Megaladon Versus Optima Fx

Mikel-Deko

That's GOOD

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Mikel-Deko
Basque Country
www.olatu.net

"DIR is the nanny state for divers who cannot think on their own" Ron Micjan

Gilles

If I ever get a 2nd Rebreather, .....

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Gilles
http://www.dirrebreather.com

SeaBass

Thanks for the info Gilles.

I have heard that some have a Mini-Meg canister for travel. Either way my thought is that it is difficult to have a "one-trick-pony" when it comes to rebreathers. That must be why most of the profiles on Rebreather World have a *list* of different ones under thier avators.

Regarding WOB: I must admit I was kind of surprised when the WOB test results posted at Dema last October showed that the Optima had:

1. Worse work of breathing than a Classic Kiss
2. The worst scrubber duration at 60 min.
3. The second to worst scrubber efficiency.

http://www.rebreatherworld.com/attac...omparisons.jpg

Was this chart way off or what?

Thom

ScubaDadMiami

The answer to your question depends upon who you ask. However, yes, the chart is way off in measuring anything close to real world performance.

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Howard Packer
IANTD CCR Instructor
Miami Beach, Florida
CCRDiveTraining.com

caveseeker7

The chart never claimed to test real world performance, nor would that make sense. Because in the real world variables differ every time you dive.

The scrubber duration was tested to an accepted international standard, and under that standard the cartridge performed like sh!t. That's all there is to it. Not more, not less.

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Cheers
Stefan



"Political Correctness is a doctrine, fostered by a delusional, illogical minority, and rabidly promoted by an unscrupulous mainstream media,
which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.'!"

Dsix36

I was also very surprised and pissed about this myself. I had just recently purchased my Optima. This has been discussed on another thread, but I can't find it now. Mark (n2diving) was able to explain the cartridge test much better and in the proper context.

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SeaBass

I have never dove an Optima or a Meg but my initial guess was that the Optima would have the best WOB. The reasons were:

1. Very short loop (probably shortest of any backmount rebreather.)

2. I had heard that the EAC's had very little breathing resistance. Not sure where I read it but supposedly the resistance in an EAC is less than the resistance in the hoses themselves.

Thom

zzzzzzzz

There are many factors from a design perspective that affect WOB. There is a lot of geometry that affects breathing characteristics. The takeaway is that it is never enough to put the package together in any particular way. It could be the total resistance budget that is higher, based on all the fittings, hose diameters and so forth. There could be some fundamental snafu based on pressure due to OPRV position and pressure.

It is possible that the package can be made to work better and the key is to understand what is driving these factors.

As far as EAC, the introduction of a cellulose membrane reduces the area exposed to the gas and forces the gas to follow a linear path through the scrubber. This may impede the diffusion process that may otherwise work better in a random-packed canister whether radial or axial for absorbing CO2.

It may also be as simple as the effect of winding the EAC and the relative amount of cellulose to absorbent, or the lack of mixing of gases, or even the preferential flow within the EAC that results in some form of channeling.

In any case, it is a reflection of how much and what type of effort goes into a design.

z

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z

Dsix36

I have only had experience with my Dolphin and Optima. The Optima breathes alot better (in all positions).

Here is a previous post regarding EAC duration:
http://www.rebreatherworld.com/o2pti...n-o2ptima.html

PM sent

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sensor330

Either everybody is super sensitive to the differences to the WOB or I must have some super human lungs. I've got to say in my career as both a professional diver and tech diver I've never noticed a difference in the WOB in Rebreather that use over the shoulder C/L. I've dove 4 completely different units that use over the shoulder C/L and 3 that have rear C/L. I've only noted a significant difference from front to back. As well I hear reports of better WOB when using trimix or heilox and again I've never noticed a difference other than I'm not narked at 300'. I think the WOB gimmick is really just a sales and marketing strategy to sell more of their RB.

Scott