Deco diving for beginners

[wreckweasel]

Originally Posted by Janos

Zak, can you expand on this a little. After a days diving I always sleep the sleep of the righteous, even if all I've done is a couple of shallow dives in Wraysbury.

How do you know when you have cut it a bit fine?

Basically, extreme fatigue is normally a good indicator of sub clinical DCS. You can generally tell when you're feel good.

The difficult part comes in that most divers will sleep inadequately the night before, they'll eat/hydrate poorly and then they'll top that lot off with a niiiice long drive to/from the dive site. Now how do you know whats causing the fatigue?

Deco is the one subject we divers seem to pay lip service to. Its foundation is your own body, you know, that glistening testament to health and fitness.

Theres a whole pile of information out there that is well worth reading, as long as you bear in mind the basic fundamentals of the mechanisms of gas transport/physiology, you'll make progress.

I'll do some digging at some point and put up a few links.....

[Narked@50]

Janos

We all get tired after diving, nitrox can reduce this to a degree but a good nights kip is best. (which is strange as we all usualy end up in the pub drinking) You have to be very careful the way you read somthing like that, Zak has meant it in best intentions and by reading his other posts has built this up over years and further quantifies it wich the rest of his post, but when your new, it can be "dodgy" to get this close to DCI. The most basic form of DCI can be tiredness, lack of energy, pins and needles, skin rash and it gets progressively more severe from there. If you get any of these, after tired, you have pushed it too much and are on the verge of a chamber visit if your not already on your way. Stick to the tables/computer model and you are likely to be ok as these have been tested and are conservative. It is dangerous to start experimenting with less, even though you may get away with it for a time. Remember what keeps getting said here: Everyone reacts differently to deco, it even changes from day to day with your body chemistry, so what is right for one person may be totaly inapropriate for another of similar build.

James, I feel like I'm getting old writting stuff like this?

[Narked@50]

Hi Pierre

I have a Vytec, and it does allow for deep stops, but you have to be doing some deep bottom time to get them, I never have. The Vytec is weighted towards shallow stops and the deep ones add considerably to deco time. They can be effectively turned off by changing the RGMB from 100 to 50.

James

[Janos]

Originally Posted by narkedat50

It is dangerous to start experimenting with less, even though you may get away with it for a time.

Don't worry - I'm just following this from a theoretical viewpoint. I'm a coward when it comes to diving. And it seems that the more diving the I do, the bigger a coward I get (especially this year). 10 minutes of deco is a big dive for me, and I'm more than happy to add an extra couple of minutes on, as although I like to think I'm a tremendous athlete, we all know that that's not true.

I often get very tired at night post-diving - can't keep my eyes open after about 10:30 - but as Zak says: is it due to the diving, the long journey down, the getting up early, or just humping the twinset around? (Currently laying foundations for the new Shed, so will sleep soundly tonight too I bet)

Right, better get back to it.

Laters,
Janos

[Pierre Farrugia]

Hello all,
I used mine for 60m 30min dives, and no deep stops were noticed or are you referring to deco at 12m (I think it was) Mine is set to 100 as well. Altough when I deep dive I use, proplanner and normally I am not that far away from it using vytec as back up!

regards

Pierre

[Mark]

Originally Posted by Mark Chase

Deco on the fly

This sounds a great system but little information is available outside Tech 1 trained students so it’s not a good one to discus. Ultimately the system relies on mental capacity and this may be disrupted during the dive. As a result I am not a big fan no matter how simple the math is supposed to be. I have had a dive where a migraine put paid to rational thought and the VR3 paid for its self in spades. Some would argue that the buddy is there in these situations and in my case they would be correct but I always plan dives as if they were solo.

Hi,

If you suffer from some kind of mental failure during a dive but can still understand what your VR3 screen is telling you to do, you would still be able to work out your deco in your head. This would not be necessary (for me) as you have correctly pointed out, the buddy/team would run the deco instead while looking after the mentally failed (or otherwise incapacitated) diver. I should point out that only one diver per team actually runs the deco (calls the shots) the other diver will normally shoot the DSMB and move/stop when told to do so. The jobs could be interchanged easily during the ascent if required as we would all know exactly what profile is being performed.

Before you say 'oooh what about the task loading' we have been trained to handle exactly this type of scenario on Tech-1 and the final two assessment dives are exactly this sort of rescue (from 36m with one guy OOG and the other with no mask. All stops must be carried out including deep stops, gas switches, DSMB deployment and sticking to the run times. Lost deco gas can be thrown in for good measure!) All that with one guy unable to see anything.

DIR divers don't ever think in terms of solo diving. Of course we are very self sufficient (no one is ever entirely self sufficient!) but DIR is all about thinking, planning and diving as a team.

When DIR procedures are discussed they should be kept within a DIR context. IE what DIR divers would really do when diving with other DIR divers, not what you may or may not do if you were using your own personal interpretation of a DIR idea or procedure within your own style of diving (not you personally Mark, but in general).

Regards,

Mark


PS. It is a great system

[Mark Chase]

Hi Pierre

Also I dive with a buddy using a Vr3 and we both use tables cut from proplanner cut 10%/10% but on ascent the Vr3 will sometimes skip the 15m stop, is this normal? If you decide to do the 1m stop as per runtime would you bend the Vr3? this thing is being a little of a problem as we have to do deco separately as sometime he has to stop deeper than me and I cannot wait for him due to my schedule!

If you do a slow ascent you can find that short stops disappear before you get there so it’s not unusual for this to happen. It’s giving you the option of continual ascent deco rather than 10m/min ascent and actual stops.

You can add as many stops as you like to the VR3 as long as they are below the deco ceiling it shows at that time it will not mind. If you are adding stops in the right place it will reduce the 6m stop. Use the look ahead button to see all the stop durations and depths before ascent then you can see how much reduction it gave you.

I also use a Vytec of which I find it useful, especially as a backup. Mark , did you say Vytec allows for deep stops?

It makes an attempt at it. It actually gives some deeper stops I had it prompt a 23m stop on a 58m dive but it usually it prompts 18m as the first stop and controls the deep stops with a very slow ascent rate. A normal deco dive ascent rate is 10m/min so a 1min stop every 3m is the same as a 3m/min continual ascent. The Vytec is a halfhearted attempt IMHO. The screen goes blank after 35mins at 60m because it goes outside its decompression calculations. If it allowed for the deco gasses it would be fine but it will only show the deco on the gas your breathing.

The Vytec is OK but it would appear that the people who designed it do not do deco diving so they didn’t understand the needs of the diver.

ATB

Mark Chase

[Mark Chase]

[quote]

Originally Posted by Mark

Hi,

If you suffer from some kind of mental failure during a dive but can still understand what your VR3 screen is telling you to do, you would still be able to work out your deco in your head. This would not be necessary (for me) as you have correctly pointed out, the buddy/team would run the deco instead while looking after the mentally failed (or otherwise incapacitated) diver. I should point out that only one diver per team actually runs the deco (calls the shots) the other diver will normally shoot the DSMB and move/stop when told to do so. The jobs could be interchanged easily during the ascent if required as we would all know exactly what profile is being performed.

Fair reply Mark and you absolutely correct if the buddy is there and sorted he will get you out. As I said the system sounds great. From what I have read I don’t know what you do about inaccurate gas blending but I expect the answer is can the dive.

The VR3 got me out OK on this one because all I had to do was look at the screen and understand the data. I didn’t have to look at a slate and try and calculate mentally what time I arrived at the stop and how long I had been there. Some times I struggled over this when my head was straight let alone when the world will not stop spinning and stars are exploding in front of my eyes. The VR3 told me in simple terms what depth I was at, what depth I should be at and how long I should stay there. Little or no thought involved and even that was a struggle. I cant explain what a migraine is like to some one who has never had one but trust me its bad.

ATB

Mark Chase

[Pierre Farrugia]

Hello Mark,

Tommorrow I have a 60m dive for 25min so this time I will pay more attention, on what stop the Vytec gives me, as normally I just check total time and depth , due to tabels and runtime. Then just check the deco it remains at 6m, which normally clears before runtime.

Thanks

Pierre

[Narked@50]

Originally Posted by Pierre Farrugia

Hello all,
I used mine for 60m 30min dives, and no deep stops were noticed or are you referring to deco at 12m (I think it was) Mine is set to 100 as well. Altough when I deep dive I use, proplanner and normally I am not that far away from it using vytec as back up!

regards

Pierre

Hi Pierre

Mark Chase has given some "real life" details on the Vytec he uses, I have never heard of it blanking the screen as it goes out of range of it's calculations, but since I don't dive that deep, and certainly not for that long, I honestly can't comment, I will have a play with it's planner though?

I did however check the manual and it does do deep stops on RGBM 100. I ran the simulator on the software you can get from Suunto based on the Vytec model and it gave me the following graph of the dive you said you did. If you look at the top right figures that say "ceiling" it has 21.2 meters on it, this would be the shallowest first stop. As I, and Mark, pointed out though, it is weighted for shallow stops and it is likely that a slow ascent will clear this and go to the next one.

Watch yours like a hawk and let us know what happens, I would be very interested in this and think it gives merit to the thread.

Regards

James

Sorry, almost forgot.

On my simulation you ran out of air and died using the 18L tank I know you love, please take a bigger one.