lairdb
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Weight and Trim diary, chapter MMMCMLXXVI; the Continuing Story of getting my rig Dialed In, Submitted in the Hopes that it might be Useful to Others:
I have been fairly happy with where I have settled a while back -- I have an SS backplate, used almost invariably with an AL80, banded directly to the plate (i.e. no STA. If more of my diving were local, rather than travel, I might consider an STA, but 6# of plate is quite enough to pack.)
I also have, at the rearmost possible position of the waistbelt(next to the plate), one on each side, small XS Scuba pockets. When I wear only the 3mm fullsuit, I put 2# each (4# total, plus the 6# plate); when I add the 3mm "core warmer", I add another 2# to each pocket (8# total, plus the 6# plate.)
I do not have a can light, but I hang a bellows pocket on the right, where a can light traditionally goes, filled with a pound or so of junk, plus 1 or 2 slightly negative backup lights (more non-DIRness: light 1 and light 2.) I also usually am carrying a camera (1# or so negative), though I wasn't last evening for this experiment.
Last evening's experiment was to see if I could move the weight from the small pouches on my waist straps, to small pouches on my lower tank band.
Positives of doing so: removes clutter from waist area, possible trim improvement.
Negatives: becomes harder to ditch (fairly minor -- I'm not a believer in ditching); possible interference with wing inflation.
Unknown: effect on trim.
Experiment outcome: sucked. I was genuinely unsure what the effect would be, and I could imagine CofM models that went either to improved trim and stability, or worsened.
I positioned trim pouches (identical to the others) as close to the plate as possible, on the lower tank strap, one on each side. I loaded them with the same 4# each I would otherwise put in the waist pouches. They did not seem to materially interfere with the wing inflation.
As we back-swam out to the descent point, I did not immediately put together the nice stable boat-with-keel feeling I had during the backswim, with the conclusion I shuld have reached -- I was now very tank-heavy, and on descending, found it nearly impossible to keep from spinning along my long axis and doing a convincing imitation of a flipped-over junebug on the ocean floor, arms and legs wiggling in the "air" as I struggled to turn tank-up.
(Fortunately for my dignity, conditions were fairly murky and my buddies distracted by the profusion of lobsters, so my junebug imitation went fairly un-noticed.)
Interestingly, I perceived that by the time I had consumed about 1200 pounds (taking the tank to 1500; my buddy had gotten a hot fill), the situation was much better. While some of this was, no doubt, the refinement of my anti-junebug skills, I'm guessing that some of it was buoyancy change in the tank (1200psi =~3 pounds of change.) From this, I'm guessing that, despite the initial pronounced junebug effect, it wasn't too far off.
This leads me to think that I might be successful with 4# on the waist, and 4# on the lower tank strap. However, this doesn't allow me to entirely remove the pouches from the waist, so it's a less attractive solution.
--Laird
I have been fairly happy with where I have settled a while back -- I have an SS backplate, used almost invariably with an AL80, banded directly to the plate (i.e. no STA. If more of my diving were local, rather than travel, I might consider an STA, but 6# of plate is quite enough to pack.)
I also have, at the rearmost possible position of the waistbelt(next to the plate), one on each side, small XS Scuba pockets. When I wear only the 3mm fullsuit, I put 2# each (4# total, plus the 6# plate); when I add the 3mm "core warmer", I add another 2# to each pocket (8# total, plus the 6# plate.)
I do not have a can light, but I hang a bellows pocket on the right, where a can light traditionally goes, filled with a pound or so of junk, plus 1 or 2 slightly negative backup lights (more non-DIRness: light 1 and light 2.) I also usually am carrying a camera (1# or so negative), though I wasn't last evening for this experiment.
Last evening's experiment was to see if I could move the weight from the small pouches on my waist straps, to small pouches on my lower tank band.
Positives of doing so: removes clutter from waist area, possible trim improvement.
Negatives: becomes harder to ditch (fairly minor -- I'm not a believer in ditching); possible interference with wing inflation.
Unknown: effect on trim.
Experiment outcome: sucked. I was genuinely unsure what the effect would be, and I could imagine CofM models that went either to improved trim and stability, or worsened.
I positioned trim pouches (identical to the others) as close to the plate as possible, on the lower tank strap, one on each side. I loaded them with the same 4# each I would otherwise put in the waist pouches. They did not seem to materially interfere with the wing inflation.
As we back-swam out to the descent point, I did not immediately put together the nice stable boat-with-keel feeling I had during the backswim, with the conclusion I shuld have reached -- I was now very tank-heavy, and on descending, found it nearly impossible to keep from spinning along my long axis and doing a convincing imitation of a flipped-over junebug on the ocean floor, arms and legs wiggling in the "air" as I struggled to turn tank-up.
(Fortunately for my dignity, conditions were fairly murky and my buddies distracted by the profusion of lobsters, so my junebug imitation went fairly un-noticed.)
Interestingly, I perceived that by the time I had consumed about 1200 pounds (taking the tank to 1500; my buddy had gotten a hot fill), the situation was much better. While some of this was, no doubt, the refinement of my anti-junebug skills, I'm guessing that some of it was buoyancy change in the tank (1200psi =~3 pounds of change.) From this, I'm guessing that, despite the initial pronounced junebug effect, it wasn't too far off.
This leads me to think that I might be successful with 4# on the waist, and 4# on the lower tank strap. However, this doesn't allow me to entirely remove the pouches from the waist, so it's a less attractive solution.
--Laird
