Technical Diving without Dive Computers

[Searcaigh]

I was taught to use Table(IANTD) back in 1998 and I am still tec diving without a dedicated dive computer

I also started my tech diving through IANTD and you learn to calculate everything using various tables, which makes you understand the whole concept of diving using mixed gases as well as gas planning and calculating how much gas you need for a specific dive.

It's a long process and best done between two people to double check the calculations especially if your maths is as bad as mine, but the IANTD calculation sheets are pretty good at keeping you on the right track. I did convert them to XL with formulae to make my life easier. The main point though is to make you think about the dive and not just jump in with a bunch of tanks and follow your computer.

 

[Diver-Drex]

Thanks a lot for the replies!

I am currently using Subsurface which I've found quite intuitive to use. However, I've yet to incorporate technical concepts such as rock bottom and decompression plans into my recreational diving. Gonna go for the TDI AN/DP courses first to ensure that I'm not missing out on any important parts.

While you certainly want to be doing has planning correctly I wouldn’t wait until you do Tech training to start.
Rock bottom calculations and gas planning should be something you do for all of your dives. Over time the process is quick as you’ll know your rock bottom for a particular depth having calculated it several times before. There are many on this board, I am certainly one of them, that consider this an essential skill that should be included in OW training.
When you get to tech training it is certainly helpful to know these concepts going in. I have just started formal tech training but I have been doing the calculations, planning and skills for years having learned from some great mentors. There are several people in the class with me and each has a different current skill level. The less prepared divers have a lot to learn. They will get a lot from the training no doubt. I would argue I will get more as I have the essentials down and can work on refining current skills and adding new ones under the watchful eye of the instructor.
Whatever you eventually do with your diving take time to become the best diver you can be at your current level. Buoyancy, dive planning, gas planning and solving equipment issues should be skills you work on during every dive. Especially so if you are considering tech diving in the future.
And at this point you should not be incorporating deco plans into your diving. Stay within NDLs. Learn the concepts but get trained from a competent diver first.

 

[Red Sea Shadow]

Deep into Deco has what seems like a pretty good survey of decompression models.. There are more than you might think, though how many are widely used is another question.

True. Thanks for pointing it out.

If you have Deep Into Deco, a bunch of models are illustrated. Otherwise stick with Tech Diving Mag. It's free and excerpts of Deep Into Deco (and other books) are frequently published.

 

[Centrals]

I also started my tech diving through IANTD and you learn to calculate everything using various tables, which makes you understand the whole concept of diving using mixed gases as well as gas planning and calculating how much gas you need for a specific dive.

It's a long process and best done between two people to double check the calculations especially if your maths is as bad as mine, but the IANTD calculation sheets are pretty good at keeping you on the right track. I did convert them to XL with formulae to make my life easier. The main point though is to make you think about the dive and not just jump in with a bunch of tanks and follow your computer.

Computer makes life a lot easier but it does take away the main function of human brain ie. planning, thinking etc etc.

 

[211ratsbud]

Computer makes life a lot easier but it does take away the main function of human brain ie. planning, thinking etc etc.

Arguably, I would say task loading can be reduced with a computer and better response to critical situations as a result. However I agree with sound understanding of why you do anything before you relinquish the task to a computer.

 

[doctormike]

Computer makes life a lot easier but it does take away the main function of human brain ie. planning, thinking etc etc.

I think that we are mixing up two types of computers. The OP was asking about dive computers (that you carry with you on your dive to track your N2 loading in real time). The post that you were replying to was about using tables to plan a tech dive as opposed to using dive planning software.

I think that most tech divers are pretty comfortable with planning dives ahead of time and writing an ascent plan on a slate as a contingency, even the ones who fly their computers and do whatever deco the magic bracelet tells them to.

On the other hand, I think that many tech divers use software to plan their dives. Yeah, there are tables available for decompression, but if you use a table and a spreadsheet for the math, you are just substituting faith in one set of data and calculations for another. I don't think that it's much better to use tables for planning tech dives. Also, one of the best parts of my training was to run multiple scenarios using dive planning software - that really gives you good sense about how changes in depth, time, mix and adjustments (like gradient factors) affect the ascent profile.

 

[boulderjohn]

I have been diving with trimix for about a decade now. During that time, I saw the following changes. These changes, of course, reflect only what I have seen personally, which is only a tiny percentage of the tech community. On the other hand, the changes were remarkably consistent--each change is pretty much universally applied among the people with whom I have dived.

1. Although I did start planning with DecoPlanner adjusted using GUE procedures (oxygen window), once UTD was created, my instructor crossed over immediately, and we were required to use the UTD flavor of Ratio Deco exclusively. Computers were not allowed unless they were in gauge mode.
2. When I left UTD and crossed over to TDI, I did a lot of diving in South Florida. I met a lot of tech divers on the boats. Pretty much everyone was planning their dives ahead of time using a VPM program like V-Planner. They would arrive with a slate with 3 plans written out on them by hand or printed from a computer printer and covered with packing tape. They used bottom timers or computers in gauge mode. When the DM walked around the boat asking people for run-times, they would show the slate with the written plan.
3. I then saw a transition in which people started using the written plans but using computers--largely Liquivisions--programmed with VPM as backups. They would follow the written plan for the most part, but I noted that when the computer differed from the written plan, they deferred to the computer, leading me to question as to which was the one they were following and which was the backup.
4. In the next phase, pretty much everyone was clearly following the computer with a written backup. These were mostly Shearwaters. They were largely using software to create a written plan, but following the computer in the water.
5. Currently almost everyone I see is using two computers. When I see a DM asking people for their runtimes, I never see anyone displaying a written plan, although they might have one in their pockets. I do see people showing a smartphone readout of a software program, and I have done that myself, so using a software program to preplan the dive is still popular. I myself use two computers, as does everyone I dive with. Every student I have had for trimix in the past two years has come to class with two computers already. I still prefer to do preplaning with software because the computer I use (Shearwater) does not plan multi-level dives the way you can with a full software program.

 

[Slamfire]

I don't think that it's much better to use tables for planning tech dives. Also, one of the best parts of my training was to run multiple scenarios using dive planning software - that really gives you good sense about how changes in depth, time, mix and adjustments (like gradient factors) affect the ascent profile.

I agree. During my training we did run 2 or 3 dive plans using paper tables. This was done just to know how it was in the olden days... and to understand deco principles from another perspective. But then the entire course was done using Z-Planner and manually entering deepstops into the Buhlmann model. I remember that we went over Pyle Stops (and modified them) and Eric Bakers GF. We also used V-Planner but our main workhorse for the course was Z-Planner. Some time after my course Ross Hemingway took Z-Planner out of commission. I then went to V-Planner and tried several others like DecoPlanner, HLPlanner, etc. Today I mainly use MV-Planner and V-Planner. All my tec training is TDI.

I have been diving with trimix for about a decade now. During that time, I saw the following changes. These changes, of course, reflect only what I have seen personally, which is only a tiny percentage of the tech community. On the other hand, the changes were remarkably consistent--each change is pretty much universally applied among the people with whom I have dived.

1. Although I did start planning with DecoPlanner adjusted using GUE procedures (oxygen window), once UTD was created, my instructor crossed over immediately, and we were required to use the UTD flavor of Ratio Deco exclusively. Computers were not allowed unless they were in gauge mode.
2. When I left UTD and crossed over to TDI, I did a lot of diving in South Florida. I met a lot of tech divers on the boats. Pretty much everyone was planning their dives ahead of time using a VPM program like V-Planner. They would arrive with a slate with 3 plans written out on them by hand or printed from a computer printer and covered with packing tape. They used bottom timers or computers in gauge mode. When the DM walked around the boat asking people for run-times, they would show the slate with the written plan.
3. I then saw a transition in which people started using the written plans but using computers--largely Liquivisions--programmed with VPM as backups. They would follow the written plan for the most part, but I noted that when the computer differed from the written plan, they deferred to the computer, leading me to question as to which was the one they were following and which was the backup.
4. In the next phase, pretty much everyone was clearly following the computer with a written backup. These were mostly Shearwaters. They were largely using software to create a written plan, but following the computer in the water.
5. Currently almost everyone I see is using two computers. When I see a DM asking people for their runtimes, I never see anyone displaying a written plan, although they might have one in their pockets. I do see people showing a smartphone readout of a software program, and I have done that myself, so using a software program to preplan the dive is still popular. I myself use two computers, as does everyone I dive with. Every student I have had for trimix in the past two years has come to class with two computers already. I still prefer to do preplaning with software because the computer I use (Shearwater) does not plan multi-level dives the way you can with a full software program.

• For several years I used MV-Planner and V-Planner and a slate with my Mares Puck either in BT mode or bending it to be locked out to BT mode.
  
• I had some friends that were UTD trained and I would agree to do their deep RD stops and they would agree to make longer shallow stops to make up for my on-gassing. I would add in their deep RD stops as a multilevel dive on V-Planner or MV-Planner to figure out how much longer shallow stops would end up being.
• I started looking into tech diving computers and narrowed down my choices to OSTC, Liquivision X1 or Shearwater Predator. I discarded the OSTC option because they were so far away and both Liquivision and Shearwater were local options for me. I almost went for the X1 because I was attracted by them using V-Planner as an optional deco software. Shearwater had no VPM at the time. But some friends at a now defunct local dive forum convinced me to go with the Predator citing customer service and ease of use. So in early 2011 I got my Predator that I still use to this day.
• So for the longest time I was using the Predator, along with a slate and the Mares Puck for depth gauge backup. Then a dive buddy of mine came back from a Mel Clark Meg course with a novel way of doing tables. He wrote down runtimes and stop depths on a piece of white duct tape and sticked it on top of his Predator's battery compartment. So from then onward the battery compartment real estate became my slate.
• I recently started using a Perdix AI along with my Predator. I gave away my Mares Puck to a newish diver. I still do plans on my laptop, mobile or occasionally in the Predator's planner. We'll email or share plans on Facebook private groups before hand, but now I'm not using the duct tape slate anymore.

 

[Red Sea Shadow]

What's the M11F6 algorithm? I've seen it being mentioned a few times, but have not been able to get any solid information on this algorithm. Also, are there any other more "modern" algorithms that's based on more recent studies and science that I should be aware about?

There's some info on the M11F6 in the most current issue of Tech Diving Mag.

 

[Michael Guerrero]

You need to know your depth, time, and schedule. How you do that is up to you.