Riding Blind with your DSMB reel

[dumpsterDiver]

I find the argument that the calculations are all performed at a shallow depth and thus narcosis is not an issue hard to reconcile with the apparent necessity to perform a weighted average computation (while at depth) in order to calculate average depth?

Depending on the profile and the computational methods used, this would seem to require a significant amount of concentration and attention to both time and depth.

And as Pete has indicted, the angle of deployment of an SMB is a function of the discontinuity or heterogeneity in the vertical distribution of the velocity, rather than simply the speed of the current.

The bubble stream of the divers appears to show the higher speed current just above the diver.

 

[rongoodman]

The reason narcosis isn't seen to be an issue when using RD is not the depth, but the use of non(or less) narcotic breathing mixtures. As someone above pointed out, take away the standard gases and it's no longer RD.

 

[boulderjohn]

You do understand that narcosis is NOT a factor here right? Ratio Deco only works within the framework of maintaining shallow END's through the use of standard gases.

The reason narcosis isn't seen to be an issue when using RD is not the depth, but the use of non(or less) narcotic breathing mixtures. As someone above pointed out, take away the standard gases and it's no longer RD.

The use of standard gases results in equivalent narcotic depths of no more than 100 feet, and we all know there is no possibility of narcosis affecting people at 100 feet, don't we?

 

[PfcAJ]

The use of standard gases results in equivalent narcotic depths of no more than 100 feet, and we all know there is no possibility of narcosis affecting people at 100 feet, don't we?

They actually shake out to 85-90ft.

In any case, you can figure the whole deco schedule out at 70' if you want.

 

[PfcAJ]

I find the argument that the calculations are all performed at a shallow depth and thus narcosis is not an issue hard to reconcile with the apparent necessity to perform a weighted average computation (while at depth) in order to calculate average depth?

Depending on the profile and the computational methods used, this would seem to require a significant amount of concentration and attention to both time and depth.

And as Pete has indicted, the angle of deployment of an SMB is a function of the discontinuity or heterogeneity in the vertical distribution of the velocity, rather than simply the speed of the current.

The bubble stream of the divers appears to show the higher speed current just above the diver.

Avg depth is a lot easier than it would seem.

Think about a wreck that's 170ft to the dirt. Before you even get in the water you know you aren't going to be digging in the sand and you avg depth will probably be in the 150' range. See something cool up at 140 and spend your dive there? Sweet 140' avg. hang out in a hold down at 160? There ya go.

It's not like you're bringing down the abacus with you to sort it out.

 

[boulderjohn]

It's not like you're bringing down the abacus with you to sort it out.

No, you don't bring down the abacus. You do it in your head.

 

[PfcAJ]

No, you don't bring down the abacus. You do it in your head.

It just takes paying a LITTLE attention to your depth. Normal scuba stuff.

 

[boulderjohn]

It just takes paying a LITTLE attention to your depth. Normal scuba stuff.

As I mentioned in another post, the friends I had who got bent while using RD and a computer in gauge mode learned when they downloaded the computer log that they had miscalculated their average depth. I remember it well--the difference was 8 feet over 30 minutes. They did not have a hard bottom, and in their exploratory mode they had too many depth changes to average it accurately. I just ran the 2 profiles through multideco, and the difference in total deco time was 7 minutes.

 

[PfcAJ]

As I mentioned in another post, the friends I had who got bent while using RD and a computer in gauge mode learned when they downloaded the computer log that they had miscalculated their average depth. I remember it well--the difference was 8 feet over 30 minutes. They did not have a hard bottom, and in their exploratory mode they had too many depth changes to average it accurately. I just ran the 2 profiles through multideco, and the difference in total deco time was 7 minutes.

Same friends that ignored altitude, too?

8ft deeper or shallower?

 

[boulderjohn]

Same friends that ignored altitude, too?

8ft deeper or shallower?

They ignored altitude because they were taught to ignore altitude when using RD. They were 8 feet deeper than they thought they were.