How much weight needs to be dumpable?

[gbenson]

Hi all,

I just got a pony, which weighs about 1.5kg in the water. I wear it on my back, with 1.5kg in the opposite trim pocket. With three kilos gone from my belt I now have only 6kg dumpable weight in fresh water. Is that enough to get me out of trouble do you think?

Cheers,
Gary

[PeteM]

Hi all,

I just got a pony, which weighs about 1.5kg in the water. I wear it on my back, with 1.5kg in the opposite trim pocket. With three kilos gone from my belt I now have only 6kg dumpable weight in fresh water. Is that enough to get me out of trouble do you think?

Cheers,
Gary

If you are properly weighted yes. I am assuming you use a single as it is a rear mounted pony, biggest size most people use is a 15, with the pony that means 18L of gas which at 232bar weighs 5Kg. So if you are correctly weighted (i.e. really neutral with empty cylinders) you will be 5Kg over weighted at the begining of the dive so dumping the belt and all gas from suits and BC will still make you positive albeit not very.

[robscubaproxlt]

Dumpable weight is always variable because your diving differs as you change your kit for cold water or warm water diving for example. If you dive your stated configuration all the time then it won't change so you need to work out the weight of you your kit and displacement in the water. you can do this mathematically as the previous post suggests and get it right, but i find it better to actually empty my cylinder or cylinders to 40 bar and do a weight check in the water. with all your kit on and 40 bar at the surface you should be able to float reasonably well whilst breathing normally,if you exhale you should sink slowly if you inhale you should float, using your mask as a guide eyes above water floaty eyes underwater sinky. add or remove weight until you can descend at will or ascend at will. you are then perfectly weighted at the end of a dive or when almost out of air. Therefore at the beginning of the dive you are only the weight of your gas (overweighted) which you can calculate as the previous thread states. Lets say it was 4 kilos for example you then know you need to dump 4 kilos at the beggining of the dive and less or none as the dive time lengthens. Ideally you should be able to swim up from depth without dumping weight as you may shoot to the surface if you dump too much! There is so much more to this topic but i hope this helps.

[Nigel Hewitt]

I just got a pony, which weighs about 1.5kg in the water.
Does it?
My 7L steel stages with regs and all are less than that empty.
I wear it on my back, with 1.5kg in the opposite trim pocket. With three kilos gone from my belt I now have only 6kg dumpable weight in fresh water. Is that enough to get me out of trouble do you think?
Loose a belt at depth and it's quite enough to get you into trouble.

I'm no fan of easy dumpable weight except on trainees. 6 kilos is huge.

[paul_c]

i dont carry any easy ditch weight

i have 2 kilo which can be removed from my BCDs pockets (oh the horror) if it ever was required, not that it will as i can do a swiming accent with my twins on.

[gbenson]

I just got a pony, which weighs about 1.5kg in the water.

Does it?
My 7L steel stages with regs and all are less than that empty.

I based it on the fact that it required 1.5kg on the other side to trim me with it. I don't know if that's valid though!


I'm no fan of easy dumpable weight except on trainees. 6 kilos is huge.

I was always taught to have enough easily dumpable weight that in the worst, worst, worst possible case scenario you can get yourself to the surface. Better bent on the surface than drowned on the bottom and all that!

[Nigel Hewitt]

I was always taught to have enough easily dumpable weight that in the worst, worst, worst possible case scenario you can get yourself to the surface. Better bent on the surface than drowned on the bottom and all that!
That's sound-bite safety planning as practised by politicians world wide. You can well end up putting yourself more at risk because you have too much safety kit and a fault with that can be worse than the thing it protects you from. As with all things the key is balance and particularly with scuba it is having something else to breathe so you have time to think hence the pony is magic.

I've watched a buddy grab for his belt as the clip broke. Just one of the little hinge rivets went. It was a big belt and he caught it but we had to tie him to the wreck before we dared move it about much so we could do our stops form 40 something meters. I have always felt that if he had missed it and just vanished leaving me with the belt that would have been the loneliest ascent ever wondering what I would find.

[Jed]

It's quite a difficult subject really. Whilst I agree with Nigel that it would be an absolute last option for me. The fact is that one of things we do during our buddy check is show each other where our weights are and how to release them.

I was talking to a very experienced diver at the weekend who once had a problem with his first stage whilst on a reef at 3 metres. Instinctively he swam for his buddy and used his octopus even thought the surface was nearer. I think that if you get into the mindset that as soon as you have a problem you are going to drop everything and head for the surface it will eventually bite you in the ass.

[PeteM]

I've watched a buddy grab for his belt as the clip broke. Just one of the little hinge rivets went. It was a big belt and he caught it but we had to tie him to the wreck before we dared move it about much so we could do our stops form 40 something meters. I have always felt that if he had missed it and just vanished leaving me with the belt that would have been the loneliest ascent ever wondering what I would find.

The reason I and all my buddies have dumpable weight that requires a minimum of two actions to dump it

[gbenson]

You can well end up putting yourself more at risk because you have too much safety kit and a fault with that can be worse than the thing it protects you from.

That's a fair point. I've been trying to think of situations where the only way for me to reach the surface would be ditching weight, but I can't think of any that don't involve the failure of both gas supplies and an unreachable buddy. Three failures.

That does make me worry about one thing. When I was looking into getting the pony, several people advised me to get a button gauge to reduce the number of pipes. Which is great, but when I was diving with it I was acutely aware of having a redundant gas supply that I couldn't monitor. What if it was happily leaking away behind me? Ok, my buddy could tell me, but I like to be self-contained. What do people think about button gauges vs gauges on hoses?

There is the possibility that I might be unconscious and in need of rescue, and the rescuer cannot achieve enough buoyancy... but that shouldn't happen unless I was seriously overweighted (and I don't think I am!)

I've watched a buddy grab for his belt as the clip broke. Just one of the little hinge rivets went.

Maybe I should move everything to integrated. My BCD can hold 9kg which is plenty for me, and the pockets are held in with clips and velcro. I've avoided it for now as it's difficult to get the pockets in when I'm kitted up, but maybe I just need practice!

[Vic]

That's a fair point. I've been trying to think of situations where the only way for me to reach the surface would be ditching weight, but I can't think of any that don't involve the failure of both gas supplies and an unreachable buddy. Three failures.

You've also got to be in a situation where you're already negatively-buoyant to the extent that you can't fin up, and you can't ditch your entire rig. So you're already up to about 5 simultaneous failures (possibly more - an SMB with a bottle on it will get yo to the surface if you need it to...)

If you really have screwed up to that level, it doesn't really matter how much kit you're carrying - the problem is not with the kit, but with how it is used...

That does make me worry about one thing. When I was looking into getting the pony, several people advised me to get a button gauge to reduce the number of pipes. Which is great, but when I was diving with it I was acutely aware of having a redundant gas supply that I couldn't monitor. What if it was happily leaking away behind me? Ok, my buddy could tell me, but I like to be self-contained. What do people think about button gauges vs gauges on hoses?

I used to use one when I carried a pony. The biggest problem with them is that some designs are quite fragile.

When on a dive, you should notice any significant loss quite quickly - either your buddy will tell you about it, or you will hear it.

If you ever actually have to switch to a pony for real - you;ve either got enough gas, or you haven't. Being able to see the gauge wind back to the red zone doesn't actually put any more gas in the bottle...

Vic.


There is the possibility that I might be unconscious and in need of rescue, and the rescuer cannot achieve enough buoyancy... but that shouldn't happen unless I was seriously overweighted (and I don't think I am!)

Maybe I should move everything to integrated. My BCD can hold 9kg which is plenty for me, and the pockets are held in with clips and velcro. I've avoided it for now as it's difficult to get the pockets in when I'm kitted up, but maybe I just need practice![/QUOTE]

[gbenson]

What do people think about button gauges vs gauges on hoses?

I used to use one when I carried a pony. The biggest problem with them is that some designs are quite fragile.

Fragile how?


If you ever actually have to switch to a pony for real - you;ve either got enough gas, or you haven't. Being able to see the gauge wind back to the red zone doesn't actually put any more gas in the bottle...

I was thinking more about being able to make a quick check on it before swimming through something, for example, or when my computer is about to click into deco.

[Vic]

Fragile how?

Some types are made of fairly flimsy material; where they are firmly attached to the first stage, that can mean quite a blow to the gauge in fairly normal handling, and the el-cheapo gauges can suffer badly (either shedding bits they shouldn't, or, more worryingly, jamming the mechanism).

Putting the gauge on a hose means that there is less momentum involved in any impact...

Note that some buttone gauges seem perfectly well engineered to deal with this sort of use.

I was thinking more about being able to make a quick check on it before swimming through something, for example, or when my computer is about to click into deco.

Re-planning your dive at depth? That's a no-no...

Vic.

[Nigel Hewitt]

Some types are made of fairly flimsy material; where they are firmly attached to the first stage, that can mean quite a blow to the gauge in fairly normal handling, and the el-cheapo gauges can suffer badly (either shedding bits they shouldn't, or, more worryingly, jamming the mechanism).I've been hit by the shrapnel when one let go. On switch on.
Re-planning your dive at depth? That's a no-no...
Heck that's my usual 'manage an incident' concept.
UP AND OUT. NOW!

I've tried to assemble a single point of failure scenario that goes against my 'no easily dumpable weight' plan and this is the best I've come up with so far:

I am CCR deco diving something deep in Norway or Shetland.
As we are about to start up the shot with years of stops to go when my neck seal lets go big time. I've split seals twice in ten years, I have a big head and a small neck.

An hour later I am so cold I am stupid, well more than normal, and just trying not to fall asleep is about my limit. I am still gaining negative as water seeps into more places and my buddy is trying to control things. The poor guy is already thinking about tyeing me to the trapeze and when we finally time out he needs to get me to the surface and then fix me to the surface. If I lose it then, and flood the loop, he needs to dump a lot of my weight fast and about the only bits not bolted on are the trim weights behind my head.

Perhaps they would write 'Should have carried dumpable weight' in the obituary.

[northern_diver]

If you sling your pony, your can sometimes read the button gauge. If you have it on the cylinder, then your need a gauge on a hose.

A forseeable requirment to know how much gas you have in your pony (irrespective of size, though 3l minimum) is that you had to switch to your pony for an ascent and have some Deco. By been able to monitor your available gas supply, you can make a calculation on the amount of deco you can do. Based on the idea that the more decco you can do, the better...depends on your feelings on deco theory really.

The face of some button gauges can getg naffed up, and hose gauges can be easier to read.

The last possible reason is the pure psychological bonus of been able to ee how much air you have, instead of making a mad rush (controlled, safe ascent) to the surface.

Some people believe that as you have switched to your pony, your'll be making post haste to the surface, so dont need the extra failure points.

I feel there is value in all sides of the ensuring debate.

John

[ChristianG]

Ummmmm,

Can I, at this late date, say "precisely none"?

If you are contemplating losing your weight, firstly, how and why did you manage to get into that situation in any case and, secondly, this is about as much trouble as you're ever likely to get into.

The whole point is not to lose your weight, or is there yet again something I'm not getting?

[Dave Lev]

Ditchable weight scares me, too. I think it is wise to limit how much could be lost accidentally.

Regarding stage guages vs button: consider a 15cm MiFlex high-pressure hose and a "real" SPG. These hoses are designed for exactly this - very thin and extremely flexible, even when pressurised. It is very easy to bend the hose out of the first stage and have the SPG itself strapped to the first stage (with a small loop of bungy cord) right where you can see it.

[Richard Whitcombe]

If you ever actually have to switch to a pony for real - you;ve either got enough gas, or you haven't. Being able to see the gauge wind back to the red zone doesn't actually put any more gas in the bottle...

The one time i had to switch id have killed to have a readable gauge. Although i knew the thing was full and knew from my calculations i had more than enough to get me up and out with loads to spare i lacked that reassuring visual marker to confirm all the above. Something to confirm my SAC wasn't 300,000,000l/min or the maths was wrong would have been nice. Surfaced expecting every breath from it would be the last.

That said id never dive back mount pony now if i dived on singles, side sling all the way now with a decent gauge on 6" hose.

As for ditchable weight, i carry none. I wear a crotch strap on my wind and one of its main purposes is to stop my belt accidentally falling off. I rate the risks of accidentally losing weight far more dangerous than the alternative.

[ChristianG]

That does make me worry about one thing. When I was looking into getting the pony, several people advised me to get a button gauge to reduce the number of pipes. Which is great, but when I was diving with it I was acutely aware of having a redundant gas supply that I couldn't monitor. What if it was happily leaking away behind me.
The only thing attached to the 1st stage of my pony is the 2nd stage.

I check that the pony is full on the surface, pressurize the line to the 2nd stage and turn it off. I used to carry it alongside my main tank but upside down, nowadays it's sideslung so in both instances I am able to get at the tap pretty well instantly to turn the tank back on.

As Vic said, if you are reduced to using your pony you will breathe it dry if necessary. Furthermore if you are reduced to using your pony, as Nigel said it's also the time to immediately go up and out because you should not be in a decompression situation, not with just a pony. If you are you quite certainly should be using more serious equipment, twins at least, and not 7 litre ones either, that's not twins, that's a single which is slightly smaller (in capacity) than a 15. Oh, and I wouldn't worry about swimming around looking for the buddy that Murphy's Law dictates will have taken precisely that moment to disappear. I'm in pony mode? I'm outta there! If the buddy's not with me, tough luck.

Note that a 3 litre pony should be perfectly adequate to get you comfortably to the surface with gas to spare, always provided you are diving it to the depths for which it is suited.

[Janos]

An hour later I am so cold I am stupid, well more than normal, and just trying not to fall asleep is about my limit. I am still gaining negative as water seeps into more places and my buddy is trying to control things. The poor guy is already thinking about tyeing me to the trapeze and when we finally time out he needs to get me to the surface and then fix me to the surface. If I lose it then, and flood the loop, he needs to dump a lot of my weight fast and about the only bits not bolted on are the trim weights behind my head.

Make sure your buddy carries a lift bag :)

I holed my suit in Malin right at the end of the planned bottom time when I had a couple of hours of deco to do.It wasn't a complete flood, but it was a lot of water. Although I was cold, I was surprised at how warm I kept. Modern undersuits are great for that.

Janos

[Janos]

The one time i had to switch id have killed to have a readable gauge. Although i knew the thing was full and knew from my calculations i had more than enough to get me up and out with loads to spare i lacked that reassuring visual marker to confirm all the above.

I know people who've bailed from CCR who have said exactly the same. Proper gauges for me!

Janos

[IainC]

I holed my suit in Malin right at the end of the planned bottom time when I had a couple of hours of deco to do.It wasn't a complete flood, but it was a lot of water. Although I was cold, I was surprised at how warm I kept. Modern undersuits are great for that.

Janos

Moving around makes a big difference, too.

I've had a year of being soaked nearly every dive for one reason and another.
(Now fixed, hurrah! :-)

I had an hour of stops to do and was shivering after only a few minutes due to beign soaked - just swimming slow circles around the trapeze warmed me up remarkably. Having a plate of pie and mash handed to me immediately post dive was even better though.

Iain.

[ChristianG]

I know people who've bailed from CCR who have said exactly the same. Proper gauges for me!
I respect what you say, a lot of divers are like that.

I have never, speaking entirely for myself, felt such a compelling need. I grant you that a "real situation" where I might need to do this has escaped me but, at least three times I have bled my primary tank close to the point of oblivion and then surfaced on the pony, mostly from 35 metres which is about as far as I would take the pony in pretty perfect conditions. For me, I make no suggestions as to anyone else, it was eminently doable but, yes, there was someone else there as cover so I don't know whether my SAC would have altered in a real situation. Given that I'm a pretty cold blooded animal at the best of times I like to think, I could well be wrong, that much the same would happen in a "real" situation.

I also, silly me, do things like swim up with my twins full and weight, oops, they're ain't any, in place. Strangely enough it seems like I can do that as well.

I'm outta here, this is turning into "instruction", or "technical" or whatever.