drdirt, I may be misunderstanding what you're saying your ideal weighting should be.
Were you saying it's 28 lbs?
Or was that the weight that seemed about 5 lbs light?
Were you saying your ideal weight should be about 33 lbs?
drdirt:
Could a new trilaminate suit require more weight because it is stiffer - and folds don't lay as flat as an old one?
You're probably right, because the folds trap a little more air, perhaps. Not much, I'd guess.
drdirt:
28 lbs worked well for me on my third dive. I did two safety stops for conservatism and for neutral buoyancy practice - I managed to hover at 35 and 20 feet well. I didn't manage to stay at 15 well (pretty much empty BCD and drysuit) - oh, and my steel 95 was at about 1000psi at the end.
Sounds like you were saying that the 28 lbs "worked well" only for the early part of the dive before your tank became lighter and your depth shallower.
Not being able to correct positive buoyancy during the dive, especially when trying to do a safety stop, is not desirable, as you appear to state ("didn't work well").
From what you said, 28 lbs seemed a few pounds light, as your recent post indicated, since your tank wasn't close to empty and, at 15', you apparently still couldn't vent enough air to keep from being positive.
Just so I can understand how close the bucket weight estimate came to your ideal weight, let me lay out a couple things.
You originally mentioned in post #3:
drdirt:
I just finished cleaning my gear when I read this thread. Got me a bucket and I estimated the volume of my undersuit garment. Looks like this rule of thumb probably would underestimate in my case by about 5 lbs.
and
drdirt:
Undergarment Vol: 3.5 gallons
Dive weight with steel 95 cuft - 28 lbs saltwater
The way I read it,
3.5 x 8 = 28 lbs estimated weight needed to counteract the buoyancy of the undergarments.
And that weight left you a bit light with 1000 psi left in your 95 cf tank.
By the way, what's the empty buoyancy of that tank?
If you were saying 28 lbs seemed about 5 lbs light, that would make sense to me.
I apologize if I seem to be a little slow in understanding what you said.
Tweaking my weighting real close to the minimum just isn't worth the occasional problems that can result, especially at the end of the dive, such as being colder with less air in the suit, struggling to stay neutral in surge or very shallow depths, not being able to maintain a safety stop depth, etc.
I'm happy to have the slight disadvantage of the more rapid buoyancy changes that result from having a little extra air in the suit. Not to mention the hassle of carrying extra weight. (The walk to the water is getting harder every year!)
drdirt:
The prediction was 8-1/3 lb/gal x 3 gal = 25 lb. (neglecting the weight of the undergarment).
I found 28 worked well - but I struggled on the first dive where 30 lb seemed too light.
Probably just had some unvented air. Happens to me often at the beginning of the first dive. Seems the undergarments get settled or less lofty after that.
drdirt:
I like as little air as possible for stable hovering during safety stops.
That's a benefit, for sure, to reduce the degree of buoyancy change.
Personally, even at 10' or less, I rarely have difficulty maintaining neutral buoyancy with my extra 5 pounds and the extra air (5/8 gallon).
Then again, I always have a flag with me and that makes it easier to keep a stable position in the water column.
But that's probably considered
cheating!
Dave C