Helping A Friend, A Ccr Diver, Do's And Dont's

[schford]

Please keep this in mind , and try to help here, rather then question my ability's , or Luke's for that matter.

Fair enough - my helpful advice would be to remain consistant....

The sentance below leads one to believe that you have not yet completed any decompression dives or training for decompression..

We talk about doing decompression diving, but yet last week, we didn't even know the basic's to go drift diving off my boat!!

but then within a few posts....

I do allot of wreck penetration, sometimes plan decompression diving.

It would appear that you are do undertake decompression dives.

I am sure you would agree, statements like that lead one to question the veracity of your other statements.

As for

I disagree, with using a Nitrox computer for CCR. How can you use something with a fixed FI02 , when your PPo2 changes, and your manually flying a unit at 130' ? Like i said, i don't know much in that area, that's why i asked these question's.

This really really should have been covered in your dolphin course, it is common especially with SCR sivders to run their decompresison form a nitrox computer.

However let me cover this for you.

What you are doing in this case is working out your decompression obligation extremely conservativly.

You calculate a Nitrox mix based on what your % of o2 will be at the deepest part of your dive, and then calculate your decompression as if you are breathing this for your whole dive - which of course you are not.

Even if you managed to cock c up maintaing your set point for the deep part of the dive - the impact on your decompression obligation will be minimal as long as you are within a few tenths of your target set point.

This is more than covered then when you come off your deepest point and ascend as you start breathing gas with a greatly increased o2 %. Your decompression computer does not know about this and thinks you are still breathing Nitrox when in reality you are gaining a significant advantage in terms of decompression obligation as you rise due to the increase of O2 in the gas you are breathing.

Ergo a much increased safety margin

Lets look at a real example to illustrate this point. Imagine we are diving CCR to 30m and a setpoit of 1.2 - that gives us an equivelant nitrox mix of 30% @ depth

If we worked out decompression obligation for this assuming nitrox then we get 6 minutes of decompression.

However as the setpoint increases when he rises he only actually has a 3 minute decompression obligation.

Now what happens if he cocks up maintaining his set point and only manages ot hold a 1.0 set point for the whold of his dive - well his decompresison obligation is only 5 minutes so you can see that by using a nitrox computer you are building in a substantial safety margin.

 

[Life-Is-Good-Diver]

Fair enough - my helpful advice would be to remain consistant....

The sentence below leads one to believe that you have not yet completed any decompression dives or training for decompression..


but then within a few posts....


It would appear that you are do undertake decompression dives.

I am sure you would agree, statements like that lead one to question the veracity of your other statements.

As for


This really really should have been covered in your dolphin course, it is common especially with SCR sivders to run their decompression form a nitrox computer.

However let me cover this for you.

What you are doing in this case is working out your decompression obligation extremely conservatively.

You calculate a Nitrox mix based on what your % of o2 will be at the deepest part of your dive, and then calculate your decompression as if you are breathing this for your whole dive - which of course you are not.

Even if you managed to cock c up maintaing your set point for the deep part of the dive - the impact on your decompression obligation will be minimal as long as you are within a few tenths of your target set point.

This is more than covered then when you come off your deepest point and ascend as you start breathing gas with a greatly increased o2 %. Your decompression computer does not know about this and thinks you are still breathing Nitrox when in reality you are gaining a significant advantage in terms of decompression obligation as you rise due to the increase of O2 in the gas you are breathing.

Ergo a much increased safety margin

Lets look at a real example to illustrate this point. Imagine we are diving CCR to 30m and a setpoit of 1.2 - that gives us an equivalent nitrox mix of 30% @ depth

If we worked out decompression obligation for this assuming nitrox then we get 6 minutes of decompression.

However as the set point increases when he rises he only actually has a 3 minute decompression obligation.

Now what happens if he cocks up maintaining his set point and only manages to hold a 1.0 set point for the whole of his dive - well his decompression obligation is only 5 minutes so you can see that by using a nitrox computer you are building in a substantial safety margin.

I would agree, same as when we plan a dive going into decompression, not having a Vr3 and being able to switch gases on my computer underwater, when I do plan for that type of dive, If my Nitrox computer clears me in say 15 min, that's because it thinks I'm breathing off my back gas, when in fact Ive switched to 100% 02, at 15' , but that will give me a more conservative deco obligation. I have done about a dozen dives , planning going into deco, planning with software, writing it down onto wrist slate's , and following a dive plan. My deepest dive was to 180' was at bottom, but I only hit 165' . I don't have allot of experience in decompression diving, but I have done enough to know at this point I'm going to take a Extended-Range course, and Advanced Nitrox course, and probably will take a Tri-Mix course as well, for those depth's.

I think you have mixed it up though. I'm diving OC, on doubles's, my friend David who is diving the converted Dolphin is running it in CCR , not SCR .
But i see now your point on running a CCR at a set-point , of say 1.2 PPo2 at 90' say.

That is where I get confused, because he is manually adding, and during his dive, he doesn't have a fixed PPo2, like if he were diving a electronic re breather. So he may get to the bottom at 90' , start with a 1.2 PPo2, but then as his body uses up O2, that will drop to say .80 . Then he Ad's o2 again. Doing that for say 30 min, up and down, you don't have a fixed PPo2, so the only way to really track that, is to have something like the Vr3, with a P connector, that will give him real time data, what am I missing here?

Thank you for helping me understand this.

 

[Life-Is-Good-Diver]

Profile InfoJoin Date: Apr 2004
Location: London, england but travel a LOT
Logged Dives: 2000+
StatsPosts: 31
Quote:
Originally Posted by FLTEKDIVER
Please keep this in mind , and try to help here, rather then question my ability's , or Luke's for that matter.


Fair enough - my helpful advice would be to remain consistant....

The sentance below leads one to believe that you have not yet completed any decompression dives or training for decompression..


Quote:
Originally Posted by FLTEKDIVER
We talk about doing decompression diving, but yet last week, we didn't even know the basic's to go drift diving off my boat!!


but then within a few posts....


Quote:
Originally Posted by FLTEKDIVER
I do allot of wreck penetration, sometimes plan decompression diving.


It would appear that you are do undertake decompression dives


Just to clarify where that was going, the diving that I Have done in the past, was also done allot in cave's where in was enrolled in a FULL CAVE class, but only completed to INTRO level, but we did do diving that required deco obligation,being enrolled in a full cave class. I have done allot of diving 2 year's ago when taking that class, and diving with my buddy back then. I also do wreck pentration , that require's us so stick to a dive plan.

But today, myself and David, were gearing up for next year to do dive's at 200' + , and that's when I got into rebreather's, as I feel they are safer at those depth's, then being on OC.

After diving my SCR Dolphin, I didn't feel comfortable with rebreather's at depth. I moved like a snail, thinking of all the thing's and failure point's on the unit.

So i went back to what I was used to, diving Double's, with a 300 Bar DIN connection, 1 fitting, less to go wrong, I'm comfortable with that set-up, been diving them for the past 2-3 year's, having 3 set's of double's in the past.

Hopefully someday I hope to regain my trust in rebreather's, and hope to be on someday something like the Inspiration, which I like. I even like the Sport Kiss for what it's designed to do.

But I ask myself, why worry about all the problem's that can occur with a rebreather for rec diving? For myself I found it to much work, and to much that can go wrong for the type of diving I'm doing at this point in my life. But if I were to go any deeper then what I'm diving now, 130' , I think they are safer down deeper, compared to OC, if that make's sense.

For shallower diving, to have to worry about Hypoxia, all the cost, sensor's needed, etc, bail-out, etc I don't think it's worth it " for myself "

But we were planning on doing dive's deeper then rec limit's by next year, and I feel some of the choice's made now were alittle sloppy, and care less, and that's why I came on here to help some of my question's, Hope this help's

 

[deepccr]

teksimple, I was trained by one of the worlds most venerated divers you can read about him at http://www.underwateradventures.com/Robert_Shourot/robert_shourot.html. He passed in Febuary and considered him like a father. I have many more dives than the 100 posted, they are the first dives I bothered to log. Most of my knowledge is self taught and gained from attending confrences like DEMA and ADC. I have two KM15 and a Drager Dolphin. I expected the "expert" statement to be noticed. Just an ice breaker to see who is watching, i have never used a board before. No one person knows everything and everyone can allways learn something, that is what life really is. Thanks for the questioning happy to answer.

 

[schford]

I bet you learnt a lot from conferences like Dema - what do you think were the best bits.

 

[deepccr]

Hello SCHFORD, I have gone to four dema events two at New Orleans and two at Las Vegas. I will be at the next one in Orlando. I went to evaluate my ideas and help the dive shop I supported. I went there as a buyer for them. Rebreathers were my main interest of the shows. I wanted to see who was up and running and get a close look at there hardware. When you see pics on the net and see pretty sales pitches it is hard to get a feel for the quality. Were I lived there were almost no one diving rebreathers. I went and enjoyed speaking to the different manufacturers. This made it very easy to weed out the fly by night models and those that are sound and of good manufacture. I will admit that I do not yet think that any of the units to date really address the Rec market very well yet. I have my opinions on what is the best design, something that non of the manufactures have figured out yet. I do not want to sound like I do not respect some of them, that would not be accurate, anyone making it to market with a good quality product and are at Dema presenting, have my utmost respect. I know how much work it takes to get that far. Currently my ideas are still relevant and will some day themselves be seen at Dema. I also looked forward to speaking with the fellows from the NEDU and the projects they were working on. They will be the first people to see and test my design. Cheers.

 

[Life-Is-Good-Diver]

Hello SCHFORD, I have gone to four dema events two at New Orleans and two at Las Vegas. I will be at the next one in Orlando. I went to evaluate my ideas and help the dive shop I supported. I went there as a buyer for them. Re breathers were my main interest of the shows. I wanted to see who was up and running and get a close look at there hardware. When you see pics on the net and see pretty sales pitches it is hard to get a feel for the quality. Were I lived there were almost no one diving re breathers. I went and enjoyed speaking to the different manufacturers. This made it very easy to weed out the fly by night models and those that are sound and of good manufacture. I will admit that I do not yet think that any of the units to date really address the Rec market very well yet. I have my opinions on what is the best design, something that non of the manufactures have figured out yet. I do not want to sound like I do not respect some of them, that would not be accurate, anyone making it to market with a good quality product and are at De-ma presenting, have my utmost respect. I know how much work it takes to get that far. Currently my ideas are still relevant and will some day themselves be seen at De-ma. I also looked forward to speaking with the fellows from the NEDU and the projects they were working on. They will be the first people to see and test my design. Cheers.

Hey deepccr, how you feeling? This pneumonia is kicking my but all week. Mind is i ask what is NEDU ? you have to remember there are some noobies on re breather's like myself, trying to follow the re breather lang. The thread kinda slowed down, most of the important thing's were answered in the beg, caveseeker7, BigJetDiver, etc, and some other's have gave some usefully info.

As for myself, I'm going to continue my deep course's on OC for now, practicing some Intro to cave diving, and doing plenty more of open water / wreck diving.

I'm hoping in a few year's to be on something like the Inspiration, but until i see most of my dive profile diving those depth's, most of time, i can't see justifying the cost for that yet, for Rec diving that i am doing now, and the little tech diving.

I printed this out so David can see it, haven't heard from him since the email, But hopefully he understands were all trying to help him, even my wife feels good at this point, that we have tried.

 

[deepccr]

Evening, The NEDU stands for the Navy Experimental Diving Unit. They are stationed in Panama Florida. They test all types of diving equipment and life support apparatus. They some of the best test facilities in the world. I hope one day to have a unit that I can take there for testing. A few things slowing that down right now, thats life. But my design is a big improvement on what is out there. Taking it easy tonight. Reading some of the other threads, fun to see all the opinions. Some good some very poor.

 

[Life-Is-Good-Diver]

Evening, The NEDU stands for the Navy Experimental Diving Unit. They are stationed in Panama Florida. They test all types of diving equipment and life support apparatus. They some of the best test facilities in the world. I hope one day to have a unit that I can take there for testing. A few things slowing that down right now, thats life. But my design is a big improvement on what is out there. Taking it easy tonight. Reading some of the other threads, fun to see all the opinions. Some good some very poor.

Sound's good, have fun reading them, i cam eon here a while back under rebreather's looking for advise. There are some Very experianced rebreather's diver's on here, as well as the rebreather world also. Here's the link : http://www.rebreatherworld.com/

Check that site out also, started up about 6 monht's ago, and turned into a great site for rebreather's, pretty awsome !

 

[jptrealty]

Do you have an insurable interest with your dive buddy???

If not create one, I have a feeling you will do very well very soon.

Cheers