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

[nereas]

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?

If necessary, and there were no choice.

Don't forget, the tank would bleed long before you reached the NDL. Then it would become much lighter. Unfortunately, with the 6 lb BPW, neutral buoyancy with this combo is the best that would be achieved.

Do the math. Did you forget that compressed air has mass? And weighs 0.08 lbs per cu ft?

Add this (80 cu ft x 0.08 lbs/cu ft = 6 lbs) to the SS backplate (6 lbs) and to the add-on (6 lbs), and you get 18 lbs of nonditchable weight, not even closely offset by the positive buoyancy of an aluminum tank. And not to mention a steel tank, which would be even worse.

I would like to see even you, Dumpster, "swim up" 18 lbs of non-ditchable weight with a ruptured wing.

Ergo, a steel tank is out of the question, the 6 lb add-on has got to go, and then with an aluminum tank, given time, the rig may become neutral again, if the wing ruptures, and if the rest of the weight is all ditchable and ditched.

 

[divechk]

Yes, something is definately wrong here...and I'm confused myself...

I normally do bob on the surface with the AL80s [or steel 80s and 85s for that matter], 14lb on weight with 10 on backplate. But not today with the new tank.

I purchase a used tank last night - steel 95 Heiser Beuchat - was short and squat just as I like it as I'm only 5'3. Buddies and I were in the water trying to surface swim out to buoy this morning. I started swimming out, otter-styled, and noticed that despite having a fully inflated bc, I only my face was on the surface. The rest of me was underwater. Yelled out to buddies that something was wrong. We came back to about 5ft of water. We all thought I was overweighted and my fully inflated bc was not able to "lift me" to the normal head and shoulder out of water position. So we started taking out weight off my belt and tried to see if my head and shoulder could get in the normal out of water position. We ditched all of my ditchable weight and I was still only to get my face on the surface, though my body was higher up towards the surface. Ended up swapping tanks with a buddy who could handle the weight on his wing.

So for clarification:
I have 30lbs of lift on wing. It is a DSS 30 LCD.
BP is about 5lbs.
BP has another 5lbs screwed in.
My weight belt has 14lbs.
I weigh 120 and wear 2 piece wetsuit.
No other neg buoyant equipment.

When we ditched all weights on belt- result- only face was on surface with a fully inflated bc.

So does this mean I need to take the 5lb screwed plates on backplate? If so, it will probably just get me to the normal head and shoulder out of the water position. And leaves me with no extra weights.

Or does this mean that I just can't dive this tank because it is too heavy for my wing?? It seems that if I dive this tank I'll have to do it without ditchable weights. Is this even recommended or advised?

Diving the AL80 is a completely different issue- as it seems that I keep on whittling down the amount of ditchable weights I have [and have been overweighted]. Though I'm at 10lbs now, but can ditch perhaps another 2. Which leaves me at 8lbs. At 8lbs- and if I get a canister light [-2 or -3] and jet fins [-1], I'm at 4-5lbs of ditchable weights - provided that I don't shed more weight.....is 4-5lbs sufficent amount of ditchable weights?

 

[dumpsterDiver]

Aren't those heiser tanks ridiculously heavy and alsosuper negatively bouyant?

 

[ArcticDiver]

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.

Take some time to read the several threads on this subject. You will find some stimulating and some not so stimulating posts on the subject. but you will find a lot of philosophizing on the subject. It is worth your time to read the posts.

My summary: A diver needs to be able to maintain neutral buoyancy at any place in the water column without adding or subtracting weight while in the water. The diver needs to do the checks necessary to determine how much additional weight must be added, if any, to achieve this. A diver also needs to be able to swim their entire kit to the surface with no assistance from the wing/bc. Once at the surface the diver must have a strategy for staying there without having to inflate their wing/bc, or their dry suit if diving dry. There is an argument for having some ditchable weight for just the eventuality you mention. But, that weight need not be additional lead. It can be part of your kit. It is all up to you.

 

[divechk]

Aren't those heiser tanks ridiculously heavy and alsosuper negatively bouyant?

sounds like im screwed with those tanks.....

 

[Brewski]

Ok I see the Heiser Beuchat steel 95 weighs 47 lbs empty.
Also a Luxfer aluminum 80 weighs about 32 lbs empty.
That means you've added 15 lbs when you changed tanks.


Edit:
source: http://www.cavediver.com/resources.htm

I re read your OP and see you already took off the belt and are still too heavy.

 

[bamamedic]

You might want to consider changing out your steel backplate for an aluminum one...that would take off 4 lbs, not to mention those weights you've got bolted on to the backplate.

 

[crpntr133]

Ok I see the Heiser Beuchat steel 95 weighs 47 lbs empty.
Also a Luxfer aluminum 80 weighs about 32 lbs empty.
That means you've added 15 lbs when you changed tanks.


Edit:
source: CAVEDIVER.COM -- Resources

I re read your OP and see you already took off the belt and are still too heavy.

To bad that the dry weight has pretty much nothing to do with its buoyancy.

 

[Brewski]

To bad that the dry weight has pretty much nothing to do with its buoyancy.

Of course not. I wanted to give her a good idea of how much heavier that tank was versus the aluminum tank whe was used to.

 

[nereas]

You might want to consider changing out your steel backplate for an aluminum one...that would take off 4 lbs, not to mention those weights you've got bolted on to the backplate.

A similar choice would be one of the ultra-modern X-designed steel plates that weights 2 to 3 lbs rather than 6.