DIR, NAUI TEC - Gear configs

[MXGratefulDiver]

Interesting you should invoke his name. How does he figure deco?

Scenario: You are diving a wall in no current. Straight rock bottom applies. Your buddy has a catastrophic (loss of gas) failure at Dmax. It takes a minute or so to sort out and has the both of you breathing heavily on the ascent (which goes as planned). You surface in heavy chop. How much gas do you have left?

In my case ... way more than I'll need unless the boat has abandoned us ... I like big tanks ...

In any case, I've dived in heavy chop plenty of times without the need for either a snorkel or a reg. If the chop's so heavy that I can't breathe while laying on my back, a snorkel isn't gonna help me anyway ...

... Bob (Grateful Diver)

 

[John_B]

Agree with the above. A snorkel with three footers will get you the occasional mouthful of saltwater. No thanks.

I find I can swim on my back with my regulator sort-of clamped in my teeth and breathe air, when the swell is going to break over my face I can breathe for a second or two off the regulator, then go right back to breathing air. A useful skill to have if you are drift diving and the boat takes its time picking you up.

 

[danvolker]

If we are drift diving, the boat will be along very soon, so the issue is moot. If we are anchor diving, I will need to have my head examined, so the answer is moot

But seriously, here in south Florida, we dive in 4 to 6 foot seas frequently, and this can turn into 8 to 10 at the end of a 2nd dive ( it has a few times over many years) ... If I was planning on diving huge seas, I would be planning on having plenty of air for when I got back on the surface.....it would be "smart" to stick my Halcyon "surf mat" into the MC storage pocket, as this would make a long swim easier ( something there is really no reason for in drift diving....but assuming the boat somehow lost us , this would be one option)....If you were really having life threatening trouble on the surface, and for some reason OOA, then drop the tank off the bands, and keep the wing ( bc). The inertia of the tank makes big waves a pain, but without the tank they are nothing. If all these horrendous issues were going on, a snorkel would be great...but we would have made so many mistakes to get to this point, that there is really no excuse for having to be using this snorkel in huge waves, with an empty tank and no boat for miles.....

Choosing the boat you go out on, and knowing how they will drop you is part of your responsibility. In open ocean, I don't like anchoring, and on any deep tech wreck where the "where is the boat issue?" is stronger, DIR buddy team concept is that we all leave the wreck at the same time, and our floating decos are similar, and the boat will be sending down a safety diver at our 50 foot stop, to ascertain if any deco issues or any complications need to be addressed by the boat, crew or captain....there should be no way for 1 or 2 divers to be separated from the main group, or for the boat to somehow loose track of someone.

Regards,
Dan

 

[Gombessa]

Scenario: You are diving a wall in no current. Straight rock bottom applies. Your buddy has a catastrophic (loss of gas) failure at Dmax. It takes a minute or so to sort out and has the both of you breathing heavily on the ascent (which goes as planned). You surface in heavy chop. How much gas do you have left?

I may be missing something here, but as presented, doesn't this depend on how much gas you have at Dmax when the failure occurs? If you descend quickly to max depth at 30fsw, the failure occurs instantly, and you ascend, using your full RB reserve, if you and your buddy were both diving AL80s you could easily have between 2200-2400psi remaining.

Also, if you're at max depth when the emergency begins, chances are you're not at rock bottom pressure. Likely, once you hit the surface, you'd have at least whatever amount of gas you would have to us for the turn.

 

[Blackwood]

I may be missing something here, but as presented, doesn't this depend on how much gas you have at Dmax when the failure occurs? If you descend quickly to max depth at 30fsw, the failure occurs instantly, and you ascend, using your full RB reserve, if you and your buddy were both diving AL80s you could easily have between 2200-2400psi remaining.

Whoops, I intended to say that the emergency happened at the donor's turn pressure.

Also, if you're at max depth when the emergency begins, chances are you're not at rock bottom pressure. Likely, once you hit the surface, you'd have at least whatever amount of gas you would have to us for the turn.

Rock bottom is defined for max depth. There is a sliding scale (rock bottom decreases as you ascend), but it's the worst case scenario that's figured into the overall gas plan, and that's a total gas loss by one party at maximum distance from the surface (in my example: depth). That's all I was getting at. Most of the time, people will have plenty of gas to breathe from their tanks in heavy chop. In the perfect storm scenario, you can surface empty even after properly planning and executing a dive.

 

[coldsmoke]

.....it would be "smart" to stick my Halcyon "surf mat" into the MC storage pocket, as this would make a long swim easier ( something there is really no reason for in drift diving...

I have seen you talk about this a couple of times. I have heard of them/seen them before, but I don't understand how they are used.

Obviously they inflate, but do you actually get on them like a raft? Do you get out of your gear and float it next to you? I can't imagine getting on top of one of those little things will all my gear on, but I can't imagine you are very mobile on top of one dragging your gear in the water.

Thanks,

Hunter

 

[danvolker]

I have seen you talk about this a couple of times. I have heard of them/seen them before, but I don't understand how they are used.

Obviously they inflate, but do you actually get on them like a raft? Do you get out of your gear and float it next to you? I can't imagine getting on top of one of those little things will all my gear on, but I can't imagine you are very mobile on top of one dragging your gear in the water.

Thanks,

Hunter

A surfmat is like a belly board--you do not need to dump any gear to use it...the liferaft I have never actualy used in water--I have carried one, but never tried floating in it...I imagine if things were so bad you needed to get in one, you would remove the tank from the harness and dump it---you may well be able to use the raft with the tank, but I don't think you would want to. But the raft is plenty big for one person to get into.

Dan

 

[ucfdiver]

Stress?

In general, I agree. I was just spelling out the worst case assumptions that go into most rock bottom calculations (often including an increased per diver consumption rate). Replace it with having to dip completely into thirds if you wish. The end result it surfacing more-or-less empty.

I might be in the minority, but I find that penetration uses way more gas, since you're looking around and taking it slow, and the exit uses less, which kind of builds in a padding.

 

[coldsmoke]

A surfmat is like a belly board--
Dan

So when you are shore diving with surf do you use the surfmat like a belly board and ride it in?

Hunter

 

[danvolker]

So when you are shore diving with surf do you use the surfmat like a belly board and ride it in?

Hunter

You could if you were using it with just freediving gear, but with the inertial mass of a scuba tank, big surf would be a little hard to predict your results --- if I was doing a beach dive, and had to come in through 6 foot or bigger waves, I would be coming in, belly to the bottom--the surfmat would be re-stowed into the storage pouch

Dan