Which Deco Computer Plan to use on Deco runs.

[Peter69_56]

I have a shearwater petral and running the VPM-B algorithm (as it matches Vplanner) and my dive buddy has a Liquavision running Buhlmann ZH-L16C algorithm.

On a deco often we mismatch significantly because of the different algorithms. So which do we run to? Currently we have both been stopping at depth as soon as either computer dictates a stop at depth and running the max time on either computer before moving to the next stop. Is this the best plan (given we stick together as buddies should).

It appears the VPM-B seems to dictate deeper stops which shortens shallower stops, while the Buhlmann has longer shallower stops with less deeper stops. So until we both have the same dive computers (yes I could run the current ones on the same algorithm but then could not do a matching plan on Vplanner).

For those using Buhlmann ZH-L16C algorithm, what gradients do you normally set. I think 30/80 is default?

For those using VPM-B, what conservative figure do you use? Currently set for +3

 

[nimoh]

Personally, my plan is to plan the deco schedule before the dive and follow it. This allows easy gas planning to ensure an adequate supply for all of the stops, and also every team member knows ahead of time where each stop will be, for how long and all gas switches will be at the same time.

A computer can be a useful backup if you lose focus during the dive or something happens to throw you off schedule. You can also run it in simulation mode with various algorithms to ensure that it will be close to the "paper" version of the deco plan.

 

[Peter69_56]

Agree, however as the dive sites were all unfamiliar territory, we planned each dive and often came up early (for a number of reasons) so rather than follow a deco plan based on max dive time at depth, we reverted to a modified plan which allowed reduced deco time as it was unnecessary due to the reduced bottom time. Had we have stayed the planned time we would have followed the deco plan as calculated before the dive. That's why I in the end I want both computers to have the same algorithm as Vplanner as that's what we use to plan our dives and should closely reflect what our dive PC's show. I see little point in planning on one algorithm and then having a dive PC that shows something entirely different.

 

[nimoh]

Agree, however as the dive sites were all unfamiliar territory, we planned each dive and often came up early (for a number of reasons) so rather than follow a deco plan based on max dive time at depth, we reverted to a modified plan which allowed reduced deco time as it was unnecessary due to the reduced bottom time. Had we have stayed the planned time we would have followed the deco plan as calculated before the dive. That's why I in the end I want both computers to have the same algorithm as Vplanner as that's what we use to plan our dives and should closely reflect what our dive PC's show. I see little point in planning on one algorithm and then having a dive PC that shows something entirely different.

that sounds like a great reason to use a computer over a paper schedule

Unfortunately, I don't have a great answer, but looking forward to the ensuing discussion.

I will offer this though, my guess is that you have already thought of it, but are you able to load different algorithms into either of your computers? I am guessing that there might still be some minor differences due to different implementations and rounding differences, but they ought to get them pretty close if using the same algorithm.

 

[Peter69_56]

If I decide to use the computers over Vplanner I can load Bühlmann ZHL-16C in the shearwater which will then be much closer to the XEO as it has Bühlmann ZHL-16C as well (think the gradients are slightly different). But it would mean that Vplanner would be somewhat different to them both as it uses 3 forms of VPM. The paper plan would not be close to both computers although they would match each other closely.

---------- Post added May 18th, 2013 at 12:43 AM ----------

Anyway I would like peoples thought on what to do "assuming" one is going to use dive computers for deco and they have different algorithms. What is the best plan? I don't like the idea of doing independent decos, as getting apart is not a desired or ideal situation in case of problems. SO hence my original questions;

It appears the VPM-B seems to dictate deeper stops which shortens shallower stops, while the Buhlmann has longer shallower stops with less deeper stops. So until we both have the same dive computers (yes I could run the current ones on the same algorithm but then could not do a matching plan on Vplanner).

For those using Buhlmann ZH-L16C algorithm, what gradients do you normally set. I think 30/80 is default?

For those using VPM-B, what conservative figure do you use? Currently set for +3

 

[Wookie]

Instead of running V-Planner, Ross has just released multi-deco, which allows a multitude of algorithms to match your computer. If you have V-planner, there is no fee for Multi-deco. I'm sure it was released specifically for this....

 

[Peter69_56]

Do I just use the same codes with Multi deco as I received for Vplanner

 

[Abdullah]

Why wouldn't you pick one computer and follow it? You and your buddy decide which one you want to follow based on your feel for which method you're both comfortable with, and set that as the rule for the dive.

I dive plan using V-Planner and carry those tables with a BT. But my Petrel uses Buhlman, and my dive buddy's computer uses Buhlman. But still, the profiles don't match exactly. Perhaps due to proprietary nuances in the algorithms, perhaps due to variation in measured depth, maybe a little of both.

You can use the gradient factors to adjust Buhlman to favor more-deeper by using a lower percentage of the M value at depth (change 30 to 25 or 20). You can also adjust Buhlman to favor less-shallower by adjusting the shallow percentage higher (change 80 to 90). Try playing with the values in MV-Plan (freeware I believe) and you'll see how the changes affect your profile.

The conservancy you choose in V-Planner is personal. I would consider level 0 the "elite specimen" level (I call it Navy Seal). If you're older, overweight, more out of shape, more stressed at work, smoker, party late into the night, or any of a list of contributors to DCI, you increase the conservancy accordingly. If you're diving a team concept, you should both be using the same identical tables. So, the conservancy should be based on the worst characteristics of your team, not necessarily on you.

There is a lot of discussion on the value of deep stops. Some recent studies seem to say that they are valuable in some profiles and detrimental in others. It's a discussion fraught with heart felt opinions on both sides, and not worth getting flamed over on SB. I would suggest you and your buddy read up on the available information and make an informed decision on which makes sense to you and go with that.

 

[Wookie]

Why wouldn't you pick one computer and follow it?

Because sharing a computer is one of the first things we learn not to do as a recreational diver. Are you suggesting that tech divers have identical profiles, so it's OK for them to share, but recreational divers can't? I didn't think so.

 

[Peter69_56]

Why wouldn't you pick one computer and follow it? You and your buddy decide which one you want to follow based on your feel for which method you're both comfortable with, and set that as the rule for the dive. - As our computers are both new to us we don't have a feel for them as to which works best hence the post and request for advice.

I dive plan using V-Planner and carry those tables with a BT. But my Petrel uses Buhlman, and my dive buddy's computer uses Buhlman. But still, the profiles don't match exactly. Perhaps due to proprietary nuances in the algorithms, perhaps due to variation in measured depth, maybe a little of both. - Bought the Petrel with VBM unlock so can use either and given it has a neat planner built in perhaps set them both for the same algorithm and use the internal planner only rather than V-Planner, but given I now have access to Multideco I think I am better set up for use of Buhlman on both and Mulitdeco although my own personal preference is for VBM based simply on how it works and gut feel.

You can use the gradient factors to adjust Buhlman to favor more-deeper by using a lower percentage of the M value at depth (change 30 to 25 or 20). You can also adjust Buhlman to favor less-shallower by adjusting the shallow percentage higher (change 80 to 90). Try playing with the values in MV-Plan (freeware I believe) and you'll see how the changes affect your profile. - This is what I want to do, play, but don't have a feel yet for what I should be setting. Currently just using the default settings. I like the idea of deeper stops as well as fairly long shallow stops but not at the expense of still taking on gas. Will take your suggestion of MV-planner or now multideco and see the difference, thanks.

The conservancy you choose in V-Planner is personal. I would consider level 0 the "elite specimen" level (I call it Navy Seal). If you're older, overweight, more out of shape, more stressed at work, smoker, party late into the night, or any of a list of contributors to DCI, you increase the conservancy accordingly. If you're diving a team concept, you should both be using the same identical tables. So, the conservancy should be based on the worst characteristics of your team, not necessarily on you. - Maybe there should be a +10 setting here. I am using the default of +3. Tried +1 but felt I was a bit light on deco time, and I like to be conservative and will just suffer the longer deco times based on safety over saving time but using +3 at least.

There is a lot of discussion on the value of deep stops. Some recent studies seem to say that they are valuable in some profiles and detrimental in others. Can you enlighten me more on this as it would be good to understand the summary of their thoughts on which profiles increase risk compared to reducing risk.

It's a discussion fraught with heart felt opinions on both sides, and not worth getting flamed over on SB. I would suggest you and your buddy read up on the available information and make an informed decision on which makes sense to you and go with that.

- Yes have been reading up on deeper stops, and I feel I prefer doing 1 min 1/2 bottom depth stops until at first deco stop. However this is based on gut feel and not based on science, and I am also sure some will have opposing thoughts. Still feeling my way on this issue, hence the post and a hope people more experienced can shed light on my thoughts and offer good suggestions. Not looking to create controversy or stir the pot, just want some good advice, perhaps based on science or on years of diving, or good solid logic.