Using SMB For Backup Flotation

[Web Monkey]

Imagine this:
You are diving a deep wall off Cayman in a 3mm wetsuit with double AL80's. Your wing fails at the threads between the inflation hose and the bladder making maintaining bouyancy with the wing virtually impossible. Any air added just easily escapes out as you add it.

You tilt slightly head down so the air stays in the bottom of the bc where the leak isn't, relax and do a normal ascent.

All this is happening while you are kicking feverishly to maintain depth due to being negative from the doubles fairly early in the dive. You are sinking against the kick initially at a rate of 30 feet per minute as you deploy your bag. Instead of clipping the snapbolt to your crotch d-ring, you decide to attach it to your reel and blow it to the surface. The bag rises above you and the line jumps the spool, tangling with the force of 50lbs pulling against your mass.

First, my spool is always attached to my bag, and there's nothing to tangle. I don't use a reel with a lift bag because it can foul.

Second, nothing that's attached to the outside world (filled bags, lines, whatever) ever gets attached to me.

In any case, I can pull out the other bag and spool and deploy it.

1. Go for a ride and get bent?

No

2. Cut the line/let go of the reel, and start your descent into the abyss?

My buddy already cut the line. If I have a bag and a spool out, he's got a cutting tool.

3. Did you bring a backup bag and reel to replace the primary in such an event?

Actually yes. I always bring two of each.

None of these are good options in this scenario, which is not fantasy. The appropriate way to use a lift bag to control bouyancy is to handle it the same way you would your other forms of bouyancy. Keep it close to the body so you are in control at all times. A proper 50lb lift bag will have a stainless steel snap bolt at the bottom of the lifting strap. You clip it to the crotch d-ring, add enough gas to it to stop the descent, then gather your wits. At this point, you will not need to add any more gas to the bag, as Boyle's Law will take care of the rest. You slowly give a few kicks to rise just a few feet in the water column, just as you would if you still had use of your wing; all while keeping the bag close to your chest, anchored at the crotch d-ring, and one hand stabilizing the top of the bag and the other hand on the OPRV at the top of the bag. As you rise a few feet, you burp the OPRV, and repeat with a few kicks.

You're welcome to do this, but I prefer to have the bag on the surface and just roll up the spool as necessary. It's much easier to move up a foot by rolling up a foot of line than by riding a floppy half-inflated bag.

In fact, this whole scenario is a little contrived, since you would need to have a bunch of dumb things in sequence to get to the point that you're going to "ride the lift-bag pony".

What would really happen is that I would reach over and grab my buddy, who would adjust his buoyancy to stop our descent. I would point at my BC, extend my middle finger to indicate that it failed, and we would do a normal ascent to the surface.

In any event, this can be avoided by not doing dumb things.

I won't dive in any configuration that can become negatively buoyant, without redundant buoyancy. That means that steel doubles = wing and drysuit. And my buddy who would happily grab me and haul my butt back to the surface if necessary.

This is any easy task with practice. I've had to do it for another reason I will explain in another post if anyone wants to hear it. Shooting the bag to the surface and reeling yourself up is not an option. Try it, and you will see that you are not going to be able to turn the spool against all that mass, even while kicking your heart out. You will very quickly tire. You need the gas in the bag to lift you, not your arms and fingers on a tiny line and spindle.

Actually, I've done it and works just fine. Mountain climbers haul their entire body weight up thousands of feet. We're only talking about 20 pounds.

Terry

 

[battles2a5]

Oh wow, I think my last post landed me on RJP's ignore list. Whoops! Guess I struck a nerve.

 

[deepstops]

No, it's more like this now:

 

[netmage]

Hello Kitty has entered the room!

I'm back on the 16th. What's the plan? I've two weeks to blow underwater. Scott, Marc, and I are going down to Largo to dive the following weekend and do a sea trial on possible boat. You in?

I've been here... no one seemed to pay my suggestions of diving a balanced rig to heart, and I refuse to 'beat people w/ a DIR stick', since further agitation along those lines typically gets labeled as such... Why solve a problem that doesn't need to exist...

I think the term "mental masturbation" summed it up perfectly...

Tentative plan is to go to the caves for a long stretch around Thanksgiving, tho deepstops is trying to talk me into abandoning that and staying local and hitting some Keys action.

For recreational purposes, since this is Scubaboard, a spool is the item of choice for bag shooting. Infinitely less complicated 'foul' wise, and more than adequate for depths. If I'm going deeper, a Halcyon\Salvo style reel is used, and I'm also in a buddy team, so we have backups in case I have to cut the line, and its happened twice; due to current sheer, not fouling...

 

[mempilot]

You tilt slightly head down so the air stays in the bottom of the bc where the leak isn't, relax and do a normal ascent.

Assuming it didn't fail on the descent where you don't already have enough gas in the bladder to sustain your current depth, let alone increasing depth via an uncontrolled descent.

First, my spool is always attached to my bag, and there's nothing to tangle. I don't use a reel with a lift bag because it can foul.

You must carry some pretty big spools to be able to deploy a LB at depth. Most spools are for running jumps and deploying a bag from a decompression stop. I have a lot of spools and a lot of reels. If I'm deploying a LB from depth, I'm using something that will allow some scope in current. A 50 to 125 foot spool is going to be useless from a deep wreck. If you are blue water, then it will work from the max depth of the line, but you'd better hope you aren't in an uncontrolled descent in blue water relying on a 125 foot finger spool. :shocked2:

Second, nothing that's attached to the outside world (filled bags, lines, whatever) ever gets attached to me.

In this situation, it would be prudent. Use whatever method you'd like. Your wing is attached to you. Your drysuit is attached to you. A LB being used for bouyancy should be attached to you. The loss of that bouyancy device would be akin to a puctured drysuit of just plain taking your wing off. You would do or want that, so why would you send your last ditch bouyancy control device to the surface? You may want to rethink that one. Sending a LB to the surface on a line makes it a Surface Marker Bouy, not a bouyancy control backup.

In any case, I can pull out the other bag and spool and deploy it.

I'll buy that. I mentioned that in an above post.

NoMy buddy already cut the line. If I have a bag and a spool out, he's got a cutting tool.
Actually yes. I always bring two of each.

Always a good plan. I keep a cutting tool close to my chest area for this reason. (tangled line, spool with a shooting bag on the other end, etc...)

You're welcome to do this, but I prefer to have the bag on the surface and just roll up the spool as necessary. It's much easier to move up a foot by rolling up a foot of line than by riding a floppy half-inflated bag.

Don't forget, you have no bouyancy control in this exercise. You are negative and possibly descending during the process. Reeling up an extra 15 lbs is a lot harder than most people think using a 4 inch diameter spool not designed to create leverage.

In fact, this whole scenario is a little contrived, since you would need to have a bunch of dumb things in sequence to get to the point that you're going to "ride the lift-bag pony".

Not really.

1. diving wet with double AL80's
2. wing fails at the elbow (cross threaded from last mx)
3. deploy LB with reel/spool and it fouls (now lost)
4. you'd better have that backup lift device

What would really happen is that I would reach over and grab my buddy, who would adjust his buoyancy to stop our descent. I would point at my BC, extend my middle finger to indicate that it failed, and we would do a normal ascent to the surface.

Good luck with that. Maybe in recreational depths with a hard bottom, there is no issue with this. Go dive a deep wall and see how that works. Your descending to depth and realize you can't stop your descent due to wing failure. Your buddy won't catch you, and you aren't going to catch him. Read the articles on uncontrolled descent. There are incidents with technical divers plumeting to 250 fsw and crashing into the wreck or bottom. No buddy is going to catch them.

In any event, this can be avoided by not doing dumb things.

It doesn't take a dumb thing for this to happen. I've had things fail, as have others around me, that had nothing to do with stupidity.

I won't dive in any configuration that can become negatively buoyant, without redundant buoyancy. That means that steel doubles = wing and drysuit. And my buddy who would happily grab me and haul my butt back to the surface if necessary.

Are you telling me AL80 doubles and a 3mm is neutral? Absolutely, you need redundant bouyancy. That is what we are talking about here. Either a drysuit, or a LB. Sometimes it's hard to see the forest through the trees.



Actually, I've done it and works just fine. Mountain climbers haul their entire body weight up thousands of feet. We're only talking about 20 pounds.

Terry[/quote]

 

[Scared Silly]

Whether you want to swim it up, shoot a SMB and crawl up it, use a lift bag and ride along, or piggy back with your buddy. The point is to practice skills and understand pros and cons of each. I have swam it up and crawled up an SMB for practice and have dealt with an inflation problem at the surface that was not practice and was after ascending due to other major but related problems. I want to work with a lift bag some point.

BTW - folks have mentioned not bring able to dump an SMB cause the OPV is on the bottom. But has anyone every thought about turing it upside down??? Something to think about ... and surely not saying it will not. But when Neptune calls you deep ...

 

[mempilot]

I've been here... no one seemed to pay my suggestions of diving a balanced rig to heart, and I refuse to 'beat people w/ a DIR stick', since further agitation along those lines typically gets labeled as such... Why solve a problem that doesn't need to exist...

Agreed, if you are talking strictly recreational. Someone had brought up different doubles configurations, and SB seems to be gaining steam with newbie techs since PADI has created some new color graphs and charts. It's impossible to dive a neutral rig with steel doubles, or even double AL80's and a thin wetsuit. Hence the discussion around redundant bouyancy needs.

Tentative plan is to go to the caves for a long stretch around Thanksgiving, tho deepstops is trying to talk me into abandoning that and staying local and hitting some Keys action.

Let's private charter one of Chris' boats and do something long. I need to break in the Shearwater head.

For recreational purposes, since this is Scubaboard, a spool is the item of choice for bag shooting. Infinitely less complicated 'foul' wise, and more than adequate for depths. If I'm going deeper, a Halcyon\Salvo style reel is used, and I'm also in a buddy team, so we have backups in case I have to cut the line, and its happened twice; due to current sheer, not fouling...

On a recreational RDP dive, this conversation is pretty much mental masterbation (this word has now been used 3 too many times in one thread for SB ). But, since doubles were brought into the fray, and some of the posters are doing light tech, spools are out for deep deployment and reels are the tool of the day.

 

[mempilot]

Whether you want to swim it up, shoot a SMB and crawl up it, use a lift bag and ride along, or piggy back with your buddy. The point is to practice skills and understand pros and cons of each. I have swam it up and crawled up an SMB for practice and have dealt with an inflation problem at the surface that was not practice and was after ascending due to other major but related problems. I want to work with a lift bag some point.

Good summary.

BTW - folks have mentioned not bring able to dump an SMB cause the OPV is on the bottom. But has anyone every thought about turing it upside down??? Something to think about ... and surely not saying it will not. But when Neptune calls you deep ...

This would not work with an open bottom bag. The gas would just spill out. It would work with a CC bag, but any good quality CC bag will have the OPRV at the top already.

 

[Scared Silly]

Right, I was thinking strictly about a close circuit SMB which is what all of ours are. Turning an open circuit upside down would not be a wise idea.

BTW Shameless plug I am selling a SCC Halcyon lift bag.

 

[mempilot]

BTW Shameless plug I am selling a SCC Halcyon lift bag.

Great bags. I own two. A LB and a SMB. I use the SMB for decompression drift, and I use the LB for lifting and redundant bouyancy. It is also a backup to the SMB in the event the line gets fouled and has to be cut/let go. I'm a believer in once you go CC with lifting devices, you'll never go back to open bottom bags again. Open bags with flaps are a good intermediate alternative.