Trim/buoyancy conundrum

[dfx]

Question: If you dived with a thick wetsuit and lots of weights, but no BCD to add BCD air to the question: With the 7 mil farmer john you have 14 mil on the core area and 7 mil on extremeties. At 33' (10m) your torso is now at 7 mil and extremeties at 3.5 mil. Now do the areas where more weight is attached become more important. Ei.- do the weights take on more importance as the difference between thicker and thinner wetsuit areas decreases?

What do you mean by importance? Importance to what?

Note that neoprene isn't all gas and so isn't subject to Boyle's Law. Only the gas trapped within the neoprene gets compressed, which is only part of the neoprene material. So at 33', your 14 mm won't be down to 7 mm, but it might be 10 or 12 mm thick (random numbers because I don't know how much it really compresses).

 

[Agility]

It is a theoretical question, so let's try to analyze it.
neoprene compresses due to increasing pressure at depth, but what percentage of its volume does it really lose?
Many wetsuits nowadays have thicker material on the torso than the extremities so their volume will be reduced more in the torso-region. point two, as C_Dale said he subconsciously alters leg position to keep in trim. I suspect he also tilts his upper body downward a little to keep the bubble in the bottom part of the BCD. Of course having a small bubble due to good weighting makes this easier.

 

[TMHeimer]

What do you mean by importance? Importance to what?

Note that neoprene isn't all gas and so isn't subject to Boyle's Law. Only the gas trapped within the neoprene gets compressed, which is only part of the neoprene material. So at 33', your 14 mm won't be down to 7 mm, but it might be 10 or 12 mm thick (random numbers because I don't know how much it really compresses).

Right. I thought of that after I posted. It's still somewhat thinner, though, so your heavier weighted area may still cause more negative buoyancy than your lighter weighted area, no? The weights want to take over from the wetsuit so to speak, in determining your trim?

 

[dfx]

Right. I thought of that after I posted. It's still somewhat thinner, though, so your heavier weighted area may still cause more negative buoyancy than your lighter weighted area, no? The weights want to take over from the wetsuit so to speak, in determining your trim?

Good question. Somehow I think it's the other way around. At the surface, your wetsuit is very floaty, let's say it's +15 lbs. For weights, let's say you use 20 lbs, so that's -20. Difference between the two is 35 lbs, which would be what determines your trim. Now you descend and your wetsuit loses buoyancy, let's say now it's only +10 lbs. So this offsets the difference between wetsuit buoyancy and weights down to only 30 lbs. Which means there's less force to put you in or out of trim.

At least that's what my layman's physics tells me