Time of Tech Dives?

[donooo]

I think that your question has to many variables and I will be surprised if one of the instructors tries to answer it.

So you answer it. Pick a depth, not 200-250, a depth, say 200 feet. Go into the Navy dive manual and figure out what the decompression requirements are for 200 feet for a time, you pick the time. Then figure out if you can haul enough air to do that time and your decompression stops. If you can do the decompression you can have the time. Then throw in the variables for a deco gas. Pick one to use ? ( If you take the class they will help you decide ) I'll bet that effects deco time, maybe bottom time.

This is not intended to be a deco self taught sales pitch. Just that you need to iron out some of the variables before these instructors can help you out.

That being said, I have never done any of that, but I suspect it will be easier to correct my simplification then it will be to give you an answer with so many variables.

Good luck, don O

 

[captndale]

Thanks for the info, but it kinda missed the mark of what I wanted to learn quickly. Please answer the following: What is the gain in time for a dive to say 200fsw?

You see I have advanced certification PADI and the allowable times for a dive to 130fsw is too short to enjoy. I am looking into future dives to 200- 250 ft for some wrecks, but how much time can you spend at those types of depth. I understand that deco diving opens up an entire new skill set. What i wonder is, what is the impact on time. I could not imagine it is as simple as calculating stops and now you can dive for as long as you have air? Or is it? I mean say you have doubles how long a deep are we talking.

Finally, can you rent any of the rebreathers or other advanced equip or is it to buy?

You don't go from PADI Advanced Open Water to Tech diving without some experience in between any more than a child goes from nursery-room books to nineteenth century Russian novels without reading a few books in between.

The question is not how much longer can you dive at 200 feet after you have taken a particular class but how long do you need to stay at a particular depth to accomplish your objective and then what skills, training and equipment are necessary.

As for renting, if you are not ready to spend the money to purchase the equipment you need it is an indication that you have not made the commitment necessary to obtain the skills and experience necessary to use that equipment safely.

 

[captndale]

Why? How is "advanced" nitrox different than "normal" nitrox? I glanced through my buddy's TDI AdvNitrox manual and couldn't for the life of me figure out what it included that hadn't already been taught in my first nitrox class. Amazingly, the equations were the same!

I learned all of the equations that I use in diving (through Advanced Tri-Mix and Gas Mixing) in my entry-level SCUBA diving class. That does not mean that I did not learn anything in the technical diving classes that I have taken. These classes include theory and application to real-world diving. Skill practice is also essential. There is a lot more to diving than knowing how to solve a problem having to do with Boyle's law.

 

[wedivebc]

Thanks for the info, but it kinda missed the mark of what I wanted to learn quickly. Please answer the following: What is the gain in time for a dive to say 200fsw?

You see I have advanced certification PADI and the allowable times for a dive to 130fsw is too short to enjoy. I am looking into future dives to 200- 250 ft for some wrecks, but how much time can you spend at those types of depth. I understand that deco diving opens up an entire new skill set. What i wonder is, what is the impact on time. I could not imagine it is as simple as calculating stops and now you can dive for as long as you have air? Or is it? I mean say you have doubles how long a deep are we talking.

Finally, can you rent any of the rebreathers or other advanced equip or is it to buy?

There have been some pretty good responses on this thread so I won't belabor the point but a couple of comments. At some point you will reach a level of training and experience where there will be no limit to depth or time other than the physical limitations of how much gas you can carry or how much time you want to spend decompressing. As you go deeper the bottom time/deco time ratio increases dramatically and there are ways you will learn to decrease that time but there are limits.
Also as has been mentioned, although you can rent rebreathers at some locations it is rare that a renter does not also own one or more rebreathers as they have made the comittment to that style of diving. A travelling diver might rent to avoid bring a rebreather to a remote location. I have rented rebreathers to students who are awaiting delivery of a unit or intend to purchase.

 

[Steve SDI/TDI HQ]

Thanks for the info, but it kinda missed the mark of what I wanted to learn quickly. Please answer the following: What is the gain in time for a dive to say 200fsw?

You see I have advanced certification PADI and the allowable times for a dive to 130fsw is too short to enjoy. I am looking into future dives to 200- 250 ft for some wrecks, but how much time can you spend at those types of depth. I understand that deco diving opens up an entire new skill set. What i wonder is, what is the impact on time. I could not imagine it is as simple as calculating stops and now you can dive for as long as you have air? Or is it? I mean say you have doubles how long a deep are we talking.

Finally, can you rent any of the rebreathers or other advanced equip or is it to buy?

OK... Your original question took us all by surprise. Let's try to give you an idea why that was.

As a sport diver, you are limited by the NDL of the table you are diving... different tables slightly different maximum times at depth before you have to conduct staged decompression.

What you wish to know is what are the time limits at depth... think you mentioned 200 feet or 60 metres.

The simple answer is that once you go beyond the NDL, time is limited by the volume of gas you carry. Typically on a training dive to 200 feet (trimix course) normal bottom time would be in the range of 25 minutes... This sort of time on the bottom would translate into a dive with a total run time (in water time) of about 75 minutes.

You asked whether "... you rent any of the rebreathers or other advanced equip." Essentially, as Dave suggested, yes. But divers conducting technical dives own their gear and only rent when transporting gear is impractical (for example if I were to fly someplace). Rebreathers are a little different in this regard since they are not as readily available as open circuit gear, and training is unit specific (training on closed-circuit rebreathers is specific to a brand and model of rebreather and if I were trained on say an Inspiration and went to a spot where all that was available for rent was a KISS, I'd be **** out of luck.)

I do hope this helps you to understand the situation.

 

[Rainer]

I learned all of the equations that I use in diving (through Advanced Tri-Mix and Gas Mixing) in my entry-level SCUBA diving class. That does not mean that I did not learn anything in the technical diving classes that I have taken. These classes include theory and application to real-world diving. Skill practice is also essential. There is a lot more to diving than knowing how to solve a problem having to do with Boyle's law.

Oh, please, do tell what "skills" are learned in an Advanced Nitrox class that are SPECIFIC to that class. Seriously, I'm all for training, especially for tech diving, training I have sought and continue to seek, but a standalone AdvNitrox class makes little sense to me. My buddy who took the class said the same about the one he took (he thought the DecoProc class was definitely worth taking).

 

[wedivebc]

Oh, please, do tell what "skills" are learned in an Advanced Nitrox class that are SPECIFIC to that class. Seriously, I'm all for training, especially for tech diving, training I have sought and continue to seek, but a standalone AdvNitrox class makes little sense to me. My buddy who took the class said the same about the one he took (he thought the DecoProc class was definitely worth taking).

You are correct that Dalton's law is Dalton's law and EAD formula doesn't change. What does change is the fact that there are great variances in a basic nitrox course from one agency/instructor to another. A well presented basic nitrox course should cover every subject in as much detail as advanced nitrox but they don't very often. When teaching tech or rebreather classes I get blank stares from students who claim to have a good grounding in nitrox when I ask a question like "what depth can I use an air computer to diving a fixed setpoint of 1.2?" Didn't we all learn Dalton's law calculations in basic nitrox?
So Advanced nitrox is essential to ensure a solid foundation for students to build their technical training on. It is not really a standalone goal for any level of diving that I can see.

 

[Rainer]

You are correct that Dalton's law is Dalton's law and EAD formula doesn't change. What does change is the fact that there are great variances in a basic nitrox course from one agency/instructor to another. A well presented basic nitrox course should cover every subject in as much detail as advanced nitrox but they don't very often. When teaching tech or rebreather classes I get blank stares from students who claim to have a good grounding in nitrox when I ask a question like "what depth can I use an air computer to diving a fixed setpoint of 1.2?" Didn't we all learn Dalton's law calculations in basic nitrox?
So Advanced nitrox is essential to ensure a solid foundation for students to build their technical training on. It is not really a standalone goal for any level of diving that I can see.

I guess I can buy that, Dave. A kind of baseline to make sure everyone's on the same page before moving forward. Still, it'd be nice if this could be taken care of earlier. I guess I had a good nitrox class...