Let's discuss dumpable vs non-dumpable weights

[Dogbowl]

So we all learned in OW class that in an emergency at depth, we might need to dump weights and ascend. Therefore, we should have dumpable weights, like those easily accessible from our waist area, whether they be on a weight belt or integrated into our bcds. But I know for trim purposes, many divers, especially tech-leaning ones, will place weight on their tank cam bands, which, of course are not dumpable. Realistically and practically speaking, are non-dumpable weights dangerous? If so, why are tech divers doing this, since they are the ones who are usually particularly safety conscious. Please enlighten me!

In another thread, I discussed how I personally put 5-5 lbs in my tank cam bands and 3-3 in my bcd waist pockets to achieve better trim. So I use a combination of both.

Edit: let's take the Halcyon Traveler bcd, for example, which is able to take 12 lbs on its plastic backplate...

 

[tbone1004]

if you dive a balanced rig and have a wing failure, you have to compensate for wetsuit compression, and mass of gas in the tank.
Rule of thumb is 2lbs/mm of wetsuit, so in a 7mm, call it 14lbs *this is part of why I don't believe 7mm farmer johns are smart/safe*
Largest tank you really see is a FX-149 which holds 12lbs of gas.

If you are diving that rig combo, at worst you have 28lbs that you have to kick up. A more "normal" setup is a 5mm wetsuit and an AL80 which is about 16lbs. Wetsuits don't actually ever lose all of their buoyancy, but can lose most of it.

In lifeguard training, and one of our pre-class tests, you have to take a 10lb diving brick up from the bottom of the pool, and bring it to the side. That is in a bathing suit. In the ocean, you'll have fins and your wetsuit will gradually get more positively buoyant. You can test this in a pool by getting a weight belt with that amount of weight, in your case taking the 16lbs you have now, and add another 8-10lbs for a wetsuit, and see if you can get it up to the surface and keep it there for a few seconds. If you can, then you don't need ditchable weight.

The issue with ditchable weight is that if you have to, you can't descend again, and if you have to stop to hold a safety or decompression stop for whatever reason, you won't be able to do that either. It also increases the risk of embolism because you will have an accelerating ascent with the fastest portion of the ascent when the pressure differential changes the fastest so that's bad.

 

[MaxBottomtime]

You should weight yourself so that at any part of the dive, even with full tanks you can swim to the surface with your weights. Most divers are badly overweighted. It also helps to have multiple lift devices such as a drysuit, wing, liftbag, smb. When I used to dive double 120 cu ft tanks with 40 cu ft deco bottles I was able to kick up twenty feet off the bottom with a little effort. I never tried to swim all the way to the surface but I believe I could have.

 

[tursiops]

@Dogbowl
You are able to dump 6 pounds from your weight pockets; the rest you can't reach. How heavy are you in the water? Well, at your safety stop, at the end of the dive, you are presumably neutral or a pound or two heavy. Do you need to drop 6 pounds? No, just 1-2 pounds at most. At the beginning of the dive, you are presumably 5-6 pounds heavy at your safety stop, i.e. the weight of the gas in your tank that you have not used up yet. So your only problem is the beginning of the dive, when you still have the weight of the gas in your tank, AND you are deep so your suit is compressed a LOT. How heavy are you then? Well, the lost buoyancy of your suit plus the weight of the unused gas.....that is more than 6 pounds. So you need to kick like crazy to get shallower so your suit will expand....

But here is the secret. You say you "learned in OW class that in an emergency at depth, we might need to dump weights and ascend." That does NOT mean you need to dump ALL your weights....just enough to ascend. Secondly, even if you could dump all your weights, you DO NOT want to do this! You become a cork and go up like a Polaris missile. Bad idea.

When you really MIGHT want to dump weights is if you are at the surface, it's a bit rough, you are low on gas so you can't drop down anyway, and you want to keep your head up high. But, if you are weighted correctly, you are still OK without dropping weights.

So, yes, keep some weights (I think your 6 pounds if fine) to drop, but kicking up to the surface is more controlled and probably safer than dropping weights. This is the tech diver logic, and they also avoid wetsuits with their inherent buoyancy loss at depth. Drysuits mitigate that problem.

 

[HantsDiver]

So we all learned in OW class that in an emergency at depth, we might need to dump weights and ascend. Therefore, we should have dumpable weights, like those easily accessible from our waist area, whether they be on a weight belt or integrated into our bcds. But I know for trim purposes, many divers, especially tech-leaning ones, will place weight on their tank cam bands, which, of course are not dumpable. Realistically and practically speaking, are non-dumpable weights dangerous? If so, why are tech divers doing this, since they are the ones who are usually particularly safety conscious. Please enlighten me!

In another thread, I discussed how I personally put 5-5 lbs in my tank cam bands and 3-3 in my bcd waist pockets to achieve better trim. So I use a combination of both.

Edit: let's take the Halcyon Traveler bcd, for example, which is able to take 12 lbs on its plastic backplate...

Tech learning ones will be usually be using a configuration which makes this impossible. So I'm not sure where you get that from.

This whole thing is a none issue. Use whatever you want. When it gets to the point where it matters you won't be thinking about it and will just do it. For now do what you are trained to do.

In answer to your direct question - tech divers won't use dumpable weight as there potential benefit is hugely offset by the possibility of blowing decompression limits. They become more of a danger than a help. To get around this we usually use drysuits or have another way of gaining buoyancy if we need to.

 

[Dogbowl]

Tech learning ones will be usually be using a configuration which makes this impossible. So I'm not sure where you get that from.

This whole thing is a none issue. Use whatever you want. When it gets to the point where it matters you won't be thinking about it and will just do it. For now do what you are trained to do.

In answer to your direct question - tech divers won't use dumpable weight as there potential benefit is hugely offset by the possibility of blowing decompression limits. They become more of a danger than a help. To get around this we usually use drysuits or have another way of gaining buoyancy if we need to.

Huh? To the first two paragraphs. No disrespect as I see you're an instructor but telling me it's not an issue, and use whatever I want isn't very helpful at all. I'm just trying to learn.

 

[HantsDiver]

Huh?

When you are doing technical diving you usually don't have a cam band to randomly add weight to. Your cylinders are held together with stainless steel bands.

Sidemount - you can put a little weight on the cylinders, but usually just a little bit to trim them out. And it's not that common outside of training courses.

 

[Dogbowl]

When you are doing technical diving you usually don't have a cam band to randomly add weight to. Your cylinders are held together with stainless steel bands.

Sidemount - you can put a little weight on the cylinders, but usually just a little bit to trim them out. And it's not that common outside of training courses.

Thanks for enlightening me.

 

[MaxBottomtime]

For my doubles I used a non-ditchable ten pound V-Weight between the tanks. That made it much easier to swim up with.

 

[tursiops]

Huh? To the first two paragraphs. No disrespect as I see you're an instructor but telling me it's not an issue, and use whatever I want isn't very helpful at all. I'm just trying to learn.

LOL! I think you can pretty much ignore HantsDiver's input! he kind of missed the point of your Basic Scuba Discussions question and got all twisted around what he does. Maybe he missed the point that some tech divers DO wear weight belts or have weight pockets, I don't know, but telling you to just do whatever you want is way off target. Especially in this forum.