RGBM model: do you get locked out a lot?

[Rick Inman]

I'm not sure I follow you? No algorithim is going to tell you that you can't dive. What it will do is tell you how much time it thinks you have a certain depth. What you do with that information is up to you.

Agree. On my first dives in Coz this year, my computer was giving me deco obligations that my superior computer (brain) said was hog wash. I did the 10 extra mins. at 10' to make the gadget happy, but I knew it wasn't really necessary (good thing, too, since at the last min I saw a shark!).
Turned out I somehow had set the altitude to 2500'-5000'.

My M1 is true RGBM, and I've never been locked out.

 

[ppo2_diver]

I locked out my Vytec on a deco dive once. Just because I forgot to set the third gas to 99% O2. When I went to do my last deco stop at 20 feet on on 100% O2, I couldn't change it on my computer (fine anyway, I follow the tables). So by the time the tables said I was done with deco, my computer had me sitting at 20 feet on 50% Nitrox for an additional 10 minutes. I decided not to hang there that long so I surfaced. Locked me out for 48 hours (except guage mode).

I normally set my Vytec to the attenuated RGBM and it clears out of deco before I surface.

 

[artusor]

I use a Suunto Cobra and a Suunto Stinger. I do not have a lot of experience here, butI have never had either lock me out.

 

[StSomewhere]

SUUNTO is not true RGBM... just RGBM limiting factors folded over a haldane model..

Technically, folded over a Buhlmann model.

Why are you in a hurry to get out of the water?? if it is requesting you to hang do it.. unless you are really low on gas there is no excuse not to stay the few extra minutes, you wll feel better in the end anyway..

Agree completely. I actually have the Vytec which has a setting to reduce the RGBM "penalty" (for lack of a better word). OTOH, what it actually "penalizes" you for is stuff like fast ascents, too short surface intervals, reverse profiles, etc. which you should be avoiding anyway. So although the Vytec lets me set the RGBM factor to less penalizing, I don't and don't get locked out. (I do like that they calculate the OTU factor differently for the Vytec than the Vyper/Cobra, but thats another thread.)

 

[Austin]

Thanks for the comments. I agree that there's no reason to exceed the limits in order for more time underwater or to rush out of the water.

It just seems that RGBM "similar" models that account for the tiny micro bubbles give you less dive time when you ascend to a certain level than the haldane or similar models would, because they don't account for "micro bubbles." I'd rather use a more liberal algorithim and stay out of the caution zone than to be locked out and not able to use the computer, but it sounds like that's not happening to many people.

I guess the underlying question that i'm trying to avoid, but hinting at nontheless, is whether the haldane and other algorithims are too liberal or whether the RGBM algorithim is too conservative, but I know that question isn't really able to be anwsered....

 

[padiscubapro]

My M1 is true RGBM, and I've never been locked out.

as far as the information I have..
the ONLY full up RGBM implementation is still The HS-Explorer.. Mares m1 RGBM is still a haldane model with RGBM limiting factors folded over it..

I have done dives with divers using the M1-RGBM and the profiles generated were veryy different than the Explorer.. The shallow stops were too long for a full RGBM implementation.. The profiles looked like your typical haldane model with deep stops added..

 

[cornfed]

I'd rather use a more liberal algorithim and stay out of the caution zone than to be locked out and not able to use the computer

I think you're missing the big picture. Computers don't just lock you out. My vyper won't lockout unless I get into a deco situation and spend three whole minutes above the shallowest depth it recommends.

If you and I dive the exact same profiles with different computers will while get different NDL information. And it's not hard to imagine the this difference would grow the more repetitive dives we did.

The same is true for dive tables. My NAUI tables have about 12 repetitive groups while my buddy's PADI tables have twice that many. That pretty much guarantees well come up with different NDL values after the same dive and same surface interval.

The bottom line is you have a lot of information available to you but you need to be smart about how you use it.

 

[diver_paula]

Austin,

I've been diving with my Suunto Solution and Companion for over ten years. Never in that time have I had a problem with them being so conservative I couldn't dive along with my buddies that had different computers. After a deep dive and SI, the NDL my computers gave may be a couple minutes shorter but that's about it. And when the SI goes over an hour, hour and a half, not much difference at all.

I've been on two live-aboard trips to Truk, with 4 or 5 dives a day. I followed the NDLs, made decent SIs and never went into decompression. Had great trips and didn't miss anything because I chose to use 'more conservative' computers.

Paula

 

[Austin]

Ok, thanks alot. Thanks for clearing that up cornfed. When I read one of Scuba Lab's experiments with different dive computers and different algorithims, there was a DRASTIC difference in bottom time allowed between the different algorithims, notably with Haldane giving almost 2 times that of RGBM. I guess Paula brought up the point I was trying to find, that using the more conservative algorithims won't usually wind up with you having to surface before your buddies that are using haldane or Buhlmann or other algorithims.

 

[cornfed]

When I read one of Scuba Lab's experiments with different dive computers and different algorithims, there was a DRASTIC difference in bottom time allowed between the different algorithims, notably with Haldane giving almost 2 times that of RGBM.

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