Critique my rig/setup

[elmer fudd]

at 10mt = 50% of buoyancy gone.
at 20mt = 75%
at 30mt = 87.5%
at 40mt = 93.75% of buoyancy gone.

Strikes me you could loose most of your buoyancy at no stop depths.

That assumes that a wetsuit loses buoyancy in a 1/1 ratio to the increase in pressure, but I'm pretty sure that's not the case.

Yes, the air bubbles will be compressed in that manner, but even with the air bubbles extremely compressed, you'll still be left with a suit that resembles crushed neoprene and that's pretty buoyant material itself.

 

[pwr2al4]

Your setup is nearly identical to mine. I also do a bunch of cold water and diving and the reason I chose to invest in diving dry wasn't so much the temp that was the issue it was the insane buoyancy problems that are just about unsolvable.

I dive a BP/W steel plate and 2 pounds woven down the center w/ a hp steelie 100 and a 30cf bottle slung. back when I was getting master diver in school, since we were all a fairly experienced group we did got in a bunch of dives in truly freezing water. So not only did I have my 7 mil full body suit, but we would all dig through the universities wet suit closets and literally stretch as much neoprene over ourselves as possible. The result of course is an insane insane amount of lead just to get neutral. Then you drop down to 80 feet, and now your heavy as a log, up to the safety stop, and again your either just ok with 2 tons of lead or your in deep trouble as you fight to stay down, the whole thing is a nightmare.

The sign of an experienced diver his his buoyancy control and his trim u/w. Which generally results in minimal lead. A bp/w steelie and drysuit are really the only way to combat that crazy yo yo effect.

 

[halocline]

at 10mt = 50% of buoyancy gone.
at 20mt = 75%
at 30mt = 87.5%
at 40mt = 93.75% of buoyancy gone.

Just out of curiosity, where did you get these numbers?

 

[StreetDoctor]

For those of you diving dry with all your weight on your rig and for Bossman with a 30# buoyant wetsuit and 10# belt; have any of you actually removed your rig at depth and re-donned it? I can imagine it would be difficult to maintain same depth as your rig. Seems like you would want about equal buoyancy as your rig, should this be necessary for an entanglement issue. Chances are remote your buddy can't help you out of a situation like this, just wondering if it is something that warrants consideration?

When you dive doubles you're going to end up EXTREMELY overweighted if you try and do that. The simple solution is to not remove your rig. Personally I don't ever see a situation where I would have to do that.

 

[Kern]

That assumes that a wetsuit loses buoyancy in a 1/1 ratio to the increase in pressure, but I'm pretty sure that's not the case.

Yes, the air bubbles will be compressed in that manner, but even with the air bubbles extremely compressed, you'll still be left with a suit that resembles crushed neoprene and that's pretty buoyant material itself.

Just out of curiosity, where did you get these numbers?

Yes, I should have stated that would only be the buoyancy lose for the gas bubbles. I could be very wrong, but I'v always thought this would be the main component.

 

[elmer fudd]

Just out of curiosity, where did you get these numbers?

Now that you point it out, those numbers are wrong. It's supposed to be the compression of gas due to depth, but he has it increasing exponentially instead of linearly.

It should be,
10m=50%
20m=66.7%
30m=75%
40m=80%

edit: actually that's an exponential progression too. X^(-1)

 

[Kern]

It should be,
10m=50%
20m=66.7%
30m=75%
40m=80%

Thats true too. Don't know what I was thinking.

 

[halocline]

Yes, I should have stated that would only be the buoyancy lose for the gas bubbles. I could be very wrong, but I'v always thought this would be the main component.

So, you just made those numbers up, right? No actual testing with weights and a mesh bag, for example?

 

[Kern]

So, you just made those numbers up, right? No actual testing with weights and a mesh bag, for example?

No, they're based on the compression of the gas in the bubbles of the neoprene. But rather than doubling the pressure to halve the volume I was just adding a bar & halving the volume. Elmer's numbers are correct, so you lose 80% of the buoyancy of the gas bubbles in the neoprene by 40mt.

I have no idea how buoyant the material without bubbles would be, but I think that by the time the bubbles have been compressed to 20% their original size that would account for a goodly amount of the suits buoyancy. It would be interesting to see some numbers on it.

 

[TSandM]

When I took Fundies, I was told that an experiment had been done with a 7 mil wetsuit, in which it was taken to 100 feet and lost 23 pounds of lift. This was, of course, only one suit, and only done once; as such, it is only anecdotal evidence. But it was enough to convince me that the phenomenon of significant loss of lift from neoprene compression is both real and of significant magnitude. The details just aren't that important.

The bottom line is, if you are diving wet in thick neoprene, you need ditchable weight -- but ditching it may render you unable to control your subsequent ascent. Redundant buoyancy is better.