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| Originally Posted by Andrew H . Does anyone use trimix with high oxygen for dives of 20-40m or is it considered too expensive? The CCR crowd must have experienced this using trimix diluents on shallow dives after deep dives, there must be a different experience even at 30m? |
If i am planning wreck penitration I would use Trimix on a 30m dive. On a 40m dive I would use it any way. I will always run a max planned depth PP02 of 1.4 on wreck dives. On higher work load dives I would drop that to 1.3 and increase the He.
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From past experience I know that a dive on a wreck in 27m of water would be planned on PADI table as 30m for 20min, But much of the dive will be done at 20m on an intact wreck so diving a computer pays hugh dividends in that respect. I am wondering diving to around 40m on nitrox with deco, the difference would be similar? I am also assuming that diving deeper on mixed gas say 60m there would be less change and at 90m much less change because of the reduced relative change in ambient pressure as the dive is deeper? Seems to me then that you need a fairly compelling reason to spend hundreds of pounds on a VR3 when you could cut tables for the dive effectively for free. Any way that's what I'm driving at, don't seem to be any nearer to solving my problem so far.
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30mins at 90m using 14/60 32 and 80% 153mins deco
30mins at 87m using 14/60 32 and 80% 143mins deco
30mins at 85m using 14/60 32 and 80% 135mins deco
A varaible of 5m on the depth reduces the total deco by 18mins. It dosent sound like much but when i wave you good buy and you have still got 18 mins to go trust me you will be pissed off.
Finding a secton of the wreck at 75m and doing 15 at 90 and 15 at 75 would reduce it to 128mins so thats 25 mins saved but I am still doing the same 20/80 profile.
Its worth it to me.
ATB
Mark Chase