Deco with too less air, options from the book

[MXGratefulDiver]

Just curious but why do you care if anyone understands/misunderstands or has never heard of RD?

Because when people misunderstand it and get hurt, it often gets blamed on the method, rather than the misuse of the method. The post subsequent to yours is an excellent example of someone who is using RD for dives it was never intended to accommodate, and making decisions based on erroneous assumptions about what RD is all about. As a result he got bent.

... Bob (Grateful Diver)

 

[orange_diver]

Well first if you are doing deep trimix dives and your sac goes to 1cf in a stressed situation you need to rethink doing these dives. Next you had better use 130's for deco gas.

i missed this. i didn't say my sac goes to 1cf but we plan for it so we have the gas when we need it. better safe than sorry.

have you tested your sac scientifically in numerous, different, truly stressful, anxious situations? what did you find it is? then did you do that for every single buddy you dive with? what are theirs?

also, who uses 130s for deco gas??

your admonishments of "you need to rethink" and "you had better" would be more warmly received if it sounded like you knew what you were talking about.

 

[Blackwood]

1. Is ratio deco used as a planning tool, or is it always used at the end of the dive to calculate/verify the deco obligation?

Like anything else, that's user dependent. Some people use software and then back that up with ratio to tweak profiles in water. We (meaning the people with whom I trained and have been diving) use it to plan dives as well as to tweak profiles in water.

surely it must be easier to have a computer track this than try to continually monitor and keep all that information on your slate or in your head, even if you ignore the algorith/calculation that your computer gives you?

Again, I guess that's user dependent. And don't call me Shirley!

If the basis of the ratio deco is that you have a set point to start from, and calculate your total deco obligation by working out from the set point, wouldn't it be sensible to break this down into table form?

Sensible, maybe. But it defeats the purpose. Ratio is powerful because it's not limited to some numbers printed on a table. As soon as you do that, you are no longer using a dynamic, on the fly system. You are using printed table.

Now, do I always sit there and do the math? No. If it's a common profile (like 150 for 30), I can spit out the deco without thinking about it. But on that dive, if we find ourselves at 160 instead, I can adjust the deco without pulling something out of my pocket.

Doing the maths (as I understand it) and comparing again deco planning software, ratio deco seems to give you relatively somewhat longer decompression profiles...?

I find that for shallow decompression dives, Vplanner, etc. are much more conservative than "MDL"/Ratio. For deeper dives, it's very close.

 

[Rainer]

I find that for shallow decompression dives, Vplanner, etc. are much more conservative than "MDL"/Ratio. For deeper dives, it's very close.

How shallow? For 100-120' dives, I wouldn't use RD (at least not modifying the 150' set point). It'd be much too aggressive for me. We were taught other means for calculating deco for these much shallower dives.

 

[Blackwood]

Ok the dive is real but I would not use the gases or the amounts I listed. The point was to see if this RD can tell me if have the gas to extend my BT or not. Some posters claimed that RD enabled them to extend a dive or depth if they wanted. What good is that if it cannot tell you if you have the gas to do it or not?

Does any in-water decompression computer tell you whether you have enough gas to extend a dive?

Seems to me that if you had a wireless pressure gauge on your back gas, stage bottles and each of your deco bottles (AND those of your buddies if you like to maintain adequate gas for two in case of emergency), all connected to a dive computer into which you could somehow ask the question "can I stay an extra 20 minutes" then the answer is yes.

But I find that scenario unlikely.

Rather, I assume that, like Ratio Deco, whatever method you use to compute deco obligation, you also have to account for what gases you have.

 

[Blackwood]

How shallow? For 100-120' dives, I wouldn't use RD (at least not modifying the 150' set point). It'd be much too aggressive for me. We were taught other means for calculating deco for these much shallower dives.

That's what I was calling "MDL"/Ratio (i.e. a 1:1 ratio on time spent over MDL with a few other considerations).

I wouldn't count down from 150 either, because I wouldn't be on 21/35 with 50%.

 

[Rainer]

That's what I was calling "MDL"/Ratio (i.e. a 1:1 ratio on time spent over MDL with a few other considerations).

I wouldn't count down from 150 either, because I wouldn't be on 21/35 with 50%.

Nor would I.

I assume we probably do these calculations similarly, but let's chat next time we're out.

 

[Blackwood]

Aside from going overboard P) I'm sure we do because I know what you and Ari did last week.

 

[orange_diver]

Aside from going overboard P) I'm sure we do because I know what you and Ari did last week.

hahaha

 

[gcbryan]

Because when people misunderstand it and get hurt, it often gets blamed on the method, rather than the misuse of the method. The post subsequent to yours is an excellent example of someone who is using RD for dives it was never intended to accommodate, and making decisions based on erroneous assumptions about what RD is all about. As a result he got bent.

... Bob (Grateful Diver)

I don't think John Chatterton was going to do any of those things.

If RD wasn't discussed on the internet as in here's how "we" do it people like KR wouldn't get bent or rather he would get bent but couldn't blame it on RD.

Most of this thread is goading people into admitting that they don't understand every detail of RD. However, those not understanding it entirely (except for KR) aren't pretending to use it either. Again, I was just wondering why some are pushing RD so hard. This response to my question. Odd question. The response to someone who doesn't like the math. Weird.

If you go to a party where there is alcohol the host usually isn't pushing it one way or the other. If the host is an alcoholic then it suddenly becomes imperative that everyone have a drink to have a good time because that's how 'we" do it when 'we" have a party.