Decompression stop for shallow dives?

[TX101]

And when he's told that he's wrong, he just keeps pounding away.

And when you are told you're wrong, you just keep pounding away..

No one can visualise what I'm describing?

There are dump valves at either end of an air cell. For air to go out of a dump valve, the dump valve has to be at the highest point.

For the valve to be at the highest point you have to be off-horizontal. Either head slightly up or slightly down - otherwise the air isn't at the highest point!

I know it's completely pedantic, but unfortunately it's true.

I haven't even brought drysuits into the discussion because that illustrates my point further - you either have to roll to the right or raise your arm and drop your knees to get the exhaust valve to the highest point - same principle. And guess what? You are no longer horizontal!

Breath control, dbulmer you are right - you have to time it right. But what if you time it wrong? (which was my point)

Regarding SMB deployment.. I actually like to be a little negative and almost pull myself up on the SMB line for two reasons: (1) it keeps the line tight and makes sure when I deploy the reel the next time it's not going to jam and (2) It makes the SMB stand up on the surface, making you more visible.

Look, I've got no problem with ascending horizontally if the DIR guys call it what it really is: Looking cool. I'll admit, it's good practice for controlling buoyancy and if you can ascend horizontally properly, then you can honestly say you have mastered buoyancy control. BUT, saying it's superior to any other method just because you can flare out if you **** it up is complete bollocks in my opinion.

Sorry for the hijack, back to the topic at hand.

 

[Buoyant1]

That's where the confusion comes in... we're told (in the texts) that if you stay within these parameters, you don't need to stop..if something unforseen happens, you can surface with theoretically "no hit"

Almost every diver I know (my instructor included) stress that if you have the air in your tanks to stop safely, do it, it won't hurt.

My biggest question, I guess, would be; Why don't the texts stress the same attitude? (granted you learn more by doing and learning in real time, I learned a boatload of stuff when I did a "resort" course that helped me in the long run to get my certification!)

But the texts leave it a bit open ended,why don't just come out and say "you may as well do it, just play it safe" People like me (conservative) will take heed and stop just because I know it helps, I'm not in an hurry to get back on the boat, and since there are probably a few people on the trip that still have 1100 psi in their tanks while I'm headed to 600psi, The boat isn't going to leave me...but some people (the ones that end up with 20/20 hindsight) will just blow through it and jump on a plane that afternoon...

Just more thoughts to chew on...(it's a great topic!)

Bouyant1,

The essence of the meaning of NDL (No Deco Limit) is that one may safely surface without required stops IF one is within that limit.

There are NO guarantees, however, and the two main reasons that the agencies have included the safety stop in their training are these:

(1) to help control ascent rates, and

(2) for, guess what, SAFETY! (That is, it increases the margins of the safety envelope.)

In short, do you have to? The short answer is "no". Should you? The short answer is "yes"!

Cheers!

 

[Buoyant1]

oh...and let me add to the above...I know full well that even if you are overly conservative and do the right things and take the right safety stops, you can STILL take an undeserved "hit"...

just wanted to get that out so no one would stick that into consideration....

 

[detroit diver]

Geez man,

Read Rich's post #84. It sums up what you can't/won't understand. The dump valve at the bottom of the wing IS at the highest point when you are horizontal.

And yes, diving horizontal is more efficient, more controllable, allows quicker reaction time, and LOOKS COOL TOO!

Your drysuit example is meaningless because the valve is in a totally different place than on a wing. The drysuit doesn't shape like a wing either. In fact, nothing about it is relevant to a wing.

Do you actually dive a wing?

And when you are told you're wrong, you just keep pounding away..

No one can visualise what I'm describing?

There are dump valves at either end of an air cell. For air to go out of a dump valve, the dump valve has to be at the highest point.

For the valve to be at the highest point you have to be off-horizontal. Either head slightly up or slightly down - otherwise the air isn't at the highest point!

I know it's completely pedantic, but unfortunately it's true.

I haven't even brought drysuits into the discussion because that illustrates my point further - you either have to roll to the right or raise your arm and drop your knees to get the exhaust valve to the highest point - same principle. And guess what? You are no longer horizontal!

Breath control, dbulmer you are right - you have to time it right. But what if you time it wrong? (which was my point)

Regarding SMB deployment.. I actually like to be a little negative and almost pull myself up on the SMB line for two reasons: (1) it keeps the line tight and makes sure when I deploy the reel the next time it's not going to jam and (2) It makes the SMB stand up on the surface, making you more visible.

Look, I've got no problem with ascending horizontally if the DIR guys call it what it really is: Looking cool. I'll admit, it's good practice for controlling buoyancy and if you can ascend horizontally properly, then you can honestly say you have mastered buoyancy control. BUT, saying it's superior to any other method just because you can flare out if you **** it up is complete bollocks in my opinion.

Sorry for the hijack, back to the topic at hand.

 

[Squalus]

On one occasion my buddies Air 2 came lose and wrapped around his tank (so he had to do a swimming ascent). Our average depth for the dive was probably 20-30 feet.


Just how long is his Air2? I took my BC out just to see if this can happen and it cannot wrap around my tank if anything can get hung up on my 1st stage.

 

[TX101]

Geez man,

Read Rich's post #84. It sums up what you can't/won't understand. The dump valve at the bottom of the wing IS at the highest point when you are horizontal.

I'm going to agree to disagree and leave it at that.

And yes, diving horizontal is more efficient, more controllable, allows quicker reaction time, and LOOKS COOL TOO!

Never said it wasn't. I was talking specifically about ascending (or is this what you meant?)

Your drysuit example is meaningless because the valve is in a totally different place than on a wing. The drysuit doesn't shape like a wing either. In fact, nothing about it is relevant to a wing.

I didn't want to bring up drysuits because I knew this would be the response. Somebody else brought it up and I simply mentioned that it's the same concept - you have to bring the valve to the highest point to dump air. Since the valve is on the front of the drysuit rather than the back, my point was that if you start ascending horizontally you're going to have to 'break formation' every now and again so you can dump air.

Do you actually dive a wing?

Diverite Classic with twin 12's.

 

[dbulmer]

TX,
It's not about timing per se- you breathe in, then out as you'd normally do keeping the airway open. There's nothing mystical in this, honest! I think maybe I don't get your point because it would never occur to me to close my airway.

As you ascend higher (even in my case as a novice) you won't be breathing heavy - just slightly slower (but with the airway open) as you'd be going up the blob line very slowly at the same time as winding in the spool. If you rush things, it goes ***s up.

With a spool it's less likely that it'll jam - all you are doing is tieing line around a spool - tieing round the spool is 100% easier when you are not fighting the line (hence being slightly + bouyant). That said, as Detroit Diver pointed out it does take some practice and it sounds a lot easier to do than in the water.

As divers we are all trained from day one to relax in the water. I try to relax and take my time coming up rather than getting tense trying to control the line. Other divers are relaxed but I have to work at it. The more tense I am in the water the worse my breathing so for me not fighting the line is important.

As for vertical - I had my first UK dives earlier in the year. On the last dive I lost control and shot up a few metres precisely because I'd gone vertical. Had I been horizontal I might still have lost control (coz my buoyancy skills are rubbish) but at a slower rate. BTW when it happened I was faffing about looking for my inflator - experienced divers would not have been in that situation in the first place.

I don't get your 2nd idea about being 'more' visible. Personally I think you either see it or you don't.

One more thing. Even a lowly newbie like me can ascend/descend horizontally (well ish! ) but to say it demonstrates mastery of buoyancy I think is mistaken. I have yet to meet a diver who says he/she has mastered buoyancy.

As a recreational diver I'm working to improve my all round skill level - the difference I see in the tech divers is that they've taken basic buoyancy skills and and refined them over time.


As for the notion of looking cool well you can be a really carp diver like me and still be cool

(Apologies for the digression)

 

[Dan Gibson]

On the wing, when you grab the string on the rear dump valve, you can also roll your arm against the wing which will force some of the air out. You don't have to get out of horizontal to dump. That being said, minor adjustments to horizontal trim (slight head up or down) are perfectly acceptable for dumping except in confined areas that cause you to stir up silt.

My drysuits are so snug fitting, they act like OPVs if I add too much gas. The valve isn't at the highest point unless I raise my arm (DC suit with wrist dump) or flex my bicep (DUI suit with dump just above elbow). I don't have to get out of horizontal trim to dump either.

The only time I can't dump without going heads up is to let gas out of the drysuit feet. I rarely have this problem since I add very little gas to the suit.

There are dump valves at either end of an air cell. For air to go out of a dump valve, the dump valve has to be at the highest point.

For the valve to be at the highest point you have to be off-horizontal. Either head slightly up or slightly down - otherwise the air isn't at the highest point!


I haven't even brought drysuits into the discussion because that illustrates my point further - you either have to roll to the right or raise your arm and drop your knees to get the exhaust valve to the highest point - same principle. And guess what? You are no longer horizontal!

 

[diverbrian]

I use one as well with twin HP100's and stage bottle(s). That "taco effect" that Rich L. refers to the reason that I use a Venture wing for single tanks. Once it starts to wrap around a tank, the classic wing does not vent well.

I ascend horizontally. Actually, if can control my ascent far more easily in that position than vertical. I have more surface area to use to control my ascent rate. As I have to look up sometimes, it is easy for my to vent my wing through those opportunities via my deflate hose which happens to be in close to the same orientation as my drysuit dump (on my left shoulder). So I do roll (slightly) to allow that point of my body to be higher. It gets difficult to describe as it is instinctive really. I just don't like using the rear dump valves. They are too touchy for my taste and I can't see the air coming out to verify that they are working like I can off my drysuit dump and the deflator hose. And yes, my breathing factors in as well.

What works at one point in a given diver's career to contol their ascent to the point of stopping at any given point in their ascent and going neutral, works. As we watch other divers, we pick up new methods and improve it. My diving stye was safe when I got out of OW training and it is safer now. There are degrees to this issue. In another couple of years, I could find myself doing things differently than I do now. Actually, I hope so because it would mean that I learned more.

As to the safety stop issue... IMHO safety stops are just that. They are a way to get to the boat with a higher degree of safety than shooting up to the surface. I *like* being underwater. Why not use the safety stop as an excuse to get more ? The difference is in degrees of risk. I know of undeserved hits that the safety stop and being within NDL's did little to prevent. But even when those happen, you have to think that the hits would have been more severe had the victim not done a proper ascent. I have seen more than one person completely blow off minor deco obligations and never get bent.

As to shallow dives, a safety stop if you have been all over the place depthwise can't hurt. Those microbubbles are really having a party in your system if you are rapidly moving between these depths. Percentagewise, this is the most severe area as far as change in ambient pressure. Think about you double your ambient pressure by going to 33 ft and you have "only" tripled it (compared to the surface) to go to 66 ft.

 

[TX101]

With a spool it's less likely that it'll jam - all you are doing is tieing line around a spool - tieing round the spool is 100% easier when you are not fighting the line (hence being slightly + bouyant). That said, as Detroit Diver pointed out it does take some practice and it sounds a lot easier to do than in the water.

Ever tried winding up a line thats slack? If the line isn't tight while winding you can tangle it without knowing it.

I don't get your 2nd idea about being 'more' visible. Personally I think you either see it or you don't.

Visible on the surface. It's the difference between the SMB lying down in the water and being hidden by waves or standing up 6ft out of the water.