Safety stop at 15'..........always

[Cacia]

They don't ever argue, they nearly always do exactly what they are asked and are generally very good divers. Far better than the average American diver (sorry to say guys but that's how it is).

You must take a lot of crap for that. But yea, its true.

Americans are something else.

 

[raymond phule]

I referred to the rate of change of pressure, not the amount of change of pressure, because that is what matters to you as a diver.

Rate of change is usually defined as the change of a parameter per unit time, (Delta P)/(delta t)

The rate of change of pressure is thus constant if the ascent rate is constant.

edit: The relative rate of change is the rate of change divided by the value of the parameter, (Delta P)/(delta t)/P

The concept is formalised with the derivative
Derivative - Wikipedia, the free encyclopedia

 

[The Chairman]

I believe it was Lamont who first told me about spinal fluid and blood having about the same rate. That's just HUGE when you think about it! I am happy to do a couple of minutes at half my depth (a deep stop) and then a full five minutes at 20 fsw. I teach my students to do the same.

I must admit at having learned about my poor safety stop protocol from my computer. When I uploaded the profiles I realized that they were more like safety PAUSES and not really stops. Then I started to learn more about how to dive with my computer which got me reading my OW manual again. I noticed that it said 3-5 minutes and that you should stick to 5 minutes if you were diving a computer. Well, it's obvious that tables have a LOT of added safety built into them. There are ways around that however, and it is possible to tweak a lot of time out of a table using somewhat unconventional means like depth averaging.

Now, I am convinced that given the preponderance of dive computers being used, that it makes sense for an instructor to teach students HOW to use them to effect a safe dive. They won't use tables, so let's teach them to use tool they are most likely to own and operate. This includes paying attention to the alarms, to the safety and/or deco stops indicated by them and how to let them make your diving a bit less anxious.

 

[raymond phule]

Well, it's obvious that tables have a LOT of added safety built into them.

I think this depends on the dive profil, i.e. square or not square. My computer gives me less time on a square profil compared to the RDP. V-planner also gives less no-deco time compared to the RDP.

 

[The Chairman]

I think this depends on the dive profil, i.e. square or not square. My computer gives me less time on a square profil compared to the RDP. V-planner also gives less no-deco time compared to the RDP.

Your table accounts for travel time, while your computer figures that on the "go". The use of a computer allows the diver to "ride" their NDL. They have the ability to extend their dive on any particular level incurring more ongassing, while the table user is coming directly to their stops.

The good guys at DAN indicate that more people get bent on computers than on tables. I believe this has a lot to do with the numbers of computers out there as well as divers not being trained in their use!

 

[raymond phule]

The use of a computer allows the diver to "ride" their NDL. They have the ability to extend their dive on any particular level incurring more ongassing, while the table user is coming directly to their stops.

My point was that it depends on the dive profil. I dont see how a square profil on a table is more conservative compared to a square profil on (at least my suunto) or V-planner.

Multilevel diving is ofcourse very different. I dont believe it is a very good idea to "ride" the NDL on a computer. I neither believe it might be the best way to approximate all profils with a square profil with the max depth. The conservatisim change a lot with the actuall dive profil in that case.

The good thing with a computer is that it actually follows the theoretical model all the time.
The best option might be to have a conservative computer and follow it in a "smart" way.

 

[The Chairman]

My point was that it depends on the dive profil. I dont see how a square profil on a table is more conservative compared to a square profil on (at least my suunto) or V-planner.

Again, the ultimate square profile is very rare for me, and I would imagine for most and it includes travel time to depth.

The best option might be to have a conservative computer and follow it in a "smart" way.

Yeah, that would be the whole point of training! Go figure!

 

[Bob]

Your table accounts for travel time, while your computer figures that on the "go". The use of a computer allows the diver to "ride" their NDL. They have the ability to extend their dive on any particular level incurring more ongassing, while the table user is coming directly to their stops.

The good guys at DAN indicate that more people get bent on computers than on tables. I believe this has a lot to do with the numbers of computers out there as well as divers not being trained in their use!

Pete,
I agree. If more divers are getting bent using dive computers, it indicates the divers don't understand what the computers are telling them, which tells me the diver was never trained properly in the set up and use of that particular unit. almtree: Bob

 

[Spimon]

Rate of change is usually defined as the change of a parameter per unit time, (Delta P)/(delta t)

And more easily visualised by the gradient of the graph of this data.

 

[The Chairman]

Pete,
I agree. If more divers are getting bent using dive computers, it indicates the divers don't understand what the computers are telling them, which tells me the diver was never trained properly in the set up and use of that particular unit. almtree: Bob

Actually, once you understand how to dive ONE computer, then using the rest is just a matter of reading the instructions. When I retired my Cobra, my very best friend wanted it, so it became his. It never even crossed my mind that he needed to be TRAINED to use it. So there we are on a wreck, and I am watching my NDL and depth closely. He on the other hand, is obviously NOT using his very well if at all.

At the end of the dive, I HEAR him up the line from me. He and his buddy are puzzling over all the beeping sounds emanating from his dive computer: He is in deco! So I indicate to him how many minutes he needed to do for his deco and wave goodbye: I am pulling the chain so I have to remain down.

On the boat, he is still perplexed: He has been locked OUT of diving. Whoops! He blew off a couple of minutes of deco. Why? He had no clue what all those numbers and sounds meant and he is a DIVE MASTER. Our instructor never took the time to teach us about how to utilize this tool.

BTW, knowing I had to outlast everyone to pull the chain, I stayed a lot higher. Not only was I down another 15 minutes or so, I never entered Deco.