Empty BCD buoyancy?

[Blasto]

Not sure what the issue could be then, other than not dumping all the air. It shouldn't add 3+ kg of buoyancy, I know people diving in it with 2 kg total (no wetsuit).

Still worth trying the steps above, try fully dumping it in the water and see if it's really all the air out or there's a lot to extract after doffing it.

 

[Rred]

Bar-
I wouldn't stay up at night worrying over this. Almost all wetsuits are made from chemically blown rubber, and every time they are taken to depth and compressed, some of the bubbles break down and they lose some buoyancy. Since yours has not had commercial use, and may well be a better material, that's all it takes to make a difference. Also, wetsuit material is not held to extreme standards of accuracy. In the rag trade, garment makers for hundreds of years have found way to cheat. If a wetsuit maker produced "2.7" mm rubber, would anyone notice? Or 2.5mm with a slightly thicker non-buoyant skin?
Find out what you need, expect that will differ with different equipment. Or even if your body weight or BMI changes less than "one belt hole."

 

[60plus]

As someone who has been buying dive gear and whose dive time is limited, and therefore does not want to waste time messing about with weight I found the lack of manufacturers information about weight, displacement etc a bit of a nuisance. It would be easy enough for them to determine and publish this information.
I have a 15L steel cylinder. It weighs (without valve) 17.6 Kg. This equates to 2.2 litres of steel. Adding that to the 15L capacity gives 17.2 litres displacement. When I actually put it (including valve) in water it displaced 17.15 Litres (or Kg). This means when my tank is down to 50 Bar it will weigh about 18 Kg so its effective negative buoyancy (valve included) at the end of the dive will be about 0.9 Kg. Just got my BCD and wetsuit to test (when I have a big tank of water) and I should be able to work out my weighting pretty accurately.

 

[Bob DBF]

Every piece of gear has it's own buoyancy characteristic. That's to be expected. So add the extra weight, dive and have fun. It's all good.

That's the easy answer.

I found that my old jacket BC lost a couple of pounds of buoyancy after the first dive after the trapped air was forced out and padding was compressed. When I switched to a BP/W I lost 10# of lead from the switch, 5 from the weight of the plate and 5 from the buoyancy difference in the BC's, and have not had the issue of BP/W changing buoyancy after the first dive. When replacing my wetsuit, 7mm farmer John, I have to add weight which is gradually lost as the suit ages.


Bob

 

[Rred]

Padding was compressed?? I really am a fossil, my old BC's had no padding anyplace. No cumberbund or sternum strap either. And yet, somehow, they can be adjusted to fit just right.

Vendors who can't answer the simple technical questions about their gear, are just peddlers and clerks who happen to sell SCUBA equipment. If they can't answer simple technical questions..."Next!".

 

[Bob DBF]

Padding was compressed?? I really am a fossil, my old BC's had no padding anyplace. No cumberbund or sternum strap either. And yet, somehow, they can be adjusted to fit just right.

My wife "upgraded" me into a poodle jacket, with all the padding and such, when my old Seatec jacket got threadbare. I didn't care for it but dove it foe several years until I bought a BP/W.

Vendors who can't answer the simple technical questions about their gear, are just peddlers and clerks who happen to sell SCUBA equipment. If they can't answer simple technical questions..."Next!".

When I upgraded, I called the jacket manufacturer and asked for the buoyancy of the jacket and used their reply to pick my wing. It was overkill for the new rig,except I sometimes use myself for a lift-bag, so it has worked out fine. Unfortunately I don't remember the name of the jacket, although it came with an Oceanic version of the air2, so it could have been Oceanic.


Bob

 

[gopbroek]

When I transitioned from a BC to a BP/W I was using 9 lbs with the BC. I got a SS back plate @ 6 lbs and found my buoyancy was the same without any additional weight. After talking with others I found that this is pretty common. I think a lot of people do not realize how much differences there are in the buoyancy of the different styles of gear.
Another big variable is the weights you use, I know that in Mexico rental weights can have a pretty large variance between them due to the use of random lead alloys (scrap lead like tire weights) being used to make them. The number stamped on them is from the size of the mold not necessarily the true actual weight.

 

[Bob DBF]

I know that in Mexico rental weights can have a pretty large variance between them due to the use of random lead alloys (scrap lead like tire weights) being used to make them. The number stamped on them is from the size of the mold not necessarily the true actual weight.

Not just in Mexico. The old weights I have picked up over the decades here in the US can be up to a pound off. I weighed all of mine after having buoyancy issues when grabbing some at random, then stamped the discrepancy + or - and amount. The recently produced weights seem to be real close, probably because they are made by machines now.


Bob