The Tank Valve Feathering/Modulation Technique

[T.C.]

1). Never waste gas if you can feather it.

This is tech diver mentality- NOT rec. diver. We get it; tech divers don't want to lose gas, because you can't ascend directly to the surface. You may need that.

You are blinded by this fact. However, what continues to escape your grasp of comprehension, is that rec. divers are under no such restriction. They do not need to worry about "wasting" gas, because they can ascend directly to the surface at anytime of their dive. This rule can be re-stated for a rec. diver as: Never linger underwater with a serious malfuction. Ascend Immediately.

This tactic is completely unuseable, un-needed, and worthless to a rec. diver. It offers zero benefit, while only increasing the risks. There are many other simpler skills that will do the job just as effectively.

It fails the common sense test.

Is that all you can think about or contribute Kate? Some seemingly personal semantic slight? Can you be motivated to think more objectively?

HAHAHA!!! You are one to talk. Ever since your idea has been exposed as foolish and dangerous, you have not tried to defend why an OW diver needs it, you have just resorted to insults, boasting and exhibiting your lack of common sense. You have failed to apply your own advice; in both lacking objectivity and creativity.

 

[markmud]

Hey Kevrumbo,

I have performed an ascent from about 50 fsw with a free flowing octo and a free flowing primary second stage, while at Anacapa Island, while diving in kelp (Northern Channel Islands? Does that ring a bell?). However, I was not wearing a drysuit.

My first stage was suffering from a case of creeping intermediate pressure. The dive shop owner that had sold me the mares reg claimed that I was opening the valve too quickly and damaging the first stage. He sold me an intermediate pressure gauge and taught me how to adjust my intermediate pressure if I made the mistake of opening the valve to quickly again. Well, finally, the crack in the first stage propagated to a point where the system completely failed.

I was a newbie AOW diver. My insta-buddy checked my tank pressure and noticed I had lots of gas and that it was not going down quickly. He pointed to the surface and signaled me to swim to the boat. While I nodded in agreement while still on the bottom, he split the scene!

I did a slow ascent, inflated my BC, and swam back to the boat. I still had more that a grand in my tank even the though the system was free flowing the entire time.

Going straight to the surface was the best and safest thing for me to do. Feathering the valve and saving gas was not even remotely necessary.

Now, I always dive with a pony bottle system, an SMB, a spare mask, two knives, two computers, a USCG whistle, and a healthy respect for the ocean. I am Solo/Self-Reliant trained even though I rarely dive solo.

Things to cogitate on:
1) Simplex very sigylum (SP)
2) Lex parsimone (sp)
3) Ockham's Razor
4) Murphy's Law.

All four are related. If you don't follow the first three, Murphy's Law becomes much more probable.

regards,

markm

 

[Diver0001]

The actual incident that happened:
Cozumel 2006, my adjustment knob on the second stage blew-out resulting in a catastrophic nonfixable free-flow, on a single-tank dive in 6m of depth, during a weightbelt lead check. I actually could see the gauge pointer/indicator hand on the SPG sweeping from 200 through 150 bar literally in an instant before reaching back to shut-off the cylinder valve. Switched to my bungied back-up reg around my neck and then modulated/feathered the tank valve behind my head while doing a CESA. (Again, this should be a skill regularly practiced starting in basic open water).

Well.... with all due respect, it doesn't surprise me to hear that this particular thing happened to you. I've seen lots of your tall tales over the years and they're a constant source of entertainment. If even half of your stories are true then you really should record some of your diving for Youtube so we can watch them on "Ridiculousness"..... Simple fact is, that I doubt your credibility. Sorry to say it, but that's the impression I've built up over time. I think most of your stories are just that.... stories. I also remember you being equally adamant about other techniques in the past, including all the childish antics and horrible debating style when people didn't agree with you .... and IIRC you nearly killed yourself proving your point.

Given your track record with these kinds of things, I think people should be warned to be careful what you believe when you read it on the internet..... because screaming the loudest isn't not proof that the author is right.

Having said that, I have seen a similar incident in the past. It was completely and adequately solved by simply ascending to the surface while breathing from the freeflowing reg as taught in the OW course. Moreover, Bowen's experiments on freeflowing regulators suggest that "sweeping through" 50+ bar in "literally an instant" is a gross overstatement, although it does seem to indicate that memory is selective and that high levels of stress can affect ones perceptions of events.

I'm glad you didn't hurt yourself (this time) trying this. Personally, I would advise others to follow their training in a similar scenario. If someone wants to learn feathering I would say, go ahead. But to require OW students to learn it when a simpler solution is available is equivalent to telling someone that they need to learn how to do back-flips to cross the road when in reality, simply walking to the other side gets the job done too.

R..

 

[DaleC]

I've been sick for the last day or two but this thread is making me feel a lot better

Although I'm very curious how Kev will vent his drysuit with the left hand or monitor his depth with his DG behind his head (?) I thought I'd offer a video of a similar scenario to the one being discussed. In this case I am trying out a prototype concept for a Le Prieur device (pre modern SCUBA) which is basically a freeflowing tank. In this case an Al 40 side slung - not what a rec diver would have to contend with. During that trial two things became evident.

1. It was easy to breath off a freeflowing tank.
2. Modulating a flow rate that was "comfortable" while changing depth was not.

I suggest, if you want, to watch from 3:00 on. There I'm in the deeper pool.

You can see there are times when I have too much flow, and times when I have just enough and this is with the tank in front of me in a non stressed, pool session. In the shallow end it's not bad but in the deep pool the adjustment was a little trickier.

Someone ascending with a freeflow would have to get use to the increased volume once, and then being adjusted, could breath as required. Someone feathering would have to become adjusted to changing flowrate every time they opened the valve, and this cannot be accurately predicted while ascending. You would constantly be facing either a rush of air, or not enough, and devoting a lot of bandwidth to modulation.

What I found, that would be more beneficial, would be to dial back a free flowing reg to a reasonable flowrate, but a modern tank valve does not give that kind of fine control at depth - it's either on/off for the most part. Behind the head, when there is enough gas to surface as it is, even that would seem an unnecessary choice. A good direct surface (not a CESA because you have air) requires close enough attention to the basics, such as buoyancy, ascent rate and observing overhead hazards.

OK, nuff of that. Back to the flogging... it's better than medicine.

[video=youtube;Y7STLNzjHnk]https://www.youtube.com/watch?v=Y7STLNzjHnk[/video]

 

[lowviz]

OK, most of us are not going to use Kevin's feathering of our tank valve wihile dealling with a free flowing 2nd stage on a recreational dive. Most of us agree that connecting with one's buddy or direct access to the surface is the best solution. There you go.

Good diving, Craig

I don't know what possessed me to wade into this mess but... scubadada, yep that is pretty much it. I would just like to add (for your possible interest) that strongly kinking the hose does significantly improve your time. http://www.scubaboard.com/forums/basic-scuba-discussions/350887-free-flow-what-do-2.html#post5459677

And I hesitate at suggesting that this "trick" be taught in OW. Probably morph into a "go to" fix for venturi free-flows...

 

[ManuLani]

Although quite entertaining, It's almost embarrassing just reading this thread.
I'd like to offer up a quote that I think may offer some sage advice
....


"It is better to keep your mouth closed and let people think you are a fool than to open it and remove all doubt." - Mark Twain

 

[Subcooled]

Nice idea but...

Feathering a valve on backmounted equipment is not a winner idea (unless you must). If you are 100ft down, you don't need to feather. Do a relaxed ascent, and if you run out of gas, continue a relaxed ascent. If you dive deeper, then are you sure that you can hold you hand back there for ten minutes or longer? It's not the most comfortable position. Will you be able to do it? Better options exist. You could dive with two tanks.

If you dive in sidemount configuration having valve knobs pointing down (NOT to the sides), then you can rest your arm over your chest and do wonderfully relaxed feathering. But this requires a specific equipment configuration.

feathering:
1) Inhale while the valve is closed. No air is beeing delivered.
2) Carefully open the valve until air is starting to flow. You'll notice it.
3) Quickly open the valve half a turn more and inhale 3/4. A proper breath.
4) Close the valve and inhale 1/4 to empty the hose.
5) After a while, exhale.
6) Repeat.

You won't loose any gas (unless the hose is severed).

 

[scubadada]

I don't know what possessed me to wade into this mess but... scubadada, yep that is pretty much it. I would just like to add (for your possible interest) that strongly kinking the hose does significantly improve your time. http://www.scubaboard.com/forums/basic-scuba-discussions/350887-free-flow-what-do-2.html#post5459677

And I hesitate at suggesting that this "trick" be taught in OW. Probably morph into a "go to" fix for venturi free-flows...

Thanks lowviz, I'll keep the fold the hose trick in mind should I ever find myself with an unfixable free flow 2nd and need more time for a reasonable ascent. To date, I've never had a free flow while breathing off a reg, only very brief free flows when it was out of my mouth

 

[Diver0001]

You won't loose any gas (unless the hose is severed).

The only time I've seen feathering used in practice was on a deco bottle. My buddy had a failed 1st stage on his deco gas. Every time he opened the valve a mass of bubbles came out from around the DIN insert. The reg appeared to be screwed all the way into the tank but something had obviously happened between the time we got in the water and the time we got to our deco stops because it was definitely not holding air. After the fact, we discovered that the DIN insert had somehow become loose and it wasn't making a seal on the inside o-ring. It was probably loose when he put it on.

When he opened his tank the first time and we saw the problem, he tried to fix it and couldn't, so we discussed alternatives. We had a short "discussion" (as far as signing goes) over several options:

- share my gas until it was empty and then put my reg on his tank and finish.
- use all my deco gas and then grind out the rest on back-gas
- feather his tank and see how far we could get with that.

We decided he would feather his tank until it was empty and then reassess where we were after that. I was actually quite surprised to see how much of his free attention this problem took. I took on the task of controlling stops and using my body as visual reference for depth to reduce his task loading and even at that and given the massive amount of diving experience this guy had, I think it would have been a challenge for him to manage this failure at the same time as controlling all of his other dive parameters.

To finish the story, we got through with feathering. Obviously in some contexts it has value but if we had had free access to the surface then we would have just ended the dive where the problem started.

R..

 

[victorzamora]

Thanks lowviz, I'll keep the fold the hose trick in mind should I ever find myself with an unfixable free flow 2nd and need more time for a reasonable ascent. To date, I've never had a free flow while breathing off a reg, only very brief free flows when it was out of my mouth

Actually, it's typically a better idea to NOT kink the hose. Most free-flowing second stages are caused by an IP that is too high. This is most often caused by an o-ring in the first stage going wonky and causing the first stage to deliver full tank pressure (HP) to the second stages instead of IP. If that's the case, and you kink your hose....it might blow the hose. That makes it less useable AND gives you a more expensive fix.

My technique for breathing off of a free-flowing second stage? It's definitely not "sipping air" like you're taught. I keep the thing firmly planted in my teeth and just....breathe. It requires a stiffer stop to keep all of the free-flowing air exhausting from the vent. If it's too much for your exhaust vent, you can dump some out of your cheeks by smiling a little bit. REALLY easy. I've done this while I was still diving BM singles. I was right at the end of my dive, first stage went wonky and second stage started free-flowing aggressively. My buddy turned to see what was wrong with me, I gave an "OK" and a "Thumbs up" and we ascended. He had his short-hose in his mouth and his long-hose deployed just in case. I was fine. Tank was practically dry by the time I got to the surface, but then again I only had a few hundred to begin with and I made a REALLY slow ascent (deep dive). More frustrating than anything. My buddy called me an air hog when we got back on the boat. I grabbed a spare reg and hopped back in for Dive #2.

---------- Post added April 28th, 2014 at 08:46 AM ----------

The only time I've seen feathering used in practice was on a deco bottle.

Dive in sidemount some more. It becomes VERY easy when the valve is easily accessible. Then, while task loaded, switch to your good reg. As a tech diver, especially in sidemount, valve feathering is a GREAT technique to learn. It really extends your gas supply and makes potential emergencies VERY minor. It's happened to me twice in a cave. Frustrating as sin, but they were both after I turned the dive so it wasn't a big deal. I didn't even miss a dive due to this.

....but expecting a backmount diver to do this? I don't see it. Expecting a rec-only, single-tank backmounter to do this instead of bailing calmly to the surface? Insane!