V-planner or Shearwater

[boulderjohn]

When you are diving one techincal comouter you have to cut tables for the dive as a backup from decoplanner or from your computer.
When you have 2 technical comouters running the same gf you can theoretically not use cut tables as you have a backup that is suitable for the task to get you to the surface.
If you knew that your back gas could last a 50m dive for 30mins and your ali80 had more than enough gas for the deco of that dive, would you continue to put future dives through deco planner or through the planning software on your computer that were less than 50m 30mins or would you just rely on your 2 technical computers.

I do dive with two computers with the same algorithm. As I mentioned in a PM but will repeat here since the question as put publically,

I frequently dive in a place called Rock Lake in New Mexico. A lot of what is in this lake (max depth around 280 feet) is unknown, and some friends and I are exploring, laying line, and mapping. We are pretty sure we know the depths of most of the bottom areas we are exploring reasonably well. When we are going to a depth we have done a number of times before, we don't bother to pre-plan in software or on the computer because the results will be the same as they were the last time we did it. We know what gas mixes to use. We plan for the deepest we think our dive will be so that anything different will be to our decompression advantage, and we ascend on our planned time. What we actually do on the dive will be different from a plan anyway because we cannot be completely sure of our bottom depth. If we end up ascending the line on the east wall, for example, before we get to that line we will ascend a débris cone from about 270 feet to 190 feet, and we will trust the computer to figure out the ascent profile accordingly.

Occasionally we plan to work on areas that are not at the usual depths--meaning shallower. In such cases, we will input planning options into the software to figure out how long we can stay at that planned depth, whether we will need AL 40s or AL 80s for deco, etc.

 

[boulderjohn]

All right--I see the problem. My fault. I was misreading your posts as being a question you were putting out for yourself rather than pointing out an issue for someone else. carry on!

 

[broncobowsher]

Make a plan, compare it to the computer. Do they match or are really close? If not, why and fix.
Now that I have a plan I set that aside and run the computer. With occasional references to make sure I am on track.

The computer is my primary. Notes and cut tables are backup. They are not ignored during the dive, they are referenced but not followed. They follow what I am doing and if not something is wrong.

I still dive with people who only run cut tables. I get the benefit of flexible. If I plan 150', but only go 145, or find something better and more entertaining at 130 I can run with it. I may not have cut tables for 130 not thinking there would be anything there. Run the computer. When the time is up, leave. Computer can get me out faster then having to stick with tables cut for a deeper dive, but if I have to switch to tables I am still safe just in longer then needed.

Just stepped up to the 2 computer game, Petrel + NERD. Have not decided how I am going to play that. Not doing deco with that setup yet. Probably run some notes at first until I am comfortable.

 

[lermontov]

So I'm coming into the 21st century here. I was raised to run your deco plan on V-planner, write it down a bunch of places, then dive your plan... With a plan and a bottom timer is how I've dove for years.

I've finally decided to come out of the stone age and buy a Shearwater. So here's my question... Do you guys:

A) run a plan using software and have the computer as backup?

B) run the plan using the Shearwater (pre dive) and write that down for backup to the computer and deco via the computers instructions?

C) just do your gas planning and hop in and ride the computer (idk about this one but I'm old school)

It seems B makes sense to me as I'm assuming I can't make the software match the computer so you have to either follow the plan or the Shearwater.

Let me know guys as I want to get the benefits of this incredible piece of technology. If you do something else please let me know.

I primarily use the MultiDeco fro gas plans and in particular the max time option.i prefer using that than the shearwater planner as i think it has a better interface and you can manipulate the times and gas quantities easily as well as seeing the plan on one page, the other thing is with MultiDeco ( or sim ) you can copy and paste and send it via messenger or email you you buddy

I use 2 DC and a slate with bottom time and TP I also have a deco time ascent prompt (tts) this primarily on a 2 gas dive . So my gas plan is primarily from multi deco and because I hardly ever do a square profile I use prompts on my slate so as long as I'm inside or on those numbers I know I'm ok

 

[boulderjohn]

I primarily use the MultiDeco fro gas plans and in particular the max time option.i prefer using that than the shearwater planner as i think it has a better interface and you can manipulate the times and gas quantities easily as well as seeing the plan on one page, the other thing is with MultiDeco ( or sim ) you can copy and paste and send it via messenger or email you you buddy

I use 2 DC and a slate with bottom time and TP I also have a max deco time ascent prompt (tts)

You can also do a multi-level dive plan with multideco.

 

[dave22387]

This is turning into a pretty good thread. Thanks everyone for your input. I'm starting to put together my game plans as far as using the computer. Keep it coming gents. This is all great info!

 

[Tassi Devil Diver]

Do you have any source for this other than an unnamed rebreather instructor?

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No sorry I don't, test it for yourself, I did and the result was clear to me MultiDeco has an inherent deep stop bias which I will take into account when I am planning dives using MultiDeco in the future.

This is definitely wrong. I have my own implementation of Buhlman ZHL16 GF and it doen't fudge anything but does agree with Ross's MultiDeco plans.

This is something my rebreather instructor raised when I was doing my MOD3 a few weeks ago. This came as a surprise to me, so I ran through a few identical profiles in MultiDeco and on the Shearwater with the same GF and on all profiles in MultiDeco the first one or two stops were deeper, by increasing the low GF in MultiDeco by 10 sometimes 15 this brought the two profiles closer together.

Make of it what ever you like but it is clear to me that MultiDeco has an inherent deep stop bias, which is not surprising given Ross's stance on deep stops.

 

[scubadada]

The Shearwater people will say 'set the MultiDeco stop resolution to 1 second and notice the first stop is only one second'. Then by the magic of interpolating the next stop is at GF high and you are free to surface.

This is one reason why GF is rather bogus for NDL dives.

Thanks @KenGordon

This is very interesting. So....I reran the 4 profiles from post #21, that used stop times of 1 min, by using stop times of 1 second. The results are significantly different:

16 minute dive to 100 feet on air:

So, there is still a very short amount of stop time when the GF lo is decreased, but it appears considerably less when 1 second stops times are used rather than 1 minute stop times. How does the dive computer deal with this? What does the computer use for stop times? My only Buhlmann computer, a Nitek Q, displays stop times in whole minutes. Are these actually whole minutes or are they fractions of a minute like planning with 1 second stops? In plan mode, the Nitek Q gives the same NDL regardless of the GF lo setting, only dependent on the mix and depth and dictated by the GF hi. GF lo does not kick in unless you exceed deco and cannot directly surface under the GF hi

 

[boulderjohn]

As I reported earlier, I ran the same profile in both multideco and a Shearwater with 1 minute stops, and the results were as close to identical as you can get.

Anyone with Multideco and a Shearwater can do this. It does not take long. Just remember to input things like altitude properly.

 

[boulderjohn]

No sorry I don't, test it for yourself,

I did. See post #28.