32 replies to this topic

[hnladue]

Memorial Day weekend I traveled to Brockville On for my first weekend of hands-on rebreather training! I am training on the Inspiration with the Vision Electronics. So far I've passed all the study materials and the final exam. Once I arrived at the hotel, my instructor and I immediately started into it! I took apart the unit and reassembled it a couple times. Repacked the scrubber and played with the electronics. The next morning we got up at 6am and went for my first confined water dive!! The water was 51degrees. We got to 25ft and I had some issues. It was very hard to breathe and I wasn't comfortable. I closed the mouthpiece and switched to OC and called the dive. Once at the surface I explained to my instructor what I was feeling and he explained a little more on what to expect from the unit and how to make it easier to breathe. Back down we went!! I wasn't giving up that easily. We got to 30 ft and sat there a bit. I was having ear troubles and was overweighted. (we weren't sure how much weight I'd need.... now I now I need less!) I got the unit to breathe better, added some dil. checked the computer. and just sat for a sec. Then my instructor and I started doing drills!! All of which I did fine. We flushed the loop, practiced switching from OC back to the loop, bouyency drills, swimming drills, and a few other things. We got back out of the water about 40 minutes later. I wasn't even cold!! Breathing the warm moist air was great! We had a charter that we had to get too and I was his crew person for the day so we had to get moving, but what a nice workout to start the day before breakfast! I wasn't able to get back in the water the rest of the weekend, but I did get to tear apart the unit a few more times and play some more with the computer. Over all the weekend was great. I won't be able to get any more hands on unitl July but I can't wait!! Anyone who is thinking about rebreather diving should go for it!! It's a lot more work and you must be dedicated to it, but the benefits are worth it!!

--Heather.

[PerroneFord]

Heather,

Congratulations! I did some of my rebreather training a while back and thought it was marvelous. I am curious though, with all the units on the market, why you chose to go wth the Inspiration. Clearly, it's got more units out there than anyone else, and its "mature". Just wondering how you came to your choice.

Thanks,

-P

[ScubaDadMiami]

Mwahahahaaa! Another one to the Dark Side. Congratulations. Let us know how your training progresses along the way.

[shadragon]

Breathing the warm moist air was great!

No doubt... Canned dehydrated air does have its down side. Hope all goes well as you pursue this in the future. All the best.

[hnladue]

Thanks everyone.

Perrone-I picked the Inspriation mostly because that's what my instructor uses. I have done a little bit of research on the others, and I'd probably still pick the inspiration (or the optima). I can't see why anyone would want a SCR over a CCR.

[PerroneFord]

Thanks everyone.

Perrone-I picked the Inspriation mostly because that's what my instructor uses. I have done a little bit of research on the others, and I'd probably still pick the inspiration (or the optima). I can't see why anyone would want a SCR over a CCR.

Not sure why you mentioned SCR, but quite honestly, I've been most impressed with the Meg and the Boros. To be fair, I still have not tried the Optima, though I plan to this summer. Might put an inspiration in the water as well.

I've been VERY impressed by what I've seen from the Meg both in deep applciation and in overheads like cave and wreck. I had thought I was going to go the KISS route, but have veered away from that in recent months.

Does your inspiration have the temperature stick? I thought that was a fairly interesting feature of the unit though I remain somewhat unconvinced. Also, I was wondering if the newest of the Inspiration units allow you to select any setpoint to dive or if they still lock you into just a few choices. And can you calibrate the sensors with any gas you want, or does the unit require air and oxygen?

Thanks for letting me pick your brain a bit.

-P

[hnladue]

Yes it has the temp stick. Neat feature, but you still have to go by the scrubber rules and watch the time on them! But if there's a problem with the scrubber that temp stick will show it(like if it wasn't packed right). As for the setpoint, yes I can pick whatever I want! And the unit I was using has the trimix software so yes, you can calibrate with any gases. You tell it what gas is in the dil bottle during setup.

I only mentioned SCR as the meg and the dragor are SCR?? right? Can't remember now. My instructor was saying something about how inefficient they are. You're actually better on trimix then on an SCR or something like that.

Why do you like the Meg? Is it the shape? Or fit? I'm not going into CCR for the depth advantage, mostly just the time (and the side effects). I like having to advantage to be able to go deeper, but it doesn't mean I want to.

I like the fit of the inspiration, I can reach my valves and gauges. The handset is easy to see and to work. I was able to move freely and can (so far) perform all the skills.

My homework has been the Gradient Factor. What does it do and what setting would you pick. That's been interesting learning about.

[PerroneFord]

The Draeger and the RB80 are two popular SCRs. The Meg, KISS, Boros, Optima, Titan, PRISM, and others are all CCR units.

SCRs are not that inefficient. Certainly not as efficient as CCR but with 6:1 to 13:1 extension, a set of AL40s on an SCR would easily outdo a set of LP121s with 2 stages open circuit. And SCR simplfies a number of things, not the least of which bailing out, and mystery mixes due to faulty solenoids and other issues.

Why do I like the Meg? It's small, it's built better than anything else on the market. It's simple. More people are innovating for the Meg right now than any other unit out there. It breathes better than anything else out there with the possible exception of the Boros. It can handle water intrusion nicely. It breathes as well inverted or upside down, as it does in a normal swimming position. You can easily modify it if that is your desire. Clearing the loop is fairly easy. You can get it with more than one size counterlung. The valves are not shrouded so they are easier to access than with units like the boros, the inspo, or the optima. It has an optional radial canister that gives you more scrubber life than any other commonly sold CCR. And the price isn't bad either. It's also available with a non-electronic head. You can fly it manually with ease unlike the Boros or the Inspo. Lots of reasons to like the Meg.

What other units did you try/dive before settling on the Inspiration?

-P

Yes it has the temp stick. Neat feature, but you still have to go by the scrubber rules and watch the time on them! But if there's a problem with the scrubber that temp stick will show it(like if it wasn't packed right). As for the setpoint, yes I can pick whatever I want! And the unit I was using has the trimix software so yes, you can calibrate with any gases. You tell it what gas is in the dil bottle during setup.

I only mentioned SCR as the meg and the dragor are SCR?? right? Can't remember now. My instructor was saying something about how inefficient they are. You're actually better on trimix then on an SCR or something like that.

Why do you like the Meg? Is it the shape? Or fit? I'm not going into CCR for the depth advantage, mostly just the time (and the side effects). I like having to advantage to be able to go deeper, but it doesn't mean I want to.

I like the fit of the inspiration, I can reach my valves and gauges. The handset is easy to see and to work. I was able to move freely and can (so far) perform all the skills.

My homework has been the Gradient Factor. What does it do and what setting would you pick. That's been interesting learning about.

[ScubaDadMiami]

I beg to differ with a few statements. As far as work of breathing goes, you should check into this a bit more. The Extend Air Cartridge on the Optima provides consistently low work of breathing throughout the dive especially when compared to scrubber pellets.

As time on the loop passes, pellet scrubber material will pick up moisture, swelling. This will cause a significant increase in work of breathing. Even if you were to start out with both units breathing equally well at the beginning of the dive (which is not the case, but which I will allow just for the sake of conversation), by the end of the dive, the work of breathing is significantly higher with any rebreather using pellet scrubber material. (See the image I have uploaded.) The scrubber cartridge does not change the work of breathing by virtue of its design.

I will be able to point you to an online reference of an article I have just written that, in part, covers this subject. It is not out there yet, but it will be available soon.

Flood tolerance is another area concerning which I would raise some additional questions. Should water ever work its way as far as the scrubber on the Meg or Inspiration, this will quickly produce a caustic cocktail. While many would minimize the chances of this happening, it does happen. I just see no reason to use a unit that keeps this as a realistic possibility. Yet, everyone seems to try to minimize this.

While no unit can be flooded indefinitely, a recent "experiment" involved a diver dipping an a piece of an Extend Air Cartridge into his cup of tea and then drinking it without incident. Another earlier test involved fully flooding an Optima for 20 to 30 minutes, clearing it, and then breathing from it without incident.

I will not nit-pick over other points raised. In fact, my intention is not to dump on the Meg (which is very well made) or other units. I am just glad to see more CCR divers out there. However, there are some basic design differences that I find important.

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[annasea]

Congratulations, Heather!

[PerroneFord]

For those coming to the discussion without a strong knowledge of rebreathers, I will defer that SDM has FAR more experience on rebreathers than I do.

I beg to differ with a few statements. As far as work of breathing goes, you should check into this a bit more. The Extend Air Cartridge on the Optima provides consistently low work of breathing throughout the dive especially when compared to scrubber pellets.

As time on the loop passes, pellet scrubber material will pick up moisture, swelling. This will cause a significant increase in work of breathing. Even if you were to start out with both units breathing equally well at the beginning of the dive (which is not the case, but which I will allow just for the sake of conversation), by the end of the dive, the work of breathing is significantly higher with any rebreather using pellet scrubber material. (See the image I have uploaded.) The scrubber cartridge does not change the work of breathing by virtue of its design.

In my limited experience, after placing 3 hours on the Meg canister, the work of breathing did not change significantly. This was with the common axial scrubber. The radial scrubber is more efficient, but I have not used it yet, though my instructor has used it qutie a lot, as have other Meg divers I know and speak to regularly. I cannot comment on the work of breathing of the Optima unit as I have not used it yet, though I will this summer.

Flood tolerance is another area concerning which I would raise some additional questions. Should water ever work its way as far as the scrubber on the Meg or Inspiration, this will quickly produce a caustic cocktail. While many would minimize the chances of this happening, it does happen. I just see no reason to use a unit that keeps this as a realistic possibility. Yet, everyone seems to try to minimize this.

Again, I disagree with this both from a physics point of view as well as what I have seen. While inverting with the Meg after a flood that partially covers the canister could in fact cause a caustic cocktail, I fail to see how expired air would penetrate the water in the canister to pick up the flooded sorb. Additionally, after doing an hour's worth of flooded loop excercises in the pool, the amount of water in the plenum was not even close to approaching the bottom of the canister. I am not saying this method is superior to the Optima, but I do not see it as the harbinger of doom that so many make it out to be.

Again, these are my thoughts and do not necessarily reflect the thoughts of anyone else.

[ScubaDadMiami]

All questions and discussions are good.

Regarding WOB, I will just add that the perception of the work of breathing is not the same as objective measurement. It just increases slowly. So, you don't notice it. However, it does increase. Perhaps this is not to an unacceptable level. Nonetheless, it does increase on one unit compared to the other.

It is quite possible to get a significant amount of water in the Meg and every other unit (including the Optima). However, if you do so and then swim with a head down posture on pellet scrubber units, the combination is not good. You can keep clearing the loop if you notice the water in it before it passes the traps. However, once it climbs past the traps: .

In that regard, even the Extend Air Cartridge will eventually go caustic. In fact, using a Titan CCR prototype with the EAC, this recently happened in a swimming pool. The user was not fully closing the Dive Surface Valve (mouthpiece), and was apparently not fully clearing the loop during two hours of practicing clearing the loop. This person took a serious caustic hit. This was a very, very serious case. So, no unit is immune from this happening. However, In the end, I want the odds in my favor even if they are not 100 percent. I'll take 90 percent over 20 percent any day. (I am making up the percentages, but there is a big difference.)

This being said, as I pointed out above, the EAC will eventually go caustic only if you allow the water to sit in it for many, many minutes. (Not sure of exactly how many, but it has been tested without a problem up to 20 to 30 minutes. My understanding is that 45 minutes and beyond is where the problem starts.) However, pellet scrubber will not even last 20 seconds once it reacts with water.

[PerroneFord]

Two fair arguments. I'll buy both.

[hnladue]

Keep it coming guys! I'm enjoying this!

So SDM-are you saying that the inspiration is bad when it comes to a caustic cocktail? In other words easy to flood and cause this issue?

Perrone-I haven't yet had a chance to try any other units out. My dive shop here might be going to the Dive Rite units. Maybe then I can try one out!

Edited by hnladue, 01 June 2007 - 06:50 AM.

[PerroneFord]

Heather,

ALL rebreathers are capable of giving a caustic cocktail. Some make it much more difficult than others. The Ourboros, for all it's wonderful design, can easily give one. I've only had the Inspo apart once so I haven't examined the loop all that well. It's built quite a lot differently to other units I've played with. Maybe SDM can shed some more light on it.

I am lucky because my shop sells and trains a lot of rebreathers, so I am able to try out, compare, and examine lots of units. Currently at the shop we have 2 KISS units both a classic and a Sport, an Ouroboros, an Inspo, 2 Megs, an Optima, and 4 Draegers. I am also able to attend the classes at my leisure and just absorb and learn.

I Know SDM likes his Optima a lot and is a huge Dive Rite fan. I am not such a Dive Rite fan, and I am still not sold on the Optima. I'm not saying the unit is bad, I haven't even had it in the water. I am just skeptical by nature!

To my mind, you should try out the Inspiration, the Optima, and the Meg before making a decision which you want to purchase. They all have some advantages, and all have some drawbacks. And you'll need to decide what is important to you. You also need to look at what people doing the kind of diving you wish to do, are using. And ask why. You RARELY see any inspirations here in cave country. But you'll see plenty of Megs. I know several people using the Optima in caves, some like them, some don't. The Ouroboros was designed for deep open water and wreck diving. It is somewhat problematic in caves. I've read enough horror stories with the Prism, to not want to go there. But that's just me.

Choose your weapon and enjoy diving silently!