Ratio deco for ccr?
- Thread starter PeterN
- Start date
nickb
The JJ Kid
As long as the actual dive matches the one you did the thinking about.............
hoffi
Member
My mathteacher urged us to use slide rulers instead of calculators for the simplier stuff, I never was really good with math but this helped me to be a bit better with it.
RD has helped me a lot to understand Deco better,
it helped to see thru the foggy zone a bit better,
it lead me to reduce the "Vodoo"-feeling,
it helped me to accept, me or my computer can get it wrong any day.
Its just reiterating patterns, checked against the very same math.
People who start with it write it down, do some very simple calcs, done in much less than a minute for a regular dive.
Very difficult to talk about it online as its so loaded, I also think the threads I've seen on the boards so far went the wrong way IMHO,
there's a lot of misunderstandings around it because it was partly abused in insenitive ways for promotion.
Indeed, people being new to it and bragging about using RD quite often make it look like vodoo, enhanceing the corridor of misunderstanding.
On a learning curve,
early use of livedeco-computers may restrict the necessary mental approach to deco.
Once one has found a good level of confidence it becomes very obvious, Deco by far is not so important to diving as it seems.
HTH,
hoffi
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'A closed mind gathers no knowledge'.
I use ancient cochranes as d-timers. My pocket has a set of pre-cut backup range tables, my brain has my own take on ratio deco (funnily enough, its based on the pre-cut range tables)
For significant dives I'll run a desktop schedule to double check stuff.
I use ancient cochranes as d-timers. My pocket has a set of pre-cut backup range tables, my brain has my own take on ratio deco (funnily enough, its based on the pre-cut range tables)
For significant dives I'll run a desktop schedule to double check stuff.
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lizardland
Active Member
It's a very good point and one of the reasons I've always shyed away from computers. Satnav makes a good parallel: a unit will take you where you want to go but you never learn how you got there. Sometimes it isn't important, sometimes it is.
With time you kind of build up a feeling for what kind of deco plan you would expect for any particular dive. Ratio deco is simply a means of fitting a few rules or patterns to it to make it a. a bit more predictable and b. a bit easier to quantify ("I just guessed" doesn't make for a reassuring dive plan). Rules of thumb exist everywhere, they are never as accurate as a calculation but most of the time they are good enough for what they are used for.
Sent from my GT-I9100 using Tapatalk 2
Chris Brown
Official CAMRA ale tester
I think you can learn from both computers and RD and tables and computer generated profiles.
They are all just tools to help you, available to you to use as you wish.
GF99 and the new tissue graph on the Petrel tells you a TON about deco and where you are at any given point on the gradient. Fantastic stuff.
RD shows you the relationship between bottom time and deco and is useful for 'on the fly' plus the regular routine repetitive stuff. E.g. for me personally, I do so many dives on the Spiegel each week (yawn) I know my deco obligation on a 1.3 set point or with 30% nitrox and 50% on OC from any depth anywhere on that wreck from 140' to the surface. There must be divers on this forum in a similar situation where they dive similar depths and profiles regularly where a computer just tells them what they expected.
As for RD being a 'fudge' or voodoo, how many of us have changed the GF on the computer to cut deco, or blown some of it off, or lied to it and told it you were not breathing any helium? I know I have, so thats a fudge too, isnt it?
They are all just tools to help you, available to you to use as you wish.
GF99 and the new tissue graph on the Petrel tells you a TON about deco and where you are at any given point on the gradient. Fantastic stuff.
RD shows you the relationship between bottom time and deco and is useful for 'on the fly' plus the regular routine repetitive stuff. E.g. for me personally, I do so many dives on the Spiegel each week (yawn) I know my deco obligation on a 1.3 set point or with 30% nitrox and 50% on OC from any depth anywhere on that wreck from 140' to the surface. There must be divers on this forum in a similar situation where they dive similar depths and profiles regularly where a computer just tells them what they expected.
As for RD being a 'fudge' or voodoo, how many of us have changed the GF on the computer to cut deco, or blown some of it off, or lied to it and told it you were not breathing any helium? I know I have, so thats a fudge too, isnt it?
PeterN
Active Member
No one has taken the time to address my question about ratio deco for fixed PO2 vs. fixed FO2.
No one can be arsed to explain how to use ratio deco in a complicated, long, up and down cave. For me, this would be for the unknown, planning for exploration.
I am not looking for a r/d leason, this info for OC is readily available. I was just hoping for some sort of a framework for a fixed PO2 model for ratio deco.
I am beggining to think that there is no such defensable model.
Peter
No one can be arsed to explain how to use ratio deco in a complicated, long, up and down cave. For me, this would be for the unknown, planning for exploration.
I am not looking for a r/d leason, this info for OC is readily available. I was just hoping for some sort of a framework for a fixed PO2 model for ratio deco.
I am beggining to think that there is no such defensable model.
Peter
nickb
The JJ Kid
Why don't you run some numbers through a deco planner and see what it comes up with?
As I understand it the 'gold standard' model of ratio deco is framed around a set of standard back & deco gases and it maps pretty well to a fixed setpoint of 1.3 for most of the dives that I do; i.e. between 40m and 75m with runtimes up to 2.5 hours.
The numbers are pretty close.
Monkey
Member
If someone feels I was attacking a person, I apologize. That was not my intent.
But I reserve the right to attack what I feel is an egregious concept that I feel is driven by the Social pressure that makes up the DIR Ethos. Especially one that I feel has a high probability of Death or at the very least a chamber ride.
I can also bank on the fact that I am not flying solo on this conclusion.
Every argument can be supported by an ideal situation. I don't give a rats ass how something performs in an ideal situation. I only care about how it performs in a life and death situation.
This goes for people as well as equipment.
As a group, 99.97% of our diving goes off without a problem (unless you dive an Optima then its more like 4% Kwinter) what matters is how something performs during the that 0.03%
There are a miriad of superior solutions to Ratio Deco for the 0.03%
I implore you to make a case for diving a decompression dive with NO COMPUTER, or back up tables, when both are readily and cheaply available.
The brain witch is what Ratio Deco is 100% dependant on is the most Complex, Flawed, Misunderstood, and unpredicable "computer" ever created.
But I reserve the right to attack what I feel is an egregious concept that I feel is driven by the Social pressure that makes up the DIR Ethos. Especially one that I feel has a high probability of Death or at the very least a chamber ride.
I can also bank on the fact that I am not flying solo on this conclusion.
Every argument can be supported by an ideal situation. I don't give a rats ass how something performs in an ideal situation. I only care about how it performs in a life and death situation.
This goes for people as well as equipment.
As a group, 99.97% of our diving goes off without a problem (unless you dive an Optima then its more like 4% Kwinter) what matters is how something performs during the that 0.03%
There are a miriad of superior solutions to Ratio Deco for the 0.03%
I implore you to make a case for diving a decompression dive with NO COMPUTER, or back up tables, when both are readily and cheaply available.
The brain witch is what Ratio Deco is 100% dependant on is the most Complex, Flawed, Misunderstood, and unpredicable "computer" ever created.
nickb
The JJ Kid
Clearly there aren't a high proportion of trained ratio deco users that are dying or taking chamber rides.
I think the problem lies with people picking-up bits of information from somewhere such as an internet forum, stitching those bits of information together and tucking them away in the back of their brains just in case the shit hits the fan.
Those using ratio deco as their part of their everyday plan, develop an intimate feel for it so that when the shit does happen, it is business as usual.
Those having it in reserve, just in case, will in all likelihood not fare quite so well and may well end-up overpadding (if the opportunity exists), again just in case.
Me, I dive with a backup computer with a fixed setpoint and if that went wrong at the same time as my controller, I'd rely on my buddy's.
If his or hers crapped-out at the same time........
Monkey
Member
I know specifically 2 instances where 1 person messed up the math and dropped back to using tables. The second instance ended in a chamber ride. the response I got was.... "well I thought I did it correctly"
and these were "routine" dives.
however that being said I know significantly more people who have ended up in the chamber using computers.
Neither are perfect. Ratio deco is off the reservation.
Mr Walker
Relax /Frankie
I totally agree, a person who by deliberate choice chooses to trust his brain to save his ass in a complex and stressfull situation runs a highly increased risk of finding himself being out of ass.
In such situations a computer (proper) continues to run unaffected of the goings on. But still, just to be safe and since computers also can fail (although rarely)we take a backup computer.
So, the question is, if you decide to trust your brain for on the fly deco calculations, how do you go about to bring a backup brain with you? :boggle:
/nils
GLOC
real name: Gareth Lock!
Which brings us right back to the point of 'Team Diving', your back up brain is your one or two other team members who are there with you and monitoring what you are doing...and helping you out when you have that poo whirly-gig interface moment...
Regards
Mr Walker
Relax /Frankie
With computers the general concensus is that each diver brings his own and a backup since no two divers will have the same profile and therefore can't fully trust each others computer.
My question stands.
/nils
GLOC
real name: Gareth Lock!
If you are diving in a team, your profile will be close enough not to make a difference if you are using the same: gases, set points, descent times, bottom times and ascent times/profiles as Mattp outlined in his team diving post. If you aren't doing these, then you aren't diving in a robust enough manner to use Ration Deco as a team, so you are solo Ratio Deco and then I can see your issues because when it goes wrong, then you are going to be task loaded. However, the profiles are created to make them easier to remember (and on the conservative side if need be).
I have only used RD in an OC context (I am not a CCR diver) but the principles will apply.
Regards
Monkey
Member
Where are they when your ass gets pulled off a wreck or line in a 2 knot current and your drift deco by your self OFF SHORE? OR Where are you dealing with the
ratio deco when you're dealing with your Team members crisis??? A team members Cardiac Event??
OR LOST IN CAVE???
Mr Walker
Relax /Frankie
I understand what you are saying. But, in a stuation, for me I'd feel more confident relying on my buddys or teams computer rather than any of their brains. I don't even trust my own brain. It has already had me fooled so many times I can't remember.
In fact one of the starting points when I was teaching navigation at the Royal Swedish Navy Academy was to let the cadets by themselves experience how easy they were fooled in to see what they wanted to see rather than what was actually there.
My friend who is a commercial pilot says that in lo vis and when there is a difference between what the instruments says and what he thinks he knows - trust the instruments.
Fibonacci is all good and fine, but my computer is way finer
/nils
GLOC
real name: Gareth Lock!
Which is why I linearise my stops...then it is really simple...Fibonacci is all good and fine, but my computer is way finer
/nils
I have a military aviation background and totally get the transition to instruments early (too many Controlled Flight Into Terrain - CFIT where they didn't) but I think it is a poor analogy because when you are IMC, you have no option other than to trust your instruments. In diving and ratio deco, you are still using your instruments to gauge time and depth, so you aren't flying blind (for want of a better term).
As has already been pointed out, you wouldn't jump in on a massive dive without having a good idea of the ratio deco schedule for your team, so it isn't as if you are going in blind.
As has already been said too, it isn't for everyone and there are a variety of reasons for not using it, but to say that it is a very bad thing without truly understanding it, is as bad as saying that all computers are shit and you shouldn't use them knowing that they aren't reliable (at safety of life levels of reliability)
Regards