Thinking Tech Diving?

[SportShadow12]

Hello,
There are many threads like this.
I have couple questions about my sac rate.
How do I find out what my sac rate would be? Another question is I am just a Open Water diver now but in the next 10 years would like to become a tech diver.
I would like to know how I can time out my tanks? How much estimated time I can use with a full tank?
Another one I am stuck between a XTX 200 reg, One of the scubapro regs, salvo reg, oxycheq and last and not least dive rite.
It will be used for ice diving in winter and very cold water were risk of freezing could happen.
Any help would be great.
Thanks

 

[bronk]

Your SAC rate is not one value but vaires with exertion. From resting to full effort you gas consumption will change by 8-12X.
You do not need to drain your tank to calculate the rate. 5 min for each rest or exercise phase is sufficient. Shorter durations lead to problems with measurement error or your breathing rate not having stabilized.
You will need a digital pressure gauge, and timer / watch with seconds. You monitor the pressure change over the time period, convert form pressure change in your tank to CFM and and correct for the depth you are at.
The calculations are fairly simple and taught in Intro to Tech and more advanced classes.
This is good fun.

On the regulator question. The reg is one of many pieces you will need as you advance. Top of the line is probably overkill. However with a bit of research you can find the "upper middle" regs that have hte same construction , but not all of the bells and whistles of the top of the line regs. I have Aqualung Legends and Apex XTX and like both. One point is go with DIN to start (saves converting later).

The "Trip to Tech" is one of continuous learning and continual purchases. It seems that for each phase you conquer, more gear is needed.

 

[DA Aquamaster]

To figure your SAC swim for a couple minutes at a steady cruising to fast swimming rate to stable lize your O2 use, then note your spg reading and depth as well as the time (either when the dive computer just kicks over to the next minute or with a watch with seconds). Maintain a constant depth while you continue swimming then after exactly 5 or 10 minutes (longer is better) note the reading on your SPG. (A deeper depth is also better and 60 feet works well.)

After the dive take all the data and figure your sac.

Assume you used 800 psi in a 10 minute swim at 60 ft while using an AL 80.

The AL 80 holds 77 cu ft at 3000 psi. (77/3000)*800= 20.53 cu ft used.

You used 20.53 cu ft in 10 minutes so 20.53/10= 2.05 cu ft per minute.

But that was at 60 feet so you need to convert that to a SAC, and to do that you need to figure the atms at 60 ft and divide the air used by that.

So ( 60/33)+1=2.82 atm

and 2.05/2.82= .73 cu ft per minute - which is your SAC rate.

This will give you a good idea of a conservative figure to use on a fairly active dive where you are swimming constantly (as if in a current etc). The other approach is to figure your sac at rest then multiply it by a constant such as 1.5 or 2.0 for working dives, cold dives, etc. That is however in my opinon exceptionally in-exact nd fraught with peril in real world situations.

A third option is if you have a dive computer that will compute average depth for a dive. In that case note the start and end SPG pressures as well as the dive time and average depth and use them in the same calculation above. That is often the most useful way to do it and if you do it on every dive over a period of time and conditions you will get a very good idea of your real world sac.

 

[Atomic_Diver]

I would reccomend Atomic aquatics M1 regulator its perfect for ice and technical diving... in fact made for it

 

[coldsmoke]

You might find this thread helpful for SAC and gas planning.

http://www.scubaboard.com/forums/basic-scuba-discussions/240133-calculating-sac-rate-rmv.html

As for regs. While I don't have personal experience with all of the regs you are asking about I do think they are all good choices. One thing that would influence my decision is the ability to buy rebuild kits. I service my own regulators and some brands make it more difficult to obtain parts. You might also check out the thread in the classifieds. Search for "$60 Balanced Diaphram Regulators". I dive a couple of these regs for my backgas and they work great. You can't beat the price and they are very well built. I have dived them pretty deep and in very cold water without issue.

Hunter

 

[k-valve]

The only addition I have to the other's advice is that you calculate two SAC Rates...working and rest. Sitting on the couch breathing from a tank with your mask on while watching Sports Center isn't going to be as accurate as those you'd take while actually diving. You can do them both underwater if you'll maintain your depth or are able to calculate your avg depth. Note your pressure and swim around at a reasonable pace for 10 minutes. Note your ending pressure. That'll give you a close working SAC. For your deco SAC Rate do the same, but hang as motionless as possible in the water, maintaining your bouyancy. Do this for 5 minutes noting your starting and ending pressure. Use DA Aquamaster's calculations to determine your SAC Rates. Remember your SAC Rates should change over time as you become more efficient underwater, so recalculate them occasionally.

As far as regs go I wouldn't recommend buying high-end regs until you're pretty close to getting into tech diving. Most decent middle of the road regs work just fine even past recreational depths. As far as ice diving goes you might want to look at regs that are environmentally sealed. You don't even have to have those, but it would be the most prudent choice.

Just my 2 cents...

 

[Dive Rite]

Another question is I am just a Open Water diver now but in the next 10 years would like to become a tech diver.

Another one I am stuck between a XTX 200 reg, One of the scubapro regs, salvo reg, oxycheq and last and not least dive rite.
It will be used for ice diving in winter and very cold water were risk of freezing could happen.

Hi SportShadow,

Check out our Solution Finder under 'What should I look for in a tech regulator?' This will give you some ideas as you make your decision. It makes sense to buy a good quality regulator that will perform well in all conditions right from the start.

The Dive Rite Hurricane and the RG3000 can both be used for cold water diving.

The Hurricane first stage is cold-water ready and the second stage is equipped with a patented heat exchanger to prevent freezing in extreme cold conditions. You can read an independent review of the Hurricane here.

You have the option to install an ice kit on the RG3000 that makes the reg perform in cold water. You can read an independent review of the RG3000 here.

All the best with your diving!

Best,
Ag

 

[texdiveguy]

A few fun calculators:

SAC Calculator