MinimumRecommended Disposable Weight?

[scubainspired]

Thanks for all the input everyone. This is what I have gotten so far.

1. I should be neutral at 10’ with 300- 500 PSI in the tank and when completely full not excessively heavy.
2. If buoyancy failure occurs, I should be in shape enough to swim my entire setup to the surface with out ditching weight.

If these two statements hold true then it follows that the only reason to have ditchable weight is in the situation that I need a buddy’s assistance. (Like a blackout?)

Example: I blackout at 80’ and I have particularly negative buoyancy due to wet suit compression and full tanks. My buddy needs to ditch my weight to surface us both. What if my belt does not have enough weight to make my body positively buoyant enough to make a somewhat controllable rapid ascent? Is it possible to have too much weight? Say with al80’s and it near the end of the dive, my buddy drops my belt and I take off like a rocket?

Thanks Thomas

 

[xiSkiGuy]

Example: I blackout at 80’ and I have particularly negative buoyancy due to wet suit compression and full tanks. My buddy needs to ditch my weight to surface us both. What if my belt does not have enough weight to make my body positively buoyant enough to make a somewhat controllable rapid ascent? Is it possible to have too much weight? Say with al80’s and it near the end of the dive, my buddy drops my belt and I take off like a rocket?

Thanks Thomas

Your buddy needs to forget the weight belt and use your wing to make you neutral while swimming you up, being careful to vent air as you both ascend to avoid rocketing you to the surface.

 

[CD_in_Chitown]

My buddy needs to ditch my weight to surface us both. What if my belt does not have enough weight to make my body positively buoyant enough to make a somewhat controllable rapid ascent?

You're buddy should have paid more attention in Rescue class, there's no need to dump weight at depth. Victim's BC, rescuer's BC in order should be used to surface a diver in need.

As for the poster's initial question, I know lots of folks diving the Great Lakes in doubles that use no ditchable weight and perhaps 3-5 lbs in saltwater.

CD

 

[redacted]

1. I should be neutral at 10’ with 300- 500 PSI in the tank

My plan is neutral with an empty tank (or 1 lb neg with 500 psi in an Al 80). No sense in losing a stop over 1 lb. If I need to, I want to be able to empty the tank at 10'. And then plan not to need to.

 

[scubainspired]

You're buddy should have paid more attention in Rescue class, there's no need to dump weight at depth. Victim's BC, rescuer's BC in order should be used to surface a diver in need.

CD

Hmm … well this just proves I need to take Rescue. I did not know that using your BC for ascent in an emergency was the appropriate way.

 

[midwayman]

The point is this act is reserved for emergencies. "Ditchable" must be ENOUGH that when you ditch it you ascend or if your buddy ditches it your body surfaces. This should be true even with a full tank. You must consider cases where the bladder won't inflate or where swimming up isn't possible - ditching should get you to the surface. A rapid bouyant ascent after losing weight - might indicate being overweighted.

The trouble with ditching weight and depth is wetsuit compression. Say you're at 100fsw and your BC fails in a 7mm farmer john. You are probably pretty negative at this point so you ditch weight to make yourself close to neutral. As you ascend your wetsuit expands and gain bouyancy. Now instead of neutral you're +12lbs and accelerating towards the surface with no way to slow down.

If you're at depth and you black out and have a BC failure at the same time, it seems that your buddy needs to Use his BC or lift bag to get you both to the surface in a controlable fashion.

The only situation I can see where ditching underwater would be an ok idea is where you are shallow, in a thin suit, your buddy has left you, you dont have alternate lift, and you cant swim your rig up (injured?). Otherwise you'll likely end up in a compression chamber or dead.

Like I said before, an alternate lift device is always perferable. And another reason to make sure you're not over weighted to begin with, that way you have less to swim up if the bc fails.

 

[Mandy3206]

I dive 3mm full body in sea water and only use 4# ditchable weight, I used to dive 6# ditchable weight, but recently, after lossing 3# and finding out after the dive, I decided to dive 4#.

When I used jacket style BCs, I used 12# on the belt, when switched to 6# SS BP + 2# STA, only droped to 8# on the weight system. After 9 or 10 dives, I got to 6# ditchble on the system until last month that I losted the 3# on a dive.

With my current setup, if I drop all weight, I'll slowly ascend to the surface.

 

[dumpsterDiver]

The only situation I can see where ditching underwater would be an ok idea is where you are shallow, in a thin suit, your buddy has left you, you dont have alternate lift, and you cant swim your rig up (injured?). Otherwise you'll likely end up in a compression chamber or dead.
\
.

If you do not have a redundant air supply and you loose all your air and have no buddy right there, then I would think that ditching the belt would be a smart thing to do. Being bent is better than drowned,

Plus, being 12 lbs bouyant is not a huge amount, This amount of bouyancy can be controlled by laying on your back and spearding eagle.. like an upside down skydiver.

If you don't beleive me, you can practice it safely in a deep pool. Put on 2 heavy weight belts which are enough to sink you with your BC at least partially inflated.
Take a couple deep breaths on the surface and hold your breath and sink (rapidly) to the bottom. When arriving there, roll on your back, and lay on the pool bottom, ditch both belts very quickly and you will be in position to practice control of your ascent rate. The fins alone make a lot of drag, if you keep your ankles bent and try to scoop some water with them. I have practiced with like 30 lbs of lead.

Note that this little practice skill is not done while breathing compressed air. You take your last breaths at the surface and you don't use your regulator. I came up with this on my own. Do any agencies teach something like this?

 

[midwayman]

Yah, but even Padi teaches a bouyant ascent is last of options you want to use in a OOA emergency. (Which is a little different that a BC failing)

I get your point about being bent is better than being drowned, but just saying that there are better alternatives to it. Ditching weight would be the last thing on my list to get to the surface.

I really should try your drill sometime though. Even though its a position I hope to never be in, it'd be a good skill to have.

If you do not have a redundant air supply and you loose all your air and have no buddy right there, then I would think that ditching the belt would be a smart thing to do. Being bent is better than drowned,

Plus, being 12 lbs bouyant is not a huge amount, This amount of bouyancy can be controlled by laying on your back and spearding eagle.. like an upside down skydiver.

If you don't beleive me, you can practice it safely in a deep pool. Put on 2 heavy weight belts which are enough to sink you with your BC at least partially inflated.
Take a couple deep breaths on the surface and hold your breath and sink (rapidly) to the bottom. When arriving there, roll on your back, and lay on the pool bottom, ditch both belts very quickly and you will be in position to practice control of your ascent rate. The fins alone make a lot of drag, if you keep your ankles bent and try to scoop some water with them. I have practiced with like 30 lbs of lead.

Note that this little practice skill is not done while breathing compressed air. You take your last breaths at the surface and you don't use your regulator. I came up with this on my own. Do any agencies teach something like this?

 

[O2BBubbleFree]

... a little off topic.

I agree with the minimum-weight-you-can-still-do-your-safety-stop crowd, and the as-long-as-you-can-swim-it-up arguments, but I have recently run across a publication where the author states that you should have at least 25% of your weight ditchable. He doesn't expound on his reasoning. Any one else run across this maxim, and know what the reasoning is?