Bottom Timer/Wrist Computer Question

[Scott L]

That's how it was covered in my class, too. 120-rule (with 20% depth credit for 32%) or 130-rule (32%, no depth credit; this is slightly more conservative) on top of average depth. Discussion covered how to average depth (5 min segments, comparison between gas used over time given known SCR, what to do when going shallow->deep vs deep->shallow, etc). The same principles basically apply to deeper dives where you come up with an average and then can apply either RD or pre-cut tables. In all cases, though, depth average plays a role. As noted by many, this isn't necessarily the same average that a gauge might be trying to give you, so as always, don't turn off your brain.

Thanks!

 

[limeyx]

Sorry Nick, just joking with Brian. We're friends in "real life" and dive together semi-often, so please understand that wasn't trying to piss him off. I figured this discussion has basically drawn to a conclusion. If there's still open discussion about what anyone's doing, I'd be glad to participate, but frankly litehedded and I do things darn near identical, and it sounds like you're applying some of the same concepts to ratio deco as we're applying to the use of tables.

Got it

I think there is still room for an open discussion in certain areas, but maybe this isn't the most useful place.

I dont know the caves in FL that well, but my understanding is that there are indeed some that go shallow then very deep then very shallow again, and I'd love to hear what kind of profiles actually work on those dives.

I have heard of one such "profile" which seemed to involve switching to 32% and scootering like heck and hoping you didn't have a problem which I guess is one way to do it

 

[LiteHedded]

Got it

I think there is still room for an open discussion in certain areas, but maybe this isn't the most useful place.

I dont know the caves in FL that well, but my understanding is that there are indeed some that go shallow then very deep then very shallow again, and I'd love to hear what kind of profiles actually work on those dives.

I have heard of one such "profile" which seemed to involve switching to 32% and scootering like heck and hoping you didn't have a problem which I guess is one way to do it

there is one that is a 15 minute swim at 80' and then drops to 240' that comes to mind. i planned that as a multilevel dive in deco planner.

another that is around 60' for 30 minutes and then drops to around 180'. i planned it the same way. although, I know of another diver that planned that with a straight depth average.

if you can get an idea of distances and depths from people who have dived it it's not that difficult to put together a profile for a multilevel cave dive. there really isn't a class that teaches how to plan these types of dives.

 

[Blackwood]

it sounds like you're applying some of the same concepts to ratio deco as we're applying to the use of tables.

there really isn't a class that teaches how to plan these types of dives.

Use what you're comfortable with.

I win

 

[ucfdiver]

Got it

I think there is still room for an open discussion in certain areas, but maybe this isn't the most useful place.

I dont know the caves in FL that well, but my understanding is that there are indeed some that go shallow then very deep then very shallow again, and I'd love to hear what kind of profiles actually work on those dives.

I have heard of one such "profile" which seemed to involve switching to 32% and scootering like heck and hoping you didn't have a problem which I guess is one way to do it

Litehedded and pfcaj recently dove a cave that dips to something like 140 and then maintains the rest of the dive at about half that.

I know that in Peacock 3, there's an area that goes to about 180ft in a room, and it's 65ft the majority of the 1000ft swim to get there. The solution that seems common is to carry the 70 bottle for deco and start your deco as soon as you hit the 70ft range on the way out (ie you're swimming back and counting that for deco).

Manatee Springs is a steady bounce between 40-50ft and 90ft for the first 3kft of that cave. I think the solution seems to be weight heavy. Here's the profile map (it's not all that accurate I don't believe). Anyways, not only is deco challenging, it's not real fun having a big gavin standard, stages, and a drysuit to all deal with in the raging flow....but it's hella fun on the way out!

Ginnie seems to be the "bender cave" here in NFL. I think extended exposures in the 2hr range, dehydration (often times from drinking), heavy fatigue (trying to get several dives a day since you're on vacation, ginnie is expensive, etc-- often 2-3 stage dives even) and the night time partying that goes on there are all directly behind this. Also the level of physical fitness around the area for many locals is certainly leaving something to be desired for tech diving.

 

[Blackwood]

I know that in Peacock 3, there's an area that goes to about 180ft in a room, and it's 65ft the majority of the 1000ft swim to get there.

How long are you usually in that room?

My predilection would be to treat the 180' portion independently from the entry/exit, and clear both decos (which is more-or-less what I gather Nick and company do in Mexico).

 

[LiteHedded]

How long are you usually in that room?

My predilection would be to treat the 180' portion independently from the entry/exit, and clear both decos (which is more-or-less what I gather Nick and company do in Mexico).

15 minutes or so I think. I don't remember. there's a deep section that goes in there somewhere but we never found it. and there's not much else to see in that room.
these ratio deco rules of thumb dont work so well when you're using multiple gases etc. we rode a 50% bottle out and a 32% bottle in, for instance.

 

[ucfdiver]

How long are you usually in that room?

My predilection would be to treat the 180' portion independently from the entry/exit, and clear both decos (which is more-or-less what I gather Nick and company do in Mexico).

I personally have not done it.

The people I've talked to who have, consider 1000ft/50fpm (swim rate = 20min of exposure, then let's say 10min @ 180. So they cut 20min @ 65ft and 10min @ 180ft in decoplanner with the proper gases, and then as soon as they get back to 65ft, swap to the 70 bottle and count the whole exit as deco.

Brian dove it within the past few months, he might want to comment on what he did?


Slightly off topic-
I dive frequently with a close friend of Eric Bakers, so I've been able to see his profiles and tables that he cuts for himself. They typically are VERY heavily weighted towards max depth for caves that aren't as well known, and then caves like cow springs, he's using swim rates and the tables state that you need to be at xxx ft by xx minutes into the dive. Either way, his tables seem to have more multiprofile variables embedded in them than anyone elses I've seen. No doubt he knows his stuff, but it's a bit too much of a schedule to keep for my personal tastes. Tables cut by someone with his level of knowledge are nice to have for cow springs however, where you have to do a 50ft stop, and there's really no good spot to do your 40 or 30ft stops.

 

[limeyx]

I personally have not done it.

The people I've talked to who have, consider 1000ft/50fpm (swim rate = 20min of exposure, then let's say 10min @ 180. So they cut 20min @ 65ft and 10min @ 180ft in decoplanner with the proper gases, and then as soon as they get back to 65ft, swap to the 70 bottle and count the whole exit as deco.

Brian dove it within the past few months, he might want to comment on what he did?


Slightly off topic-
I dive frequently with a close friend of Eric Bakers, so I've been able to see his profiles and tables that he cuts for himself. They typically are VERY heavily weighted towards max depth for caves that aren't as well known, and then caves like cow springs, he's using swim rates and the tables state that you need to be at xxx ft by xx minutes into the dive. Either way, his tables seem to have more multiprofile variables embedded in them than anyone elses I've seen. No doubt he knows his stuff, but it's a bit too much of a schedule to keep for my personal tastes.

Well, luckily 10 @ 180 with a 50% bottle handy is basically min deco

If these profiles were more like

30 mins at 30
30 at 180-240
30 at 30

then I can really start to see some issues where you simply arent going to do the entire 240-30 deco on the way in, and then again on the way out I would assume.

Maybe there arent any caves like that though.

10@180 I wouldnt sweat.

 

[LiteHedded]

Well, luckily 10 @ 180 with a 50% bottle handy is basically min deco

If these profiles were more like

30 mins at 30
30 at 180-240
30 at 30

then I can really start to see some issues where you simply arent going to do the entire 240-30 deco on the way in, and then again on the way out I would assume.

Maybe there arent any caves like that though.

10@180 I wouldnt sweat.

there are some like that. more like 270...but yea, shallow and then really deep