[quote=Brian Donaghy]
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Okay, I'm curious as well. I've never understood why anyone would do this. I don't understand what benefit the computer provides as a primary deco indicator. Could you explain how you would plan the deco & gas management for a simple one switch stage deco dive? What is the difference between your tables/gas management plan vs what the VR3 says?
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Basically for OC I plan the dive on Decoplanner using 20/80GF. I will put in planned maximum depth or multilevel if I am definite that I will multilevel the dive and insert the deco gas plan. This will map my dive in terms of maximum bottom time for the available gas and provide data on required deco gas quantities.
Then (prior to having two VR3's) I will slate this with the normal +/- profiles and 100/100gf bail out plan.
The actual dive on the VR3 will almost always have less deco than the planned dive, as the actual dive depths are almost always shallower than the estimated dive depth. As an example here is a dive on the Duke planned for
35mins at 55m
As you can see we were above 55m for most of the dive and then dropped down to 57 to look at the prop.
With two VR3s I don’t use tables at all and I can do any profile I like within gas planning limits. The VR3 will show me time to surface on available gas and from experience I know exactly how much deco I can squeeze out of my two 7ltr stages. When I get to my pre set limit of deco gas time I can choose to go up then. Bottom time and depth are not particularly relevant any more. The TTS figure controls the dive.
I like the freedom this gives me I just do the dive with little or no consideration of depth or time. All I need is a worst-case bail out 100/100gf plan in case both VR3s pack up. I normally commit this to memory before the dive. For the above dive its 35mins with 25@6. That’s all I need to know for this dive. I divide the remaining time over the 9,12,15m stops so it would be 5@9 3@12 2@15
When I was on the VR3 and Andyp was still on tables I would usually beat his tables by 10 or 15mins using the VR3 on this sort of dive. However shaving deco is not the reason why I got it. I got it so I am not restricted to the dive plan.
ATB
Mark Chase