Pony for Dry Suit only... Thoughts?

[LenC]

For any effect at all with argon the suit must be completely filled (to the point of overpressure) before the dive to remove the air otherwise dilution makes it worthless.
Even after that its debatable whether theres a difference. Personally i haven't noticed any difference at all so dont bother with it. Trimix diving now i just feed it off my leanest non-helium stage (usually a 50%).

That is an approach which had not occurred to me. How do you deal with the situation where you have to hand off your bottle to a team mate? Would that just be a case of "we are on our way up anyway"? That's not a criticism, just curious.

 

[String]

That is an approach which had not occurred to me. How do you deal with the situation where you have to hand off your bottle to a team mate? Would that just be a case of "we are on our way up anyway"? That's not a criticism, just curious.

Depends on your diving philosophy as to whether handing off is part of the plan or not. I personally dont do "team bailout" or similar and the backup plan involves buddy breathing for that.

If you do decide to hand off then you're on the way up so unlikely to need to put anything in your suit anyway (you're certainly not carrying on a dive). Failing that make sure the DS inflate is the same as wing inflate so you can simply disconnect, pump some air in, return to wing. This would be my first choice as its quick and simple.
Or have 2 stages with inflation hoses on them (but i wouldn't recommend that due to failure points etc).

 

[String]

I thought about that but as my leanest stage is likely to be 80%, the worry that there might be a suit fire (however unlikely that is) just put me off, my drysuit still smells of what I would imagine to be quite flammable glue and with a dive to say 40m a ppO2 of 3.2bar just seems like asking for trouble to me.

Depends how you dive. Personally all trimix dives for me are a minimum of 2 stages so i've got a viable bailout should i lose one tank (i don't believe in the team bailout philosophy and certainly dont want to back-gas deco). Generally that means ive got a 50% and 100% (or 50% and 80%) always as a minium on trimix.
Not sure id want to ram in 80 or 100% into my suit but im happy with 50%. Even then i suspect the volume and dilution in the suit coupled with how little gas you put in im not expecting someone to spontaneously combust.

EDIT: I just had another thought (2 in one day) presumably this means do the dive with the the cylinder turned on, not sure that's such a good idea from the POV of having a reg turned on with an unbreathable gas for the depth.

Not overly If you think about how often you adjust your suit its typically just on the descent and then thats it. The bottom portion its unlikely, ascent you wont at all and the only other fill may well be on deco if you want some more gas in for warmth.
Quite easy to keep it off, turn it on for some squirts then back off. You get a fair bit just from residual pressure in the hoses even with the tank off (just remember to re-pressurise after it).

 

[Slamfire]

I just had another thought (2 in one day) presumably this means do the dive with the the cylinder turned on, not sure that's such a good idea from the POV of having a reg turned on with an unbreathable gas for the depth.

Not taking descent or the use of travel gas into consideration and assuming your bottom gas is in your back, on ascent, your first switch will be to your leanest mix. In other words the regulator that is on is the one you will have to switch to first. Before that 1st switch, nothing except your back gas is suitable for depth. In the best interest of your health you should not do any switches. At the bottom depth there is no reason to be playing around with different regs. And when you ascend to an adequate depth for a switch, the only other reg that is on is the one you have to switch to.

Another element that helps here is that you distributed your stage/deco bottle on both sides, so you know to always go first to the left and then to the right.

 

[LenC]

Depends on your diving philosophy as to whether handing off is part of the plan or not. I personally dont do "team bailout" or similar and the backup plan involves buddy breathing for that.

If you do decide to hand off then you're on the way up so unlikely to need to put anything in your suit anyway (you're certainly not carrying on a dive). Failing that make sure the DS inflate is the same as wing inflate so you can simply disconnect, pump some air in, return to wing. This would be my first choice as its quick and simple.
Or have 2 stages with inflation hoses on them (but i wouldn't recommend that due to failure points etc).

Gotcha. I normally dive CCR so a hand off is my typical plan. I've only had to bail out once so far and even then I got back on the loop within a couple of minutes. I get your reasoning though. The only issue I would see is if your second stage on that bottle had a slow leak. You wouldn't have the valve shut down during the dive because you would need it for the suit - so you could end up at your first stop finding yourself without enough gas. That happened to a friend of mine. Shouldn't be a problem as long as you monitor the pressure. He didn't because he just forgot to shut it down. It's the little things that get ya.

 

[String]

The only issue I would see is if your second stage on that bottle had a slow leak. You wouldn't have the valve shut down during the dive because you would need it for the suit

Yeah you would. Bottle is off as normal, turn it on for 5 seconds to shove some gas in the suit then turn it back off. I don't leave the bottle on so it works exactly as a normal stage.

In reality its usually on for the entire descent as i try to make it 30-40m/minute (open circuit is a bitch with gas and deco obligations as im sure you're aware!) as i need a squirt every few seconds. Once im established on the bottom tank goes off and the above is used if i need any more gas (its rare i do until deco). A leak doesn't bother me for that 3-4 minutes of descent as i can see the stage clearly so would see leaks (and see the spg).

 

[LenC]

Yeah you would. Bottle is off as normal, turn it on for 5 seconds to shove some gas in the suit then turn it back off. I don't leave the bottle on so it works exactly as a normal stage.

In reality its usually on for the entire descent as i try to make it 30-40m/minute (open circuit is a bitch with gas and deco obligations as im sure you're aware!) as i need a squirt every few seconds. Once im established on the bottom tank goes off and the above is used if i need any more gas (its rare i do until deco). A leak doesn't bother me for that 3-4 minutes of descent as i can see the stage clearly so would see leaks (and see the spg).

Sounds like a reasonable approach. Thanks. I will mention it as a possibility in my next class. Even if they don't do it, I like my students to think about why they use a particular configuration rather than just do what I tell them to do.