Buoyancy Characteristics Info

[Trace Malinowski]

Something like this? DUI Thermal Guides for Dry Suit Diving / SCUBA

 

[rjack321]

I dont think this is totally unreasonable. Surely there must be a range of buoyancy figures that can generally work. If they dont exist then I accept that, but I would think people would generally be happy with having an IDEA of where they should start their weighting. Clearly a chart would only be a starting point and not something to base your final weighting on--im not sure why everyone here thought I was going to calculate on paper and be done with it.

Considering that "equivalent" undergarments from various manufacturers can vary by 6lbs or more nevermind the differences in size and how they are used/inflated by the diver... its a totally plausible idea that won't work in reality. Kinda like taking the majority of 20degF sleeping bags to 20degF. A few will work, most will have vastly different realities.

You've been hanging out here long enough you should have a reasonable idea of differences anyway.

 

[Gombessa]

I advanced this same idea in a thread a couple of years ago; same conclusions and consensus here.

I still feel a "ballpark" estimate for wetsuits would be useful for newer divers (if manufacturers can say their 7mm suits are for 40-60 degree water temps or "cold water", and a sleeping bag maker says -20 degrees, why not "estimated buoyancy in fresh water when new"). It may not be completely accurate, but the difference between "5lb" and "20lb" would seem informative and well within some standard deviation to account for batch variations.

The problem is that so few new divers have any idea, or will ever really learn, the real buoyancy of their suit. This would at least let them start somewhere with more accuracy than they currently have, without resorting to learning about SB and searching through threads for the same information. I doubt it'll ever happen, but it seemed a good idea on paper.

As for the guy needing 18lb with a 3mm suit and 22lb with a 7mm, something is definitely off with the math there; it sounds like you're either doing something different or some equipment/environment has changed between the two (steel or alu tanks, fresh or salt water, mistaking the thickness of one or both suits, etc. or possibly a combination of the above). I'm sure it'll all get sussed out in time, but my money definitely isn't on anatomy being the answer

 

[LakeCountyDiver]

I had to test my bare 3/2 mm wet suit in the pool I held it under water and got it soaked. I then sat a 5 pound weight on the stomach area and it was just about right. So I average my 3/2 to be 5+/- pounds positive my .5mm is 2 pounds positive. but I cant just drop 5 pounds from wearing my 3/2 to nothing so it is hard to say. I still have a lot to learn.

 

[kanonfodr]

As for the guy needing 18lb with a 3mm suit and 22lb with a 7mm, something is definitely off with the math there; it sounds like you're either doing something different or some equipment/environment has changed between the two (steel or alu tanks, fresh or salt water, mistaking the thickness of one or both suits, etc. or possibly a combination of the above). I'm sure it'll all get sussed out in time, but my money definitely isn't on anatomy being the answer

Actually, that can happen. The first rule of thumb I ever learned for weighting came from free-diving: 3-5% of your body weight, plus 1 lb for each mm of wetsuit across the core. So when I traveled to Monterey last year and went from diving a 3mil to a 7mil plus a 5mil hooded vest I added the commensurate weight (10 lbs) and when I weight checked myself I was right on the money.

Peace,
Greg

 

[Gombessa]

So when I traveled to Monterey last year and went from diving a 3mil to a 7mil plus a 5mil hooded vest I added the commensurate weight (10 lbs) and when I weight checked myself I was right on the money.

Is that a 10lb difference between the suits? Without knowing the particulars of the suits you're wearing, that's within the realm of possibility (a very good hooded 3mm suit at ~8lb versus a worn 7/5 at ~18lb, for example). A mere 4lb difference in the buoyancies between a 3mm and 7mm suit however, really requires more of an explanation.

I dunno, maybe it's true, but it would be way out of the norm since the differences in suit buoyancies are measurable facts. Assuming all the equipment is the same, my initial guess for someone requiring 18lb to sink in a 3mm and 22lb in a 7mm would be that the 3mm may be trapping air.

 

[kanonfodr]

I dunno, maybe it's true, but it would be way out of the norm since the differences in suit buoyancies are measurable facts. Assuming all the equipment is the same, my initial guess for someone requiring 18lb to sink in a 3mm and 22lb in a 7mm would be that the 3mm may be trapping air.

Could be any number of reasons for that small of a gap between weight requirements: neoprene material, cut of the suit, bells and whistles, etc. If you have a generously cut 3mm using a "squishy" neoprene like Yamamoto 45 with lots of floaty extras like padded zippers on the ankles and wrists, compared to a plain-jane 7mm made with a not so "squishy" neoprene like Yamamoto 38 (or in dreams: Rubatex G-231, but that's reserved for custom suits nowaday) and cut very tight, it's super possible.

I also don't consider surface weight checks of neoprene very useful, instead a check at 10 or 15 feet is much more representative of what you will actually need for the suit.

Peace,
Greg

 

[LakeCountyDiver]

4 POUNDS Is a very small change from a 3mm to a 7mm. There are a number of reasons that could cause a small change but just a educated guess I would have to say that if properly weighted at 22lbs in a 7mm that they are a little over weighted in the 3mm. Cause there is an 11lb difference in my 3/2mm to 7mm. I'm just saying.

I am sure this has been touched on before it is just the way I see it. Who knows maybe it is only 4 pounds.

 

[Gombessa]

I think you can set up extreme cases where you'd get a 4lb difference between a 3/2 and full 7, but taken with the other facts as given, to me it still sounds like just that (not to be overly skeptical of the OP but I'd be looking to many other factors before settling on a combination of extremes --either extremely buoyant physiology or 3/2 suit to require 18lb, while making 22lb sufficient for a 7mm).

On a neoprene tangent, I've never had the pleasure of diving a rubatex wetsuit, but my first assumption is that all things equal, its benefit is less compression at depth over less buoyancy when uncompressed at the surface? I've seen the neoprene samples in pressure pot video, but is rubatex really significantly less buoyant than other neoprenes when uncompressed?

 

[Gombessa]

Cause there is an 11lb difference in my 3/2mm to 7mm. I'm just saying.

Not to force my own situation or personal expectations onto the OP, but I have a habit of wearing extremely old, worn rental 7mm suits in cold water, and doubling up two 3mm full suits in the tropics, and still end up with ~10-12lb difference between the two. So just armchairing from 3,000 miles away, the situation makes me raise an eyebrow.

I am sure this has been touched on before it is just the way I see it. Who knows maybe it is only 4 pounds.

Yep, maybe it just is what it is.