Sea sick on an RB or double-hose rig?

[BigJetDriver]

When you say, "hurl through the mouthpiece in closed position into water" I guess that would require a mouthpiece with integrated OC reg? I think I can see a second stage just underwater in your avatar pic.

I guess if you have a DSV without second stage OC the only option is going OC as quickly as possible.

3dent, et al,

FOR THOSE WHO ARE SQUEAMISH, SELECT ANOTHER THREAD.

Okay, if you do not have a DSV (a name I find not to be accurate for that device IMO), and you do NOT close the mouth-piece off with its lever or switch, your vomitus will go through the one-way check-valve, into the exhale hose, and possibly on into the exhale counter-lung.

If you close that switch or lever, you will have to vomit AROUND the mouth-piece. It has no other outlet at that point.

IF you have a DSV, as I and others do, AND you manage to turn the switch in time, the outlets to the RB hoses are closed, and it is no different than vomiting through your regulator.

That is as accurate as I can be, but my apologies for anyone who is disturbed by the reality of this discussion.

 

[O2BBubbleFree]

Thanks, Rob, and others who've taken the time to educate this wanabe.

Your description is exactly what I was thinking, but I guess the terminology gets confusing.

I have seen three different types of RB mouthpiece (ignoring Pendulum RBs for this discussion):

The simplest being a tee with a hose attachment on each end and an OC-like mouthpiece in the middle.

The next level of complexity is like above, with a valve to shut out the sea water when you have it out of your mouth. I thought that this type was called a DSV. I've read that that stands for Divers Surface Valve, but personally believe that Dive/Surface Valve would be more fitting.

The third is like the above DSV with the addition of a regulator second stage. Rather than block the seawater out, the valve (in 'closed' position) routes air from the OC reg to the mouth, while blocking the RB hoses off.

Does that sound right? Maybe they are all called DSVs to get around the ‘RB mouthpiece with an OC mouthpiece on it’ statements like I made above?

FWIW, I was only thinking of the first two types when I asked about stomach difficulties and their possible effect on RB/dual hose diving.

 

[caveseeker7]

DSV does stand for Dive/Surface Valve.
The ones that have an integrated OC second stage for bailout are usually referred to OC/DSV.

Most all rebreathers, and certainly all commercially available ones in current production have some sort of valve to prevent flooding the loop (and loosing a lot of bouyancy).

While OC/DSVs make it possibel to throw up threw them, there is more dead space (where the hoses connect) than in a normal second stage. Furthermore, there is still the danger of messing up the mushroom valve on the exhale side as the vomit os likely to take the path of least resistance. That seal is important however as it keeps the gas flow in one direction.

Switching to a normal OC 2nd is a better way to go, or let go.

 

[BigJetDriver]

(1) The simplest being a tee with a hose attachment on each end and an OC-like mouthpiece in the middle.

The next level of complexity is like above, with a valve to shut out the sea water when you have it out of your mouth. I thought that this type was called a DSV. I've read that that stands for Divers Surface Valve, but personally believe that Dive/Surface Valve would be more fitting.

(2) The third is like the above DSV with the addition of a regulator second stage. Rather than block the seawater out, the valve (in 'closed' position) routes air from the OC reg to the mouth, while blocking the RB hoses off.

Does that sound right? Maybe they are all called DSVs to get around the ‘RB mouthpiece with an OC mouthpiece on it’ statements like I made above?

3Dent,

The worst-case scenario for re-breathers is that of water pouring in and flooding the loop; i.e. displacing the gas volume you are breathing, and wetting the "kitty litter".

To avoid this problem, re-breather mouthpieces are fitted with a lever or ring to move a blocking device of some kind into position to close the opening to your mouth. Without this, you cannot take the mothpiece out of your mouth without being completely OUT of the water. I know of no modern re-breather made like (1) above.

(2) As for your second case, I and many other re-breather divers have a mouthpiece with a second stage attached. If we want to got to OC, we simply turn the lever, and we are breathing on our OC gas supply. We do this if there is a problem with the re-breather and we need to bail out to our OC back-up. I prefer to call this unit by the name of its function; i.e. BAIL-OUT VALVE.

The historical name for it is Dive / Surface Valve. The meaning is clear, in that if your valve is in the RB position, you are probably going diving. If it is in the OC position, you are probably going to be working your way to the surface.

 

[DA Aquamaster]

Vomiting into a double hose reg would obviously not cause problems with filling/flooding a counter-lung, but it would still be really messy.

I am also pretty sure that if the effluent were on the chunky side, that things would not flow smoothly out the duckbill valve at the end of the exhaust hose. The result would be a lot of stuff remaining in the exhaust hose where it would increase exhalation resistance.

A stategically placed chunk stuck in the duck bill could also cause the exhaust hose to flood and a similar chunk stuck in the mushroom valve at the same time could make the reg very difficult to use as it would create a path to inhale water through the exhaust hose, along with whatever was mixed with it. If you decide you absolutely have to vomit in one, stick with thin watery vomit.

 

[Pawel]

Thanks, Pawel! Great info.

BTW, when you say, "hurl through the mouthpiece in closed position into water" I guess that would require a mouthpiece with integrated OC reg? I think I can see a second stage just underwater in your avitar pic.

I guess if you have a DSV without second stage OC the only option is going OC as quickly as possible.

Hi 3dent,

No, I don't have an OC integrated DSV, I don't like them because they cause jaw fatigue and I am of a view that there is not much difference between grabbing a well positioned separate OC bailout and turning a knob on the DSV. The DSV I use (as well as many others), when in off position not only disconnect the mouthpiece from the loop (hoses), but connect it to the ouside, which means you can hurl stuff through the mouthpiece into the water. Above water you can breathe air from outside when in off position.

Cheers,

Pawel
OMG/Apollo Australia

 

[O2BBubbleFree]

Hi 3dent,

No, I don't have an OC integrated DSV, I don't like them because they cause jaw fatigue and I am of a view that there is not much difference between grabbing a well positioned separate OC bailout and turning a knob on the DSV. The DSV I use (as well as many others), when in off position not only disconnect the mouthpiece from the loop (hoses), but connect it to the ouside, which means you can hurl stuff through the mouthpiece into the water. Above water you can breathe air from outside when in off position.

Cheers,

Pawel
OMG/Apollo Australia

Thanks, again, Pawel.

In my research to date I hadn't run across info on a DSV like you've described, but I admit I still have a lot to learn. Is it a major advantage to be able to breathe through it when closed, as opposed to just removing it on the surface?

WRT the OC/DSV, I was concerned as well about fatigue, not only from the drag created by the second-stage, but also the increase in ‘stiffness’ from the third hose.

I’d like to hear what you consider a 'well positioned' bailout reg? I read one recommendation (and posted elsewhere) regarding a 'necklaced' or 'bungied' reg positioned below the chin DIR-style. I see the benefits, but it seems you would have to carry a separate second stage to donate to another diver, or use some kind of breakaway necklace.

I just read a post on another thread from an OC diver that said she carries her octo on an upper d-ring, where it's still available to donate, but she can also get to it quick (and hands-free).

Right now I'm leaning toward a slung pony with one second stage positioned on an upper d-ring. I like the idea of a pony for bailout since it's completely separate (as opposed to using diluent for bailout), can be handed off to another diver if necessary, and the second is still positioned on the chest where most OC divers are taught to look for it. I’m thinking that this is something I can implement now with my OC rig, and carry over as I transition to RB.

Also, for those of you that use a OC/DSV, do you carry an additional second for donating?

I realize that this is off-topic, but by golly, it’s my thread and I’ll hijack it if I want too!

 

[Mako Mark]

you dont even want to burp in a RB loop. I did it once and was breathing onion/beans/eggs for the rest of the dive. In the event you do feel the urge to burp, breath it out of your nose.

 

[O2BBubbleFree]

you dont even want to burp in a RB loop. I did it once and was breathing onion/beans/eggs for the rest of the dive. In the event you do feel the urge to burp, breath it out of your nose.

LOL.

Maybe the scrubber or exhale CL should include activated charcoal!

Thanks for the advice!

 

[Pawel]

I’d like to hear what you consider a 'well positioned' bailout reg? I read one recommendation (and posted elsewhere) regarding a 'necklaced' or 'bungied' reg positioned below the chin DIR-style. I see the benefits, but it seems you would have to carry a separate second stage to donate to another diver, or use some kind of breakaway necklace.

I just read a post on another thread from an OC diver that said she carries her octo on an upper d-ring, where it's still available to donate, but she can also get to it quick (and hands-free).

Hi 3dent,

That's probably a good placement. Almost everyone has a different idea for placing OC bailout, but make sure it is very easy to reach with either hand at all times and does not require "searching for it" or releasing fiddly retainers when you need it. I am mostly diving solo (with my camera as a buddy, who has some more bailout) so I don't need to donate. I have a 6cf strapped with velcro on top of my camera housing right in front of me. In other cases, I attach an octopus on my chest.

Cheers,

Pawel