked the edge, and impacted the ski body, but only over a very short length, and there was no base bulging, but this was also fatal damage and the skis were unsafe to ski on.

So what’s the problem? Skiing is a very dynamic activity that’s tough on equipment, so shouldn’t we expect skis to wear out? Not so much. Skis will break in extreme circumstances like hitting rocks, but when using them exactly as intended, I don’t expect them to simply lose structural integrity, and they should last for many years. Also I wouldn’t mind so much if this was a one-off, but this is the 5th pair of skis that I’ve done this to, and it’s getting expensive! These are the skis I’ve done this to so far – multiple manufacturers across several years, so it’s not like I’m suffering from a bad batch!

Rossignol Scratch BC
Volkl AC50 Unlimited
Fischer RC4 slalom skis
Dynastar Cham 97 freeride skis
Elan Wingman 82 prototypes

So please, dear ski manufacturers, make your skis stronger! If you ask me nicely, I’ll help you test them (maybe to destruction)!

March 7, 2023March 7, 2023

Ode to a ski pole

My 125cm ICE Lightning carbon graphite ski poles get an honourable mention on my “ski equipment I have killed” page, praising the fact that I have failed to kill them, and I thought I’d expand on why I like them.

My ski poles, standing up, stuck in the snow

Ski poles are one of those things you don’t tend to think about much, until you break or lose one, and you find yourself feeling rather lost and annoyed. Poles are vital for balance and propulsion on the flat. Back in the pre-carving days, they were important for timing too, something that still applies a bit in powder and bumps.

“The best ski poles ever made”
Unofficial Gear Review

These poles were made in the USA by ICE Composites, based in Park City, Utah, who no longer seem to exist, though they could have morphed into this ICE Composites. I bought them in Vail, Colorado in 1998 during a very nice 10-day Christmas ski trip with my wife. Prior to these I’d had many other pairs of aluminium poles, all of which had failed in some way. Aluminium poles are light and flexy, and usually die by being bent near the middle, then break when you try to bend them back, because aluminium just doesn’t like that. They’re also prone to being sliced off by ski edges just above the basket.

The reason these poles have lasted so long is that they are made of carbon fibre. Carbon fibre is associated with super-lightweight ski touring and race equipment, which is often very high performance, but also not very strong because all the extra strength the carbon gives is traded against weight. These poles take a different approach: they are not light, but they are very stiff and incredibly strong, still solid and dead-straight after 25 years on the slopes.

The bottom of the pole just above the basket has a plastic sleeve to protect the thin bottom section from damage by sharp steel ski edges.

The handles are pretty unremarkable – a softish, grey, rubbery material. The straps are nice and strong, and very firmly attached (straps rarely break, but their attachment to the pole often does). My only complaint here is that the exit of the strap from the pole is vertical rather than horizontal, which means that the strap doesn’t sit flat against your palm.

That white bit below the handle is a bit of Sugru I used to increase the diameter of the pole from the standard 18mm to 22mm. Why do that? Because that’s the standard size for bicycle handlebars, and I use it for mounting a bike light for night expeditions! Pole-mounting a light is generally better for night skiing than a head torch, because with a head torch the light source is very close to your line of sight, so you get no shadows to see surface relief and texture. The offset position on the pole means that it casts useful shadows, and also means you don’t shine your light in friends’ eyes when you’re talking to them… This can also be used as a camera mount, but hopefully you’ve seen that there are better ways of mounting cameras.

I’m not the first to wax lyrical about these poles – back in 2012, Unofficial Gear Review described these as “the best ski poles ever made”, and I’m not going to argue!

I’ve used these poles for about 800 days of skiing, and they have accumulated a few scars, but they’re so strong that they’re still as solid as ever.

One thing that has become a bit annoying is that the tips are wearing out. These are made of hardened steel with a kind of crown shape, however, the points wear down on rocks and ice, and lose grip, something that’s especially annoying in lift queues and icy conditions. I have tried to resurrect them by reshaping the crown shape using a Dremel-like tool, but I’d really like to replace them with more pointy race-type cylindrical tips.

I’ve had about 4 sets of baskets, as they just wear out; I tend to go for medium size ones.

Nobody seems to make bombproof poles like this any more, so I’ll just have to make these last another 800 ski days…

February 8, 2023April 13, 2023

My Skiing Videos

I post skiing videos fairly often, and people keep asking me how I make them, since by most normal understanding of shooting video, they seem like magic.

Skiing fast in Combloux, France on a nice sunny day, filmed by my talented, invisible friend

Is there a drone that follows me? Do I have a friend that can ski backwards very fast while filming, staying out of shot, and not casting a shadow (a vampire?)? Nothing quite so exotic, but it’s still pretty clever.

The Camera

I use an Insta360 One X camera. As you might guess from its name, it shoots 360° video, that is, it captures a complete sphere, looking in all directions at once instead of just a rectangle pointing in one direction. It achieves this by using two cameras and two fisheye lenses, mounted back-to-back, each capturing slightly over a 180° field of view as two square images. These are then mapped into a 2:1 rectangular representation (which conveniently works with common image and video formats like JPEG and MPEG-4) where the poles are the top and bottom edges, which implies a lot of distortion, a bit like a Mercator map projection. This is a full spherical frame image in this format – the distortion is clear (my skis are not the size of surfboards), but the pixels on the left and right sides will match when wrapped around:

A spherical image mapped to a 2:1 rectangle

The combined resolution of these two sensors is 5.7k (i.e. more than 4k), however, you need to bear in mind that all those megapixels have to cover a complete sphere, so you really need it to be this high if you’re going to render out videos that only look in one direction, and thus only use a small portion of the original view.

The “slightly over 180°” field of view is important as it means that when the two video streams are combined, there is a discus-shaped region centred around the camera that is hidden from view, and this is used to make the camera itself (and the selfie stick it’s mounted on) effectively invisible, without having a visible discontinuity (join) between the two image sources.

It’s possible to see the join sometimes, especially when only one lens is exposed to the sun – modern optics are good, but there’s only so much they can do! In this weird perspective, the join is running roughly vertically a bit to the left of me, roughly perpendicular to the lens flare ray from the sun, which stops at the join. The sky is slightly lighter on the left side of the join, probably due to lens flare:

You might have noticed that using spherical images requires a new perspective (ha!) on taking pictures and planning shots; Since you can rotate the view in all directions and zoom in and out, you can produce some very unusual perspectives that are not possible any other way. In the image above, the camera is effectively looking straight up and is zoomed out a long way, so the horizon around it appears as a circle.

One advantage of fisheye lenses is that they have effectively infinite depth of field, so everything is always in focus, and it doesn’t need autofocus. On the other hand, you’re not going to get any subtle bokeh effects!

Stills

You can extract still images from the video stream as either rectangular frames, or full 360° images (as I did above). The camera has a higher-resolution stills mode, however, that’s not really possible to use at speed. The stills quality from video streams is remarkably good.

I’d be delighted if someone had taken this picture of me (no doubt after much setup) – that it’s a selfie is borderline miraculous!

I’m particularly pleased with this shot – the spray of snow was caused by the camera hitting the ground at speed, and the camera itself made a gap in the spray, which happened to line up with me!

Stabilisation

The camera has “FlowState” stabilisation, which uses accelerometers and gyroscopes to keep track of where the horizon is and keeps it flat and steady, regardless of what angle the camera is held at – when you’re filming in all directions at once, it doesn’t really matter which way the camera is “pointing”, in fact the whole concept of pointing it at something doesn’t really apply. This stabilisation is extremely good, keeping things nice and smooth even during really quite violent movement and vibration, but it’s also partly responsible for the viewpoint feeling disconnected from the subject.

Mounting

The traditional place to mount an action camera like your average GoPro for skiing is on top of your head, attached to a helmet. That’s fine as it points forwards, but it means you never star in your own movies, and the resulting footage tends to be pretty monotonous. Mounting a 360° camera there is going to be a bit dull too – it means you lose the view of the ground because your helmet will get in the way, but your friends might be nicely captured. To get a nice perspective on yourself, you need to shoot from a bit further away – selfie stick to the rescue!

The camera isn’t that heavy, but when it’s waggling about at the end of a 1.2m carbon fibre telescopic selfie stick in a fast moving situation, it can be hard to control. When skiing you use your hands for holding your poles and partly for balance, and it’s actually painful to hold stick and pole at the same time. To counter this, I designed and 3D-printed a mount that clamps the stick to my ski pole fairly rigidly, and also offsets the angle a bit – otherwise there would be a risk that the “invisible selfie stick” feature would also make my ski pole disappear, but it also gives you a bit of creative control as you can easily move it between front and side viewpoints with a twist of the wrist.

The camera mounted on my bracket – finger space is a bit tight with fat gloves on

This mount is a great improvement, and makes for much steadier shots and safer precarious camera positioning (like 2cm from the ground at 100km/h!). You still lose a bit of motion in that arm (watch how little my left arm moves compared to my right in the video above), and the balance of your poles changes a lot, but it’s quite workable.

Snowboarding is a bit easier because you have your hands free, and the results can look straight out of a video game:

I also printed a bracket to mount it on my mountain bike’s down tube, and this taught me a couple of things: Vibration on bikes is much more violent than on skis, so the selfie stick rattles (the telescopic parts rattle inside each other) and wobbles a lot more; you go a lot closer to things on a bike, and it’s easier to hit the camera.

The end result still looks quite cool though.

Editing

Insta360 have an iPad & iOS app called… Insta360. The iPad version is great, but the phone one is quite usable too. You have a choice of aspect ratios, trimming and editing, adding soundtracks, colour enhancements, filters, and more. As well as nicely smoothed view angle and zoom factor manual edits, it has some very clever features for auto-tracking a subject. Remember that if you’re rendering out a normal-looking video, as I’ve done here, it’s not just that you can choose your view angles – you have to; clips of the ground whooshing by or the tops of some trees and a bunch of clouds are not that interesting!

The software has some enhancement filters, though they are not very controllable – you can’t for example just “make it brighter”, you have to pick a filter preset that happens to look like what you want, then twiddle an amount slider. The dynamic range is really good – notice that in all these clips you can still see the snow texture in direct sunlight, the highlights are not blown out, yet there is still detail in dark areas.

Extras

Insta360 have some other mounts that could be interesting for skiing including a back mount that puts the camera above and slightly behind you for a 3rd-person perspective – just don’t ski under any low branches, and be careful on chairlifts!

They also have a GPS Action Remote gadget, which in addition to controlling the camera remotely, injects a GPS data stream into the video recording. In the editor this data can be used to drive on-screen speedometers and maps. I’ve not tried that, but I’d love to given that I’ve long had a thing about going quite fast. Here’s a clip of me doing that on the Mont Fort World Cup speed skiing track in Verbier, now sadly defunct due to the glacier’s retreat, which also shows how much video quality has improved since 2013 (it was shot on a Contour 1080p camera):

At the start you can see just how steep this is! I managed 147km/h (92mph) on this run.

Posting online

For the most part I share videos via Mastodon, Twitter, and Strava. All of these have similar restrictions/requirements for videos regarding size, video format, bit rate, duration, etc. I usually render full-resolution output from the Insta360 app at 100Mbit/sec, do any simple edits using LosslessCut, and then compress for final output using ffmpeg. The ffmpeg command I use is:

ffmpeg -i in.mp4 -vcodec libx264 -vf 'scale=1280:-1' -filter:a "volume=0.1" -pix_fmt yuv420p -strict -2 -vb 4900k -minrate 1024k -maxrate 4900k -bufsize 4900k out.mp4Code language: JavaScript (javascript)

This compresses to just under 5Mbit/sec using the H.264 codec (sadly, vastly superior H.265 video is not accepted by these sites yet), scales the video down to 1280px wide (720p), sets the pixel format that most of these sites want, and also includes a 90% audio volume reduction, as it’s just really noisy otherwise.

Youtube has support for 360° videos, however, I find that these are actually mainly annoying to watch; rendering out a conventional rectangular clip just works better for me, and I’m the director around here…

Gripes

There are a few annoyances with this camera:

The tiny OLED screen is completely unreadable in bright sunlight.
There are only two buttons to navigate through all its menus and options, but I never know which one to press.
It’s very picky about the SD cards it will work with, though that’s understandable.

The battery life is reasonable, even in the cold, and while I printed a lens cover, the lenses seem to be surprisingly resistant. It doesn’t mind getting covered in snow. For some unknown reason, the 3 threaded sections of the selfie stick use a left-hand thread, which is annoying as it means that the action of tightening the camera undoes the selfie stick.

The One X is a few years old now, and Insta360 have since released newer One X2 and X3 models which solve the screen and controls problem by adding a small touch screen that’s more readable. It also makes the standard case a bit more robust and waterproof, has a bigger battery, better image sensor, and improved audio. Should Insta360 like to give me one to test, I wouldn’t say no!

December 30, 2007July 15, 2013

Speeding again

Something of a result yesterday. On the same run as on my previous attempt, I clocked 125km/h (that’s 78mph). Skis were Stöckli GS 166cm (i.e. short, not particularly stable) on fairly hard-packed piste. Given a better opportunity, run and equipment, it would be pretty straightforward to do better than that.

Today was an astounding powder day, just lots of bouncing about, really good fun on some nice fat Stöckli Stormrider XXL 178s. Tomorrow we have a guide booked and it’s due to be sunny – I can’t wait!