Why deeper in the morning?

[Charlie99]

Here's a link to the article on repetitive dives on the WKPP website.

Quote from George Irwin's article:

See my article on "why we do not bounce dive" for all the reasons.

Otherwise, repetitive diving is a good thing, and you should do your shallower dive first and then your deeper one. The stupidity taught in that regard is beyond the pale.

 

[wombat]

I'm glad I asked this question because of all the interesting information it generated (some of which I even understood). Here I was concerned about not having an answer, and it turns out there are lots of different answers. Guess we need to teach rats to dive.

 

[teksimple]

I'm glad I asked this question because of all the interesting information it generated (some of which I even understood). Here I was concerned about not having an answer, and it turns out there are lots of different answers. Guess we need to teach rats to dive.

Thanks. I had not previously heard about the "deeper dive second" theory, nor the fact that these guys would regularly omit their gas accumulation from their first dives when planning consecutive dives. Bruce Wienke was involved in the Karst Plain porject, but I don't recall him mentioning this aspect of dive planning.

So, considering that the decreasing depth profiiles are indicated in the "modern" VPM and RGBM algorithms, does this warrant creating an even more modern algorithm to test?

 

[Mako Mark]

To tell you the truth, I even have trouble remembering how to spell Weinke, his book sits on the shelf unread. I think I am just too intimidated to open it..

 

[Charlie99]

Thanks. I had not previously heard about the "deeper dive second" theory, nor the fact that these guys would regularly omit their gas accumulation from their first dives when planning consecutive dives. Bruce Wienke was involved in the Karst Plain porject, but I don't recall him mentioning this aspect of dive planning.

So, considering that the decreasing depth profiiles are indicated in the "modern" VPM and RGBM algorithms, does this warrant creating an even more modern algorithm to test?

Wienke and WKPP/DIR aren't always on the same page. For example, George Irwin and some GUE instructors don't believe in taking altitude into account. Wienke doesn't agree with that. He also isn't in favor of reverse profiles.

OTOH, many find BRW's choices of gases strange.

There are lots more opinions than proven facts in the realm of decompression.

 

[boulderjohn]

I wonder about the origins of the "deepest dive first" philosophy in the first place.

A few years ago I was in Australia, and I read an article in a local newsletter. According to my feeble memory, the article said that DAN and PADI did a joint literature review to find the origin of "deepest dive first." The first written reference they could find was (I think) a 1972 PADI document of some kind. This document flatly stated that deepest dives should always be done first, but it did not explain why or cite any sources. They could not discover who wrote that particular piece. The practice eventually took on the authority that comes with time. "We've always done it this way."

Just after I read it, I met a former instructor who insisted he had seen all sorts of studies that proved the importance of deep dives first, but the article said there were no such studies, and reading through the materials on this forum has not revealed any.

I suspect his memory is like the story of the movie theater that supposedly showed subliminal ads and got a big increase in snack bar sales--everyone refers to that "study," but in truth it is an urban legend and never happened. When you hear something enough times, it is hard to sort out objective fact from hearsay.

Please note that I am not making a recommendation one way or the other. I am just wondering how the practice started, and what evidence there truly is for it today.