Re: [TomAiello] BASE Canopies
Yes, ok, wow. Lots of different items popping up in this thread, most of which I'm really not qualified to comment on. Of course, that won't stop me from commenting. . .
1. Backsurge: while Tom states that this a proven phenomenon based on video analysis (and I'm sure if he says he's seen it, then he has), I think the magnitude of the movement here is trivial. According to Tom, he's seeing around 1/2 a canopy depth movement which he attributes to bottomskin venting. Again, assuming this is accurate, this is trivial.
There are very few jumpers who have ever opened so close to an object that a "backsurge" of approximately four feet would have resulted in an object strike and/or injury with an on-heading opening. Tom is one; I'm another, as are some of my jumping mates.
Seriously, though, we really shouldn't be opening so close to an object that 4 feet of backwards movement is substantive. Too, even an incredibly small wind can cause a canopy to move four feet in any given direction on opening, no problem.
Net net, no jumper has ever been injured or killed due to "backsurge." It may be an interesting technical phenomenon, but I don't see it as being relevant to actual gear choices. DW, who first posited the existence of backsurge (and who first explored the ideas of bottomskin venting in BASE) and I discussed this, and he concurs.
2. The moniker of "Deep Brake Settings" (DBS) is a misnomer. No brake setting is inherently "deep" or "shallow;" just because a canopy has two different brake settings on it's lines does NOT make one "deep" and one "shallow," save (trivially) in reference to each other.
It is quite common to see jumpers using their deeper (which I prefer to "deep" since both may in fact be too shallow) brake setting on slider down jumps and their shallower setting on slider up. However, it is equally common to see that BOTH the deeper and the shallower settings are way, way too shallow for safe use with hard objects behind a jumper. Being too shallow, remember, simply means that on opening the canopy is moving forward with some speed, versus sinking straight down.
There's good video of a jumper in Malaysia suffering the consequences of too-shallow brake settings on a legal building jump. With helmet cam footage, the sound of him repeatedly impacting the building while his canopy surges forward into it is. . . sobering. Too-shallow brakes can kill you.
Conversely, if a canopy ships with one brake setting only, this setting is neither "deep" or "shallow." It just. . . is (kinda Zen-like). It might be too deep (unlikely with most gear manfacturers), or too shallow for safe jumping. In any case, it likely needs to be customized for a given jumper.
Tom's advice both on why to customize brakes and HOW to customize brakes is terribly important. BASE jumpers today die from object strike, for the most part. Too-shallow brake settings are a major - if not the major - cause of object strike injuries or fatalities (this is my opinion, but even if it isn't the #1 reason, bad brake settings always make a bad situation even worse).
Tom is also right that I'm skewed by my locale, perhaps. In Portland, we jump lots of low and often underhung objects, and have been known to do this with "non-optimal" winds. Consequently, we take proper brake settings as a given; I've been jumping a new canopy with brakes too shallow for a few months now on and off, and every jump I am aware of the impact this oversight will have and plan accordingly. To simply not know that improper brake settings are a huge issue is hard for me to understand, but I think it is more common than I imagine given my Portland-jumping roots.
3. In terms of venting for new jumpers, I think Tom and I have as much a difference in perspective as we have a difference of opinion. Again, in my home area there simply aren't any "safe" objects for beginners. So my concept of "beginning" BASE is skewed, certainly. However, in other places in the world I guess folks can flop off easy stuff for years during their BASE career and wouldn't ever really need venting.
Frankly, I'd say this however: if a beginning jumper is poor enough with BASE canopy management that bottom-skin venting is a "complexity" that is hard for them to manage, they aren't anywhere near good enough to be jumping "real" BASE objects. Now that I'm sliding into "Pacific NW BASE snobbery," I'll just stop typing before I get any deeper. . .
4. Landing with one rear riser and one toggle is not too bad. I've done it three times slider down, due to blown brake lines. Never done it slider up, so I can't comment on that. I learned to do it after I blew a brake line jumping in South Africa - a 500 foot to impact cliff with a 2000+ foot canopy flight to landing. So I had lots of time to play with the riser/toggle "flare" before setting up for landing. Once I'd found the sweet spot, I got a MUCH better flare than both rear risers - important on that jump as I was landing on pavement with a slight tailwind.
I'm not sure toggle/riser is "better" than riser/riser, but once I learned both I was able to get a better landing with the toggle/riser setup. Not sure why, maybe that only applies to fat-assed, horny Dogs.
5. Final metaphor (or is it a simile?): vented canopies are cars with anti-lock brakes, unvented are without. Non-ABS is "less complex" and "simpler," but one wouldn't recommend that a new driver avoid the "complexity" of ABS, right? Vented canopies behave like unvented ones, but with a bigger envelope of responsiveness and more options for off-heading correction.
6. I'd much rather see a student of mine have "backsurge" of a few feet on opening with a vented canopy than a snivelly, jellyfish opening on an unvented one (brake settings held constant for both). Why? Simple: jellyfish openings are much more likely to evolve into full-on off-headings; a bit of backstall isn't going to cause anything worse than a strange visual from above, and the need to pop the toggles off quick to get the canopy flying forward.
In general, I look at every tech element mostly in terms of how it will affect off-heading percentages, and how it will help or hinder the correction of off-headings after the fact. This is, again, because the majority of jumpers have died from off-heading openings, plain and simple. They are the true "black death" element of BASE, and the more we plan for and understand them, the longer we'll live.
From another angle, we can control almost all other BASE risk factors - but not off-headings. We can minimize them, but we don't fully understand them and they happen to ALL jumpers sooner or later. They are the one great "Russian roulette" element of BASE - many of us have done jumps where an off-heading would have been fatal, no question. <cough>Aiguille du Midi in 20+ mph winds<cough>
7. Tom knows more about BASE than I do, so listen to him and not me! I'm just a fat-assed BASE canine from the land of dodgy objects and rainy weather
Good thread, Tom. I hope folks appreciate the time and energy (and knowledge) you are investing here. What's up, too sunburned down there to get out and jump?
Peace and happy holidays,
D-d0g
ddog@wrinko.com
www.wrinko.com
ps: "I am sorry, that is not possible."
Tom: "but we're FLYYYYYYYING down. . . (flaps arms to demonstrate)
Dog: "I have a Norwegian friend. . . "
Dog: "That jump is only safe if you pull the slider down. . . "
- William Butler Yeats
