V-planner or Shearwater

[JohnnyC]

If you just go by the DC deco plan and you suddenly need or have to donate gas then how do you know you will have enough?

I think it's important to point out that what you're saying is significantly different than planning a dive beforehand, and relying on the computer for accurate depth, time, and decompression information, which is what those of us who utilized computers are promoting.

The idea that you fall off the boat and piddle around until you rack up some deco without regard to any other factors because you've got a computer is absolutely not a practice that anyone should be endorsing. Nor do I know anyone who does so when it comes to technical diving.

 

[DanielRJones]

If I am diving OC the slate plan is most important as it was how I figured out I had enough gas. So I must follow the slate for the bottom part of the dive. Then I will be following it for the ascent until the last stop when I might go up when the computer is clear. If the computer is really showing much shallower stops than the plan I might move to the computer earlier, but I will be stopping for gas switches anyway so I might as well stop as planned.

The gas plan, especially how everyone gets to the first gas change in the case of a failure, is what matters. Usually there will be more than ample deco gas unless you choose silly cylinders.

If you just go by the DC deco plan and you suddenly need or have to donate gas then how do you know you will have enough?

I have used decoplanner before i get in the water so know my gas usage for the dive and know i have enough for the dive.
Even though i have a comouter i am still running ny bottom time to the plan. My cut tables are +5m, +5min, +5m +5min
If i end up +1min due to slow dsmb by team my computer will give me a better profile than me running my +5min. Also my dive may not have been a square profile so may not have some of the stops that my tables dictated so my computer will get me out sooner.

Yes it is a very expensive bit of kit for saving me a few mins here and there

 

[DanielRJones]

I think it's important to point out that what you're saying is significantly different than planning a dive beforehand, and relying on the computer for accurate depth, time, and decompression information, which is what those of us who utilized computers are promoting.

The idea that you fall off the boat and piddle around until you rack up some deco without regard to any other factors because you've got a computer is absolutely not a practice that anyone should be endorsing. Nor do I know anyone who does so when it comes to technical diving.

People diving 2 computers is where things can get lost.
You know you have enough gas for 50m 30min in your setup from past plans.
Somone asks you to do a 45m for 30 dive. Would you cut tables or would you just trust your 2 computers.

 

[Tassi Devil Diver]

Be aware (which I don't think many divers are) that running the Buhlmann GF algorithm in Multideco Ross H has incorporated an inherent deep stop bias. By this I mean a dive plan using say a GF of 50/70 on the Shearwater will produce a dive plan more like 40/70 in Multideco, so to match the Shearwater GF50/70 plan in Multideco you will need to plan with a GF 60/70, it does not make a great deal of difference just that the first stop of a minute might be 3 or 6m deeper. Something to be aware of if using Multideco. I did not realize this until recently when it was pointed out by my rebreather instructor, who advocated against using Multideco because of this and just use the Shearwater planning function on the Shearwater computer, however Multideco does a better job of gas planning. Would be great if Shearwater produced a desktop dive planning program to match their computers.

Regarding general dive planning, I use two computers, and as a team we agree on a max time to surface, I will use Multideco if I am likely to be diving a new profile (depth or bottom time) for bailout gas planning.

 

[TrimixToo]

People diving 2 computers is where things can get lost.
You know you have enough gas for 50m 30min in your setup from past plans.
Somone asks you to do a 45m for 30 dive. Would you cut tables or would you just trust your 2 computers.

Why are you asking? And, what kind of computers?

With my two Shearwaters, I would not bother to recheck the gas plan, and they do the deco plan on the fly. With my prior setup of a Shearwater and a VR3, I wouldn't have, either. With one computer that knows what I'm breathing and one that doesn't, yes, I'd rerun the deco plan on my phone and write it down.

 

[TrimixToo]

Be aware (which I don't think many divers are) that running the Buhlmann GF algorithm in Multideco Ross H has incorporated an inherent deep stop bias. By this I mean a dive plan using say a GF of 50/70 on the Shearwater will produce a dive plan more like 40/70 in Multideco, so to match the Shearwater GF50/70 plan in Multideco you will need to plan with a GF 60/70, it does not make a great deal of difference just that the first stop of a minute might be 3 or 6m deeper. Something to be aware of if using Multideco. I did not realize this until recently when it was pointed out by my rebreather instructor, who advocated against using Multideco because of this and just use the Shearwater planning function on the Shearwater computer, however Multideco does a better job of gas planning. Would be great if Shearwater produced a desktop dive planning program to match their computers.

Regarding general dive planning, I use two computers, and as a team we agree on a max time to surface, I will use Multideco if I am likely to be diving a new profile (depth or bottom time) for bailout gas planning.

The way I use MD, for gas planning and general info only, this is mostly OK for me even though I didn't know about it before; having more gas is mostly good. However, at some edge conditions this would make me carry more cylinders than necessary, which is less than good. Thanks much for posting this. I'll have to play with MD and the SW planner to see what's what. Thanks again for posting.

 

[boulderjohn]

f I am diving OC the slate plan is most important as it was how I figured out I had enough gas. So I must follow the slate for the bottom part of the dive. ...

If you just go by the DC deco plan and you suddenly need or have to donate gas then how do you know you will have enough?

People diving 2 computers is where things can get lost.
You know you have enough gas for 50m 30min in your setup from past plans.
Somone asks you to do a 45m for 30 dive. Would you cut tables or would you just trust your 2 computers.

I have no idea what is being said in these quotes. People are writing as if people who use computers just jump in the water with no idea what is going to happen. You do just as much planning for a dive using computers as you would for a dive using no computers.

When you use desktop software (at least the ones I have seen) or when you plan on the Shearwater, you input your expected RMV for the bottom time and the deco time, and the program tells you how much gas you should use for the dive, assuming all goes as planned. Using that basic information, you plan a reserve. You can use any system you want to plan that reserve. Many people use thirds, meaning they add 50% of that expected total so that if the dive goes exactly as planned, they will finish with a third of the gas with which they started, with that last third available for any issues that arise. I have done a number of dives with someone who always carries twice what the computer says.

What do past plans have to do with it, other than giving you the RMV you input when planning the coming dive?

 

[dave22387]

I have no idea what is being said in these quotes. People are writing as if people who use computers just jump in the water with no idea what is going to happen. You do just as much planning for a dive using computers as you would for a dive using no computers.

When you use desktop software (at least the ones I have seen) or when you plan on the Shearwater, you input your expected RMV for the bottom time and the deco time, and the program tells you how much gas you should use for the dive, assuming all goes as planned. Using that basic information, you plan a reserve. You can use any system you want to plan that reserve. Many people use thirds, meaning they add 50% of that expected total so that if the dive goes exactly as planned, they will finish with a third of the gas with which they started, with that last third available for any issues that arise. I have done a number of dives with someone who always carries twice what the computer says.

What do past plans have to do with it, other than giving you the RMV you input when planning the coming dive?

I haven't touched a Shearwater yet so this may be a stupid question... If I read this correctly you're saying the Shearwater can do basic gas planning as well? I've seen the schedule planning.

 

[boulderjohn]

Be aware (which I don't think many divers are) that running the Buhlmann GF algorithm in Multideco Ross H has incorporated an inherent deep stop bias. By this I mean a dive plan using say a GF of 50/70 on the Shearwater will produce a dive plan more like 40/70 in Multideco, so to match the Shearwater GF50/70 plan in Multideco you will need to plan with a GF 60/70, it does not make a great deal of difference just that the first stop of a minute might be 3 or 6m deeper. Something to be aware of if using Multideco. I did not realize this until recently when it was pointed out by my rebreather instructor, who advocated against using Multideco because of this and just use the Shearwater planning function on the Shearwater computer, however Multideco does a better job of gas planning. Would be great if Shearwater produced a desktop dive planning program to match their computers.

Regarding general dive planning, I use two computers, and as a team we agree on a max time to surface, I will use Multideco if I am likely to be diving a new profile (depth or bottom time) for bailout gas planning.

I have never heard this before. Do you have any source for this other than an unnamed rebreather instructor?

In a past thread on ScubaBoard, rebreather diver and well known dive theorist @Dr Simon Mitchell said he uses Multi-deco for dive planning. That is significant because in many threads, both on ScubaBoard and in other forums like Rebreather World, Simon and Ross have clashed repeatedly, with Simon clearly pointing out the many times Ross has made statements that reveal a serious lack of knowledge of decompression theory. If anyone in the world would be expected to distrust anything Ross wrote, it would be Simon.

The thread in which Simon said he uses Multideco was one I started because I was becoming afraid to use a program created by Ross and asked for alternatives. In that thread, no one mentioned anything about Ross corrupting Bühlmann and GFs that way.

 

[boulderjohn]

I haven't touched a Shearwater yet so this may be a stupid question... If I read this correctly you're saying the Shearwater can do basic gas planning as well? I've seen the schedule planning.

Sure it can. You input your RMV in the dive planner, and it tells you how much gas you should expect to use. It has done that since at least the first Shearwater I owned, which was quite a few years ago.

Multideco does that as well.