Rebreathers and fast current

[Ianstephenzs]

I think I would like to get a rebreather in the future because diving silent sounds assume. Aswell not having bubbles to scare away fish (sharks) is also a major bonus.
Something i was thinking about is that. I really like diving in fast current where you are definitely working harder and can be going up and down with the current. Would this be hell on a rebreather or dose it just take more skill and mental preparation.

 

[down4fun]

To me there would be a couple of concerns diving a rebreather in strong current. I suppose if you were going with the current it wouldn't be as bad. However, changes in depth on the rebreather are more cumbersome than o/c. Maintaining optimal loop volume can be a challenge if your depth is constantly changing. Diving the rebreather while going into the current, I would be very wary of. The risk with the rebreather while working hard is over-breathing the scrubber and taking a CO2 hit, which could be fatal. Not that it can't be done, we dive rebreathers into the flow in caves. We are just very cautious to pace ourselves, pull and glide to minimize workload, and rest when ever necessary.

 

[vinegarbiscuit]

Diclaimer: I don't dive a rebreather myself, but I've learned enough to be dangerous by witnessing first-hand my fiance's learning curve with his (KISS Classic). Drift-diving on the loop looks awesome. Fighting a current in open water, distinctly less so. (He's not yet to be CCR cave certified, so I'm yet to see him deal with flow in a cave, and see how the ol' pull-n-glide works for him.) down4fun has hit the nail exactly on the head, especially regarding the dangers of over-exertion when faced with a current. There is no way to monitor CO2 content yet, so the onus is on the diver to pace themselves and breathe slowly, to avoid hypercapnia. My SO is always monitoring himself on the loop in those situations, asking himself to take a step back and truthfully answer if he feels light-headed or anything out of the ordinary. As his open-circuit buddy I've had to adapt myself to his pace, and ensure that he's not racing to keep with me. No bad thing, really.

 

[Ianstephenzs]

Well that is good to hear. I hate going agenst curent so having a good excuse to avoid that is always good. I guess is should have said that I love diving with the current.

 

[bletso]

I dive a MCCR and can testify to the fact that being caught in a high current can be a challenging experience. One should be able to handle it, though with the proper training and EXPERIENCE.

The worst I was in was several knots in a jetty where it was difficult to pull from rock to rock. To add to the challenge I became aware something was not right with the unit. It remained diveable, but at an increased task load above what the current demanded. (The problem turned out to be a partially occluded manual add orifice. It still added but at a slower rate, which required more attention). BTW, the flow rates were normal on the pre-dive checks, but that is another story.

Diving any breather requires an intimate knowledge of both the unit and how your body reacts to various external demands. This can only be attained with lots of hours diving in varying conditions.

Dale

 

[danvolker]

I think I would like to get a rebreather in the future because diving silent sounds assume. Aswell not having bubbles to scare away fish (sharks) is also a major bonus.
Something i was thinking about is that. I really like diving in fast current where you are definitely working harder and can be going up and down with the current. Would this be hell on a rebreather or dose it just take more skill and mental preparation.

You know, you are raising an excellent point....and it really relates to more foolishness within the dive industry itself.....

The deal is, you can use an open circuit scuba tank AND have no noisy bubbles. This is NOT news to the Rebreather Manufactures, or to the industry...but you sure don't here most divers talking about this...

Way back when rebreathers for the recreational market first began coming out..back with Jack Kellon's BMD and then Odyssey Rebreather, one of the things they played with was a "bubble diffuser", as the intent of the rebreather was to allow some air out of the counterlung on each breath, so that any potential injection failure would not require electronic alarms---the diver would empty the counterlung, and know they had a problem--so hypoxia and death would not result....anyway, getting back to the topic.......
kellon created a bubble diffuser that was very much like a sponge that exhaust air from the divers breath would be channelled through---the air hits the sponge like filter, and comes out into the water in a billion micro bubbles, and the result is zero noise. The big bubbles that come out of our 2nd stage regs with zero filtering are what makes the big noise.

All you need is a way to route the exhaust to behind your neck, to a sponge like filter, and your open circuit scuba will be effectively as silent to fish as the closed circuit rebreather at 100 times the price, and 100 times the danger of open circuit. Of course, for the rebreather mfg's and the industry, this means they might make 1/100 as much money selling rebreathers
They really don't want YOU to have this solution.

If you had a double hose regulater with your scuba tank, then the filtering via a sponge like media would be simple for almost any of us to cobble together. The standard 2nd stage we use makes this more complicated, because we would need to route exhaust gas behind us....either you add another hose that routes exhaust back behind you--or we look for a brand new well designed double hose reg---and this would be easy for a manufacturer to create with the real purpose being just movement of the exhaust to behind the head ( the Lloyd Bridges/ Sea Hunt position of air discharge )

My point is , for a "typical open water diver" ( which the OP sounds like) drop the idea of a rebreather for now, and check in to a new version of a double hose reg that is easy to adapt to a filter. This is a smarter direction for most divers..Most of us are not allowed by the diveboats to do 4 hour bottom times on a rebreather while everyone else is limited to a 1 hour dive....most of the scuba diving masses are not diving a "mission" that justifies the massively more dangerous and complicated issues a rebreather adds to the activity of diving.
Obviously a rebreather can be safe, and add enormous range and flexibiity to a skilled diver that needs this.....my issue is that for most of the diving world, the rebreather would be the wrong solution for what they want---"they" want : dive it, throw it in the garage till the next dive, grab it just before you dive again next month and fill it on the way to the boat--no checking, no setup routine to speak of--put it on and go---this is the mass market of divers..

 

[bletso]

Danv,

There are a few very tangible advantages to a breather; I can dive the whole weekend, let's say 5 dives at any desired depth on less than 13 cf of O2 and about 15 cf of diluent. The diluent can be anything I want it to be from nitrox to trimix. Cost is not that big.

I can do all these dives without disassembly / re-assembly of the unit. I never get cotton mouth. The gas is above ambient unlike OC scuba so I retain more body heat.

It is is not all about noise, though I do like the critters getting in closer.

To be sure there are some drawbacks but the task loading, at least with an MCCR is not that great. Initial cost really depends on what you buy, but I have seen some very expensive OC rigs that cost more than my unit! Mod 8 BTW, whilst my unit is weighted for an 1/8 in suit, it ways about the same as a normal OC setup.

I do like your idea on quiet OC diving, but all those tanks being hauled to and from the dive site just makes me tired.

Dale

 

[Ianstephenzs]

Danvolker that sound like a good idea but isn't it the bubbles that also scare the fish away or do you think it's mostly the sound.
Ian

 

[vladimir]

Danvolker that sound like a good idea but isn't it the bubbles that also scare the fish away or do you think it's mostly the sound.
Ian

Dolphins and whales herd fish using bubble curtains, presumably without all the noise our regulators make, so it is reasonable to believe that the bubbles themselves do scare the fish to some extent.

 

[Gill Envy]

to speak to the OP, diving in current with a rebreather is different, it's harder at first but also comes with some perks. there are pros and cons.

the cons: changing depths, particularly being forced to change depths by the current is, as has been said, cumbersome and, if not done carefully, can lead to uncontrolled ascent, plummeting po2 or it can lead to uncontrolled descent, collapsing counter lungs and spiking po2. in general, heavy exertion is to be minimized if not avoided all together due to co2 build up in the blood stream and or co2 breakthrough in the loop. you can get yourself in a world of hurt of you do not gain experience gradually, staying within your training and capacities. Before I transitioned to a rebreather I felt like a seal in the water, I've never regained that level of confidence diving a rebreather... buoyancy is way more tedious.

that said, the Pros: a rebreather allows you to dive in some current situations for extended periods of time when doing so on OC would just not be practical. eg: We've done some pretty amazing dives gradually working our way out and down along a ridge, swimming hard from rock to rock, then resting for a while, watching pelagics feed on swarms of fish with hours of gas to spare. We've done 200 ft dives in heavy current. the current is where a lot of the action is and on open circuit you are limited to how much of that you can handle before you run out of gas. that nagging feeling that you get on an OC rig that you must keep your respiration down for fear of running out of gas is replaced with a nagging feeling that you need to stay on top of your po2 all the time for fear of passing out... it's a trade off, but once you get the hand of it, it's bliss!

on one hand diving a rebreather is like diving unleashed, on the other hand a rebreather can feel like a ball and chain; expensive, complex, and at times just a pain in the ass.

if you decide to go the CCR route, do it with your eyes open to the risks, substantial investment and time required to maintain your skills and kit.

Kind Regards,
George