Skipping surface intervals - DIR or not?

[*Floater*]

If that were even remotely close to true then a diver could do a 100' dive, make a 10 min. ascent and then jump on an airplane with no worries.

Joe

actually that's also fine according to my DIR-F course if you dive DIR to begin with. :eek_2:

 

[Charlie99]

Also I did email martin and he made some suggestions but basically okayed this......... Or to make this more specific, is it possible for a diver using ean32 on a 100' 30 min dive to off-gas almost completely during a 10 min ascent?

To be very specific. NO!

With a series of 30 minute 100' dives followed by 10 minute ascents, one would eventually load up the slow tissues/compartments well beyond acceptable levels, even if using EAN32. This is particularly true since your 10 minute ascent is close to a linear ramp, rather than the proper "longer when shallow" curve.

Could you clarify what your instructor said? He's ok with zero SI time like you describe, and he's OK with zero time to fly?

 

[Spoon]

and he's OK with zero time to fly?

we had the same instructor and he said that we could literally hop into a plane after diving.

 

[Charlie99]

If that were even remotely close to true then a diver could do a 100' dive, make a 10 min. ascent and then jump on an airplane with no worries.

actually that's also fine according to my DIR-F course if you dive DIR to begin with. :eek_2:

Was that also Martin Lorenzo, or "board-with-wet-hair" MHK?

 

[Doc Intrepid]

It wasn't MHK, Charlie.


(I'm unclear regarding your adjectives, though...but lets take it up in PMs)

 

[Charlie99]

It wasn't MHK, Charlie.


(I'm unclear regarding your adjectives, though...but lets take it up in PMs)

No PM needed. Just follow the links in this post. It's better to look at the actual posts by a GUE instructor than to rely upon the memory of DIR-F students as to what was communicated verbally only. In this case however, the posts by the instructor agree with what the students report they were told by another instructor.

The adjective relates to things like

DAN recommends 12 hours, down from their previous recommendation of 24 hours. On almost any given weekend I can be found getting out of the water and rushing to an airport, often times with my hair and my gear still dripping wet and that is often times after very deep and lengthy decompression dives, so I wouldn't worry too much about doing a few recreational dives and jumping on a puddle jumper...

 

[*Floater*]

To be very specific. NO!

With a series of 30 minute 100' dives followed by 10 minute ascents, one would eventually load up the slow tissues/compartments well beyond acceptable levels, even if using EAN32. This is particularly true since your 10 minute ascent is close to a linear ramp, rather than the proper "longer when shallow" curve.

Could you clarify what your instructor said? He's ok with zero SI time like you describe, and he's OK with zero time to fly?

You do have to be more careful with repetitive dives. When I emailed my instructor I mentioned 15-20min surface intervals because I would need some time to change the tanks, go over the new dive plan, do the checks, have a drink of water, and so forth. But FWIW George Irvine has written than two back to back dives are far safer than one longer dive if you do it his way.

Here are more of his thoughts on repetitive (deco) dives: http://www.wkpp.org/articles/Decompression/repetitive_dives.htm

 

[RTodd]

actually that's also fine according to my DIR-F course if you dive DIR to begin with. :eek_2:

The only time I have ever had a problem on a plane was when I got on one while already bent. Cameron's comments apply here too. Not much of a big deal, but depending on the risk level of your profile not generally a great idea.

You are making very poor risk assesments with the proposed profiles. While I wouldn't have a problem doing back to back 100/30s assuming I had O2 to get a bit cleaner, I would only do it if there was a true need. In this case, there isn't. Agressive profiles, assuming good physical conditioning aren't the problem. The problem is that if you screw anything else up, such as over-exerting or not getting enough water, you get hit. They simply don't leave room for error. Having said that, I doubt you will actually dive a 100 for 30 profile anyway which will reduce the risk some but not as much as a real surface interval. A better way to get more time in the water would be to do 25 minutes at 100 and save enough gas to spend the next 40 minutes at 70-50'. Then, do a reasonable SI.

 

[Charlie99]

Here are more of his thoughts on repetitive (deco) dives: http://www.wkpp.org/articles/Decompression/repetitive_dives.htm

Hopefully you also noticed that he recommends that the repetitive dives should be the same depth or deeper (reverse profiles)

"From a decompression point of view, we have seen that repetitive diving makes no difference, so we ignore the first dive in calculating the second. The only trick is that the second dive should be deeper than or equal to the first, and you can not bounce dive after a dive of any kind."

 

[RTodd]

You do have to be more careful with repetitive dives. When I emailed my instructor I mentioned 15-20min surface intervals because I would need some time to change the tanks, go over the new dive plan, do the checks, have a drink of water, and so forth. But FWIW George Irvine has written than two back to back dives are far safer than one longer dive if you do it his way.

Here are more of his thoughts on repetitive (deco) dives: http://www.wkpp.org/articles/Decompression/repetitive_dives.htm

You are misreading what George is saying. He does surface intervals. From a decompression standpoint, one longer dive with a proper deco will always be cleaner than two "back to back" dives with no real surface interval. What George is saying is that in the open ocean where conditions can change, it is safer to reduce your bottom time and your decompression obligation to allow you to get out of the water with less risk if you have to before completing your deco.