Deep6 Excursion - Repetitive Dives, Surface Intervals, Residual Nitrogen and Dive Planning

[scubadada]

Shearwaters are the exception to the difficult user interface rule. Have you used one of the typical 4 button watch style computers? Stupid complicated. Why do I need to do short AND long AND combination presses? There are FOUR buttons! One button computers were easier to adjust! Sorry rant over...

Yes, the Teric is a 4 button, watch style computer. It is extremely easy to navigate and program. It has the look forward NDL planner brought up by @SpecialTest

I still have my Oceanic Geo 2, my son uses it for backup now. I always found it simple to use, don't know why some folks found it difficult. No short and long or combination button presses

 

[dmaziuk]

I was actually looking for something closer to @sea_ledford said, and @scubadada described.

You won't normally find that function on a lower-end computer, they only tell you about now. You can easily guesstimate it with tables after the first dive or two, but it gets tedious after that and the differences between decompression models mean your guesstimate will never match your computer.

In practice you probably don't want SIs of less than an hour if you're going for more than 2 dives/day and multiple days.

 

[Belzelbub]

I still have my Oceanic Geo 2, my son uses it for backup now. I always found it simple to use, don't know why some folks found it difficult. No short and long or combination button presses

Same here. Mostly. My VT4.1 is still in use with my oldest daughter. Younger daughter dives with a Veo 2. The VT is 3 button, the Veo is 2. Menus are pretty easy to navigate. The extra button on the VT adds the ability to go back up in the menu, but both are pretty easy to use. There is one long button hold action, but it’s consistent so not really confusing. Holding the select button will bring you out of the sub menu.

Shearwater is way easier, though.

 

[scubadada]

You won't normally find that function on a lower-end computer, they only tell you about now. You can easily guesstimate it with tables after the first dive or two, but it gets tedious after that and the differences between decompression models mean your guesstimate will never match your computer.

In practice you probably don't want SIs of less than an hour if you're going for more than 2 dives/day and multiple days.

There are many places where the SI will be less than an hour. It is good to be able to plan. There may be a significant difference between half an hour and 45 min

 

[tursiops]

There are many places where the SI will be less than an hour. It is good to be able to plan. There may be a significant difference between half an hour and 45 min

It is probably more than the OP wanted to know, but the NDL is set by an interplay between depth, time, and the m-value of each of the compartments in the decompression model. Whichever compartment reaches its m-value first controls the dive. The fast compartments (short on/off-gassing times, i.e. short half-times) fill up quickly, but only control the dive for deep dives, because they have large m-values so don't reach their max unless the ambient pressure is high. Conversely, at lesser depths, the controlling compartments are those with longer half-times; shallow dives ae controlled by slow compartments, so you get long dives. What the Planner in the Excursion does (as in other computers) is model all the compartments and their saturation status. the longer the surface interval, the more of-gassing from the compartments. But the fast compartments -- those that control the deeper dives -- off-gas quickly, so a SI of 45 mins or 60 or 90 mins is the same to them...they are already off-gassed. The longer SI allows the slower compartments to off-gas, which gives you time back at the shallower and intermediate depths. Since the range of half-times for the typical suite of compartments in a Buhlmann model (like in the Excursion) goes from 4 mins to 635 mins (ZHL-16), a SI of 30-45-60-90 mins is just that range tht begins emptying out those compartments that began to fill during a dive of duration....wait for it.....30-45-60-90 minutes. So, the preferred SI is at least the length of the preceding dive; less SI that that you'll see the NDL significantly shorter, longer SI than that will only help the NDL a little bit. Thus endeth the epistle.

 

[KenGordon]

So Plan Mode's displayed NDL is affected by any residual gasses? If so, that basically solves what I want, but displays it in a different way... so it'll work fine.

Yes. That is why I said upthread the method of comparing bottom time available (with residual nitrogen loading) vs. dive time desired is what most all do with repetitive dives.

I think what the OP was looking for was just the normal Plan function, but he didn't know what it did.

What the Planner in the Excursion does (as in other computers) is model all the compartments and their saturation status. the longer the surface interval, the more of-gassing from the compartments.

I know anything else would be mad, but has anyone checked that this IS the ACTUAL behaviour of this particular computer?

This is the computer that shows a negative NDL when it gets into deco, so all bets are off in my opinion. Tell me if they have improved that.

 

[lowwall]

I've got one and it does the normal run through of depths and times during an SI.

They really do need to add this to their manual though. BTW, the manual is still at "V 1.0 (Beta)" and is desperately in need of an update. It appears to be nothing more than the original Crest CR4 manual with Deep6 info pasted onto the ends. As well as being incomplete, it was clearly written by someone who did not have English as their primary language.

The display in deco is unusual. But it's not hard to understand once you are aware of it. And it is covered in the manual.

This does mean that this is not an acceptable computer for someone who plans on going into deco. But for most divers, who are only trained to respond to exceeding NDL by ascending as soon as possible, it is appropriate.

 

[kelemvor]

There are computers that give you desaturation time, separate from no fly. My Oceanic computers are an example. This is completely unrelated to planning repetitive dives. Just use the planning function and it will give you NDL time on your current mix at whatever depth you anticipate.

The Shearwater computers give you the tissue loading graph, this will give you an idea of desaturation.

Scubapro computers also give this. Here's what the galileo screen shows after diving.

 

[scubadada]

I've got one and it does the normal run through of depths and times during an SI.

They really do need to add this to their manual though. BTW, the manual is still at "V 1.0 (Beta)" and is desperately in need of an update. It appears to be nothing more than the original Crest CR4 manual with Deep6 info pasted onto the ends. As well as being incomplete, it was clearly written by someone who did not have English as their primary language.

The display in deco is unusual. But it's not hard to understand once you are aware of it. And it is covered in the manual.

View attachment 649731

This does mean that this is not an acceptable computer for someone who plans on going into deco. But for most divers, who are only trained to respond to exceeding NDL by ascending as soon as possible, it is appropriate.

For me, the biggest problem is that you do not know your stop time until you hit the stop depth. This is a very unusual way to handle deco.

 

[tursiops]

I guess if you accept the fact that it is NOT a deco computer, and only provides the info you need to get you back safely if you should violate NDL, then everything is fine.
After all, that is how it is marketed.