Ditchable weights...are they needed and is there a minimum?

I think I'm approaching a point where I'm running out of ditchable weights. I'm curious what is the minimum ditchable weights that one should dive with. Also- do people dive without ditchable weights? What has been your experience with ditchable weights?


I dive a bp/w with 5 integrated weight on bp which I may have to take out to put on belt. On AL80 I've been wearing 14lbs on belt. BP with weight is about 10. I switched the tank to a steel 95 today. And had to ditch all ditchable weight- and was still not quite on the surface with my wing fully inflated with air coming out of vent- only my face was on the surface [not head- just face]. I have a 30lb lift weight. I weigh 120lbs. Don't have any other extra "neg" buoyant gear on me [eg can light or heavier fins - as I'm still on snorkel fins]. I dive wet with a 7mm 2 piece. Could it be that my wing does not have enough lift? I ended up swapping tanks with buddy who had an al80. He was fortunately able to handle the extra weight. I want to dive with this tank again, as I do own it, however, I'm under the impression that even if I take out the 5lb plates, I'll can't add any ditchable weights. I ended up taking 2lbs off belt today with AL80, and feel that I can probably take out more weights.

Ok, let's say the tank full is -10, add in the plate and you are -16, even taking your weight as being lean and negative that puts you at most -18. The 7mm suit should be about 8+ to 10+ within 15' of surface (it will compress and lose buoyancy at depth.) So you should be at the very most about -10 with a full tank... even without the wing lift. And you have a 30+ lift on the wing? Something is wrong here.

I'm confused. You had to ditch weights even though your wing was working? AFAIK you should definitely not have to ditch weights to surface when your wing is working!

You seem to asking two different questions here.

As to your first question, about ditchable weight in general, that's opening a can of worms and there are a number of different philosophies.

In my humble opinion, you need ditchable weight only if you are wearing a wet suit and can't swim off the bottom in the event of a BC failure with a full tank. You need to be able to ditch enough weight to get off the bottom. There aren't many configurations that would require ditchable weight, though. I can think of double steel tanks with a thick wet suit as one of them.

As to the the second part of your question -- I agree with vshearer. Your story doesn't make any sense. You're 120 pounds in a 7m wet suit with a 30 lb. wing? You should bobbing on the surface like a cork.

You have opened the can of worms. Or Pandorah's box, as it were, dearest Divechk.

By combining your 80 cu ft alum tank with your 6 lb SS BPW, you have a neutral rig, perfect! Someone taught you well. I wish everyone dived like this, with a wetsuit.

However, the 6 lb add-on to the plate could turn out to be a major problem for you, yes.

When diving with a thick wetsuit, all your weight should be ditchable, especially if you have a backplate on. Because the suit compresses to -0- buoyancy at 100 ft. Then if your wing failed, you would need to ditch everything, and if not able to kick up, then wait for the air mostly to vent from your tank, until the tank became positive, offset by the 6 lb wing, to -0- buoyancy.

Now you could surely easily kick up, to safety and the surface. That is why all of your weight, besides the backplate, needs to be ditchable.

Until you buy either a drysuit or else a double-bladder wing, you should be able to ditch all of your weight besides the backplate.

Or else you would be unsafe, and anyone who tells you otherwise is telling to do something unsafe. And you will need to ignor the hecklers who know very little about diving, other than what PADI taught them when they put their dollar in.

When you finally switch to a drysuit, then the picture changes, and you then no longer have a wetsuit compression problem. In that case, you only would need an amount of ditchable weight equal to the weight of your gas in your tanks(s), computed as 0.08 lbs per cu ft.

So take the add-on off the plate, at least until you get a drysuit.

nereas and I have the same basic philosophy, we just differ on how we put it into practice.

I have actually tested all of my dive configurations and have had no trouble getting off the bottom in all cases. Once I took double AL80s down to the deck of the Speigel Grove (90 feet) with a 7mm wet suit, dumped all the air from my wing, and still had no trouble getting off the deck. (Of course, I also had redundant buoyancy just in case.) So I'm not sure that all of your weight needs to be ditchable.

Maybe some people can do the math the figure out exactly how much weight you need to have as ditchable. I can't. So I just jump in and actually test my configuration. I carry redundant buoyancy just in case I get in over my head.

The numbers don't add up for me, either. My personal rule of thumb is to wear as much of your weight as possible on a belt or harness so that you can dump it in the event of an emergency. Therefore only used fixed weight when (1) there is no more room on your belt for all of your weight or (2) the belt is too heavy to carry on your hips. My guess for your gear combination is that neither condition will occur.

In regards to the general question of how much ditchable weight, that depends upon your goal for ditching weights. I am able to swim back to the surface from depth with a full tank with my BCD empty. My only need for ditchable weights is to become positively buoyant on the surface if I need to stay there for a long time with full tanks.

Since I'm setup to be neutral a few feet below the surface with a near empty tank, all I need to be able to ditch is lead in roughly the amount equal to the weight of air I am carrying --- 6 pounds for 80 cubic feet. In practice, even just dumping 4 pounds is enough for me to comfortably stay on the surface with an empty BCD and a full tank.

Ditching lead at depth in order to get neutral to come up off the bottom means that I will have an uncontrolled ascent when shallow. NOT a good thing. Dumping lead at depth is a bad idea, unless you are overweighted and are just dumping lead that you shouldn't have been carrying in the first place.


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The specifics of your situation sound like you are grossly overweighted, even with no additional lead on a belt or in pockets. If you have to fully inflate your wing to get your head out of the water, what happens when you have an empty wing???

Charlie Allen

nereas:

When diving with a thick wetsuit, all your weight should be ditchable, especially if you have a backplate on. Because the suit compresses to -0- buoyancy at 100 ft. Then if your wing failed, you would need to ditch everything, and wait for the air mostly to vent from your tank, until the tank became positive, offset by the 6 lb wing, to -0- buoyancy.

Now you would kick up, to safety and the surface.

Or else you would be unsafe, and anyone who tells you otherwise is telling to do something unsafe.

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Let me make sure I'm reading this right...

You really mean to say that in the event of a (rare) total wing failure at depth you advise a diver to ditch all weight and wait for the tank to become positively bouyant, then once neutrally bouyant at depth swim up? How do you expect a neutral at 100 feet diver in a thick wetsuit to remain neutral as he/she ascends if everything was ditched?

First the "clipped off to a neklace reg", and now this - Who's offering unsafe advice here?

nereas:

......


Because the suit compresses to -0- buoyancy at 100 ft. Then if your wing failed, you would need to ditch everything, and wait for the air mostly to vent from your tank, until the tank became positive, offset by the 6 lb wing, to -0- buoyancy.

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where do you come up with this crap? Seriously. A diver develops a problem at 100 ft that necessiates ditching of lead and you would want them to remain at 100 feet to breath down their tank (absorbing more nitrogen) before starting their ascent?