So you want to purchase a Decompression Computer...

[waterpirate]

That is the real point of tis thread, I think. To illustrate the lack of knowledge in todays average diver, now extends into " the new tech ". The cavalier attitude in regard to dive computers and safety is appalling IMHO, rec and tec. The ever so true statement that "all dives are deco dives" is a finer point that is glossed over. It was that understandin many years ago that prompted me taking a pony bottle on every dive because I understood that a direct ascent to the surface for me was not acceptable. Here on SB people are still waging war over the semantics of that concept, the bottom line while the odds favor your choice to CESA, I would never include CESA as a part of any dive plan, for any reason, as I am not that lucky.

Eric

 

[beester]

I have a Suunto Vytec DS which can run RGBM 100 & 50, add deep stops, plus it can handle three different nitrox mixes.

All of which is useless as I run it gauge mode all the time.

As far as I know your Suunto doesn't run RGBM... it runs a propriety based own model named 'SUUNTO RGBM' which is a different beast. Because of the relation between Wienke and Suunto it's called RGBM, but basically it's Suunto adding padding to a standard 1-phase model, based on Wienkes RGBM theory.

Of course in gauge.. you're using your 5-phase brain instead of a 1-phase or dualphase model.. and in "deco-lalaland" a model is still a model... no matter what you use.

 

[DCBC]

I have a Suunto Vytec DS which can run RGBM 100 & 50, add deep stops, plus it can handle three different nitrox mixes.

I believe with the Vytec it's possible to adjust the algorithm of the RGBM model. As I understand it, this can reduce the conservation built into the tables by half, or conservation may be added through (two different settings). I'm aware that the Suunto RGBM calculates a multi-day factor based upon a SIT of 100 hours. Is this the RGBM 100 & 50 to which you refer, or is this entirely something different? I'm obviously not up-to-date on Suunto products...

 

[Ste Wart]

I believe with the Vytec it's possible to adjust the algorithm of the RGBM model. As I understand it, this can reduce the conservation built into the tables by half, or conservation may be added through (two different settings). I'm aware that the Suunto RGBM calculates a multi-day factor based upon a SIT of 100 hours. Is this the RGBM 100 & 50 to which you refer, or is this entirely something different? I'm obviously not up-to-date on Suunto products...

The 50 and the 100 refer to levels of conservatism, the 50 being the leaner of the two.

TBH I've never really bothered looking into the details of it beyond that. I bought it prior to doing tech courses assuming that I would need a computer. The reality was I was either using IANTD tables or cutting my own. So the Vytec ended up becoming an expensive gauge. I've had it running in the background when I've done deep air dives and the 100 is so conservative as to be absurd, an extra 10 minutes of deco on a 20 minute bottom time!. I've sat scowling at the thing, doing the extra deco as I didn't want to send it into 'sulk' mode for 48hrs.

 

[DCBC]

The 50 and the 100 refer to levels of conservatism, the 50 being the leaner of the two.

TBH I've never really bothered looking into the details of it beyond that. I bought it prior to doing tech courses assuming that I would need a computer. The reality was I was either using IANTD tables or cutting my own. So the Vytec ended up becoming an expensive gauge. I've had it running in the background when I've done deep air dives and the 100 is so conservative as to be absurd, an extra 10 minutes of deco on a 20 minute bottom time!. I've sat scowling at the thing, doing the extra deco as I didn't want to send it into 'sulk' mode for 48hrs.

LOL... When it comes to decompression, I have to admit that I dive like an old lady. They told me that after a treatment ride in the chamber, I'd dive that way. It seems like this is the kind of DC I should be using, so I could tell everyone that I'm just following the algorithm...

 

[waterpirate]

" send it into sulk mode for 48 hours " Now that is really funny. I dove a duo for a long time as back up, untill the day I forgot to " push the button " while in Fl. and sent that poor thing into freak out mode for the next couple of days. lol
Eric

 

[windapp]

I do no decompression diving and I own recreational no decompression computer. My computer can calculate stops in an emergency but I never exceed the ndl so they are irrelevant.

Anybody who does actual trained decompression diving knows exactly what decompression algorithm he/she is using whether doing it manually or using a computer.

This "all dives are decompression dives" is a just an argument in semantics, and only encourages the unwary to start thinking they should be using their computers to do untrained decompression dives. What is the difference you ask? In a decompression dive, you intentionally put yourself in a situation where the model you are using predicts you will suffer decompression sickness if you surface. In a no decompression dive, you are never in this situation.

 

[Abdullah]

I do no decompression diving and I own recreational no decompression computer. My computer can calculate stops in an emergency but I never exceed the ndl so they are irrelevant.

Anybody who does actual trained decompression diving knows exactly what decompression algorithm he/she is using whether doing it manually or using a computer.

This "all dives are decompression dives" is a just an argument in semantics, and only encourages the unwary to start thinking they should be using their computers to do untrained decompression dives. What is the difference you ask? In a decompression dive, you intentionally put yourself in a situation where the model you are using predicts you will suffer decompression sickness if you surface. In a no decompression dive, you are never in this situation.

In no deco dive your model is predicting that it is unlikely that you will require decompression stops to avoid DCS. You are relying on a statistical probability that your body will behave in accordance with your models' algorithm. That relationship occasionally fails (the so called undeserved hit).

If you consider every dive to be a deco dive, and routinely practice appropriate ascent techniques, you substantially reduce the probability that you will be the occasional failure of your model.

 

[beester]

I do no decompression diving and I own recreational no decompression computer. My computer can calculate stops in an emergency but I never exceed the ndl so they are irrelevant.

Anybody who does actual trained decompression diving knows exactly what decompression algorithm he/she is using whether doing it manually or using a computer.

This "all dives are decompression dives" is a just an argument in semantics, and only encourages the unwary to start thinking they should be using their computers to do untrained decompression dives. What is the difference you ask? In a decompression dive, you intentionally put yourself in a situation where the model you are using predicts you will suffer decompression sickness if you surface. In a no decompression dive, you are never in this situation.

I'm sorry windapp but with all due respect what you are stating is WRONG. The statement made that all dives are decompression-dives is not mere semantics, it's not said to win an argument, it's a fact!

On every dive how undeep and short it may be, you are increasing pressure = increasing the pressure of the gas/air you breath. Meaning that the stuff that's not metabolized in that gas remains in your body until you decrease pressure (ascend), it comes out of resolution again and you breath it out. (not going into detail here peeps).

The only thing that a deco-model (and every computer is based on a model) does is trying to "predict" in a statistically meaningfull way how to get rid of this excess N² in your body without causing bodily harm. This deco-model (computer) is not based on any scientific law, it's just a mathematical model that tries to emulate biological/chemical/physical processes in YOUR body. So it is prone to errors. Luckily there is enough statistical data up til about 120feet(40m) so that the computer can add enough buffer to keep you safe in most cases.

However as Abdullah already said, there is no golden line set in stone, dividing a decompression dive from a no-deco dive. If you believe that as long as you stay within NDL and follow your computer to the minute, you could be in for a nasty surprise some day. Don't you think it's better to backup your computer with your brain. Gain knowledge on how deco works (every dive) so you can change your ascend irregardless of what your computer says based on what you know (additional safetystop, deepstops, etc).

I'll give you some examples (there are many more) where you could be completely safe according to your computer but in reality you are far from it:
- doing a 100 foot dive and staying within NDL (1-2min) ascending 20 feet, staying until again within 1-2min of NDL, raising 20 feet, rinse and repeat. You'll be doing a nice multi-level dive, stay perfectly within your computers "NDL" but this is not a safe dive.
- Repetitive diving: doing a liveaboard (4 dives a day), yes your computer will probably start to add "padding" to your dives on day 2-3-4-5-6 but still you are going to be diving with alot of residual N² still in your body.
- Yoyo-diving: Everybody knows it's bad, but still it happens from time to time and most computers/models don't react to this.
- Fast ascend: you're ascending to fast during a NDL dive. Your computer warns you, giving you in some cases an additional safety-stop. What you are basically doing at that moment is going through your decompression ceiling.

Anyway I'm not saying you shouldn't use a computer, only to be aware of it's limitations (on every dive). This awareness comes from learning a bit more about decompression even if you don't do decompression dives. Knowledge is always a good thing.

 

[waterpirate]

The statement that all deco trained divers are aware of the model they are implementing and the risks associated with it is also untrue. Saying that not all dives are deco dives, you are simply repeating and pepetuating the wall of ignorance errected by your rec instructor in hopes of saving you from yourself. It has nothing to do with computers or winning arguements.
Eric