Reverse dive profiles

[ScubaJeep]

Just for the record, I was using internet downloaded tables for those calculations. My PADI tables are at home.

 

[cornfed]

SCORE ResQ once bubbled...

Your cutting it pretty close to the no-deco limit for recreational diving IMHO. If you flipped those dives around then you would have a 26 minute margin instead of 2 minutes in the adjusted no-deco limit. Try it out on the Navy tables and see how it compares.

That's kinda the point but you ruined the fun of letting ScubaJeep figure it out himself.

I banish you back to TDS. Be gone!

 

[ScubaJeep]

Wait a minute, you both are assuming that a dive profile's end pressure group should be same group if the profile is reversed. I'm not quite sure that dive physiology works that way.

Anybody know for sure?

 

[Waterborne]

I'll be going now (packing up toys and going back to TDS)

You're on your own now ScubaJeep

 

[Don Burke]

SCORE ResQ once bubbled... ScubaJeep, according to the PADI tables, after the first dive with an hour surface interval, you would be in group B. Now when you follow that over to the repetetive table, it shows you an RNT of 9 and an adjusted no-deco limit of 31 for the next dive. Take the RNT and add it to your bottom time of the second dive to get 29 for your actual bottom time ABT. Your cutting it pretty close to the no-deco limit for recreational diving IMHO. If you flipped those dives around then you would have a 26 minute margin instead of 2 minutes in the adjusted no-deco limit. Try it out on the Navy tables and see how it compares.

It appears you counted residual nitrogen twice.

I come up with 43 vs 11 minutes using the PADI tables.

 

[Don Burke]

ScubaJeep once bubbled... Wait a minute, you both are assuming that a dive profile's end pressure group should be same group if the profile is reversed. I'm not quite sure that dive physiology works that way.

Anybody know for sure?

With the normal profile and the PADI tables, I come up with the first dive taking me to group "I", the surface interval taking me to group "C", and the second dive taking me to group "L".

With the reverse profile and the PADI tables, I come up with the first dive taking me to group "E", the surface interval taking me to group "B", and the second dive taking me to group "N".

The reverse profile cost me two pressure groups. In this case it wouldn't be a big deal, but with dives running closer to the edge, it would make me shorten the second dive.

Figure it with both dives lasting 30 minutes. You'll just barely make it on the Navy tables.

 

[cornfed]

ScubaJeep once bubbled...
Wait a minute, you both are assuming that a dive profile's end pressure group should be same group if the profile is reversed. I'm not quite sure that dive physiology works that way.

Anybody know for sure?

No we didn't

 

[cornfed]

SCORE ResQ once bubbled...
I'll be going now (packing up toys and going back to TDS)

You're on your own now ScubaJeep

Hmm... maybe I shouldn't have been so quick...

 

[ScubaJeep]

Well, if you put all of your faith into the dive tables then you are safer with a normal profile. My question is whether those tables deserve that amount of trust.

Is a normal dive profile easier on your body than a reversed?

 

[SCUBAMedicBill]

Using ScubaJeeps dive plan, is shows, as shown by Don, that doing the deep dive first and the shallow last leaves you with a bigger span between ABT and NDL (43min vs 11 min). There's the SAFETY. On this dive plan, it doesn't make too much of a difference, but it could on other dives plans.

Plan your dive and dive your plan, yea, as long as the dive plan is planned correctly.

If your doing reverse profile, just make sure you plan it correctly and follow it strickly. The idea is to enjoy the dive and go home safe.