Beach dive planning thoughts.

[ShakaZulu]

The problem with going into DECO mode is that your gas planning will be off, and you could potentially have an OOA situation (because of the unplanned extended safety), with DECO a ceiling preventing you from surfacing......... Oh well, there is always DAN right??

 

[Uncle Pug]

There is no line and every dive is a deco dive. Plan to spend time shallow for time spent deep and exit clean.

 

[pasley]

I just quickly glanced at a small array of different dive tables and it appears that they all agree that anything after a 12 hour surface interval is not considered a repetitive dive.

No more than a handful of tables were used when I did my quick check and I do not have any RGBM tables. I would be interested in seeing those some day. I think everything I have is based on the US Navy tables.
...

That is correct as far as I know. But I have corresponded with SUUNTO and their computer uses 99 hours in its calculations if I remember right. That question came up after a night dive followed by a dive the next day about 13 or so hours after the night dive. The computer gave less bottom time than the other divers who had not been diving the night before.

Now, given that as beach divers we run the following DCI risk as a normal course of diving:
1. We wear dark rubber suits in the sun and walk quite a ways to get to the dive site. If there is a SI, we are often out in the open with no shade for that hour. Dehydration is always a risk.
2. We climb down and back up stairs (if we are luckily) or steep hillsides or cliffs to go diving. DocDeco has written about this and he recommends you don't even change tanks out for 1 hour after a dive, and avoiding strenuous exercise for 6 hours after a dive. Yeah, right, like we ever do that.

So taking into account the two items above, adding to the mix diving two or more times a day, and several days in a row with some of those dives pushing the NDL, should we not start factoring in the previous days dives and back off the NDL a bit?

Now about the Navy dive tables. How were they derived? Was it through scientific study? How long ago and what was the level of knowledge and instrumentation at that time? Military tables are obviously meant to be used by military divers who, one would assume, are in good shape and young (18-25) with a military mission to accomplish. That may mean (but I do not know one way or the other) that they are more aggressive than might be good for a diver of age 50 or so. I will agree they are a place to start.

Finally, if dives over 12 hours no longer are a factor, then why the 24 hour no fly recommendation? I wonder if the dives of the previous 24 to 48 hours were deep dives (70-130 feet) and particularly ones that run on the long side then should we somehow factor them in? The long deep dives would I would think load the slow tissues which by definition do not quickly off gas would become a factor.

So what is the right answer? I don't know, that’s why I asked the question.

 

[ryanarcher]

Well the right answer in my opinion is to dive often, dive safe and just dive shallow. I really like to stay at 50 or above on a beach dive - unless we go to La Jolla Shores. I don't have a real computer so I don't usually push any limits. But like Shaka said - I guess that's why DAN is in business!

 

[ScubaSeanMaui]

The problem with going into DECO mode is that your gas planning will be off, and you could potentially have an OOA situation (because of the unplanned extended safety), with DECO a ceiling preventing you from surfacing......... Oh well, there is always DAN right??

This is true. I was lucky to have had 1500+ psi when going back up. I have much to learn of course! Profit from my mistake!! Those who dive without a computer have no idea that they should be heading to the chamber after they dock the boat And yes I do belong to DAN !!

Sean

 

[ShakaZulu]

This is true. I was lucky to have had 1500+ psi when going back up. I have much to learn of course! Profit from my mistake!! Those who dive without a computer have no idea that they should be heading to the chamber after they dock the boat And yes I do belong to DAN !!

Sean

DAN is not an option (I really need to start using smilies (insert sarcastic smiley here), then I loose my dive buddy!!!!!!!!!!

 

[divinman]

This is true. I was lucky to have had 1500+ psi when going back up. Sean

I had 1500 when I got back on the boat. Had your back Sean.

 

[Robert Phillips]

Mel, if you tabled these dives by max depth, they would be way past limits, but using the average depth they are within the limits according to my old Version 1 RDP, although the last dive would have required an 3 minute stop at 15'. But this is according to PADI and thinking of dives as no deco dives. As UP said, every dive is a deco dive. According to the profiles Terry posted, the only thing I could see that would have made the profile better would be to add min deco stops and make the ascent rates slower to smooth out the profile.

Deep stops and pauses will give you a better arc to your profile. This is what I was talking about with you on Sunday. Uncle Pug knows a hell of a lot more about this than I do so listen to what he has to say.
Here is a link to a rather lengthy post he made several years ago. It was intended to make people think about their dive profiles and understand that your best computer is the one between your ears. Please be sure to read the disclaimer at the beggining of the post.

 

[headhunter]

That is correct as far as I know. But I have corresponded with SUUNTO and their computer uses 99 hours in its calculations if I remember right. That question came up after a night dive followed by a dive the next day about 13 or so hours after the night dive. The computer gave less bottom time than the other divers who had not been diving the night before.

Now, given that as beach divers we run the following DCI risk as a normal course of diving:
1. We wear dark rubber suits in the sun and walk quite a ways to get to the dive site. If there is a SI, we are often out in the open with no shade for that hour. Dehydration is always a risk.
2. We climb down and back up stairs (if we are luckily) or steep hillsides or cliffs to go diving. DocDeco has written about this and he recommends you don't even change tanks out for 1 hour after a dive, and avoiding strenuous exercise for 6 hours after a dive. Yeah, right, like we ever do that.

So taking into account the two items above, adding to the mix diving two or more times a day, and several days in a row with some of those dives pushing the NDL, should we not start factoring in the previous days dives and back off the NDL a bit?

Now about the Navy dive tables. How were they derived? Was it through scientific study? How long ago and what was the level of knowledge and instrumentation at that time? Military tables are obviously meant to be used by military divers who, one would assume, are in good shape and young (18-25) with a military mission to accomplish. That may mean (but I do not know one way or the other) that they are more aggressive than might be good for a diver of age 50 or so. I will agree they are a place to start.

Finally, if dives over 12 hours no longer are a factor, then why the 24 hour no fly recommendation? I wonder if the dives of the previous 24 to 48 hours were deep dives (70-130 feet) and particularly ones that run on the long side then should we somehow factor them in? The long deep dives would I would think load the slow tissues which by definition do not quickly off gas would become a factor.

So what is the right answer? I don't know, that’s why I asked the question.

I follow you on this one, Melvin.

I'm wondering if the RGBM model takes into account multiple days. It is my understanding that the Suunto computers use some sort of adaptation of the RGBM model.

It seems that given the 1. - 2. punch that you mention above for the typical California beach diver, we should learn more about this aspect of our risk.

I'm looking forward to moving out of the stone age a bit, since all I know is the old square profiles. I'd like to learn more about RGBM and multilevel profiles.

I hope we get some more wisdom from someone familiar with our typical SoCal beach dive senarios.

Thanks for posting this one. I think it's something that those of us that aren't sure about the answers should learn more about.

Christian

 

[Uncle Pug]

This one might give you some more to chew on.