Sunday, January 4, 2009

Tactical calculations

Strategy and tactics will be critical to success (or otherwise) in the X-Alps. I'll talk about strategy and flight planning in a future blog post, but first here's a quick analysis of tactics: deciding the quickest way to get a few tens of kilometres along the course line.

A few back-of-the-envelope calculations quickly show how important flying is. On the ground you can reasonably expect to average about 5km/h. In 2007 almost all competitors managed this, the notable exceptions being Coconea (ROM) who averaged 6km/h over long distances day after day and Etike (TUR, '07) who seemed barely able to walk up one mountain, let alone down the other side.

In terms of altitude gain, 600-800m per hour seems a fair average over a two to three week event. You'd certainly expect to be faster in a shorter one-day event like a mountain ultramarathon, but if you're walking hard up the slopes of Mont Gros above Monaco at 800m/hour then you can be happy with your physical preparation.

In flight, in typical XC conditions, you can cover 20-25km/h along the course. In favourable conditions you might average 30km/h but in the X-Alps were racing East to West which means that we're fighting against the prevailing winds. History has shown that conditions are rarely ideal. So, let's assume that you average 15km/h when flying, and that you've got a modern glider that glides at 8:1 (allowing for a bit of sink and/or headwinds).

With these figures - 5km/h walking, 800m/h height gain, 15km/h flying, and 8:1 glide - we can answer a few simple questions that will help us plan our strategy.

Is it worth walking up a hill just to glide straight along the course line?

Walking up 1600m takes two hours, add a few minutes on launch to get prepared, fly down, and a few minutes packing up, say three hours total. You glide 1600m * 8 = 12.8km. In the same three hours you could walk 15km, but it's close. If you can glide over a lake or other obstacle that you'd normally have to walk around, then even a fly down can be a winner. Plus you get a rest, of course!

If you're flying, how weak does the lift have to be before you'd be better off gliding down to land and walking?

Assume you're in the last thermal of the day, it's smooth but weak. On the ground your competitor will cover 5km in one hour. In that same hour you only need to gain 5000/8 = 625m, i.e. a shade under 0.2m/s, and you'll cover the same distance as the walker but with much less physical effort. To Alpine pilots, 0.2m/s barely registers as a thermal, but compared to slogging it our on the ground it's the best tactic.

These simple calculations show that you're almost always better off flying. Even a walk up for a fly down is almost worth it. The only time you'd chose to walk if it's flyable would be to get through airspace or if the headwinds were so strong that couldn't even make 5km/h average forward speed. But you have to wonder...

Would a professional ultrarunner carrying the minimum kit win the Red Bull X-Alps?

After Coconea's incredible performance in 2007, many asked if you really needed a paraglider. Would you be quicker just running? In 2007 Hofer (SUI1) took 15 days to cover just under 1500km from Austria to Monaco, that's 100km - two and a half marathons - per day every day for two weeks. The shortest route was taken by Muller (SUI2) who covered 1279km. It's likely that a runner would have to cover a greater distance.

There are road races that cover that sort of distance, such as the Trans Gaule (1150km across France from Roscoff to Perpignan), but they tend to be split into daily stages. For example, the Trans Gaule takes 18 days, an average of 60km each day. There are some non-stop races, such as the Sydney-Melborne race where the Greek Yiannis Kouros set the world record for 1000km on roads of 5 days 2 hours and 27 minutes in 1989. Multiplying up, he might be able to complete the X-Alps course in 8-9 days. However, a direct comparison with the X-Alps is hard: the ultrarunners are covering predominantly flat terrain and without a rucksack.

A minimal rules-compliant pack would probably weigh about 4.5-5kg: 2.5kg for an ultralight mountain glider, 0.8kg for a minimal reversible rucksack-harness, 0.2kg for a helmet, 0.6kg reserve and 0.5kg of tracking devices and other compulsory equipment. Such a set-up would be good enough for a fly down, but you'd be hard pressed to cover significant distance flying with it: it would have poor performance and be rather uncomfortable!

The new course for 2009 follows many classic flying routes through the Alps and this year I think the flying will be more important than ever before. Fitness will be very important, but my focus will be on the flying. In the words of my supporter Alex Raymont "No-one out-walks a 200km flight".