RAID Cave 1 - Good Course?

[wetb4igetinthewater]

I don't understand why you wouldn't use the contour up here, at least with steel tanks its far easier to trim them out.

I got rid of the Contour as I wanted a harness to handle both steel and aluminium cylinders. I don't use rails anymore either, but clip off to a D-ring on my waist belt (and have another one lower when the bottoms of my Faber HP100s get floaty).

Everything goes to hell (tank trimwise) with SM and trimix sadly.

Really? When I took normoxic trimix, I felt great with 4 cylinders. I actually found it easier to keep the cylinders trim as they were all quite snug.

 

[rjack321]

Really? When I took normoxic trimix, I felt great with 4 cylinders. I actually found it easier to keep the cylinders trim as they were all quite snug.

They want to float up in the butt as if they are empty.
Sure you can front clip them. But you have to have someplace to do that.

 

[wetb4igetinthewater]

They want to float up in the butt as if they are empty.
Sure you can front clip them. But you have to have someplace to do that.

If we are going too OT, happy to take this to PM.

Have you ever watched Steve Martin's videos on setting up additional bottles? That's the way I do it and it works really well for me. It avoids the floating problem.

 

[rjack321]

If we are going too OT, happy to take this to PM.

Have you ever watched Steve Martin's videos on setting up additional bottles? That's the way I do it and it works really well for me. It avoids the floating problem.

Steve doesn't have suit heat, suit gas, a scrubber heater, a canister light plus dual canisters of sorb and a RB loop riding on top of the SM bottles. I use standard stage rigging for my deco gases. The first bottle rides underneath on the left hand side (right where it would in BM). The rest have to go on my butt rail.

I would have kept the Contour for local diving. I still occasionally dive my Hollis SMS 100 (minus the sidewinder) which is a precursor to the contour. Works pretty well with hp100s and similarly negative (when empty) steel cylinders. Having the right SM BC optimized for the job is pretty important. But I only SM for cave diving anyway.

 

[wetb4igetinthewater]

Steve doesn't have suit heat, suit gas, a scrubber heater, a canister light plus dual canisters of sorb and a RB loop riding on top of the SM bottles. I use standard stage rigging for my deco gases. The first bottle rides underneath on the left hand side (right where it would in BM). The rest have to go on my butt rail.

I would have kept the Contour for local diving. I still occasionally dive my Hollis SMS 100 (minus the sidewinder) which is a precursor to the contour. Works pretty well with hp100s and similarly negative (when empty) steel cylinders. Having the right SM BC optimized for the job is pretty important. But I only SM for cave diving anyway.

I do believe Steve has a canister light. I'll admit that I don't like the canister light on my butt, nor the argon bottle there. But, I didn't think we were talking about CC. If you were to dive SM OC, then I think you may find that Steve's method works nicely. I can see how standard rigging for stages would be a mess in SM. Now I've never gone beyond 4 bottles. I won't get into hypoxic OC dives as it is just too expensive helium wise. I do believe that is CC territory.

 

[cerich]

Blown o ring on the right post first stage and a torn diaphragm on the right post second stage that caused it to deliver more water than gas. Happened several months apart. The blown O ring was about 1000' back in a cave at 80'. Torn diaphragm was at stage drop about 2000' in (still not sure what happened there, it wet breathed fine in predive checks). Simple solution both times. With the blown o ring, I just shut down, swapped to the necklace, and called the dive. With the diaphragm, I just swapped right back to the stage and called it, but all of the backgas was still accessible from the left post. I don't know that I could've handled breathing off the busted reg, even in an emergency. It was bad.

in Sm it would have played out exact same wayin both cases.

They want to float up in the butt as if they are empty.
Sure you can front clip them. But you have to have someplace to do that.

I bungee them, even without tmix in, less noise and better trim.

 

[helodriver87]

in Sm it would have played out exact same wayin both cases.

Yes and no. You would've effectively lost all the gas in one tank without hot swapping a reg. Feathering would've just meant manually waterboarding yourself instead of automatically. Granted, I didn't need my backgas in that situation, but if I had (delayed exit or additional issues) accessing all of it would've been trivial. And the first situation is similar. I probably exited on significantly less gas than I had remaining in even one of my tanks. So regardless of configuration, I would've been fine just breathing the other reg. Until the snowball happens. At which point, being able to access both tanks through one reg would've been a huge advantage. On both of those dives, sidemount would've cut into my safety margin and given me zero benefit (it was all big cave).

 

[leadduck]

For sure one can think of a kind failure that renders the gas in one sidemount tank unusable, whereas a manifold closed in a short time will preserve more gas.
Now instead of digressing into feathering and reg swapping under water, I think it's more important to understand the purpose of independent tanks: the goal is preserving the guaranteed minimum needed to exit. The manifold method may preserve a larger amount of gas on average for some failure modes, but it may leak too much gas if the leak is detected too late or valve handling is too slow or wrong.
In sidemount gas planning, you do not rely on feathering or reg swapping. These are nice-to-have and feathering works in many cases, and there's a good chance you identify a first stage defect earlier in sidemount than in backmount preserving even more gas, but all of this must not be safety critical, and the worst-case planning scenario is the complete loss of one tank. You gain more safety margin by more conservative gas management (rule of 3rds may be a bit too aggressive for a solo dive) or using more tanks, but not by relying on feathering in gas planning.
Whereas for a backmount solo diver, noticing the leak, identifying its location and closing the correct valve in time, all located behind his head where he can't see anything and may have trouble reaching it, is critical for survival. His worst-case gas planning scenario is the complete loss of all gas, hence generally not considered sufficient without another backup such as a stage bottle, pony, or gas sharing with the buddy.

 

[helodriver87]

For sure one can think of a kind failure that renders the gas in one sidemount tank unusable, whereas a manifold closed in a short time will preserve more gas.
Now instead of digressing into feathering and reg swapping under water, I think it's more important to understand the purpose of independent tanks: the goal is preserving the guaranteed minimum needed to exit. The manifold method may preserve a larger amount of gas on average for some failure modes, but it may leak too much gas if the leak is detected too late or valve handling is too slow or wrong.
In sidemount gas planning, you do not rely on feathering or reg swapping. These are nice-to-have and feathering works in many cases, and there's a good chance you identify a first stage defect earlier in sidemount than in backmount preserving even more gas, but all of this must not be safety critical, and the worst-case planning scenario is the complete loss of one tank. You gain more safety margin by more conservative gas management (rule of 3rds may be a bit too aggressive for a solo dive) or using more tanks, but not by relying on feathering in gas planning.
Whereas for a backmount solo diver, noticing the leak, identifying its location and closing the correct valve in time, all located behind his head where he can't see anything and may have trouble reaching it, is critical for survival. His worst-case gas planning scenario is the complete loss of all gas, hence generally not considered sufficient without another backup such as a stage bottle, pony, or gas sharing with the buddy.

Complete loss of backgas is a two critical failure event, assuming you're somewhat competent in the shutdown/analysis process. If you're a team oriented diver, it's not really a concern. Besides, you're not taking doubles anywhere that having a buddy will be detrimental like you can in sidemount. It's always better to have a competent buddy in doubles.

When my o ring blew it was very obvious. I had a buddy knock one of those exposed burst discs loose awhile back. Also very obvious. If you're well trained on the manifold and have a good buddy, you're gonna get it right as a team every time. With reg failures being significantly more common than valve failures, that means fewer lost resources most of the time. Yes, in theory you only need half your gas if diving thirds. In practice, once things go pear shaped, you can't have enough. No point giving up that safety margin without a reason.

 

[leadduck]

Complete loss of backgas is a two critical failure event, assuming you're somewhat competent in the shutdown/analysis process. If you're a team oriented diver, it's not really a concern. Besides, you're not taking doubles anywhere that having a buddy will be detrimental like you can in sidemount. It's always better to have a competent buddy in doubles.

It's everybody's personal choice if you trust your life to the shutdown/analysis process and to your buddy's competence and presence, but you may one day notice that for many people this is not OK at all. They want to be self-reliant even when diving with a buddy, and they do not trust the valve shutdown in a stressful situation enough to trust their life on it.

When my o ring blew it was very obvious. I had a buddy knock one of those exposed burst discs loose awhile back. Also very obvious. If you're well trained on the manifold and have a good buddy, you're gonna get it right as a team every time.

So you had two incidents and survived, congratulations. Now you believe that's proof it works every time and there's no need for further redundancy. Good luck with that.