Back up computer for Perdix AI

[boulderjohn]

Do you not know how to plan multi level dives?

So what is the problem? The BT is to be used as a backup device as per original question, not as a primary DC. Even if you are in a "tight" spot you can use a BT with avg depth information to calculate an ascent profile...

Tables and a bottom timer

Okay, folks, this past may I did a long series of 3-tank dives in Palau, diving with a group and a DM. We had 1 hour surface intervals. Here are the first dive numbers for several of those days, with the planned maximum depth for the 2nd dive listed. Please pick any of those days and tell me how I could plan the second dive using a bottom timer and tables if I discovered that my computer was not functioning after the first dive. Use any tables you want. (Note that I made it easy for you by not including the 3rd dive.)

May 8
First dive: 92 feet for 67 minutes
Second dive: 59 feet

May 9
First Dive: 100 feet for 60 minutes
Second dive: 77 feet

May 10:
First dive: 91 feet for 66 minutes
Second dive: 87 feet

 

[Rollin Bonz]

 

[stuartv]

Okay, folks, this past may I did a long series of 3-tank dives in Palau, diving with a group and a DM. We had 1 hour surface intervals. Here are the first dive numbers for several of those days, with the planned maximum depth for the 2nd dive listed. Please pick any of those days and tell me how I could plan the second dive using a bottom timer and tables if I discovered that my computer was not functioning after the first dive. Use any tables you want. (Note that I made it easy for you by not including the 3rd dive.)

May 8
First dive: 92 feet for 67 minutes
Second dive: 59 feet

May 9
First Dive: 100 feet for 60 minutes
Second dive: 77 feet

May 10:
First dive: 91 feet for 66 minutes
Second dive: 87 feet

ajduplessis mentioned planning using average depth. He must have some way of doing that with which I am not familiar. Perhaps you should include your average depth on Dive 1 as well?

I, too, am curious for the answers to your question.

 

[boulderjohn]

ajduplessis mentioned planning using average depth. He must have some way of doing that with which I am not familiar. Perhaps you should include your average depth on Dive 1 as well?

I could include that average depth, but I am trying to make it realistic. If while preparing for dive #2 I realized my computer had failed, I would not have that information. I might not even have the first dive maximum depth or time, either. I could have left those items out to make it more realistic, but my point for this exercises is that all of those first dives were well off any table, making it impossible to compute a second dive.

And, no, I don't know how to take an average depth (including safety stop, etc.) on a dive and do anything meaningful with that information for planning the next dive. Perhaps we will be enlightened on that methodology.

 

[KenGordon]

So what is the problem? The BT is to be used as a backup device as per original question, not as a primary DC. Even if you are in a "tight" spot you can use a BT with avg depth information to calculate an ascent profile...

I am somewhat assuming that the OP wants a backup so they can carry on diving later in the day, not only make an ascent at the time of failure. They have a buddy for the ascent.

You can’t use average depth for deco ascent planning. It depends if the deeper than average part of the dive was early or late. In general it depends on the actual profile. On the other hand a BT will let you execute a backup plan on a slate, but that plan is likely to be very conservative for multilevel dives. For square dives, you could just remember how you did it last time,

But really none of that is required, just take two computers. If you can’t afford that buy cheaper ones.

 

[rjack321]

Okay, folks, this past may I did a long series of 3-tank dives in Palau, diving with a group and a DM. We had 1 hour surface intervals. Here are the first dive numbers for several of those days, with the planned maximum depth for the 2nd dive listed. Please pick any of those days and tell me how I could plan the second dive using a bottom timer and tables if I discovered that my computer was not functioning after the first dive. Use any tables you want. (Note that I made it easy for you by not including the 3rd dive.)

May 8
First dive: 92 feet for 67 minutes
Second dive: 59 feet

May 9
First Dive: 100 feet for 60 minutes
Second dive: 77 feet

May 10:
First dive: 91 feet for 66 minutes
Second dive: 87 feet

Gas(es) used?
If I knew your profile I would have no problem doing a second dive on "tables" but this isnt enough information to know. For instance was the 92ft for 5mins? the remaining 62mins at 35ft?

 

[boulderjohn]

Gas(es) used?
If I knew your profile I would have no problem doing a second dive on "tables" but this isnt enough information to know. For instance was the 92ft for 5mins? the remaining 62mins at 35ft?

EANx 32

 

[outofofficebrb]

At depth and @18', Perdix and Zoop are showing the same no-deco numbers.

That would depend on the conservatism set on the Shearwater. In rec mode, medium conservativeness is closest to the Suunto. Over repetitive diving, the Suunto yields lower NDLs as time goes on. My data points have been diving with my buddy over a 37 repetitive dive count. I used to dive a Suunto primary and backup. I am now on a Perdix primary with an Oceanic backup.

 

[divad]

Correct, but I only do 1, 1 to 2+ hour dive a day.

 

[dmaziuk]

Anecdotally, at least, RGBM counts 30-ish hours as "repetitive" dives. I'd have to look the exact number up in Dr. Wienke's article, IIRC it's over 24 hours.