Rock bottom, 500 PSI, or something else?

[scubadada]

I'm so glad I dive solo

 

[boulderjohn]

I don't mean to add to the confusion between the theoretical 10fpm ascent rate for gas calculation purposes and actual ascent rate between stops, but I think I was taught to ascend at 30fpm to the first 30-second stop (at half maximum depth) and take 30 seconds to get from each 30-second stop to the next. That's not 10fpm between successive stops, but it evens out to 10fpm over multiple 30-second stops. That's for recreational dives for which most non-GUE people would say to just do a continuous 30fpm ascent to the safety stop, etc.

...and the purpose is to train people to be able to make such stops, not because it is a better profile for decompression--do I understand that correctly?

 

[PfcAJ]

I don't mean to add to the confusion between the theoretical 10fpm ascent rate for gas calculation purposes and actual ascent rate between stops, but I think I was taught to ascend at 30fpm to the first 30-second stop (at half maximum depth) and take 30 seconds to get from each 30-second stop to the next. That's not 10fpm between successive stops, but it evens out to 10fpm over multiple 30-second stops. That's for recreational dives for which most non-GUE people would say to just do a continuous 30fpm ascent to the safety stop, etc.

30second stop and 30second slide up to the next stop comes out to be 10fpm.

 

[stevensamler]

what's wrong with discussing gas management with all of the instructors on here? Especially since the recreational agencies don't really teach anything about gas management....
anyone know of a recreational course taught by one of the large agencies where calculating your sac rate is actually required?

A little before your time tbone NASDS 1973 before AAS and spg's we used j valves with a 300psi reserve. Depth ,Time ,Sac and be shallow before before your need for the 300 psi reserve. Safe diving.

 

[PfcAJ]

SAC rates and ascent rates are entirely different things. I would think that the best idea would be to select the SAC rate which is most likely to produce a safe result, and an ascent rate which is most likely to produce a safe result. Then put the two together to see what happens. I do see the point in simplification--if someone were to magically determine that 0.83 is the best planning SAC rate, I would not be in favor for that.

I 100% agree. Unfortunately gue isn’t teaching it that way these days. *shrug*

 

[seeker242]

If agency 1 and agency 2 assume different SAC rates for that ascent it might not be all that different.

According to the excel spreadsheet I made a while ago to compare the two, a 100’ dive is a difference of 14 ft3 additional using GUE method vs padi method. Although, that’s with the same sac of .75. With padi method of 1.0 sac for each, GUE is additional 5 ft3. So that’s like 200 psi additional using GUE in AL80.

 

[boulderjohn]

According to the excel spreadsheet I made a while ago to compare the two, a 100’ dive is a difference of 14 ft3 additional using GUE method vs padi method.

So about 18% of an AL 80?

 

[seeker242]

So about 18% of an AL 80?

Sorry, I was editing as you were asking. if the sac is the same 0.75, about that yes.

 

[Lobzilla]

In GUE classes, I used their procedure out of respect, with an open my mind. Also, when hitting their very generous reserves in AL80 doubles, everybody I dove with in a class had reached their "enough fun" point already.

Outside of the class environment, the ascent plan is a team decision dependent on condition. Regardless of what that decision is, I am grateful that GUE taught me the tools to reliably crank the numbers in my head on land and during a dive.

Even in domains where reserves are defined by law, like fuel reserves in aviation, only fools assume that being 'legal' equates to being prudent. Reminds me of the three most useless things in aviation: fuel on the ground, altitude above you, and runway behind you. I look at reserve gas in a similar way. Nobody ever complained of having too much when things go sideways.

If prudent gas planning leaves you with too little dive time, then you need to relax (lower SAC rate) or hump bigger tanks. Skimping on critical resources is not the solution.

 

[boat sju]

Oh yeah, sorry. Let’s keep it basic.

Back on the boat with 500psi and ascend no faster than yer smaller bubbles.

Ok good luck have fun!

(depth x 10) + 400 psi and don't dive deeper than the volume of your tank. Easy peasy for us RECREATIONAL divers to figure on the fly. Luck has nothing to do with it. Do your math and tell me how reckless I'm being. And yes I am having fun.