hafilax

The unit used in measuring scattering cross sections in Physics is the barn=10^(-24)cm^2. It was coined as a joke on "Couldn't hit the broadside of a barn".

Off like a Jewish foreskin.

It's blowin the dog off the chain.

Beecher, sounds like you're talking about Maxwell's demons.

I agree that there is a dynamic force that depends on the velocity of the ski over the snow. What I'm saying is that there is a transfer of momentum from displacing the snow not a force due to differential velocities over opposite sides of a surface like with a wing. This is an effect similar to a boat planing which you have describes although the actual equations describing it would be much different since snow is not a fluid.

Halifax, I've gotta disagree with your statement, and I think you might too (hence the surfboard reference). Snow is not air or liquid water. But water is not air either (air being compressible, water not so much), and yet somehow the physics of a rudder, keel, or propeller blade in water are very similar to the physics of a rudder, wing, or propeller blade in the air. I am not saying there's no difference. Is it just coincidence that the community agrees that the area underfoot is what counts? Area underfoot = Boot length x Ski width. My boot length is the same no matter what ski I'm on, so the agreement is really that the width of the ski is most important. Same conclusion the basic physical models based on fluid (or aero) dynamics would come to. We all get the same fun results no matter how (or whether) we think about it.. yeeha! You keep referring to Bernouli principal in fluids which does apply to both water and air but not to snow. The ski deflects the snow but there is no restoring force. I don't think snow behaves as a fluid. It's more like a foam. It doesn't break under small forces so it can creep, stretch and compress slightly but it crushes under larger forces without restoring much. The area under foot is a rule of thumb for judging the relative area of skis of the same length. My girlfriend and I have skis of similar length and max width but mine have much less sidecut. Mine therefore have much more area for the length and float way better. Wider skis generally have less sidecut because area is important in powder and sidecut isn't so the width under foot is a better indicator of the total area than the max width. I also speculate that area further from the feet isn't as useful in providing float as the area under foot because of the flex of the ski. I think the reason that people have been trending toward short fat skis in the backcountry is that they are more manageable for short quick turns in varying conditions. The width gives the float in the powder and since the moment of inertia goes like m*r^2 it quickly gets harder to turn a longer ski. Especially if you start piling heavy snow on the tip and tail. Kick turns are way easier with a short ski. The trade off is less stability at high speed and in tricky edging conditions. A long fat ski is just plain heavy. The biggest problem with snowblades (which are an embarrassment) is that it is easy to get your center of mass past the tip/tail. This is completely unstable which is why snobladers do more running than skiing in deep snow. A taller person needs a longer ski regardless of weight. There are other trade offs as well. A stiff heavy ski with heavy boots and bindings will be more stable at speed because of the increased momentum. Less of the forces from choppy snow are felt my your legs. A lighter setup will bounce you around. So it's an optimization problem with compromises. There is no best setup for all applications otherwise there would be only one ski company. The best advice will come from someone of a similar size, ability and who skis in similar conditions but even then tastes vary. Demo's are your friend.

The short/fat vs. long/skinny float is a pretty complex question physically. Water and air analogies don't work well because snow isn't a fluid. It compresses and doesn't return to the previous equilibrium. It's also a dynamics problem in that you get more float the faster you go. The snow has some momentum that is imparted to the ski and provides a velocity dependent lift. The consensus in the ski community seems to be that the area underfoot is most important in giving float and that a softer ski is usually more forgiving in lighter snow. OTO wide skis take more torque to transfer from edge to edge and the for-aft stability is less. If you want the extreme example of a pure powder ski look at the Spatula/Pontoons/Praxis reverse-sidecut reverse-camber skis. They're like little surf boards on each foot. They're supposed to be amazing in bottomless powder.

I second that. On my band's tour of Switzerland and Germany we could always count on MacD's for a clean bathroom with no questions asked. I used one of those pay booth dealies in Stutgart but the needles and blood on the wall turned me off of the idea.

A pox on your first born you ugly wart on a salamander's tongue. Your mother was a hamster and your father smelt of elderberries. Now go away or I'll taunt you a second time you silly K-N-I-G-H-T!

Is the new VeggieTales movie (The Pirates Who Don't Do Anything) a Christian attack on the Gospel of the Flying Spaghetti Monster? Maybe it's just a little tongue in cheek since the movie apparently has no outwardly Christian imagery unlike its predecessors.

Here ya go Am in mah hat prtcted frum ur rayz

All the DWR guys have a wash and a DWR restorer. Arc'teryx, AFAIK, used to go with Revivex but recently have switched to Grainger's. I used spray on Revivex for my softshell-XCR hybrid and it worked well on the softshell part but not so well on the XCR. May have been the way I did it though. Revivex and Grainger's are more similar and need heat to bind the coating to the fibers. Nikwax uses a different chemical that isn't as heat activated dependent. Based on my research Nikwax is a less effective product but YMMV. Spray on is more appropriate for softshells with a wicking liner and wash-ins are recommended for membrane type garments.

I tried to get into running a couple of years ago and got shin splints. I did some reading into it and decided my problem was the following: AFAIK the shin muscle is encased in some kind of membrane that grows much more slowly than muscle does. As a result if you increase muscle mass too quickly in the shin it tears at the membrane causing pain. It also heals slowly like, tendinitis, so once the pain appears it takes a lot of rest to remedy. Correct me if I'm wrong. If I were to try it again I would do a more gradual introduction with more walking.

I didn't say I was looking hard

I've been looking for landjaeger in Van but haven't found any yet. It was everywhere in Switzerland. It's like meat candy.

I know I've set off a few scary sluff slides in Whistler that could have carried me into trees/rocks if they were any bigger. As can be seen in the Big White slide, avalanche danger evolves with changing conditions. You still have to use your head a bit even in avalanche controlled areas.

See job thread, I'm a physicist (almost). Way to edit out the end of the quote where I say 'I don't know'. It was meant as a thought provoking question. I'm all for personal responsibility but I also hate the loss of life and if there's a cheap way to let people know what they don't know then I'm for the inconvenience of ripping off another tag. I'm a firm believer in risk homeostasis and think that the availability of beacons probably does endanger as many people as they save. I try to be conscientious of not increasing the risks I take due to the perceived safety of the technological devices I carry.

Every piece of climbing gear you buy has a giant label saying 'This activity is dangerous. Are you sure you know what you're doing?' Would a similar giant label warning about tree wells and avalanches placed on anything that can be used to access the backcountry save a life at little cost? They seem to think it's a good idea for climbing gear. I don't know. I guess, in the end, the current rash of fatalities will certainly reach most of the mainstream that are (were?) ignorant of the danger of avalanches. Helmets are an entirely different argument in that many feel that they cause more harm than good in general.

I agree.

Avalanches are probablistics; ergo the only means to remain safe is to never be in the realm of probability. In short, to never enter avalanche terrain. I'm not sure if there's an argument in there other than to say that you think I'm overly cautious through some kind of straw man statement in response to one by me. I keep thinking about surfing and some of the dangers that are hidden to the inexperienced but obvious to the masters such as rip tides, shallow reefs etc. (I'm inexperienced there as well). It only takes a second for someone to say don't go there. A big surf is like a big snow fall; dangerous to the inexperienced but manageable for and craved by the master. Unstable slopes are similar in that the danger is hidden from the inexperienced. Someone who has seen that some slope has slid under similar conditions is way ahead of someone who has to dig a pit to evaluate a slope. I know analogies rarely make good arguments but I do think it's an interesting parallel. I will continue to be (hopefully) over cautious until I gain some more experience but feel free to ski within your comfort zone. I'm sure I'll be envious of your lines.

I knew that rebuttal would come because I overstated my case. How about those guys in Kananskis who died digging a pit to evaluate the slope? You can't learn if you're dead. A bunch of people who just took Avi 101 will learn exponentially faster after a couple of weekends with a dedicated mentor who explains the nuances of the decisions he makes in the backcountry than if they go it alone.

It scares me to think that people will find that joke funny in a non-ironic way. Now I have that song stuck in my head. At least I like this one.

I quickly skimmed it since I have an interest in lung imaging but more from an in vivo point of view using hyperpolarized gas and MRI. I couldn't quite figure out what the conclusions are in this study. Isolated positively charged nano-particles are more likely to be toxic? If I find time I may examine it in more detail since I'm always interested in other people's research. It's hard to read scientific papers that aren't in my field though.

Avalanche science is not exact at all. It is incredibly difficult to predict slides. This can be seen in how many experienced and knowledgeable people have been lost in avalanches. The recreational avalanche course I took barely scratched the surface of what I feel one needs to know to be safe. To come away from that thinking you know everything is dangerous (I don't know if anyone actually feels that way). I think more than any other activity it is hard to replace the experience of a mentor like figure who knows the terrain and can pass along the experience of a lifetime or more if they had a mentor as well. What I have taken from my avalanche course, the mentoring of my good friend with a master's in avalanche science and from the unfortunate accidents I have read about is that you must err on the side of caution... WAY on the side of caution. I can see the argument that ski films can encourage a certain negligence because people don't think about all of the work that goes into evaluating the slopes and the long waits for good conditions. It is mentioned in all the films but how many take notice? Also, most of the deep powder shots are in trees or on mellow slopes. Again, how many take notice? I don't think that the blame is warranted though. I just watched the trailer for Steep (below) and one of the guys says something about losing track of how many big slides he's set off. Cr7_4LrF8As So there's a bunch of random thoughts in this post but I guess my point is that I think self education through books, videos, bulletins, courses etc. will fall far short of what can be gained from a mentor and time in the backcountry in unarguably safe terrain.

I read somewhere that someone did some tests on the sharp reverso and found that it took a lot of force to cause sheath damage and that the metal folded before cutting. A quick search turned up the article below. Reverso review referencing sharp edge tests. I guess the sharp edge rumors are affecting sales because they've redesigned it to be very similar to the ATC-Guide only with the anchor loop rotated.