How Much Reliance on Dive Shop Planning?

[Bob DBF]

Let's see, we were between 75-90 feet for 12 minutes, so I will make 90 feet my first level. Then we were between 60 and 75 for 26 minutes, so I will make 75 my second level--oops, go to round that to 80. OK, then we were between 38 and 60 for 12 minutes, so I will make that my next level. Then we ascended, so, according to my multi-level device, I came out of the water as a Q diver." (Don't check those numbers--I just made them up.)

Do you really think anyone will be doing that?

Well The Wheel was made waterproof so those calculations could made on the fly. Perhaps that was why everyone went to using computers, much easier.


Bob

 

[JohnN]

You are completely ignoring the reasons computers give you more bottom time--multi-level diving. If you are diving a completely flat profile, then computers will NOT give you more bottom time. I once did a dive to 100 feet, stayed a few minutes, ascended to mid reef for a while, and then finished up at the top of the reef. My total bottom time was 80 minutes, and my computer would have let me stay longer--I was just out of air at that point. According to PADI tables, my maximum time would have been 20 minutes, and according to Navy tables, my maximum time would have been 25 minutes.

That is pretty much how diving is done in much of the world. Let's look at the first place I ever dived with computers required, which was in Cozumel over a decade ago. The dives must by law be led by a DM. The dive will be multi-level, with total dive times FAR beyond the maximums allowed by tables, so any planning would have to be done with multi-level dive planning software or special tables that allow it. However, the DM cannot tell you ahead of time what the different levels will be, so you can't pre-plan the dive. The only thing you can do if you want to use tables is pay constant attention to your depth throughout the dive, probably writing it down every minute or so. After that, you could go over the notes and group your numbers. "Let's see, we were between 75-90 feet for 12 minutes, so I will make 90 feet my first level. Then we were between 60 and 75 for 26 minutes, so I will make 75 my second level--oops, go to round that to 80. OK, then we were between 38 and 60 for 12 minutes, so I will make that my next level. Then we ascended, so, according to my multi-level device, I came out of the water as a Q diver." (Don't check those numbers--I just made them up.)

Do you really think anyone will be doing that?

The only way you can track a dive like that is a computer. If you don't have a computer and go on a dive like that, you have no way of tracking your dive.

Isn't this basically what GUE pushes as ratio-deco (the multilevel running calculation, not reliance on tables when you exit) ?

 

[boulderjohn]

Isn't this basically what GUE pushes as ratio-deco (the multilevel running calculation, not reliance on tables when you exit) ?

Not exactly, but close. GUE wants you to plan the dive and dive the plan, using Ratio Deco to help in case the plan goes awry.

What I described is often called derogatorily "flying the computer." That is considered an insult, but it is by far the way the world dives now. In the case I described, I don't see anything wrong with it.

 

[dhaines429]

Definitely get a computer. There are many inexpensive ones out there. The eRDP and the tables only account for max depth and make your dive far more conservative than it should be.

 

[YukonJack]

I used a computer (Puck Pro) on my certification dives and it was like heaven. It started logging as soon as I dropped below 5 feet, told me my total dive time, my current actual depth, and my no deco limit time. When we all were in our surface interval and had to admit to our deepest depth for the surface interval times, I knew exactly what my max depth had been. Plus, and this has not been mentioned, when I downloaded the data to my computer, I could see just how bad my buoyancy was during each dive I love that it estimates very closely my actual nitrogen loading and times my surface intervals, all without me doing anything. And, based on my previous dive(s), tells me how long I can stay at depth for the next dive. Also, the no fly indicator is super awesome. All for about two dinners out during the week, this can all be yours

 

[Neilwood]

I think, for most recreational diving ie within NDL, computers are by far the easiest solution and potentially the safest.

Bearing in mind that the typical recreational diver is not generally the type to log in here (or any other forum) and keep updated about developments and try to improve their diving. That typical diver (as a generalisation) is the holiday diver who may get one or maybe two trips a year in blue water with no experience in between. They almost certainly aren't the type that would want to form a rigid plan and stick to it 100%.

Reason I say the safest is it would be all to easy for the diver above on a recreational dive on a new site to get carried away with looking at the sights or following a turtle/shark/fish and forget to log their depth/time. The computer automatically tracks it (after automatically starting on descent) so takes that responsibility from the diver so all they have to do is track the screens readout.

Divers will always get bent - the only sure way to prevent it is never to dive. Physiology and medical issues will mean that some divers will be at high risk (PFO etc) but possibly never know it until they do get bent. Unexpected issues during a dive might contribute as well (currents etc). What the computer is very good at is minimising the risk.

 

[Dive Cochran]

These days, the navy is using dive computers: Cochran Undersea Technology Not that I'm suggesting I like that model computer.

You wrote "these days" I think not..........................................

Twenty four years ago, Mike Cochran and Capt. Ed Thalmann, MD (of the U.S. Navy) consulted for over a year to implement the VVAL-18 algorithm into a dive computer. This involved converting tables, equations, and Fortran programs into microprocessor firmware, and extensive testing.



1994 Implementation of the VVAL-18 Algorithm into a Commercial Off the Shelf (COTS) platform



1996 The first Navy Dive Computer (NDC) delivered to the Navy Experimental Dive Unit (NEDU) for testing and qualification



1998 The NDC is approved for field testing in January



1998 The NDCs are tested by SDV teams



2000 The NDC is recommended for SEAL team use



2001 Naval Special Warfare (NSW) NDC added to the Approved for Military Use (AMU) list



2001 The U.S. Navy’s first decompression computer dive occurs off Barber’s Point Hawaii



2003 The 2nd generation NSW NDC is added



2004 The 3rd generation NSW NDC is added (NSW III)

2005 The AIR III NDC is added for use for Ships Husbandry/ Salvage divers



2006 The NSW 50/12 is added for use Mod 1 version of the MK16 Rebreather



2006 The Low Magnetic Signature (Low MU) EOD DT/DG is supplied to the Explosive Ordnance Disposal (EOD) divers kit



2010 The Low Magnetic Signature (Low MU) EOD III NDC is supplied to the Explosive Ordnance Disposal (EOD) divers kit for use with the Low Mag version of the MK16.



2010 The NSW HE III is added for use with the Heliox version of the MK16



2014 The AIR III NDC is upgraded from the VVAL-18 to the VVAL-79 algorithm

2015 Proprietary to Cochran & USN
2016 Proprietary to Cochran & USN
2017 Proprietary to Cochran & USN

Curious kelemvor have you ever owned or dove a Cochran dive computer?
Thank you

Have a great day
Safe Diving
John
Sales Manager Worldwide
Richardson, TX
www.CochranMilitary.com

 

[kelemvor]

I'm not sure what you're trying to say. Unless you're in the know and suggesting that the navy is no longer using dive computers, I think my statement is correct.

Are you offended that I linked to your site as an example of how the navy is using dive computers? If so, I will remove it from the previous post.