Deco diving without a written out dive plan?

[a878bob]

So now you have two computers go down and you have tables, what are you using for time?

 

[packrat12]

So now you have two computers go down and you have tables, what are you using for time?

I will answer this with a rhetorical question... So your Computer and BT go down, what are you going to do???? If I am with a team, I will use their timers/depth indicators for my ascent. If not... just like any other tech diver with 2 methods of ascent and losing both without any other deco schedule method, I will be writing my epitaph... or maybe I may make best guesses, use run out of gas at 20' etc. Lots of unknowns for anyone here.

I have yet to lose a single computer on a dive, let alone two. I have lost my Heuer dive watch (drown) and my BT on the same dive.

 

[Centrals]

Written plan is a must because I never use a computer on tec dive.
I used to carry IANTD soft tables as the back up as well.

 

[Steve_C]

Be curious about the relative frequency of loss of buddy contact vs computer failure. Stuff happens. Down drafts etc that can separate divers even buddy conscious divers. Relevant if your buddy is your backup device.

 

[a878bob]

That's what I thought, that's why it's two SWfor me. Then my partner, then best guess and remaining gas.

Tag

 

[DevonDiver]

Firstly, we plan for reasonable failure. The chances of two computers simultaneously failing is very low. It's generally deemed 'unreasonable' in respect to contingency planning. Losing the buddy/team is irrelevant - we've already planned to mitigate reasonable failures so that we can complete the dive alone, if necessary.


Secondly, we have to pre-plan our dive. Having done that, we should be aware of the key points of the dive. If diving two computers, there is no need (IMHO) to take a 'reminder' on the dive... unless, of course, our memory and awareness is insufficient to guarantee we'll remember the pre-dive planning 'key points' against which we check our diving instruments in real time.


The 'key points' might include the bottom time, depth, total run time, depth of first stop and gas volumes used. When teaching, I quiz students on these... to develop the habit of retaining them in memory for the dive. It's not that hard.


Understanding concepts like ratio deco make a good 'last ditch' option in the event of unreasonable failures - you lose both computers AND your team on the dive. Even if you don't understand formal ratio deco... if you know the key points of the dive - you could use experience (if you have it) to calculate an approximate stop schedule based on a logical curve. It wouldn't guarantee safety from DCS... but given the extremity of failures that'd have to have occurred... it'd be a fair shot at safety... or, at least, the consequences would chamber-resolvable.


I sometimes play a 'game' with my tech students... where I create a dive plan on multideco and brief them of the key points. Then I have them guess/approximate the stop schedule. We compare it against the real plan and note the variations etc. It is a fast-track drill to understanding how the curves work.

 

[stuartv]

Thanks, everyone. It seems like there's a reasonable number of experienced folks who feel like 2 tech computers is sufficient to save oneself the need to manually write out dive plans on a slate or in wet notes to take in the water.

That seems like a reasonable plan, to me, but I haven't even done my first real deco dive yet....

Don't take any of this the wrong way. My instructor is teaching us to write out the plans on a slate and take that on the dive. So, that is what I'll be doing.

I just like to understand all the ways a thing could be done, even if I'm not planning to do it that way. I think knowing all my options helps me to better evaluate the way I'm doing things as I go forward gaining more experience.

 

[jhh]

I have yet to lose a single computer on a dive, let alone two. I have lost my Heuer dive watch (drown) and my BT on the same dive.

I've seen it happen. Some random guy (not my buddy) had both his computers shut down on him. Judging by his response, the proper way to handle this situation is "find the nearest person (unfortunately me), scream into regulator unintelligibly, gesticulate wildly, rip my mask and reg off, and try and drag me to the surface". It was an unpleasant dive because I thought he was having a stroke or something.

I try and minimize the chances of bad things happening by carrying multiple copies of the dive plan on multiple slates (wrist, L pocket, R pocket), and they're planned normal, +10t, and +10d, with lost gas options for each (six total). This currently works for me because I haven't worked my way up to doing insane amounts of deco yet.

 

[stuartv]

I've seen it happen. Some random guy (not my buddy) had both his computers shut down on him. Judging by his response, the proper way to handle this situation is "find the nearest person (unfortunately me), scream into regulator unintelligibly, gesticulate wildly, rip my mask and reg off, and try and drag me to the surface". It was an unpleasant dive because I thought he was having a stroke or something.

I try and minimize the chances of bad things happening by carrying multiple copies of the dive plan on multiple slates (wrist, L pocket, R pocket), and they're planned normal, +10t, and +10d, with lost gas options for each (six total). This currently works for me because I haven't worked my way up to doing insane amounts of deco yet.

How many depth gauges and dive timer devices do you carry? And are they combo units (e.g. a Xen bottom timer)?

 

[jhh]

How many depth gauges and dive timer devices do you carry? And are they combo units (e.g. a Xen bottom timer)?

Two: a Petrel 2 and Nitek Q. It's conceivable they could both fail, and even if they don't... I still don't trust them. They're mostly used as timing and depth devices; I don't actually pay any attention to the deco time they display unless it's for a longer period than what I have in my plan.