Re: Ditchable -v- Non Ditchable weights

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Posted by Gerry on November 14, 2000 at 14:04:32:

In Reply to: Ditchable -v- Non Ditchable weights posted by MHK on November 14, 2000 at 09:55:15:


First let me correct two errors.

You misstate my position (inadvertently I’m sure.) I agreed that all the weight should not be in one “basket”. In fact I cited DUI, Zeagle and At-Pac as systems that distribute ditchable weight in discreet units. Put your weight in as many “baskets” as you want, just make sure that each and every basket can be dropped if the diver needs it.

Next, the navy example was submariners, NOT divers. (Real specifically Mike, amazing you missed that.) The distinction is important because submariners are not divers, have no diver training, and still do a safe ESA from 100 – 110 fsw.

So, back to the real question, “Should the weight be ditchable or non-ditchable, or a combination of both in OW (non tech) diving?” You say combination, I say ditchable, right? Your combination position is based on the idea that some non-ditchable weight will slow an ascent in an emergency, which you say is necessary because “John Q. Diver” can’t be trusted to exhale going up (even though untrained submariners can.) Somehow Mike, you miss the point that it’s not the speed of ascent that causes the AGE, It’s the holding of breath. It doesn’t matter whether you are ascending fast or slow, if you ascend as little as 5-6 feet while holding your breath you can embolize. Your position, “some non-ditchable weight” unnecessarily slows an OOA diver and perhaps drowns him/her. IMO that’s not just illogical, it’s folly!

Let’s look at three scenarios where ditching weights apply. The first is the OOA diver who wants to get to the surface quickly in order to avoid drowning. He/she can ascend fast (no un-ditchable weight) or slower (some un-ditchable weight). In either case, if he holds his breath, he embolizes, if he exhales he doesn’t. Mike, do you really advocate slowing this divers ascent with non-ditchable weight?

There’s a breath or two made available on the way up by pressure differential, so we teach keeping the reg in the mouth and trying to breathe as we ascend. That breath or two isn’t enough to get to the surface normally, and if you either breathe water, or black out from hypoxia before the surface, you’ll likely drown & die. So we teach ascending fast without regard to normal ascent rates and safety stops. This might put you at some additional risk of a bends hit, but it will more likely get you to the chamber alive. Non-ditchable weight is a liability here.

Now consider the second scenario where you might need to ditch weight. You’re deep; you lose the buoyancy of the BC and find yourself negative. This is NOT an emergency unless you happen to be doing a blue-water dive. On the bottom, I’d simply shoot a line to the surface on a lift bag, attach it to the weight, and ascend the line using it to control my rate. If that’s not possible (for whatever reason,) or you’re in blue water (a real emergency) you ditch and ascend by swimming. Either way there’s no risk of holding your breath because you’re not OOA, so ditch whatever weight necessary - some, or all, until you regain your buoyancy. If you’re really worried about losing buoyancy at the same moment that you run OOA then I suggest you carry your Anti-Loch-Ness-Monster-Torpedo just to be real safe. (Prying tongue out of cheek.) But non-ditchable weight still confers no advantage.

I do blue water diving for AOP. If I lose buoyancy control (including the safety tether) on one of those dives, I want to ditch every ounce I can as fast as I can. Ditching some of my weight while I’m sinking deeper might or might not make me buoyant. If I ditch too much I get to the surface a bit too fast, but again, I’m not OOA so not holding my breath. If I ditch too little I end up at 3000 fsw in the Catalina Channel. (We use safety divers and tethers to protect against this possibility.)

Finally the third scenario: A diver is in distress on the surface. (Far and away more common than the first two scenarios.) In this case the more buoyant you can get, the better. Breathing is easier if you’re higher out of the water. The victim is less likely to panic if he/she can get the face dry. Again non-ditchable weight is not a benefit, strictly a liability.

Your post said that JJ, JW and others are working on the application of DIR to OW. From that I assume that DIR in OW is not as cast in stone as it appears to be in the cave diving arena. Is this correct? Is this topic still up in the air as far as the DIR gurus go?

OK three scenarios, in each I say that weight you cannot drop is either dangerous, or gives no advantage. I tried to build the argument carefully and cover the possibilities. Any time I talk this long I leave nits to be picked, please ignore these. If I’m wrong, either I missed a scenario or I blew the logic in one or more of the ones I called. Which?

Jim, John, Terry or Kendall, feel free to weigh in (or anybody else for that matter.)


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