I'm planning a trip with 2 dives in a day with dive depths of approximately 55m and bottom times of 30 minutes for each dive.
Since I have one set of twins to take with me and only have access to air top offs on the boat, I am thinking of having the tanks filled with 20/50.
For the first dive that gives me a max PO2 of 1.3 and an END of 15m.
Assuming I use 2/3 of the gas then top off with air, I get a mixture of 20/16 for the second dive which will give me an END of 42m - not brilliant, but better than nothing.
Neither of these mixtures is covered by the IANTD tables I am familiar with and that I usually use to calculate deco schedules. For this type of dive where I had access to trimix fills or multiple tanks, I would normally use the 20/25 table.
If I use Zplanner or similar to generate my schedules the only significant difference for this dive profile is a lengthening of the deco for the first dive (on 20/50) and slight shortening of the deco for the second dive (on 20/16) as compared to 20/25.
Is there anything else that I should consider when planning this schedule ?
I would particularly welcome any comments about the difference made by the relatively high helium content in the first dive.
Thanks
Since I have one set of twins to take with me and only have access to air top offs on the boat, I am thinking of having the tanks filled with 20/50.
For the first dive that gives me a max PO2 of 1.3 and an END of 15m.
Assuming I use 2/3 of the gas then top off with air, I get a mixture of 20/16 for the second dive which will give me an END of 42m - not brilliant, but better than nothing.
Neither of these mixtures is covered by the IANTD tables I am familiar with and that I usually use to calculate deco schedules. For this type of dive where I had access to trimix fills or multiple tanks, I would normally use the 20/25 table.
If I use Zplanner or similar to generate my schedules the only significant difference for this dive profile is a lengthening of the deco for the first dive (on 20/50) and slight shortening of the deco for the second dive (on 20/16) as compared to 20/25.
Is there anything else that I should consider when planning this schedule ?
I would particularly welcome any comments about the difference made by the relatively high helium content in the first dive.
Thanks