Cutting tables

[scottsax]

I've heard this expression many times, and I get the gist of it, but what are you actually doing when you cut tables? I'm assuming this means you're planning your profile, creating a custom deco schedule, and then printing that schedule and literally cutting it out to strap to your wrist? What software do you use?

Do you do this for recreational dives, too? (Again, I assume so, since you're probably diving with a bottom timer as opposed to a computer.)

Thanks!

[Sounder]

It's kind of like cutting the cheese, but less entertaining.

[Pez7378]

It's kind of like cutting the cheese, but less entertaining.

This is the "Technical" forum Sounder. Responses like that belong in the recreational forum!

[vbcoachchris]

For me I do not “cut” table for recreational dives. I just dive 32% all the time recreationally. So I have those tables memorized and just stay on the conservative side of it.

30 min at 100 feet
35 min 90 ft
50 min 80 ft
60 min 70 ft
All day (not really but you know what I mean) at 60 ft

I start doing 1 min stops at about 50% of my max depth and continue those to 20 ft. It then takes me 3-6 min to surface from 20 ft.

If I do a repetitive dive I usually do at least a 90 min SIT and you will see the bottom times are about the same limits for the second dive. You can double you 30 ft and 20 ft stops to stay conservative.

Scott

[CaptnJack]

For deco dives, "cutting tables" generally refers to using software and (typically some deep stop rules of thumb) to generate tables for planned depth, planned +10ft, planned minus 10ft, planned time, planned time plus 5mins, planned time minus 5mins, and some sort of "oh shit this is just mud let's leave after 3 mins" kinda profile. Maybe more contingencies/scenarios depending on the dive (including lost deco gas).

[Sounder]

It's kind of like cutting the cheese, but less entertaining.

This is the "Technical" forum Sounder. Responses like that belong in the recreational forum!

"Off-gassing." SORRY PEZ!!

[boydski]

Pretty much what Richard said.

In my case, the software would be V-Planner. You put in the depth, time, gases, ascent and descent rates, and it prints out a "table" for your dive. Oddly enough, I actually cut out the table and tape it to my wrist slate. A 200' dive would look something like (the numbers in the parentheis are run times):

DIVE PLAN

Dec to 200ft (4) Trimix 19/44 50ft/min descent.
Level 200ft 16:00 (20) Trimix 19/44 1.34 ppO2, 76ft ead, 97ft end
Asc to 120ft (22) Trimix 19/44 -30ft/min ascent.
Stop at 120ft 0:20 (23) Trimix 19/44 0.88 ppO2, 39ft ead, 53ft end
Stop at 110ft 1:00 (24) Trimix 19/44 0.82 ppO2, 34ft ead, 47ft end
Stop at 100ft 1:00 (25) Trimix 19/44 0.76 ppO2, 29ft ead, 41ft end
Stop at 80ft 2:00 (28) Trimix 19/44 0.65 ppO2, 20ft ead, 30ft end
Stop at 70ft 2:00 (30) Nitrox 50 1.56 ppO2, 32ft ead
Stop at 60ft 2:00 (32) Nitrox 50 1.41 ppO2, 26ft ead
Stop at 50ft 2:00 (34) Nitrox 50 1.26 ppO2, 20ft ead
Stop at 40ft 3:00 (37) Nitrox 50 1.10 ppO2, 13ft ead
Stop at 30ft 5:00 (42) Nitrox 50 0.95 ppO2, 7ft ead
Stop at 20ft 16:00 (58) Oxygen 1.60 ppO2, 0ft ead
Surface (60) Oxygen -10ft/min ascent.

Off gassing starts at 145.9ft

OTU's this dive: 84
CNS Total: 54.5%

115.7 cu ft Trimix 19/44
19.4 cu ft Nitrox 50
16.0 cu ft Oxygen
151.1 cu ft TOTAL

[spatman]

could you clarify what these mean, for us technical diving ignorami?

76ft ead, 97ft end
OTU's this dive: 84
CNS Total: 54.5%

and are these the various bottles and their contents you dive with?

115.7 cu ft Trimix 19/44
19.4 cu ft Nitrox 50
16.0 cu ft Oxygen

[Joshua Smith]

could you clarify what these mean, for us technical diving ignorami?

76ft ead, 97ft end
OTU's this dive: 84
CNS Total: 54.5%

ead= equivilant air depth
end= equivilant narcotic depth, ie how narced you are going to feel- this dive would "feel" like a 76 foot air dive....at 200 feet.

and are these the various bottles and their contents you dive with?

115.7 cu ft Trimix 19/44
19.4 cu ft Nitrox 50
16.0 cu ft Oxygen

Close- that's the estimated volume of each gas used for this profile. I would do this dive with 2 40 cf stages.

[boydski]

Close- that's the estimated volume of each gas used for this profile. I would do this dive with 2 40 cf stages.

OK, rub it in!

In reality, it wouldn't take that much gas even for a bubble blower, but we have to plan for the worst case, so use very high SAC rates for planning.

CNS is central nervous system clock
OTU is Oxygen Toxisity Units

both are related to how much oxygen you are breathing for how long at what partial pressure. Too much makes you do the "hurky jerky"... Not good.

[spatman]

thanks guys. that chart makes a lot more sense now.

[Sounder]

Too much makes you do the "hurky jerky"... Not good.

"Kickin' Chickin'?"

[Pez7378]

Sounder's been spending way too much time with the Junior! Come hang out with us grownups!

Thanks for that very detailed explanation Scott. Both Scott's actually, fine examples of both a recreational dive, and a technical dive. Is everyone pretty much using V-Planner? Why does that seem to be the program of choice? Is it expensive?

[vbcoachchris]

You can get free copies of VPM, but V planner is only $85 and you can do a lot of cool things with it.

Scott

[Joshua Smith]

Close- that's the estimated volume of each gas used for this profile. I would do this dive with 2 40 cf stages.

OK, rub it in!

In reality, it wouldn't take that much gas even for a bubble blower, but we have to plan for the worst case, so use very high SAC rates for planning.

CNS is central nervous system clock
OTU is Oxygen Toxisity Units

both are related to how much oxygen you are breathing for how long at what partial pressure. Too much makes you do the "hurky jerky"... Not good.

Ooops- I didn't mean it that way! Would you sling an 80 and a 40 for this dive? I meant independent of whether I had a CCR or doubles on my back......Are you supposed to calculate 1/3rds for OC deco gas? 1/2s? On a CCR, I try and shoot for taking twice as much OC deco gas as I need, until the really deep stuff- that's where we start coming up with team bailout strategies.

[boydski]

Would you sling an 80 and a 40 for this dive? I meant independent of whether I had a CCR or doubles on my back......Are you supposed to calculate 1/3rds for OC deco gas? 1/2s? On a CCR, I try and shoot for taking twice as much OC deco gas as I need, until the really deep stuff- that's where we start coming up with team bailout strategies.

You "should" carry an 80 of 50% and a 30 or 40 of Oxygen based on the lost gas calculation for the dive I posted above. That is simply based on needing 43 cubic feet of Nitrox if you loose your Oxygen. There are several different schools of thought on how much deco gas to carry and how to handle a failure. In my case, since this scenario was based on an absurdly high SAC rate, and I know that if I loose my Oxygen I'll really still use less than 30 cubic feet of Nitrox, I'd probably just haul along a 40.

Other options would include using your buddies Nitrox once he switches to Oxygen, his oxygen once he's done, or even getting an extra cylinder from the boat. All are better than the long, cold deco on back gas! BRRRRR!

Gases Used Calculations:

No failures - normal dive
115.7 cu ft Trimix 19/44
19.4 cu ft Nitrox 50
16.0 cu ft Oxygen


Lost or missing deco gas: 100
118.0 cu ft Trimix 19/44
43.1 cu ft Nitrox 50


Lost or missing deco gas: 50
161.1 cu ft Trimix 19/44
20.8 cu ft Oxygen

[Burntchef]

one thing i love about v-planner is that you can set your sac rate and leave it high on purpose. i like knowing that its padded as well if it says i need 111cf of back gas ad 25cf of deco i am well ahead of the curve.

you can download v-planner for free for 30 days i think but it wont let you go above 25% he and 50%o2 i think. after that its a very cheap investment.

since we are on a tables discussion how do people here write theres or rather pad it if you do?? i know i lie to v-planner across the board and tell it +10 to depth, +1 min to b/t then add minutes to my stops until my 20.

[boydski]

since we are on a tables discussion how do people here write theres or rather pad it if you do?? i know i lie to v-planner across the board and tell it +10 to depth, +1 min to b/t then add minutes to my stops until my 20.

That's a good question, and I'm also curious to hear what others do. I use +3 conservatism, and tend to "arrive late" and "leave early". For example, if I'm divining with someone that is running a VR3, I know they'll have to do a 2 minute deep stop, so we leave tthe bottom 2 minutes early, go up and wait at the first deep stop for the run times to catch up, and then follow the table (this keeps the VR3's happy).

Very conservative, but no niggles.

[Tom Nic]

Really enjoying this thread!

[Burntchef]

might of thrown a bit of confusion scott, i meant i add 10 feet to my target depth so if i am planning a max of 150 i program 160, then add a minute longer to my b/t so if i do a 20-22-24-26 minute spread i program a 21-23-25-27 minute program. and when ever the last person clears we all surface.

[Joshua Smith]

since we are on a tables discussion how do people here write theres or rather pad it if you do?? i know i lie to v-planner across the board and tell it +10 to depth, +1 min to b/t then add minutes to my stops until my 20.

That's a good question, and I'm also curious to hear what others do. I use +3 conservatism, and tend to "arrive late" and "leave early". For example, if I'm divining with someone that is running a VR3, I know they'll have to do a 2 minute deep stop, so we leave tthe bottom 2 minutes early, go up and wait at the first deep stop for the run times to catch up, and then follow the table (this keeps the VR3's happy).

Very conservative, but no niggles.

Good discussion so far! Yes, I add depth and b/t to any plans I dive- I like knowing that I'm comfortably inside some kind of safety margin, even if it's theoretical. I'm currently using vplanner with the +3 conservatism as well. I usually cut a table for my estimated max depth/ time, and then cut another for ten feet deeper/ five minutes longer, then another one for bailout to OC. Then, I compare it with whoever I'm diving with. We use the most conservative plan as default.

[vbcoachchris]

since we are on a tables discussion how do people here write theres or rather pad it if you do?? i know i lie to v-planner across the board and tell it +10 to depth, +1 min to b/t then add minutes to my stops until my 20.

That's a good question, and I'm also curious to hear what others do. I use +3 conservatism, and tend to "arrive late" and "leave early". For example, if I'm divining with someone that is running a VR3, I know they'll have to do a 2 minute deep stop, so we leave tthe bottom 2 minutes early, go up and wait at the first deep stop for the run times to catch up, and then follow the table (this keeps the VR3's happy).

Very conservative, but no niggles.

Good discussion so far! Yes, I add depth and b/t to any plans I dive- I like knowing that I'm comfortably inside some kind of safety margin, even if it's theoretical. I'm currently using vplanner with the +3 conservatism as well. I usually cut a table for my estimated max depth/ time, and then cut another for ten feet deeper/ five minutes longer, then another one for bailout to OC. Then, I compare it with whoever I'm diving with. We use the most conservative plan as default.

I do not wish to start o decompression holy war, but I have a few questions for those of you that use this method. This was one of several decompression procedures I learned as well. It seems as though many of you are using V planner as you sole bases for decompression. V planner uses VPM B and it allows you to manipulate the program as you see fit.

Ross Hemmingway the developer of V planner is publicly very adamant about NOT adding random minutes and stops to his software. I just did several dive plans using the 10 ft deeper and 1 min longer method on a +3 conservatism and then just used the normal VPM +5 conservatism. The all profiles were within 1 min of matching.

For example here is the 19/44 profile we have been discussing on a +3 (10 ft deeper and 1 min longer) conservatism and +5 for the normal depth and time.

+3(10ft deeper/1 min longer) / +5
Stop at 130 00:00:20 / :40
Stop at 120 00:01:00 / 1:00
Stop at 110 00:01:00 / 1:00
Stop at 100 00:01:00 / 1:00
Stop at 90 00:02:00 / 1:00
Stop at 80 00:02:00 / 3:00
Stop at 70 00:02:00 / 2:00
Stop at 60 00:02:00 / 1:00
Stop at 50 00:02:00 / 3:00
Stop at 40 00:04:00 / 4:00
Stop at 30 00:05:00 / 5:00
Stop at 20 00:19:00 / 20:00

Ross is a pretty smart guy; much smarter than I for sure. My question is if you are going to do a decompression profile based on just one program, why do we add our “own” additional conservatism when the genus we are getting our profile from has already given us a method to add additional conservatism.

I could see doing this method if you are already doing a +5 and you wanted even more.

I personally try to use what I consider to be the best of all theories to come up with a conservative decompression that is flexible for the unknown conditions we may encounter underwater. What this entails is trying to understand what we believe to be happing to our bodies as we ascend and descend underwater. I compare different profiles for several depths and times and try to look for patterns or similarities in profiles just in case I need to alter my decompression due to unforeseen circumstances.

Every dive I do has a profile that is compared to VPM, Bühlmann and now even RGBM.
I am for sure not saying my method is correct, but I am very curious “why” you do what you do.
As a tech instructor I stress to my students they should always know WHY they are doing what they are doing. Listening to why some people do thing one way and why others do it another is very interesting to me.

Scott

[Joshua Smith]

Well, I add a longer/ deeper profile to my plan in case a go deeper or overstay my bottom time. Seems pretty obvious.

I'll be the first one to admit I don't know a hell of a lot about decompression theory.......but these v-planner tables have been working for me so far.

I read something once....I think it was actually in a PADI text....The Encyclopedia of Recreational Diving, perhaps? It said, in effect:

If you ask an average non-diver what causes DCS, they'll probably shrug, and say "I don't know."

Ask an open water diver the same question, and they'll tell you that ascending too fast or overstaying the No Deco limits can cause disolved nitrogen in the bloodstream to come out of solution , creating gas bubbles in the diver's body, and so forth.

Ask someone who has spent a great deal of time studying and reading about DCS, and you're going to hear a lot of stuff about micro bubbles, cavitation, oxygen windows, tissue compartments, algorhythms, etc.

Ask one of the top scientists studying DCS, and they might shrug and say "I don't know."


The last one might not be entirely true, but it illustrates a point: It's decompression theory. I dive profiles that have either worked for me in the past, or worked for someone I trust in the past. This method seems more practical than theoretical to me. And we can still get bent. Perhaps the Zinc levels in my body are lower than normal before a dive, or some other arcane facet of my physiology is out of kilter, totally unknown to me......something as odd and beyond my control as that could land me in a chamber one of these days.

Decompression is a fascinating topic, but at a certain level of abstraction, it starts to look like witchcraft to me, just like quantum mechanics.

[vbcoachchris]

Well, I add a longer/ deeper profile to my plan in case a go deeper or overstay my bottom time. Seems pretty obvious.

No it is actually not obvious to me at all.

I guess I might have misunderstood the original idea of 10 ft deeper and a min longer. I was under the impression that this procedures was done to EVERY profile; including contingency plans for ADDED conservatism.

i.e. You have a plan for going to 200 for 20 min, but you plan for 210 and 21 min.

If you happen to go to 210 for 21 do you have a contingency table for 220 for 22 or do you just use the original plan?

I guess what I am looking for here is some clarification.

Do you do the addition decompression on EVERY dive for added conservatism or as a contingency just in case you go deeper or longer?

I have always thought of conservatism and contingency as two separate topics, so I would have a means in place just in case I went deeper, longer or both, but that would not impact my conservatism.

I am not trying to be difficult. I am truly trying to understand why you do what you do?

I'll be the first one to admit I don't know a hell of a lot about decompression theory.......but these v-planner tables have been working for me so far.

I read something once....I think it was actually in a PADI text....The Encyclopedia of Recreational Diving, perhaps? It said, in effect:

If you ask an average non-diver what causes DCS, they'll probably shrug, and say "I don't know."

Ask an open water diver the same question, and they'll tell you that ascending too fast or overstaying the No Deco limits can cause disolved nitrogen in the bloodstream to come out of solution , creating gas bubbles in the diver's body, and so forth.

Ask someone who has spent a great deal of time studying and reading about DCS, and you're going to hear a lot of stuff about micro bubbles, cavitation, oxygen windows, tissue compartments, algorhythms, etc.

Ask one of the top scientists studying DCS, and they might shrug and say "I don't know."


The last one might not be entirely true, but it illustrates a point: It's decompression theory. I dive profiles that have either worked for me in the past, or worked for someone I trust in the past. This method seems more practical than theoretical to me. And we can still get bent. Perhaps the Zinc levels in my body are lower than normal before a dive, or some other arcane facet of my physiology is out of kilter, totally unknown to me......something as odd and beyond my control as that could land me in a chamber one of these days.

I actually use this quote to open my decompression workshop. It is so true

Decompression is a fascinating topic, but at a certain level of abstraction, it starts to look like witchcraft to me, just like quantum mechanics.

Am I mistaken or did you make a case for ratio deco?


Scott

[Pez7378]

I knew I had heard that somewhere before.

I read something once....I think it was actually in a PADI text....The Encyclopedia of Recreational Diving, perhaps? It said, in effect:

If you ask an average non-diver what causes DCS, they'll probably shrug, and say "I don't know."

Ask an open water diver the same question, and they'll tell you that ascending too fast or overstaying the No Deco limits can cause disolved nitrogen in the bloodstream to come out of solution , creating gas bubbles in the diver's body, and so forth.

Ask someone who has spent a great deal of time studying and reading about DCS, and you're going to hear a lot of stuff about micro bubbles, cavitation, oxygen windows, tissue compartments, algorhythms, etc.

Ask one of the top scientists studying DCS, and they might shrug and say "I don't know."

I actually use this quote to open my decompression workshop. It is so true.

Am I mistaken of did you make a case for ratio deco?