Backgas Reserve in a Stage Bottle?

[kramynot2000]

You might be able to work a travel mix in the plan. Saving your back gas for BT

Actually, I was thinking of using the 36% as a travel gas down to 110' then doing a switch. I'm sure I have more than enough of that to deco but I haven't sat down and worked out volumes yet.

 

[kramynot2000]

I'm no tech diver, but I notice that you're doing thirds as "1/3 of the gas on your back." I believe GUE teaches to take 1/3 of the gas on your back after you subtract out a rock bottom, which seems like a good idea to me. I sort of assumed this is just how thirds was done by everyone. Is there something I'm missing?

I seem to remember that out of my Fundies class as well....

But yes, as with virtually everything in diving, there are different opinions on the 1/3 and reserve. Actually I think there is a thread on this board about how much reserve to use in OW diving and there are opinions as to whether its 1/3 after subtracting RB, 1/3 of BG, or whether you even need 1/3, etc.

Lots of opinions and I think something to learn from each one.

 

[novadiver]

Actually, I was thinking of using the 36% as a travel gas down to 110' then doing a switch. I'm sure I have more than enough of that to deco but I haven't sat down and worked out volumes yet.

To answer your question about breathing the stage down. I think it is common practice to breath the stage down and then drop it off, saving the back gas for the remainder of the dive.

In reality, you might want to plan the dive to only 15 min of bottom time, This will really save back gas and shave deco time also.

 

[kramynot2000]

To answer your question about breathing the stage down. I think it is common practice to breath the stage down and then drop it off, saving the back gas for the remainder of the dive.

In reality, you might want to plan the dive to only 15 min of bottom time, This will really save back gas and shave deco time also.

Thanks for the reply.

Our last couple of dives have been limited to 15 min but we're going down to Monterey and wanted to extend our time to check things out down there.

 

[Dryglove]

Thanks for the reply.

Our last couple of dives have been limited to 15 min but we're going down to Monterey and wanted to extend our time to check things out down there.

Just out of curiosity where in monterey are you doing these dives? Im guessing monastery if your shore diving.

 

[wedivebc]

Thanks for the reply.

Our last couple of dives have been limited to 15 min but we're going down to Monterey and wanted to extend our time to check things out down there.

Just making some huge assumptions here but I have to wonder if you are prepared for the looong cold deco ahead of you? I have not dove Monterey but I understand the water temp at depth is very similar to diving up here. I am usually limited by temperature, not back gas on my deep dives. I dive twin 85s and that keeps me under for longer than I care to stay. With 20min bottom and 60 min deco you guys may be a little chilly in that water. For dives like that I try for 15 min BT and 45 min deco which gets me out before I freeze.
Just a thought.

 

[kramynot2000]

Just making some huge assumptions here but I have to wonder if you are prepared for the looong cold deco ahead of you? I have not dove Monterey but I understand the water temp at depth is very similar to diving up here. I am usually limited by temperature, not back gas on my deep dives. I dive twin 85s and that keeps me under for longer than I care to stay. With 20min bottom and 60 min deco you guys may be a little chilly in that water. For dives like that I try for 15 min BT and 45 min deco which gets me out before I freeze.
Just a thought.

This actually is something we are considering in our planning although I think we're a bit more toasty than you are up there. I think water temps in Monterey are in the low 50's right now with surface temps a little warmer and I remember my last (and unfortunately my only so far...) trip to BC was this past January and temps were in the mid 40's with surface temps... lower! Now that was cold! I remember having 20 min of deco diving the Cape Breton. It was one of the longest 20 minutes I can remember....

 

[Scubaroo]

Tony,

I'm not qualified to do the dive you're planning, but I have done a fair bit of diving in Monterey, both wet and dry. Dave may have a point about 60 minutes of cold water deco after the deep dive. How about doing a shallower non-deco or limited-deco dive first in the same planned gear configuration with the same bottom time, and then doing a simulated deco for the 60 minutes just to make sure it's achievable? That way if you find after a period of time that it's just "too bloody cold", you can cut it short, instead of being stuck shivering your butt off on the big dive, with real deco obligation keeping you in the water. Would also be a good practice run for the actual dive, which sounds like it's not going to be a small undertaking.

cheers

 

[Spectre]

We're both new to diving to this depth so we plan our dives fairly conservatively.

No offense, but perhaps you should cut the plan back more in that case... shorten the bottom time to handle the gas limitations in your gear.

 

[MechDiver]

Just making some huge assumptions here but I have to wonder if you are prepared for the looong cold deco ahead of you? I have not dove Monterey but I understand the water temp at depth is very similar to diving up here. I am usually limited by temperature, not back gas on my deep dives. I dive twin 85s and that keeps me under for longer than I care to stay. With 20min bottom and 60 min deco you guys may be a little chilly in that water. For dives like that I try for 15 min BT and 45 min deco which gets me out before I freeze.
Just a thought.

We normally do 90 to 100+ minute run times in the PNW during the winter. As the bulk of the time is spent at 20 ft, you can dump some wing air and blow some argon in to warm things up if needed.
I would think Calif. would be a piece of cake. Whether the dive should be made is another story.

MD