Errol Kalayci
Contributor
I am a passenger being driven home to S Fl from cave country as I write this so excuse typos. Today's dive was conducted as 3 man team each equipped with a bottom stage, oxygen bottle, Suex Dpv (xk1 or joy 37) and 104's on the back. We dove for a 80' bottom time starting time when we finished tie off into main line and hit trigger. We only used our stage and never touched back gas. Having not been in this cave in a decade, I took the lead and a team mate called it when we were at 3,900 feet into the cave. Total bottom time was 80' to beginning of ascent at 50' and we were on trigger the whole time. Our avg depth was 80 feet. We stayed on bottom stage until O2 switch and had 700psi left (started with 3,000) when we loaded truck. During the dive we saw side mounters swimming in of passage, rebreather divers, etc.
Thinking of the dive, I realize that we only used 66 cubic feet for 80' bottom time plus ascent to 02, including wing and dry suit inflation. To determine our scr simply divide 66 cubic feet used by 80 minutes x 3.4ata) and you come out with .25. Therefore, with a Dpv in a flow cave using only 66 cubic feet we covered 7,800 feet round trip, had 80' bottom time at avg depth of 80 feet. This is a huge gas savings over the average swimming diver's scr of .75, where that diver would need to use 205 cubic feet of gas to dive for 80 minutes at 80' ( .75 x 3.4 is 2.55 cubic feet per minute times 80 minutes bottom time is 205cubic feet needed). So we had an immense gas savings and was able to cover way more ground than a swimmer would during same amount of time. As you can see, a Dpv gives you a huge distance and gas leverage advantage and thus you get Speed plus a somewhat like rebreather gas advantage without the inherent risks associated with rebreather's. Historically, divers find about a forty (40%) percent reduction in gas usage while using a Dpv vs swimming on open circuit with the addition of being able to move more gear effortlessly and quicker without raising work rate or travel much further (Dpv is typical 300-400%) distance advantage as well as gas leverage advantage. With all this said, why do many divers choose a rebreather over a Dpv? It seems logically that a diver should choose a Dpv as next step in the evolution and then add a rebreather as a tool when further gas savings is needed to to extreme depth or real logistical concerns. Probably, most rebreather divers would be better served with choosing a Dpv instead of a rebreather or if they need the rebreather most all would need or should certainly use a Dpv (or two) as well.
The point of this post is not rebreather bashing but to reflect that a Dpv is a wonderful tool used in cave as well as ocean to reduce gas consumption by 40%, increase distance by 3-400% potentially, add some further safety and just have a whole lot of fun!
Thinking of the dive, I realize that we only used 66 cubic feet for 80' bottom time plus ascent to 02, including wing and dry suit inflation. To determine our scr simply divide 66 cubic feet used by 80 minutes x 3.4ata) and you come out with .25. Therefore, with a Dpv in a flow cave using only 66 cubic feet we covered 7,800 feet round trip, had 80' bottom time at avg depth of 80 feet. This is a huge gas savings over the average swimming diver's scr of .75, where that diver would need to use 205 cubic feet of gas to dive for 80 minutes at 80' ( .75 x 3.4 is 2.55 cubic feet per minute times 80 minutes bottom time is 205cubic feet needed). So we had an immense gas savings and was able to cover way more ground than a swimmer would during same amount of time. As you can see, a Dpv gives you a huge distance and gas leverage advantage and thus you get Speed plus a somewhat like rebreather gas advantage without the inherent risks associated with rebreather's. Historically, divers find about a forty (40%) percent reduction in gas usage while using a Dpv vs swimming on open circuit with the addition of being able to move more gear effortlessly and quicker without raising work rate or travel much further (Dpv is typical 300-400%) distance advantage as well as gas leverage advantage. With all this said, why do many divers choose a rebreather over a Dpv? It seems logically that a diver should choose a Dpv as next step in the evolution and then add a rebreather as a tool when further gas savings is needed to to extreme depth or real logistical concerns. Probably, most rebreather divers would be better served with choosing a Dpv instead of a rebreather or if they need the rebreather most all would need or should certainly use a Dpv (or two) as well.
The point of this post is not rebreather bashing but to reflect that a Dpv is a wonderful tool used in cave as well as ocean to reduce gas consumption by 40%, increase distance by 3-400% potentially, add some further safety and just have a whole lot of fun!
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