JackC1

This one always cracks me up.

It is often said that an Optimum 160 packs smaller than a PD160R. I want to know if that is because a PD160R is actually 175 sqft whereas an Optimum 160 is only 160 sqft. People also think that a Smart 160, a PD160R and an Optimum 160 are all the same size. But are they? We're talking almost 10% here, that's almost one full size step. Does one size matter, or is it bullshit?

You have to wonder, jumping at night with a bergen, weapon, O2 and NVGs is par for the course but a little tiny GoPro is a snag-tastic distract-athon of epic proportions.

This is a great can of worms to open. According to the Paragear canopy sizing charts a PD160R is allegedly 175sqft. It would be interesting to measure an Optimum 160 against a PD160R.

People often say that helmets like Protec or the Benny are the best protection, but that isn't necessarily true. Helmets like the Benny use EVA foam liners which as far as I can tell won't meet any official impact protection standards (but then I've not seen a skydiving helmet that has passed any standard). I'd say a half decent full face would offer as much impact protection as a Protec with the added bonus of face protection. I had a Parasport Z1, which only had EVA liners but my current Cookie G3 uses D3O foam which has at least been designed specifically for impact protection. The G3 isn't perfect by a long shot, but it's about as good a skydiving helmet as I've come across.

It sounds weird but try not to land. The aim is to keep your canopy in the air for as long as you can until it just won't fly any more. By that stage you should be close enough to the floor to just step onto it. To do this, don't use all of your flare in one go, use just enough to get your canopy flying level, then as it starts to recover into a dive again, add a bit more flare so it flies level, and repeat until you run out of flare and you've timed it so right at the end you are inches away from touchdown. Practice up high to see how long you can keep your canopy flying level without sinking. If you need to bury your toggles to stop yourself from piling in, you're flaring too low. If you sit there on half brakes for ages waiting for the ground to come up, you're flaring too high. A few people say look down, a lot say look at the horizon, I tend to look where I'm going. But really, there is no better method than getting a video debrief from a good canopy coach.

Pan fried mini fillets of cod rolled in golden breadcrumbs, served in lightly toasted pain de mie and a sweet tomato redux.

Orbital decay is one thing but satellites don't stay in the orbit you've put them in. They require periodic maintenance to their station keeping via thrusters to stop them from being sucked towards these hot spots. When the fuel runs out, the satellite just drifts without anything to stop it. It's like having a car cruising down the freeway with no driver. And since a high orbit is very long lived, these driver-less satellites stay on the freeway virtually indefinitely wandering around wherever the gravitational fluctuations take them.

Not only are there corridors of "useful" orbit that most of the junk gets dumped into, but due to the gravitational variations of the planet's field there are also orbital hotspots where junk tends to want to migrate to. Unfortunately, as the junk gets sucked into these gravitational wells, the motion isn't damped so it passes too and fro like a pendulum, until it meets something to collide with. Science is rarely as simple as you might want to think. http://www.bbc.co.uk/news/science-environment-12911806

I've seen cut away mounts that chop the camera bracket, not the entire helmet. It involved drilling 2 holes in the top of your lid and fitting spring loaded pins held in with a Teflon cable. Something like that might be your best (only?) option with a G3. Personally, I don't like the idea of having bolts through my helmet where they can hammer into my head during an impact but I haven't seen this system up close to know how much of an issue it might be.

Pretty fucking presumptuous of you. Go away. Damn, shame on me. I thought you "had it" there for a while but I see you really have no clue. DocPop isn't being presumptuous, nor do I think he's trying to insult you. You should attend canopy coaching, especially if you're coaching students. All skydivers should, imo. Ian ^This.

I never expect to get anything useful from dropzone.com, but there does seem to be an anecdotal shift towards the excellent/athlete end of the scale (69%) compared with similar polls elsewhere on the net. Now part of that may be down to dz.com's contingent of bullshitters and egotists. Part of it might be down to skydiving attracting active type people (but I somehow doubt that 69% of skydivers are also marathon runners or competitive cyclists). Or skydiving may attract the type of people who have a naturally low heart rate for some reason. Or just maybe part of it might be down to the effect I hypothesised, or the fact that a lot of skydiving happens at high altitude (which can increase cardiovascular fitness). Or it might be something else altogether. Who knows, but at first glance it does at least look like there may be a correlation between skydiving and cardio fitness.

This was actually my reason for asking. I'm a total couch potato who drinks, smokes and eats junk and yet my RHR is around 45-50. My doc reckons I'm as fit as a flea which given my lifestyle came as a bit of a surprise.

I have a hypothesis that releasing lots of adrenalin into your system on a regular basis might reduce your resting heart rate. This may or may not be of medical significance for skydivers but it would be an interesting study. But first I need to know if it is at all likely that skydivers have lower resting heart rates than "normal" people I would request that only regular skydivers with at least 1 year in the sport and a average of more than 50 jumps per year respond to the poll. So if you fit the above criteria and wish to find out if skydiving gives you the ticker of a marathon runner or not, then check your resting heart rate according to http://www.topendsports.com/testing/heart-rate-resting-chart.htm and then answer the poll above [inline HeartRate.png]

Don't you believe it. Watching a snivelling Sabre2 before it decided to spank me put me in a neck brace for 3 months. Watch the horizon until it's finished being funky.

That would be anything by Flogging Molly. http://www.youtube.com/watch?v=N4iW6L8lAXo&list=AL94UKMTqg-9BO63OI3ZQzXcwxhOs6Y9Dk

I did something similar on Sabre2's at about that wing loading. They turn a bit quicker, dive a bit more and fly a bit faster. It took me a couple of jumps to figure out how to stop it so I didn't have to run when carving it in on nil wind days and I increased my final turn altitude a bit to compensate for the increased dive but apart from that, it wasn't a problem.

Ethanol is also hygroscopic. E10 can absorb about 40 times more water than pure gasoline and has a shelf life of only about 3 months. A table spoon full of water in a gallon of E10 is enough for it to start separating out. Ironically, if you do have water separating in your fuel you can absorb it again by adding more ethanol. Or if you add more water, it will leech out all the ethanol and you can simply siphon the pure gas off the top.

I copied all my old log card entries into a new book. I still have the old card if anyone wants to see it. No one ever has.

Boobies?

Meh... we've been doing that for years without a problem.

If you're getting your American car registered in Europe and will be requiring a vehicle inspection certificate, you'll probably need to do something about it. If you're in Belgium you may have bigger problems as modified cars are subject to strict rules about what can and can't be done.

From the photons point of view, you could say it is at rest. The photon sees time slow to a complete standstill so it can be everywhere in the universe all at the same time. But the gravitational field from a black hole doesn't really stop a photon in the sense that it slows it down, it just red shifts it away to zero frequency. That's not stopping the photon at all, it's killing it stone dead. If you want to slow a photon down, you need to pass it through a material. Super cold sodium for example will slow a photon down from 186000 miles a second to a mere 38mph (the current record)

Photons do not have mass, but they do have momentum. Any talk of photon mass is misleading, as is it not a real mass, it's not even a useful concept to think of a photons mass. If you absolutely must think of photon mass, think of it as an effective mass in the sense that a photon has momentum which would be equivalent to a particle of mass m traveling at speed c, but that's as far as it goes. No real mass. This comes from E=Pc from relativity. E=hf from Quantum mechanics P=mv from Newtonian physics. If you put the first two together you have hf=Pc, rearrange to get P=hf/c, then equate this to P=mv where v=c for a photon, and rearrange to give m=hf/c^2. But this isn't real mass, it's mathematical trick mass. Physics is full of stuff like this and it is confusing unless you really grasp the basics of where it all came from. You'll often see a particles mass quoted in units of MeV (mega electron volts) which is a unit of energy, not mass. What they often neglect to say (because physicists already know) is that you need to convert to mass by dividing by c^2 (and a factor of electron charge but that just confuses things even more). But no one ever bothers because quantum mechanics deals with energies easier then it does with mass, so all those c^2 terms just get in the way. Another example is noise temperature. Take the power P (in Watts), the bandwidth B (in Hz) and divide P by B and you have units of energy. Equate this to Boltzmanns constant k multiplied by a temperature T and again we have units of energy. You can then rearrange for T. Noise however, is not really hot.

Yeah, right! Quantum tunneling makes perfect sense. Someone (Neils Bohr?) once said that if you think you understand Quantum Mechanics, then you really don't have any clue. QM seems more intuitive to me than GR, but then I've studied a lot more QM than GR. The trick is to forget all the "interpretations" and realize that in the same way that Pythagoras Theorem doesn't necessarily predict the existence of an anti-hypotenuse, QM doesn't necessarily predict many worlds or wave function collapse, it's just a useful theory so shut up and calculate.