How do you feel about upside down trim pockets on waist for BP/W ballast solution?

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A wetsuit diver could lie on the bottom with an empty tank and no air in the BC, yet still need to struggle to keep from rising to the surface at 15 feet as the suit regains its buoyancy. In my opinion it is best to do a weight check at 15 feet with a near empty tank in the same type of water you want to do the dive. However, I was taught to check using fin pivots and floating on the surface at eye level neither which really gives a good idea of weight needed during the safety stop.

Fair point, I was thinking of a particular case in a cenote. The bottom was probably only 3m by the steps.

My point is that no amount of adding up or thinking is a substitute for getting in and dropping weight till you can only just stay down.
 
I have only suggested that 1) the OP verify he needs as much ballast as he is using, and 2) he consider the impacts of how he is configuring this ballast.

Not once did I suggest he was using more than required.

What exactly is wrong with either of these suggestions?

Tobin

---------- Post added April 23rd, 2015 at 08:50 PM ----------



You do realize that pretty much the largest singles wings offered by any brand is a 45 lbs wing, and that most are far smaller?

Do you consider it good practice to configure a singles rig so that it will be 45 lbs negative with a full tank. Please explain.

Tobin

I think the "Wow!" after adding up the ballast and the suggestion to verify the dry suit buoyancy qualify you as someone who thinks the OP is overweight.

I dive a BCD so don't have the ballast of a BP but if I could drop my lead to 30 lb I'd be a happy camper. How does 44 lb sound to you? Plus the air in my steel 100 and my reg and a heavy flashlight. I like being warm in cold water. I could drop a layer of underwear and shrink wrap my suit and drop 10 lb off but I don't like to freeze.

So far as distributing weight I am in full agreement. You want some on the body and some on the scuba unit. Some ditchable and some not so much.
 
I think the "Wow!" after adding up the ballast and the suggestion to verify the dry suit buoyancy qualify you as someone who thinks the OP is overweight.

I dive a BCD so don't have the ballast of a BP but if I could drop my lead to 30 lb I'd be a happy camper. How does 44 lb sound to you? Plus the air in my steel 100 and my reg and a heavy flashlight. I like being warm in cold water. I could drop a layer of underwear and shrink wrap my suit and drop 10 lb off but I don't like to freeze.

So far as distributing weight I am in full agreement. You want some on the body and some on the scuba unit. Some ditchable and some not so much.

"Wow" denotes my surprise that somebody needs that much ballast to dive in the temperate waters of San Diego, it's well outside of my experience, and I speak with divers all over the world daily concerning weighting and wing lift requirements..........

Tobin
 
BRT, are you diving with 50# of neg weight?


Sent from my iPhone using Tapatalk
 
Sorry I've been late getting back to this thread. A lot of good points made. Here are my thoughts:


  • I'm looking to simplify my setup, not make it more complicated. So adding a DUI weight harness or moving ballast from my rig to my person isn't a consideration for me.
  • Currently, I use the Dive Rite gravity weight pockets, which I can see have now been discontinued. Problem is I don't really trust them. I feel like I have to wedge my lead ballast into them with some effort, so how can I expect them to work properly when they're supposed to? (And inferring from their discontinued status apparently others feel the same way?)
  • Yes, the point of putting the trim pockets upside down would be to let gravity assist; and I do believe that a person is very likely to be in an upright position when needing to ditch weights
  • What I was really looking for was someone saying what a terrible idea this is, and providing the reasons for it. But it seems like it is a viable solution and at least some others have used it w. success.
  • That said, Tobin really made a great point about how I should re-examine why I dive w. so much ballast in the first place. I've done many a safety stop in my current setup, and have emptied pretty much all of my air, and have been quite close to neutral. So intuitively I've always just assumed my rig was well weighted. But really I just need to bite the bullet and go down to my community pool and do a proper weight check. At least get that question out of the way for certain.

Add 3% for salt water? So if I need 30lbs of ballast in fresh water and I weigh 200lbs, add 6lbs for salt water?

I should finally add that I use an OxyCheq 40lb wing. And yes, it sinks even when fully inflated (really it's almost neutral). All the more reason to do that weight check...
 
Weight belts are pretty simple. :wink: Moving just a bit of ballast to a belt solves your wing capacity problem.

If you want to verify the buoyancy of your suit I'd suggest the following procedure:

Put on your under garment and dry suit.

Jump into neck deep water holding a bag full of lead.

Vent your suit.

Pick up your feet, if you sink remove some ballast and repeat until you just barely sink.

Weigh the bag of lead. This is the buoyancy of your suit (and you, if you significantly personally positive or negative)

Tobin

---------- Post added April 24th, 2015 at 09:26 PM ----------

I'll add that i encourage every diver verify the buoyancy of their exposure suit, particularly moderate to cold water divers. Armed with this info weighing becomes pretty simple.

Tobin
 
Weight belts are pretty simple. :wink: Moving just a bit of ballast to a belt solves your wing capacity problem.

If you want to verify the buoyancy of your suit I'd suggest the following procedure:

Put on your under garment and dry suit.

Jump into neck deep water holding a bag full of lead.

Vent your suit.

Pick up your feet, if you sink remove some ballast and repeat until you just barely sink.

Weigh the bag of lead. This is the buoyancy of your suit (and you, if you significantly personally positive or negative)

Tobin

---------- Post added April 24th, 2015 at 09:26 PM ----------

I'll add that i encourage every diver verify the buoyancy of their exposure suit, particularly moderate to cold water divers. Armed with this info weighing becomes pretty simple.

Tobin

The problem with this is that jumping into water feet down holding your weights and venting your suit will shrink wrap the suit on you. No question that you can make your suit less buoyant by doing that but is that the way you want to dive it? If so, go for it. If you want some insulation then you will need more lead and more air.
 
Add 3% for salt water? So if I need 30lbs of ballast in fresh water and I weigh 200lbs, add 6lbs for salt water?
...

Salt water is about 3% denser than fresh water. So you need to balance yourself an extra 30g per litre of water you displace (1l of water weighs 1000g) How much do you displace? When neutral your average density will be 1000g/litre. So if you weigh yourself and your gear you can find your volume. Say you weigh 90kg and your kit (inc lead) 40kg (total guess) so 130kg total. Thus you are displacing 130l so need an extra 130*30g or about 4kg.

Since the volume cancels out you can just weigh yourself AND all your gear in whichever archaic units you like and take 3%.
 
The problem with this is that jumping into water feet down holding your weights and venting your suit will shrink wrap the suit on you. No question that you can make your suit less buoyant by doing that but is that the way you want to dive it? If so, go for it. If you want some insulation then you will need more lead and more air.

Humm, I've been doing testing this way for 10 + years. Odd that this "problem" hasn't presented itself before in at least one of the many thousands of people I recommended it to.

Here is the reality. In neck deep water you will have what? 6ft or ~2.7 psi *at your feet* reducing all the way to zero at your neck. This will hardly "shrink wrap" a dry suit, or compress the undies very much. It represents the same conditions one sees if they are floating at the surface feet down.

Does one need to conduct the entire dive in this condition? Of course not. When the cylinder is full they have the added weight of their gas to allow additional gas in their dry suit.

The only time one would need to replicate these conditions would be if they had to conduct a shallow stop with *zero* gas in their cylinder. Most divers choose to end their dive before they have exhausted their breathing gas. The day things don't go as planned thye *might* have to spend a few minutes in the shallows in a suit with minimum gas in it.

Of course anyone who has sought my advice on wing capacity and weighting for use with doubles will tell you I recommend an extra 2-3 lbs of ballast to allow them to increase their suit inflation at their shallow stop if they, due to a deco obligation, need to breathe their tanks down to zero.

Actually knowing the minimum buoyancy of the exposure suit one is using is very useful thing, it makes weighting choices pretty clear cut, and it easily allows one to adapt if presented with different tanks etc. Sadly very few divers have any idea how buoyant their suits actually are.

Tobin
 
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Humm, I've been doing testing this way for 10 + years. Odd that this "problem" hasn't presented itself before in at least one of the many thousands of people I recommended it to.

Here is the reality. In neck deep water you will have what? 6ft or ~2.7 psi *at your feet* reducing all the way to zero at your neck. This will hardly "shrink wrap" a dry suit, or compress the undies very much. It represents the same conditions one sees if they are floating at the surface feet down.

Does one need to conduct the entire dive in this condition? Of course not. When the cylinder is full they have the added weight of their gas to allow additional gas in their dry suit.

The only time one would need to replicate these conditions would be if they had to conduct a shallow stop with *zero* gas in their cylinder. Most divers choose to end their dive before they have exhausted their breathing gas. The day things don't go as planned thye *might* have to spend a few minutes in the shallows in a suit with minimum gas in it.

Of course anyone who has sought my advice on wing capacity and weighting for use with doubles will tell you I recommend an extra 2-3 lbs of ballast to allow them to increase their suit inflation at their shallow stop if they, due to a deco obligation, need to breathe their tanks down to zero.

Actually knowing the minimum buoyancy of the exposure suit one is using is very useful thing, it makes weighting choices pretty clear cut, and it easily allows one to adapt if presented with different tanks etc. Sadly very few divers have any idea how buoyant their suits actually are.

Tobin

Try this. Sit on a chair with your drysuit on. Balance a 2 lb weight on edge on your thigh. See if it compresses your undergarments. Now imagine each square inch of your suit having that same pressure. Shrink wrap.
 
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