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Beginning of my Tech Diver adventure

Discussion in 'Rocky Mountain Region' started by Waterskier1, Sep 2, 2008.

  1. amascuba

    amascuba Instructor, Scuba

    # of Dives: 500 - 999
    Location: Austin, TX
    No problem. :) The computer issue is pretty complex and there are several computers that are fine for single deco gas, nitrox deco diving. Those computers run around $500 (Aladin tec2g for instance, which also has a guage mode to act as a bottom timer) From there is a huge leap in functionality and price. The most flexible computer on the market right now appears to be the Liquidvision X1, which runs around $1700. I think Liquidvision is about the only company making computers that "gets it". The platform is open to different algorithm models (vpm and RGBM)... and I'm fairly certain that anybody can develop the software for the computer and incorporate any algorithm they want. It's pretty sweet, but at it's cost, you won't see one on my arm any time soon. :)
  2. jerryn

    jerryn Nassau Grouper

    # of Dives:
    Location: Divide Colorado
    It is true that bottom timers use batteries and fail. I wear two and could presumable wear two computers. But you need to already know your decompression, so the extra money for the two computers (now we are up in the $1200 to $3000) range hardly seems worth it when it is not adding additional information.

    You are right that you need to track these things on multiple days. I do it on my laptop using VPM software. When you are doing technical diving there are long surface intervals so the tracking of residual nitrogen and residual helium becomes less of an issue. For example one dive in the morning, SIT for 4 hours, one in the afternoon SIT for 15 hours and skip a day here and there.

    I think Liquivision X1 is the best computer. It seems to track the dive pretty well. What I don't like about it is that it gives you credit for multi level dives, but typically there is a saw tooth pattern and it is multilevel because you are ascending out of the hold of the shipwreck or room of the cave and then descending into another. I think it is too liberal in that regard and prefer to use a square profile to calculate my deco.

    For recreational diving I use a Suunto Vyper and like it a lot. Different kind of diving, different tool.

    As an answer to the question about what if your bottom timer goes, what then? An example of a dive I just did.

    204' for 25 minutes. Deco began at 140' and was 1 minute each 10' until 80'. Then it was 2,3,3,4,5,6,8,25 and 3 minutes from 20' to the surface. A fairly simple pattern to remember. If my bottom timer craped out I can count these times out. As far as depth, 3 fists make a foot. So without a mask and without a bottom timer I can do this deco pattern and come up the line safely. So a computer is nice, just not a necessary expenditure.

    Onto the X1. For that dive it gave me 1,2,3,4,4,6,7,20 because I had ascended from the props to the deck, swam along the deck and then descended to go into the inverted section. I was also carrying a camera, kind of a draggy thing, and working hard. Probably I would have been okay with it, but the few extra minutes do do a clean profile seemed worth it.

    All of this is a long way of saying that a. you are right, if your intention is to become a technical diver (most do not intend this) then get equipment that you can use in both technical and recreational applications and b. a computer is not one of them. I often use my Suunto as a bottom timer. Works great.


  3. ShakaZulu

    ShakaZulu Great White

    # of Dives: 200 - 499
    Location: San Diego, CA
    I don't even understand why recreational divers get into tech, only to spend a lot of money and dive to 150ft...woohoo. Opens up cans of worms all over the place, see posts above, for what?
  4. jerryn

    jerryn Nassau Grouper

    # of Dives:
    Location: Divide Colorado
  5. battles2a5

    battles2a5 Divemaster

    # of Dives: 200 - 499
    Location: Charlotte, North Carolina
    I just want to throw a couple of practical scenarios out there for computers. Do you need one? Absolutely not. By all means you should learn how to plan and execute dives on tables and timers. Are they good to have? Absolutely. I still use tables as my primary but I back up my dives with my computer. I'll give you a couple of scenarios:

    1. New Dive Site: Typically, I cut tables for my plan, plan +10 min, plan +10ft, lost gas(es), bail-out, and max deco for carried gas (just so I know how far into the s*** I can get out of). This generally gives me enough leeway to handle most situations. I went to a new site recently with someone who had 100's of dives there. We were searching for a downline in near-zero vis that had apparently been moved. The line is located in about 70 ffw. Typically, we would just ride the lines all the way down to out planned bottom but we got hung up on looking for the line for about 20 min at 70ffw. So once we were at depth (200ffw), my tables were essentially garbage. I ended up cutting my planned BT short by 5 mins, and running my +10 min plan just to be safe since I didn't have a table cut for this profile (please do not turn this into a ratio deco discussion). So I ended up cutting my dive short and doing 15-20 mins more deco than I needed to. A computer would have been nice. I still could have run my tables if I needed to but the computer will generate a good profile if the dive plan varies a bit.

    2. Emergencies: Again, using the same tables I cut above, if we had an emergency underwater I would have to fall back on my tables. I cut my bail-out at 1/2 BT. If I am between 0 and 1/2 BT, I use my bail-out plan. Anything beyond that, I have to BS my way through my full schedule. I have been planning my dives on Freeplanner using Buhlmann 30/85 which is moderately conservative. But I usually set my computer to something a little more aggresive like 20/90 and know that if I have to get out of the water the computer will get me out much faster than my tables will at any given point of the dive. I always have the option to run the tabels, but I can get out quicker if I need to.

    So again, they aren't needed but they are certainly nice to have. It's not an excuse to forego planning by any means but it gives you a lot more options during your dive. Another option would be to learn ratio deco or one of its variants but I think that's something you have to do on a regular basis to be proficient and I haven't fully bought into the theory yet (although I plan to learn more about it). Just another perspective.
  6. RiverRat

    RiverRat Instructor, Scuba

    # of Dives: 200 - 499
    Location: Connecticut
    Well hey you got to start somewhere right? Not sure I quite follow you. It takes more money to get into tech so you should have a real interest before you embark on it. In the Northeast US there are MANY MANY wrecks in the 125 - 200 fsw range so tech training is not a bad thing. That is if you want to visit any of these deeper wrecks and spend some amount of time down there safely. Or maybe one wants to ice dive, or cave dive or just spend lots of time on the bottom at shallower depths using doubles. It's just another set of tools to reach new goals in diving. I'll tell you what I had a blast learning to tech dive this season. I got in 6 dives on the U853 and it was the coolest thing exploring inside that sub. I didn't get too crazy, kept the penetration dives to a minimum as I learn but I couldn't have done it without the training or gear. Well some people do but you're playing with fire. I'm now able to plan some really cool dives and do some awesome exploration, safely and confidently. I think the rec divers that try it for the wrong reasons bail when the going gets tough anyway. You learn real quick that tech diving is a whole new game. Gotta take it seriously.
  7. Daxter

    Daxter Barracuda

    # of Dives: 100 - 199
    Location: Denver,CO
    Well said River Rat
  8. georoc01

    georoc01 Manta Ray

    # of Dives: 200 - 499
    Location: Denver, Colorado
    Exactly. For me, it is a future planned trip to Chuuk Lagoon on a boat that supports tech diving. And a couple of the dives are down to 165 feet. So I have a particular goal in mind that requires this level of training. If you are going to spend between $5-10 grand on a trip, why wouldn't you do everything you can to maximize your bottom time while you are there and be able to enjoy all of the stops that the boat will take during the week?

    And if it makes me a better diver along the way and increased my awareness when I have future goals of divemaster and and instructor, wouldn't that be worthwhile also?
  9. jerryn

    jerryn Nassau Grouper

    # of Dives:
    Location: Divide Colorado
    Exactly, I just came back from Truk. Most people bounce the deck of the San Francisco Maru (165) and are narced out of their minds. I have 90 minutes on it. And I was on He so I was completely clear. At 190 there is more ordenance than you can believe. Totally awesome. And sitting in the sand looking up at the bow -- unbelievable. I went through the expense and training and training and training and practice and more training and more expense because this is what I wanted to ultimately do. I have been on some really amazing wrecks and I'm looking forward to the next one. But...you really have to be methodical, patient, and into planning if you are going to do this kind of diving. If your goals in diving are to see animal and plant life, to enjoy the beauty of a reef, or just the underwater experience, then there is no better way than to put on an Al80 and dive within NDL's.

    So let's take the tech Truk report to another thread as there is a lot to report.

  10. boulderjohn

    boulderjohn Technical Instructor ScubaBoard Supporter

    # of Dives: 1,000 - 2,499
    Location: Boulder, CO
    I am sure that some of you have been following the John Chatterton thread, but in case you haven't, I thought you might be interested in some of his comments that relate to one of the topics in this thread.


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