Skipping surface intervals - DIR or not?

[Doc Intrepid]

So what minimum deco rules would you recommend?

Floater, because my name was mentioned earlier, in regard to the thread started by TS&M, I feel obliged to add a cautionary note of my own.

I do not know Martin Lorenzo. I make no comment on his class nor his curriculum. But I've had the pleasure of attending four fundies courses, instructed initially by Sonya Tittle @ Fifth D and thereafter by MHK and Brando in Virginia. I do not recall any of these instructors, at any time, suggesting anyone eliminate Surface Intervals.

My comments to TS&M were not meant to imply that I endorsed elimination of surface intervals. I do not believe that a diver, even a diver who conducts an appropriate decompression profile, ought to be exchanging tanks on the boat and then immediately descending again on a second decompression dive. It strikes me as unwise in the extreme, and I wonder if you perhaps have not misconstrued what Martin Lorenzo was teaching. I also encourage you to put this question to your instructor directly, whether or not you choose to post his response - your instructor is by far better qualified to address your proposed dives than a thread on ScubaBoard.

That said, your plans are potentially dangerous for other reasons. Lets examine them:

You live in the US. You'll be flying on an international flight to your destination. I do that frequently. The air in the plane is dry, and the jetlag induced by crossing some 8 time zones can be considerable. You may well arrive fatigued, whether you perceive yourself to be fatigued or not. Your sleep or rest patterns will be disrupted.

You will travel on a boat some 2-4 hours to remote dive sites. Simply traveling on a boat that long can also induce fatigue, not to mention nausea - particularly if there are any sort of seas running at all. You MAY also be dehydrated, due to the change in environment and the travel. I assume you don't drink alcohol at all, which may help to some extent, but traveling can take it out of you - by plane OR by boat.

In the midst of all this unaccustomed stress on your mind and body, to then perform two back-to-back decompression dives is simply not wise - considering how little we actually know about DCI and it's various potential causes.

Moreover, suppose for a minute you DID get bent. The very reason you would consider such dives is because you're so remote. If you're that remote, Floater, how long will it require you to get back to the mainland and into a chamber?

For what its worth, particularly as my name has already been brought up, I strongly encourage you to plan your dives in Eygpt far MORE conservatively, rather than far less. I also encourage you to discuss this matter at length with your GUE instructor. I doubt that the boat captain would allow you to dive this way anyway, because of their liability, but even if they would - you are the one responsible for your safety, not the operators. You need to plan for your own survival.

I hope you enjoy your trip,

Doc

 

[*Floater*]

Just to clarify: The profile I posted was aggressive on purpose because that's what Jonnythan requested, it was supposed to be a nominal profile using the limits of rules I was taught. Were I to dive it I'd add in a few degrees of conservatism. But I still believe in those rules as basic guidelines for safe diving based on what I was taught and rationale I was given.

 

[CD_in_Chitown]

Please don't misconstrue anything I've written as agreeing with or providing a basis for understanding Floater's *deco plan*.

I didn't mean to construe the comments of either of you in regards to TSandM's discussion to have bearing on Floater's dilemma. Only meant that in reading the linked thread I think I understand from where the OP's confusion stems.

 

[CameronMartz]

Things that can go wrong when skipping a surface interval:

1. You think you ascended "correctly" and deco'd well, but that was not the case. It can take time on the surface before this becomes apparent. If you dive again while bubbling, you risk allowing the bubbles to shrink, get past the lungs, then cause CNS hits as you surface from your second dive.

2. You place some artificial time constraint on switching your tanks out and over-exert yourself. Again, you bend yourself, but descend before knowing it, and again, setting yourself up for a CNS hit as you ascend from your second dive.

3. You piss off your buddies who think they are on vacation. <g>

If everything goes well with the first dive, then skipping a surface interval might be fine. However, we are very poor at knowing when we are bent, even when symptoms are beginning to appear. A surface interval is a great chance to prove to yourself that you deco'd out of your first dive well before starting a second dive.

Cameron

 

[Diver0001]

I didn't mean to construe the comments of either of you in regards to TSandM's discussion to have bearing on Floater's dilemma. Only meant that in reading the linked thread I think I understand from where the OP's confusion stems.

I dont' think that he got this opinion from the linked thread, especially now when I see big-guns like UP and DocI telling him he needs to reconsider and he would appear to be resisting listening to them.

Actually, this is a good thread. There must be a lot of people out there with the same kinds of notions as Floater has about surface intervals and ratio deco.

Just to add something to Cameron's post. I think skipping a surface interval may also mask symptoms of DCS, which could come back even harder after surfacing from a subsequent dive. IIRC this is how Richard Pyle nearly killed himself.

Just a thought.

R..

 

[Web Monkey]

From 80' to 130' it's the same as the SSI tables. From 40'-70', I have no idea. SSI has an NDL at 40' of 130 minutes.

Terry

Martin Lorenzo. Here's the table for air dives (the version I was taught):

40' 90 min
50' 60 min
60' 50 min
70' 35 min
80' 30 min
90' 25 min
100' 20 min
110' 15 min
120' 10 min
130' 5 min

 

[Derek S]

Moreover, suppose for a minute you DID get bent. The very reason you would consider such dives is because you're so remote. If you're that remote, Floater, how long will it require you to get back to the mainland and into a chamber?

Doc - Excellent point I hadn't thought of. That right there would be enough for me to reconsider.

Floater -

IMHO, skipping an SI just isn't smart or safe diving. Nobody wants to squeeze more out of a dive vacation than I do, believe me, but I have serious reservations about what you're proposing and how much we still don't know about DCI and all the incidental causes.

Have a fun trip, and come back safe. There will always be time for another dive.

 

[amascuba]

First dive (on ean32):
100' 30 min (including a quick descent)
70' 31.5 min (ascent + 30 sec stop at 70')
0' 38 min with a 30 sec ascent followed by 30 sec stop each 10 ft

On the surface I would replace the tanks and do whatever else I needed to do (change batteries, go over dive plan, etc.)

Then I'd repeat the first dive profile. Since I'm still new to the system I would add an extra minute to the last 3 stops just to be a little more conservative and to see how I'd feel afterwards.

edit: i simplied the profile a little to remove the pauses. same total time though.

With that profile you are very likely to get Oxygen Toxicity, especially with repeditive dives with little to no SI. Personally, I don't think you will ever make it to technical diving as you will most likely have some injury that will prevent you from diving or you will be dead.

 

[StSomewhere]

From 80' to 130' it's the same as the SSI tables. From 40'-70', I have no idea. SSI has an NDL at 40' of 130 minutes.

This is a minimum deco table, not the mythical "NDL", and there are additional parameters like profile shape and ascent rate that have to be taken into consideration. There's more to this than just optionally popping up to 15' for 3 minutes at the end of the dive. FWIW.

With that profile you are very likely to get Oxygen Toxicity, especially with repeditive dives with little to no SI.

WT? are you going on about? Go back and calculate the ppO2 of EAN32 at 100' (the worst case from his extreme example profile) and get back to me on that...

Personally, I don't think you will ever make it to technical diving as you will most likely have some injury that will prevent you from diving or you will be dead.

What is a solo diver doing in the DIR forum anyway, telling people they "will most likely have some injury that will prevent you from diving or you will be dead"? Some of us think the same thing about the way you dive... :roll: So much for the no trolling zone, I guess.

Nice buddah hover though...

 

[amascuba]

This is a minimum deco table, not the mythical "NDL", and there are additional parameters like profile shape and ascent rate that have to be taken into consideration. There's more to this than just optionally popping up to 15' for 3 minutes at the end of the dive. FWIW.

WT? are you going on about? Go back and calculate the ppO2 of EAN32 at 100' (the worst case from his extreme example profile) and get back to me on that...


What is a solo diver doing in the DIR forum anyway, telling people they "will most likely have some injury that will prevent you from diving or you will be dead"? Some of us think the same thing about the way you dive... :roll: So much for the no trolling zone, I guess.

Nice buddah hover though...

Re-read the guy's post. He's talking about doing repeditive dives to 100' using EAN32 for 30 minutes (and over 90 minutes for a total bottom time) WITH little to no surface interval. Diving like that will get your PP02 to 1.6 in no time and he will be lucky if he doesn't go into convulsions. It's pretty easy to figure out, just look at your nitrox tables (which are conservative to begin with) and you will see how fast he will end up with a PP02 of 1.6. I'm not trolling, I'm just pointing out that this person has a very unsafe attitude towards diving and it's likely that he's going to seriously injure himself, others around him, and/or kill himself. I would rather dive solo than dive with him or even be in the same waters as him.

I've not taken ANY DIR classes, but I do know that the main point of DIR is diving as safely as possible in your environment and what this guy is telling us is not safe, which is not DIR.

lol about the buddah comment.