Ditching isn't *ALWAYS* bad!
Genesis once bubbled...
.. I believe that ditching at depth (.vs. on the surface) is a poor choice in nearly all cases....
First of all, I highly commend you on doing your own analysis of what's going on, regardless of what anyone else says. Ultimately, you are responsible for your own life, regardless of what anyone else recommends.
Having said that, I disagree that ditching at depth is *never* the right solution. I've read most of your posts regarding ditching on DB the last few months, and I agree with most everything you've said.
Ditching a *LOT* of weight at depth and turning yourself into a Polaris missle is not a great solution if there is a better solution to be had. (And, we're having this discussion to see if there is a better solution.)
One of the solutions you've thrown out is using an AL plate, which gives you 3# of ditchable weight. I'd like to see more like 4-6# of weight with doubles, but I think ditching that much weight (at depth) is not the end of the world.
Heck, if you can swim UP 22# of weight, then you should be able to easily swim DOWN the extra 6# of buoyancy (worst case) you're going to have as you approach the surface.
Ditching a few pounds of weight isn't going to cause you to become a missle, and unless you're completely out of air and have no air left in your tanks, the loss of a few pounds will still allow you to control your ascent.
At the two extremes we have way too much weight at the beginning of a dive. Losing your wing at this point is *VERY* bad, and is probably the most likely time for it to occur. (Forgot to turn on the tanks, forgot to hook the inflator hose, the wing snagged and ripped off entering the water, it didn't work and you didn't realize it until after you're in the water, etc..). Dropping 6# of weight at this point would still require you to swim up your rig, regardless of where in the water column you're at since you'd be negative. Ditching is a good thing here.
At the other extreme, we're going to assume somehow you've lost your wing at the end of the dive. Again, this is *much* less likely simply because generally speaking, usually things break when they're first used. However, Murphy would tell us otherwise, so we'll plan for it. Somehow we screwed up, and we've got just enough air to get to the surface (assuming we have to work our tail off). At this point, we're no longer 22# negative. There are two solutions at this point.
1) Don't ditch the weight, and swim up the rig. Heck, assuming we've done a dive, we're no worse off than we were at the beginning of the dive when we chose to ditch the weight last time this happened.
2) Ditch the weight. (Note, if we can handle dropping weight at this point, then we should be able to handle dropping weights at *any* other time during the dive, since at this point it will make it the hardest to deal with)
So, instead of -22# at depth, we've lost 15# of gas, so we're at -7#. If we ditch the weight (let's say 6#), we're still at -1#, which is easily managable. Unfortunately, the -1 is going to end up at +9 at the surface (due to wetsuit compression adding 10# of buoyancy).
I guess I'm of the opinion that if I can swim *UP* 22#, I can pretty easily swim *down*, or more realistically, slown down my ascent even with +9# of buoyancy.
Again, doing a risk analysis, I believe the most likely chance of failure is at the beginning of the dive. Ditching a small amount of weight at this point I would not only say is acceptable, but optimal. (Again, the amount of buoyancy change would be far less than the shift due to air consumption). This is *ESPECIALLY* important of you've got no bottom, or the bottom is deep enough to be unsafe for your mix/training.
At the end of the dive, even those there is the risk of becoming 'overly buoyant', you can offset that risk by either not dumping your weightbelt, or by understanding that the loss of weight will cause buoyancy issues, but these issues can easily be overcome by swimming down to slow your ascents to a managable.
(I'd argue that one should feel comfortable with ditching the weightbelt in *ALL* situations, since if you're in a bad situation, task loading will be hard enough that you don't want to have to determine if you've got enough 'air' in the tanks to offset the loss of the ditched weight.)
Feel free to flame away where I've missed out on some important detail!
Nate
