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

[cool_hardware52]

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.

The procedure I recommend for determining the buoyancy of your suit with minimum gas in it is valid.

The choice to use this value for weighting remains with each diver.

I haven't yet heard a single reason why knowing your suit buoyancy is a bad thing, but I'll speculate it's because I'm focused on finding solutions, not inventing problems.

Tobin

 

[redacted]

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.

Hold a half inflated balloon in one hand and push one finger into the other side of the balloon until it touches your hand. Now place the balloon between two large sheets of wood and push until the two boards are in full contact. Different problems.

Pressure times volume is constant (at constant temp). No shrink wrap.
.

 

[00wabbit]

Get a weight harness it is a much more comfortable solution and you can position the weights up or down on your hips as you need.

I used to think I needed that much weight too 6'2" 300lbs. Turns out I was always running too much air in my drysuit. I managed to cut it down a good bit then switched to sidemount doubles and need even less weight. Now on a freshwater dive I carry 12lbs on my back with no steel plate or anything.

 

[BRT]

According to some peoples calcs I am diving with 54# of neg weight. 44 lb of lead plus 7 lb of air plus 2 lb of regulator plus a pound or so of flashlight. It is not all on my BCD! 3 lb of ankle weights and about 20 on a DUI weight harness. Last PNW trip I did a dive and then added 2 lb. I can stay down with less but I'm not running a big bubble in my drysuit and don't need any air in my BCD as my air gets to 700. I'm 5' 11" and about 205-210 lb. I apparently float really well. In warm water with a Lavacore and neoprene booties I need 16. At 14 I swim down hard on safety stops and I hate that. Yes I know how to get air out of my BCD. I also know how to get water out of it after the dive because at the end of dives I vent all different ways to make sure and it picks up a fair amount of water. I have no problem floating motionless either in a drysuit or wetsuit, I don't bounce off the bottom going down and have no problem controlling buoyancy when coming up, unless some divemaster has convinced me to dive with less weight.

I consider this preoccupation with less and less weight to be a hazard. In cold water we dive by ourselves but in warm water the weight Nazis try to convince me to dive with less and when I refuse they have told me 4's are 5's and 3's are 4's. Then when I struggled at 15' I wondered what my problem was. Until I put my scales on the weights.

I only have 4-500 dives I suppose, but I was diving a drysuit in the early 90's so I'm not a complete novice.

---------- Post added April 25th, 2015 at 01:12 PM ----------

If the end of your finger is .5" diameter the area is the radius of that squared times Pi or .196 square inch. the pressure on .196 square inches at 1 lb pressure is .196 lb. The pressure on 1 square inch at 1 lb is magically 1 pound. And at 1psi (pound/square inch you have that pressure on every square inch available. And that is why the balloon gets smaller as you take it down from the surface. At 1 psi each square foot has 144lb pressure against it. The example with the sheets of wood would have the pressure against each square inch and would squish that balloon right down. My example with the 2 lb weight Assuming the weight on edge is .5" x 2" for 1 square inch of surface area, is also valid if you dominoed them flat side to flat side all the way down your thigh on edge is the equivelent pressure of 2 psi. It will and does shrink wrap your suit

 

[redacted]

According to some peoples calcs I am diving with 54# of neg weight. 44 lb of lead plus 7 lb of air plus 2 lb of regulator plus a pound or so of flashlight. It is not all on my BCD! 3 lb of ankle weights and about 20 on a DUI weight harness. Last PNW trip I did a dive and then added 2 lb. I can stay down with less but I'm not running a big bubble in my drysuit and don't need any air in my BCD as my air gets to 700. I'm 5' 11" and about 205-210 lb. I apparently float really well. In warm water with a Lavacore and neoprene booties I need 16. At 14 I swim down hard on safety stops and I hate that. Yes I know how to get air out of my BCD. I also know how to get water out of it after the dive because at the end of dives I vent all different ways to make sure and it picks up a fair amount of water. I have no problem floating motionless either in a drysuit or wetsuit, I don't bounce off the bottom going down and have no problem controlling buoyancy when coming up, unless some divemaster has convinced me to dive with less weight.

I consider this preoccupation with less and less weight to be a hazard. In cold water we dive by ourselves but in warm water the weight Nazis try to convince me to dive with less and when I refuse they have told me 4's are 5's and 3's are 4's. Then when I struggled at 15' I wondered what my problem was. Until I put my scales on the weights.

I only have 4-500 dives I suppose, but I was diving a drysuit in the early 90's so I'm not a complete novice.

---------- Post added April 25th, 2015 at 01:12 PM ----------

If the end of your finger is .5" diameter the area is the radius of that squared times Pi or .196 square inch. the pressure on .196 square inches at 1 lb pressure is .196 lb. The pressure on 1 square inch at 1 lb is magically 1 pound. And at 1psi (pound/square inch you have that pressure on every square inch available. And that is why the balloon gets smaller as you take it down from the surface. At 1 psi each square foot has 144lb pressure against it. The example with the sheets of wood would have the pressure against each square inch and would squish that balloon right down. My example with the 2 lb weight Assuming the weight on edge is .5" x 2" for 1 square inch of surface area, is also valid if you dominoed them flat side to flat side all the way down your thigh on edge is the equivelent pressure of 2 psi. It will and does shrink wrap your suit

To me, "shrink wrap" implies all the air volume is eliminated and that is not going to happen (except in the small area under your weight). Sure, you may experience squeeze, severe with enough pressure, but that will take quite a bit of pressure differential.

When you wear just a bathing suit in a swimming pool (FW), are you able to exhale and descend without swimming down? What is the buoyancy of your lavacore suit. I am also 5'11" and 225 to 230 (some say fat) and would need 12 to 14 lb in a 3mm suit in SW.

 

[cool_hardware52]

The reality is the undies are primarily what keeps you warm in a drysuit. Gas helps a bit, and I typically use argon, mostly because I have easy access to it. (I use it to weld)

Gas always goes to the high point of any container and a drysuit is no different. If you are vertical the gas is around your neck and shoulders, if you are horizontal face down the gas is on your back, not your chest. That's just simple physics.

Regarding "shrink wrap" BRT is your suit pinching you if you vent it at the surface? If not why? Would it pinch you if you fully vented it at say 20 ft? If so why?

BTW BRT, please dive anyway you see fit.

I will continue to try and help divers understand suit buoyancy and how it impacts weighting and required wing lift as I see fit.

Tobin

 

[decompression]

BRT, is there a UTD facility or instructor near you? I would be willing to pay for you to take the extreme scuba makeover (ESM) course. And if, at the end you find that you still require the same weight (54#) you've lost nothing (that's funny). But I'm confident they will be able to show you that you can dive safely with less weight than you're using now. Seeing the logic of a balanced rig calc doesn't make you a weight Nazi, just well informed.


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[BRT]

I said already I could dive a drysuit with less weight than I do. Using an online surface area calculator my body has a surface area of about 2.2 meters square. Do the calcs and each 1/10 inch of insulating air around my body displaces 12 lb of seawater. Obviously by removing a layer of underwear and tightening my suit slightly I can drop 12 lb. By tightening my suit a little more I can drop 12 lb more. Then I would be a hero diving 20 lb of lead instead of 44. If I were swimming a lot I would do this to avoid over heating. My second to last dive at Keystone Jetty I was under 75 minutes and came up with 700 lb of air. This included swimming against a slight current from the jetty to the pilings. I'm not doing enough to stay warm without a lot of insulation. I got out of the 48 degree water after 75 minutes with cold hands and everything else warm. I like that.

I do appreciate the offer.

 

[cool_hardware52]

I said already I could dive a drysuit with less weight than I do. Using an online surface area calculator my body has a surface area of about 2.2 meters square. Do the calcs and each 1/10 inch of insulating air around my body displaces 12 lb of seawater. Obviously by removing a layer of underwear and tightening my suit slightly I can drop 12 lb. By tightening my suit a little more I can drop 12 lb more. Then I would be a hero diving 20 lb of lead instead of 44. If I were swimming a lot I would do this to avoid over heating. My second to last dive at Keystone Jetty I was under 75 minutes and came up with 700 lb of air. This included swimming against a slight current from the jetty to the pilings. I'm not doing enough to stay warm without a lot of insulation. I got out of the 48 degree water after 75 minutes with cold hands and everything else warm. I like that.

I do appreciate the offer.

Diving with less weight doesn't make you a "hero" in my book. It does go a long way towards reducing the impacts of a BCD failure, or a panicked diver. (anybody can panic)

Tobin

 

[decompression]

I said already I could dive a drysuit with less weight than I do. Using an online surface area calculator my body has a surface area of about 2.2 meters square. Do the calcs and each 1/10 inch of insulating air around my body displaces 12 lb of seawater. Obviously by removing a layer of underwear and tightening my suit slightly I can drop 12 lb. By tightening my suit a little more I can drop 12 lb more. Then I would be a hero diving 20 lb of lead instead of 44. If I were swimming a lot I would do this to avoid over heating. My second to last dive at Keystone Jetty I was under 75 minutes and came up with 700 lb of air. This included swimming against a slight current from the jetty to the pilings. I'm not doing enough to stay warm without a lot of insulation. I got out of the 48 degree water after 75 minutes with cold hands and everything else warm. I like that.

I do appreciate the offer.

Have to admit, 75 mins is a long rec dive in my waters (PNW as well, Victoria BC)......brrrr
My deco dives are longer but I've got a lot more gas and therefore a thicker undergarment.......hey, maybe I could use that for my rec dives......just add more lead.......you might be on to something.


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