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DiverMole · 03-03-2003, 05:10 PM,

I actually use a VR3 on the dive which has its own dopplar proven algorythm and deep stops. But plan using DDPlan 80/30 and cut backup tables using this

Proplanner gives me 57mins run time. We are comparing apples to oranges. I'm pretty certain that some table some where would say this is a no stop dive. Its if you did something like 10mins and 60m and then come up to the deck of the wreck at 45m for another 25mins that you'd start to see a big difference as your PPO2 will drop, offset by you probably being at 1.4 for the first 10 mins

This proves nothing, both ways of doing the dive are valid and work and as its fairly square, would give the roughly the same profiles. But the advantage is I will be carrying less, have warm gas, silent and my fill will cost $10 and last for several more dives, Oh and I have access to hours of 100 O2 on the surface if there is a roblem

john j · 03-03-2003, 05:52 PM,

DRE: "CCR's do not have an advantage over OC with regards to deco"

I think even George I. would disagee with this statement.

If numerical data won't convince you, what else will?

03-03-2003, 05:53 PM,

[quote author=john j
In addition, I would have never exposed myself to a 1.6PO2 like you did.

I'm sorry but what's wrong with 1.6ppO2 at deco - I wouldn't run a 1.3ppO2 bottom mix for more extended dives, which I consider too high, but don't tell me you'd be using a 1.4 for deco????????

john j · 03-03-2003, 06:11 PM,

I'll perhaps steer the subject in a little different direction and show another advantage of CCR's. A couple years ago I calculated, just for fun, how much less gear we bring on trips to the Gunilda with CCR's than with OC. There's nowhere up there to get any fills so you have to bring everything with you. For a 4 dive trip, people who bring all OC equipment travel with about 750+ pounds of gear per person and the CCR dudes are bringing about 225 pounds per person. We do one dive each day, afterwhich the CCR folks remove their scrubber chemical and rinse the mouthpiece hoses, then go and relax all afternoon. The OC dudes spend the next several hours transferring gasses, lugging tanks around and rigging their next set of doubles and stage bottles. Oh yeah, the CCR dudes had less deco too. On the last trip I went on, we had to re-arrange the dive order because on the first dive, the CCR dudes had to pass the OC people on the way up the ascent line, even though the CCR dudes got in the water first! The CCR guys had longer bottom times yet less deco.

Just another of the many advantages of CCR's!

03-03-2003, 06:16 PM,

Furthermore, for the shorter dives you have to do a minimum amount of deco you can't get around - I wouldn't want to do the profile you showed me and do it again the same day after a couple of hours SI.
Once you get into much longer dives in order to properly decompress you need to bring the bottom PPO2 down anyway in order to keep the CNS clock within limits, which also goes for the actual deco stops. The trick becomes to toggle bewteen opening up the O2 window and offgassing in bubble form at lower PPo2's by using the gradient - so what exactly is the benefit of having a CCR in this case?
If you maintain the higher PPO2 constantly you're heading for an oxtox, and if you lower it you get the same result as OC or SCR for that matter.
The benefits with the CCR do lie in the shorter range, where the differences are fairly minimal anyways - again the only major benefit of the CCR lies in terms of gas used, but those whave to outweigh the inherent risks of the unit, which they don't to me - at all...

03-03-2003, 06:21 PM,

Most people do too much deco on OC anyways, so that's why you guys passed them on teh ascent line - as I said earlier, the perceived benefit lies in carrying less gear (which doesn't become that much less if every single CCR diver uses proper bailout, which is something a lot don't - see earlier post by Divermole), but I'd rather lug around OC and feel safe during the dive than having to worry about all the electronic crap that can go wrong on a CCR>

rcojr · 03-03-2003, 06:25 PM,

Jason Baker (the administrator) has given the Rebreather divers their own forum separate from the Advanced Divers Forum. At the moment he is the moderator, but would like someone more informed to take over that spot. If anyone would like the job contact Jason. If not I will go out looking.

rcojr · 03-03-2003, 06:54 PM,

Most people do too much deco on OC anyways, so that's why you guys passed them on teh ascent line - as I said earlier, the perceived benefit lies in carrying less gear (which doesn't become that much less if every single CCR diver uses proper bailout, which is something a lot don't - see earlier post by Divermole), but I'd rather lug around OC and feel safe during the dive than having to worry about all the electronic crap that can go wrong on a CCR>

That's why rebreathers aren't for everybody. Just a difference risk tolerance.

03-03-2003, 09:14 PM,

...which sums up very nicely the why of this entire thread in the first place...

DiverMole · 03-04-2003, 03:21 AM,

But DRE, your whole premise that OC will get out faster than CCR is bunkum, and its easy to prove. I can get out at the same time as you every dive

If we were to do the same dive together, I can set my box to run the same PPO2 as you at all times, hence I could do exactly the same profile as you, on every dive, if I wanted. I have complete control over my PPO2, you only have the ability to pick a few set mixes. So a CCR can ALWAYS mirror ANY OC dive exactly (unless you want to use a PPO2 over 2.5)

If I choose to use the advantage of a CCR (which I do on every dive) I can leave my unit to run an optimum PPO2 throughout the whole dive and therefore will off gas faster than you who will only run higher PPO2 at the MOD's for each gas you carry

I can run at any PPO2 between 0.18 and 2.49 that I choose at any time, so at a minimum I can always mirror your deco. I look at each dive before I do it and if I was to start clocking up a serious CNS% I would do the dive on a lower setpoint. I can also do the equivavlent of air breaks and all the other stuff you do

Now you have chosen to listen to the GI3 WKPP oxygen window theory. A theory that has a rather small test group that are not exactly representative of most divers (No beer guts) and who have had a HUGE incidence of DCI (minor I must admit) while running it.

You say most divers do too much deco, I say good, rather too much than too little.

Ask yourself why Weinke and the other deco masters out there dont subscribe to the profiles WKPP do. The whole WKPP operation would be shut by the Health and Safety Exec if it was done in the UK due the bend rate they have (mind you they wouldn't be allowed to use RB80's as they are not CE approved either). I hear that Jarrod lost the use of his arms last week for a while, thats doesn't sound like a working deco theory to me

I'm older, fatter and wiser than the days 20 years ago when I did 50m No Stop dives, and 70m on a single 12L of air. I'll do my conservative profiles thank you. But like wearing a rebreather thats a personal choice I consider reasonable after knowing the facts. And 3000 dives later with a max of 143m I've still to have a hit (and I intend to keep it that way)

Also ask yourself why your hero "speedo man", uses a rebreather to do his big dives if they offer no deco or other advantages over OC. Or why the great Halcyon sells a rather nice SCR if they are so bad.

Over here in the rainy Isles, RB's have a much greater take up than in the US, you see them at every dive site now and there are 1 or 2 on virtually every boat that is going out. People that have them are normally very active divers doing on average 55 dives a year to a ave max depth of 70m. The average RB diver is a mature male (93%) of age 39, who has 15 years diving experiance and 1500 dives under his belt (Source Inspiration users survey 2002). These folks tend to be very experianced mature divers who can think for themselves and have the mental attitude to safely run a RB. Virtually every RB owner I know (several hundred) states that they feel safer on their box than on OC

I dont think we will ever convince you that a CCR is a viable way to dive. Likewise you wont convince me its not. What I want is that folks on these forums get to see the FACTS and the arguments so they can make their own informed descisions. I will be the first to point out the negatives of an RB and particularly the Inspiration. What I wont tolerate is the half truths and lies spread by certain individuals who have a vested interested in promoting a unit manufactured by their main sponser, a unit that has a rather major single point of failure that is undetectable and will (and has twice now) kill without any warning, unless you modify the unit by fitting an electronic PPO2 meter, but which of course gets no mention in any of his normal rebreather rants.

Folks the Inspiration manual is downloadable and open to ALL divers, it holds no secrets and will teach you a lot about rebreathers in general. Its availble from my site and the APD site, so I suggest you go download it. The Dolphin SCR manuals are also downloadable on the Drager site as are the Azimuth manual. Go read, learn and be informed, make your own descisions

If you wish to know more, feel free to ask me any questions, there are also several general RB books out there (reviewed and details on my site) and its possible to do "Try Dives" on most units