As a long time Cochran diver I have my own reasons for the apparent falling out of favor. The bad press they got some years ago still haunts them for one. The fact you can’t edit your gas selection once your dive starts is another reason. It is a plan your dive…dive your plan computer. You set your gases you will use before you dive. You set your change depth and time before hand. Several factors go into choosing your setup. But it must be laid out ahead of time.
If you only dive one gas it is the best computer on the market in my opinion. Once you set the mix it stays set. It never reverts to a “preset mix” and it will never lock you out. It holds a crazy amount of data that if you download and go through will tell you how good you really are and where you could use some work.
Doing a multi gas dive you must know at what depth you want to switch to your second gas and how long into the dive when you ascend thru that depth you want to switch to that gas. Sounds odd but in practice it’s rather ingenious.
Let’s say you are planning a 150fsw dive with a combined decent and bottom time of 15 minutes. Your back gas is air (21%O2) and you have 80% in your sling bottle that you plan on switching to at 30fsw. Now we have a standard decent and as soon as we reach 130 feet we realize we have a dry suit leak and want to abort the dive. If I were to abort this dive I would not want to go to my deco gas on my way back to the boat. Are you tracking so far? OK what would we do if our leak happened at 10 minutes into the dive at 150fsw? I would need to do a couple short deco stops before I could safely exit the water. So to shorten that deco time as much as possible I would want to use my deco gas.
You need to put some thought into the when do you want to go to your deco gas on ascent when passing thru your switch depth and when you don’t. For me it’s all about deco. If I have deco to do I want to switch. If I don’t have deco to do I’ll save the gas for another dive.
I use V-Planner to plan deco dives and use it to quickly get an idea of about when to do the switch. I round it down to be safe. If I’m close to deco and it switches over I’ll do the switch anyway.
All this planning is done before you get wet all you need to do is remember to change regulators at the right depth.
I have a Shearwater and my Cochran that both play well together and always go with me on deco dives (and most every other dive). A week in Bonaire doing my extended range class and both weeks in Chuuk diving AWESOME wrecks, they were never more than a minute or two minutes diffrerance to clear deco. I had to play with the conservative setting some but if I do my part in setting each one to the dive I’m planning neither has ever let me down.
Clear as mud…right?
Edited by Jerrymxz, 04 April 2015 - 02:40 PM.
