Basejumper.com - archive

G'day

Just wondering if anyone has any data on glide angles for BASE canopies (canopy types, wing loadings etc would be good too).

There's a few cliffs near me that are probably around 250-300 ish high and they're up on some steep ridge lines. The landing areas look kind of far away, but the ground does drop away pretty quickly too.

I'm not planning on jumping anything based on what I read here, I just want a rough idea if any of these places might be possible before I bush bash out there for a better look.

Cheers

BJ

just go jump something with your canopy, on a no wind day, at the same altitude, fly a straight approach, and keep a gps in your pocket. itll tell you all you need to know.

about 2.4-2.8

 
We nead a colapssble PC.I think it could be done with a standered multi. A sheathed bridle above the multi lines. Run the kill line through the center ring to the back ring.

Lee

Awesome, thanks. That's enough for the start point I was after. Now too see if there's anything that resembles an exit point and landing area out there...

I assume you mean 2.4 horz : 1 vert. Other way around seems too steep eh.

do you realize that the glide angle will vary with many factors, including:
- wind
- turbulence
- thermals
- choice of PC
- parachute model
- parachute material
- parachute wear
- pilot skill
- probably a bunch of others

what are you jumping now, and what kind of glide are YOU getting? do you prefer trusting your safety to your own experience, or an internet opinion? (although robibird is highly credible.)

Yeah, fully aware of that.

Like I said, for now I'm just after a rough guide of whether the site will be impossible/borderline/dead easy/whatever (to put it broadly) to save me hacking through lantana, wait-a-while and scree for no reason.

I've already scratched one site as not worth the effort and I'm going to rap down another for a more detailed look. I've still got a lot of work to do finding out how many canopy flies.

BTW, can anyone recommend a good 5 Hz GPS logger?

Buy an inclinometer.
GPS is hindsight if one is looking for glide angle.
Take care,
space

Not necessarily. crwper is developing a 10 Hz real-time (but also logging) GPS glide angle system for wingsuits that could certainly be used for canopy work if a person were interested. I'd recommend firing off a PM to him if you're curious.

you can buy an inertial navigation system for $100 and answer the same question.

Can you share a link? Have you used this system in a BASE environment?

I'd love to know more, but have never seen a 6-DOF IMU for less than $120 (and am quite sure I couldn't build one for less than that) -- and at that, it's a module onto which you'd have to build your own interface/logging/whatever. My limited experimentation leaves me with doubts, too, about the feasibility of integrating IMU data to get accurate velocities in a BASE environment, since most components are limited to 300 degrees per second of yaw and 6g range (though perhaps that could be corrected using compass and barometer). If you can share experiences with a particular IMU, I'd love to hear them.

I'd also love to hear more about this. I've done a bit of poking around, and a decent IMU for $100 would be a big surprise to me. Integration's a bitch, too, so I think you'd have a hard time getting accurate velocities for the duration of a flight.

Michael

I'll find out. We may be using one on a project soon. One of my scientist colleagues mentioned a cheapy inertial navigation system that might me our accuracy needs.

i thought an inertial navigation system would be great because I am uncertain how accurate the altitude measurements are on GPS. Secondly, an INU could be used on a jumpers to determine there actual fall distance versus time as well as the jumpers orientation, for example, to let you know that you suck at exits or how well you are doing your aerials.

http://www.blincmagazine.com/...140-glide-ratio.html

Cheers dude, that was an interesting read. Kind of elaborated what I was already thinking about variability and margins for error.

I had a look at the other exit point on the weekend and canned the idea anyway. The only shear section of rock I could find was heaps shorter than I expected (thanks to a small ledge) and there was nothing you'd want to land in anywhere close by. Everything else was underhung and ugly as hell