Where does the 60ft/minute ascent rule come from?

[mbacarella]

I'll WAG base e will work pretty well.

how much?

30ft/min with a 10ft/min slowing (either as one 15ft stop or sliding through the ~30ft to 0 ft zone) is pragmatic and it works. Many of us start slowing down to ~10ft/min at roughly 1/2 our depth.

I think you're describing log(x):

(http://www.wolframalpha.com/input/?i=logx+from+1+to+8)

But you're saying you're describing e^x:

(http://www.wolframalpha.com/input/?i=e^x+from+1+to+8)

One of those will get you bent more than the other, I imagine.

Sorry if this sounds like nitpicking.

 

[mbacarella]

Either you're trying hart to pick a fight, or you missed something in high school algebra.

I thought it was pretty clear I'm missing his description.

 

[ucfdiver]

I thought it was pretty clear I'm missing his description.

If you work your way back from the surface (to depth) and it's logarithmic, it's going to be exponential working from depth up.

So someone who has a chart written like this

10ft - 20min
20ft - 10min
30ft - 7min
40ft - 4min
50ft - 2 min
60ft - 1min

Is going to refer to that as exponential because it's growing exponentially as we reach the surface, even knowing the graph aka profile is really logarithmic. I guarentee no one in this thread who passed high school algebra was confused by what Richard said.

 

[Slamfire]

Give it a rest, guys. We're discussing semantics here. On side is saying 6/2 = 3 and the other side is saying 6 x 0.5 = 3. "Its a multiplication" "No! you're wrong. It's a division". A logarithmic function is an inverse exponential function. In other words, you just swapped x for y.

I think people get the idea that the closer you are to the surface the slower you should go, irrespective of it being called a logarithmic or inverse exponential curve.

 

[Peter Guy]

Hey, I passed high school algebra 45+ years ago and I have NO IDEA what you guys are discussing! More to the point, does it have any practical relevance?

 

[ucfdiver]

Hey, I passed high school algebra 45+ years ago and I have NO IDEA what you guys are discussing! More to the point, does it have any practical relevance?

You know, after thinking this through, I believe it's Calc 1 stuff, but either way since most people take calc 1 in high school these days via AP or dual enrollment, it's high school math

 

[rjack321]

how much?

Buhlmann generates logarithmic curves (inverse exponential, exponential decay, whatever you chose to call it since it depends on how you orient the axes)

Pure Buhlmann with 100/100 gradient factors is closer to base 2.
The lower the GF low the more and more the curve will shift towards base 10
The higher the GF high (especially if >100) the steeper & flatter the curve
A typical GF 30/90 or something like that looks roughly like base e

You have no data and this is just a thought experiment anyway. The best dataset is Ross Hemingway's collection of VPM dives. Recreational technical divers don't use 60ft/min ascent rates btw, its all 30ft/min up to the first stop nowadays.

 

[texdiveguy]

It's quoted in several books I have read..... LOL

 

[emoreira]

What we were told in the OWD course is that you should go up slower than your bubbles.
Bubbles go up at 18 mts/minute or 60 ft/minute.
Taking a safety factor of 2, you should ascend at a rate of 9 mts/minute or 30 ft/minute.
Bubbles go up at the same speed no matter the size of the bubble. As the depth decreases, the bubbles become bigger, but ascend at the same rate.

 

[Thalassamania]

What we were told in the OWD course is that you should go up slower than your bubbles.
Bubbles go up at 18 mts/minute or 60 ft/minute.
Taking a safety factor of 2, you should ascend at a rate of 9 mts/minute or 30 ft/minute.
Bubbles go up at the same speed no matter the size of the bubble. As the depth decreases, the bubbles become bigger, but ascend at the same rate.

Use your watch and your depth gauge. 5 ft every 10 seconds. Ascend 5 feet, make sure that 10 seconds have passed, then ascend for 10 seconds, make sure 5 feet have passed, repeat as needed.