Basejumper.com - archive

Thinking out loud:

After watching videos like the green line exit it shows that the days of the rock drop maybe numbered for WS (good job, those rocks were expensive and hard to find..)

I've heard the Frenchies have a type of laser that measures the terrain vert / horiz under the exit. Does anyone have the details of this instrument?

In the future rather than talk about rock drop in terms of a 'let go', 'little toss' and 'cricket bowl' - will we simply look at a plot of the terrain instead? OR blindly follow the guy in front of us?

I use a laser. rock drops cause to much fuss in an urban area

https://www.youtube.com/watch?v=9ie8VEtQHmE

The FBA bought a couple of these TruePulse 200 series. http://www.lasertech.com/TruPulse-Laser-Rangefinder.aspx

I don't know if the rock is dead, but when you're standing at a new exit point and you have the laser data to compare with previous measured jumps, you just have more clear and concrete data to base decisions. None of the local wingsuit new schoolers around here are talking about exits in terms of rock drops anymore.

For example, the last time I asked a buddy for info on an exit this was his response:

-120/25, -140/50, -180/90, -220/120, -300/180

translation: short and fairly flat behind it :)

ok now who is going to pick that up?

I think dying but never dead is the answer. A couple of people have the trupulse around here too. Exactly as Lau said, its most usefully not even for the start on the new jumps that are being opened, but for the first 10-15 seconds of flight after the initial exit. I still use rocks :)

We typically use Russians and Ozzie's to check....

Don't know about you country/mountain boys but to keep rock alive on urban jumps I prefer the Moon technique and use a TV out of the window.

I let my mate Pete go first.

me. 20 minutes after the jump. since we knew exactly how high it was, we jumped.

The rock drop is great for determining the relief/'steepness' of a cliff and where the "vert" begins to plane out. But it should not be used to reliably determine distance EVER. Rocks are strange shapes and all have different, usually significantly slower terminal velocities than falling people do.

Good for anything sub rock terminal. I like to know where im going to hit. And then I throw my laser at it and count to know exactly how high it is.

Been awhile since I've done " 3+ sec and it's good to go"...

That being said, idiots abound and I think its a good way to determine SL height. Used to be one of those idiots... Glad I lived thru it........

-Harry

http://www.nikonsportoptics.com/en/Nikon-Products/Product-Archive/Rangefinders/8371/Forestry-550%252F-Hypsometer.html

Thanks for the info guys, my faith is restored in the usefulness of internet forums

I disagree. It depends on the planform of the rock. Aspect ratio is the key. The higher the Reynold's value, the more likely it is to behave in a spiralling way. Which would add credence to your post. That is great to know if you are throwing a rock off (a rock) that is shaped like a paddle. Simples physics state that surface area and density determine the terminal velocity and acceleration. A low Reynold's value would give a higher laminar flow resulting in less drag vs the surface area and mass ratio. Glaciated rocks rock. Because they are closer to being round than striated rock. Limestone vs sandstone vs granite blah. Freefall with your stone's type before you rock drop them and then you can make an accurate judgement. this is not really a joke.
Take care,
Space.
(But she bounced at 12.7secs said the 11sec dropped rock to the sound delay calc.)

I'll make a mental note to never get into a stone skipping competition with you

Lets do this, It would make a great Youtube video.
Mythbusters and Penn&teller could get some side work.