OW RDP Confusion!

[partrir]

Now, it's not hard to confuse me, but the Padi OW manual has managed it even more easily than normal. I managed to suss out that I needed stylish, colourful kit, according to the manual (black just doesn't cut it apparently!), but theres a question in Section 5 (section review question 6), that has me a little confused.

I've been fine using the RDP so far, but this one seems a little different to previous questions.....

What is the minimum surface interval required between a dive to 20 metres for 29 minutes, followed by a dive to 14 metres for 39 minutes?

So...here's my working...

1) Using the RDP table 1, my pressure group after dive 1 is M
2) Using the RDP table 3, I need to be in pressure group P before I can do dive 2.
3) Therefore, this suggests that I would have an interval time of zero if I wanted, as I do not have to wait for the pressure group to lower from M to P. If I'm right, I assume this is a theoretical time only, and some form of minimum time should apply?

Is this right, or am I doing something wrong here?

Thanks

Rob

 

[jhelmuth]

Not having any expertise with PADI tables, I would agree with your premise. However... I'll also answer your question using NAUI OW table (both are derivatives of the Navy tables and their algorithms are identical if nothing else).

1) My end-of-dive (EoD) letter group is F (per table 1)
2) Using table 3, I find that for a 14m dive planned for 39 mins would require me to have a new group letter (NLG) of E (or better)
3) finding the intersection of F (EoD) and E (NLG) gives me a SIT (surface interval time) range of 0:46 (min) to 1:29 (max)

therefore... to answer the question (via NAUI tables) I need to take the minimum, which is 0:46 (forty-six mins.)

I'd be shocked if PADI has a radically different answer...

 

[rivers]

It sounds like technically, you can just jump straight back in.

 

[dfx]

I would agree. According to the tables that I found online, your adjusted NDL after the first dive is 51 minutes for the second dive with no SI.

 

[jhelmuth]

It sounds like technically, you can just jump straight back in.

I doubt it... when you consider those profiles, one would have to believe that it would not be a good idea. I doubt that NAUI is vastly conservative over PADI with their model, and - as you can see from my reply - NAUI would tell you that your minimum SIT would be forty-six mins.

 

[rivers]

I doubt it... when you consider those profiles, one would have to believe that it would not be a good idea. I doubt that NAUI is vastly conservative over PADI with their model, and - as you can see from my reply - NAUI would tell you that your minimum SIT would be forty-six mins.

I just looked it up on the tables, using the PADI formula. Would I do 2 back to back dives with no SI? Nope, but according to the padi tables, this is okay.

 

[jhelmuth]

Hmmm..... just looked at the PADI tables too. I can't say I've used (or been instructed on their use), but if I interpret them correctly, is would seem to suggest a minimum surface interval of 0:13 (thirteen mins.)

 

[partrir]

Hmmm..... just looked at the PADI tables too. I can't say I've used (or been instructed on their use), but if I interpret them correctly, is would seem to suggest a minimum surface interval of 0:13 (thirteen mins.)

13 minutes would be correct if you need to move from P to group M, but this profile suggests a move from M to P.....

 

[jhelmuth]

OK... as I read them (again - not trained on their use), I thought you needed to be a "P" diver (going to 14m for 39 mins.) going from "M". My bad...

No surface interval????? Who'd a thunk!

---------- Post added July 22nd, 2014 at 10:25 AM ----------

No wonder no one wants to be a NAUI diver.... we're too darn conservative!

 

[rivers]

OK... as I read them (again - not trained on their use), I thought you needed to be a "P" diver (going to 14m for 39 mins.) going from "M". My bad...

No surface interval????? Who'd a thunk!

I just ran it through multideco using a 30/85 GF. Gives me a 1 minute stop at 6m and 9m for both. It's a doable dive, but I wouldn't want to do it.