I finally get it (or, gauges and why they make sense)

[gsk3]

90 min of surface interval is easier said than done... i just looked at my Maui trip dive log and the longest surface interval I had on the boat was about 1:08. that was even stopping to look at a rainbow on the way back from Molikini to Red Hill. I was also the last person in because i had camera so some people had easily 5-10 min shorter SI. I don't think that the boat we were on was unusual with regards to the 1hr SI schedule...

Agreed, but then you just double the shallow stops. Although I will say the strategy always amused me because if you're doing it on the second dive of the day then technically it's probably decompression. Ideally you'd do the doubled stops on the first dive so you could do a normal MDL ascent if you needed to on the second dive, assuming the algorithm is symmetric.

Hasn't been an issue for me yet so I haven't really sat down and run the numbers. When I do maybe I'll make some pretty graphs

 

[Cave Diver]

Ideally you'd do the doubled stops on the first dive so you could do a normal MDL ascent if you needed to on the second dive, assuming the algorithm is symmetric.

I'd guess that's probably a bad assumption.

 

[LiteHedded]

your time is probably better spent hydrating than worrying about exactly how long that SI was. pad the shallow stops and go on about your business IMO

 

[ScubaFeenD]

I have to say that my experience was a bit different from Ari's. After my intro to tech with Malinowski I couldn't wait to drop my computer. I have found that with proper pre-dive planning that I have felt very comfortable using BT, avg depth, and pre plans/rules of 120/130 to execute very safe dives. I did start out more conservatively though, using the rule of 120 when diving 32% to give a bit of extra margin of safety. Now, I am confident enough to not be as concerned about adding that extra margin especially if I am not at the extremes of the MDL limits or depth ranges (ie I would not use the rules for >115').

In fact, I have actually had using the "rules" come in very handy when calculating minimum deco limits. In some cases my dive buddy, still wed to their computer, will indicate that their computer has just locked them out while I KNOW we are well within MDL limits--its happened more than once.

I have noticed that releasing my attachment to my computer has increased my situational awareness greatly (i now check my gauge out of habit every 30-40 seconds at the least), because I KNOW i cant really afford to stop paying attention and shut off my brain--it worked/works for me. Further, I have been getting a great deal of practice and improving my on-the-fly calculations, which I am not sure I would have if I was leaning on my computer as a crutch. I do carry a backup though, just in case

Note: this is all for two-three tank dives a day. If i were to do more diving or more extreme dives (repetitive deeper dives) I would probably want a BT/Depth gauge AND computer to help monitor my N2 loading. ALSO, Im NOT saying that slowly becoming more comfortable with not using a computer is bad, I just thought I would try and offer the counter story here too, since I am sure I am not the only one that has felt more comfortable from the beginning--whatever allows you to enjoy the dive safely and without undo stress should be the way you do it, right?

Thanks for posting this story Ari! I look forward to diving with you in your new found comfort zone

 

[ScubaFeenD]

Agreed, but then you just double the shallow stops. Although I will say the strategy always amused me because if you're doing it on the second dive of the day then technically it's probably decompression. Ideally you'd do the doubled stops on the first dive so you could do a normal MDL ascent if you needed to on the second dive, assuming the algorithm is symmetric.

Hasn't been an issue for me yet so I haven't really sat down and run the numbers. When I do maybe I'll make some pretty graphs

I would probably have to argue that doubling or tripling the stops if you have the gas might not be a bad idea anyway. Maybe overkill, but I've def been on training/practice dives where I have probably come out cleaner than when I went in and only started on-gassing N2 when I got to the surface.

 

[Rainer]

I've done up to a week of 4-5 "rec" dives / day using min deco. Doubled the shallow stops (maybe a few extra minutes shallow), but otherwise, no computer. SITs of 60-90 minutes. Was totally fine.

 

[ScubaFeenD]

I've done up to a week of 4-5 "rec" dives / day using min deco. Doubled the shallow stops (maybe a few extra minutes shallow), but otherwise, no computer. SITs of 60-90 minutes. Was totally fine.

Thats actually really useful info for my diving. It gives me a bit more comfort for my future dives, thanks for posting.

 

[flots am]

So far, I've read about at least four different methods of determining decompression requirements, just in this thread alone.

Is there a single, documented, written-down and verified DIR decompression method, or is it pretty much "roll your own"?

flots

 

[ScubaFeenD]

So far, I've read about at least four different methods of determining decompression requirements, just in this thread alone.

Is there a single, documented, written-down and verified DIR decompression method, or is it pretty much "roll your own"?

flots

From what I can ascertain it isn't "roll your own." At least at the fundamentals level tables are taught and used for dive planning. From what I understand dive planning software (ie decoplanner) is used in higher training, and some ratio deco is taught as well. However, I can only say for sure what is covered in fundamentals.

 

[gsk3]

The rule of thumb seems to be a bit hush-hush. In fact, there's some dispute apparently about 90 vs. 120 minute SIs.

Looks like more time sitting down with tables in my near future ;-)