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

[ligersandtions]

I mostly agree with your 1st sentence, but not the second. If you can't swim a full tank back up from depth, then you have a dangerous situation. If you ditch more weight that the weight of gas currently in your tank, then you will not be able to control your ascent when shallow or do a shallow stop. (Unless you started off overweighted in which case some of the lead you are ditching you should have never been carrying anyway.)

Or to put it another way, if you are relying upon ditchable weight to get you up off of the bottom, then you should never dive to a depth & duration beyond which you are willing to do an uncontrolled ascent directly to the surface.

The only people that should be facing this sort of problem are people with very thick wetsuits, such as a full 7mm over a 7mm vest or farmer john. Of course, there are also some people that just keep piling on more and more lead and are grossly overweighted, but this problem - in theory at least - should be correctable simply by doing a proper weight check.

Even if you can swim a full tank up off the bottom, you may still want sufficient ditchable weight to give yourself good positive buoyancy on the surface in case you need to wait a long time for a boat. Usually ditchable weight equal to the weight of your air, or even a bit less, will be enough to make staying on the surface easy. IMO, this 'surface ditching' weight doesn't have to be instantly ditchable. I'm OK with this weight being on a weightbelt beneath a crotch strap or being weights that need to be removed from a pocket in order to ditch them.

Charlie Allen

I'm not quite sure I understand....so let me see if I can say this in another way and you can correct me when I go off track. Say you're diving with an 80 cubic foot tank - the weight of air in there (when it's completely full) is 6 pounds. So, I take it you were saying that 6 pounds is the maximum amount of ditchable weight you should have....but here's where I get confused. You said "If you ditch more weight that the weight of gas currently in your tank, then you will not be able to control your ascent..." So are you saying that the amount of weight you should ditch varies based on how much air you have left in the tank? If that's the case, how do you control how much you ditch at a time?

Also, if the difference between the amount you can swim up with a full rig and the amount you need to maintain your safety stop is less than the weight of the air in a full tank, would the way I described it be the correct way to set up your ditchable weight?

I completely agree with your surface ditchable weight. That's why I wear a weight belt under my crotch strap

Anyways, if I misunderstood anything, please point me in the right direction as I'm always trying to dig up as much accurate information as I can. Thanks!

 

[JeffG]

I'm not quite sure I understand....so let me see if I can say this in another way and you can correct me when I go off track. Say you're diving with an 80 cubic foot tank - the weight of air in there (when it's completely full) is 6 pounds. So, I take it you were saying that 6 pounds is the maximum amount of ditchable weight you should have....but here's where I get confused. You said "If you ditch more weight that the weight of gas currently in your tank, then you will not be able to control your ascent..." So are you saying that the amount of weight you should ditch varies based on how much air you have left in the tank? If that's the case, how do you control how much you ditch at a time?

If you are weighted right. You should start the dive with a negative weight equal to the weight of gas on your back. (That way...if your tanks are empty, you are not positively buoyant.)

At your heaviest point (the start of the dive), you would drop your weight. (Making you close to neutral and able to control your ascent.)

At your lightest point. (the end of the dive), there would be no need to drop any weights because you would be close to neutral anyways.

Somewhere in the middle of the dive it becomes interesting and much depends on how big of tanks you are using. (ie how much gas "weight" exists) But you might be light enough to swim the rig up without dropping any weight.

But then again...the chance of catastrophic failure of gear would more than likely be at the start of a dive (ie jump in with a big hole in your BCD) and thats when you are the heaviest. Its the most dangerous part of the dive. Thats why the ditchable weight should be approx the weight of the gas on your back.

 

[RonFrank]

Ditchable weight is NOT necessary. What is necessary is that one can swim their rig to the surface in the event of a bladder failure, or drysuit failure.

I know divers that use no ditchable weight. This is a highly debated subject for whatever reason.

 

[JeffG]

Ditchable weight is NOT necessary. Was is necessary is that one can swim their rig to the surface in the event of a bladder failure, or drysuit failure.

I know divers that use no ditchable weight. This is a highly debated subject for whatever reason.

Ditchable weight IS necessary, if you are unable swim their rig to the surface in the event of a bladder failure.

and it is an easy way to establish positive buoyancy at the surface in the event of an emergency.

 

[Charlie99]

So, I take it you were saying that 6 pounds is the maximum amount of ditchable weight you should have....but here's where I get confused. You said "If you ditch more weight that the weight of gas currently in your tank, then you will not be able to control your ascent..." So are you saying that the amount of weight you should ditch varies based on how much air you have left in the tank? If that's the case, how do you control how much you ditch at a time?

You can have as much ditchable weight as you want. But if you ditch a large amount of weight at depth, then you will have an uncontrolled buoyant ascent.


As I've posted in another recent thread, how much ditchable weight and how securely attached vs. how quickly released is just a typical risk tradeoff. Unintentional ditching a weight may lead to an uncontrolled ascent. Wetsuit compression and/or overweighting when combined with a BCD or wing failure means that you will have to swim up against the negative buoyancy.

Since I dive single tanks, and usually just an AL80, it's a total non-issue for me. The only time I had a BCD failure was in my first dive of the season with my 5mm full wetsuit and I was carrying a couple extra pounds in addition to my normal 16. So I was overweighted a couple pounds. Even so, I still managed to have a nice 130' dive on a near vertical wall, even though after 5 minutes or so I found staying at 130' was too much work and ascended to 60' where staying at a constant depth was less work.

For me, the right tradeoff is to have 4 to 6 pounds in my integrated BCD pockets -- this means just 2 or 3 pounds in each pocket, which makes accidental ditching very unlikely. Since I'm weighted such that to hover at 3 or 4' under the surface that I will have to be breathing towards the bottom of my lungs, ditching even just 4 pounds gets me nice and buoyant on the surface with a full 80 cubic foot tank. The additional 4 to 12 pounds are in the BCD pockets. I can ditch that weight, but it is a much slower process.

Charlie Allen

 

[RonFrank]

I have 10lbs of weight on my belt, and my BP/STA is the rest of my weight. If I had to ditch the belt, I'd be headed to the surface, no doubt with the exception of maybe the very beginning of a dive. If I had the need to ditch weight while at depth, I'd likely be trying to do so by releasing one pocket (5lbs) at a time. I need to get some 2/3lbs sand weights at some point to replace my 5lbs chunks.

 

[dpbishop]

I split my weights- 7 1/2 in my backpack + a 13 cu pony ; 15 on a belt. At 200 + lbs and a 7 mil suit that gets me down, and the trim is pretty good. Ditchable weights, as has been noted, a subject to accidental ditching. That happened to me last Friday; I was wrestling with a lobster and knocked the belt off on a rock. Even as shallow as 10', I was able to stay down, retrieve the belt and keep the bug, but it took a lot of kicking. At 20 ft. or greater it takes less effort to stay down, but I am still positively buoyant, which I think is a good thing.

While the danger of an uncontrolled assent can not be overstated, there is always this to consider: You can recover from a chamber ride but it's hard to recover from drowning. As an absolute last ditch effort, you should be able to drop weight, blow & go. IMHO.

 

[ligersandtions]

Thanks everyone, I think I understand now!

There seems to be a lot of misinformation out there regarding things like ditchable weight (do you need it and how much?), diving in a wetsuit with a steel tank, and probably other things that I am either forgetting or haven't researched enough.

 

[Teamcasa]

Thanks everyone, I think I understand now!

There seems to be a lot of misinformation out there regarding things like ditchable weight (do you need it and how much?), diving in a wetsuit with a steel tank, and probably other things that I am either forgetting or haven't researched enough.

Good! Now go out and buy the Fusion Dry suit and you will get to figure it out all over again!

(Have fun in Laguna, we will miss you at the dive park!)

 

[gsk3]

You can recover from a chamber ride but it's hard to recover from drowning.

Unless you embolize, which seems to happen in a large number of incidents posted in the relevant forum.