tonaskai:
Its rather important if you want to maintain neutral buoyancy and not sink like a stone.
Thats not to say you need a 100lb BC, but you have to match the BC ability to the needs of the diver, and the dive.
How much BC lift do I require?
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Its rather important if you want to maintain neutral buoyancy and not sink like a stone.
Thats not to say you need a 100lb BC, but you have to match the BC ability to the needs of the diver, and the dive.
Scubaroo
Contributor
Very important. To all divers.
You want at least enough lift to counter the negative weight of your full tank, and your weightbelt. Ignore the latent buoyancy of your exposure protection (eg wetsuit - they lose most of it at depth). Figure that number out and it's a good starting point.
One of the problems with jacket BCs is the limited buoyancy they can fit into the design in smaller styles. My partner almost got into trouble in Monterey diving in a rental XS jacket BC - it was the only one in the rental fleet that fit her, but it was also about 10lb short of the amount of buoyancy she needed to stay afloat.
Conversely,there's also not much point dragging around a bladder that's 20lb or more than you need in capacity.
You want at least enough lift to counter the negative weight of your full tank, and your weightbelt. Ignore the latent buoyancy of your exposure protection (eg wetsuit - they lose most of it at depth). Figure that number out and it's a good starting point.
One of the problems with jacket BCs is the limited buoyancy they can fit into the design in smaller styles. My partner almost got into trouble in Monterey diving in a rental XS jacket BC - it was the only one in the rental fleet that fit her, but it was also about 10lb short of the amount of buoyancy she needed to stay afloat.
Conversely,there's also not much point dragging around a bladder that's 20lb or more than you need in capacity.
NickR
Registered
Having just sold my old BCD I'm looking for a BP/W set up. I did a rough calculation of my lift requirement and it seemed to be around 36lbs. Given my old BCD had 35lbs of lift and it was fine for me then I thought that this calculation must be fairly accurate.
I thought I would get a 36lb Pioneer set up, that is until I read some posts saying that there is a possibilty of problems with it's durability. That led me to look at the Eclipse, it costs more but I could accept that if the quality is better. But the closest lift to my requirment would be 40lbs, and I've read other posts about having too much lift causing problems when on the surface, and the larger wing causing trim/drag issues underwater.
So, should I get the 36lb Pioneer or the 40lb Eclipse?
I will be diving probably no deeper than 32m, 5mm wetsuit, up to 24lbs of weight (depending on the tank) and either AL80 or steel tank (single cylinder).
Sorry for rambling on, I've tried searching as much as possible to get an answer to my question.
Cheers everybody.
Nick
I thought I would get a 36lb Pioneer set up, that is until I read some posts saying that there is a possibilty of problems with it's durability. That led me to look at the Eclipse, it costs more but I could accept that if the quality is better. But the closest lift to my requirment would be 40lbs, and I've read other posts about having too much lift causing problems when on the surface, and the larger wing causing trim/drag issues underwater.
So, should I get the 36lb Pioneer or the 40lb Eclipse?
I will be diving probably no deeper than 32m, 5mm wetsuit, up to 24lbs of weight (depending on the tank) and either AL80 or steel tank (single cylinder).
Sorry for rambling on, I've tried searching as much as possible to get an answer to my question.
Cheers everybody.
Nick
FredT
Guest
NickR:
The 4 pounds of lift delta is in way down in the noise. You'd never find it either way.
For reefs and open water the Pioneer is good. The "advantage" of the Eclipse is you can patch or replace the bladder if you tear it inside a wreck or cave.
Try OxyCheq for some more options. I had the Pioneer, gave it to me daughter and bought a OxyCheq 45# single tank wing. It's virtually identical in size to the Pioneer, but has more lift. It also has the expanding gussets next to the tank vs. outside like the Pioneer has that I found interesting.
Which every way you choose to go, the BP&Wing is better IMO than a "standard" BC anyday.
Which every way you choose to go, the BP&Wing is better IMO than a "standard" BC anyday.
ocpaul
Contributor
Nick,
I just went through the same thought process and settled on the Pioneer 36. I don't do cave diving or confined space diving and the Pioneer certainly appears to be build ruggedly.
One thing you might review is your calculation of your lift requirements. It is not the same as your weight requirements. You need to have enought lift to offset the weight of air in your tank, the loss of lift due to compression of your exposure suit, and the weight you carry in EXCESS of that which is required to be neutral at 10ft or at the surface (this is the subject of much discussion)with an empty tank or near empty tank plus an appropriate factor of safety.
Based on your description you would probably need to lift to offset 6# of gas and maybe 4# for suit compression. So, if you are perfectly neutral you would theoretically need only 10# of lift. Doubling your actual lift capabilty would result in a minimum of 20#. The 36# Pioneer would allow you to overweight by 9# and still have a F.O.S. of 2.
This analysis didn't make sense to me when I first had it presented to me - I had previously thought you needed to have enough lift to offset the change in gas weight + suit compression + weight carried.
Hope this helps - good luck with your new purchase.
Paul
I just went through the same thought process and settled on the Pioneer 36. I don't do cave diving or confined space diving and the Pioneer certainly appears to be build ruggedly.
One thing you might review is your calculation of your lift requirements. It is not the same as your weight requirements. You need to have enought lift to offset the weight of air in your tank, the loss of lift due to compression of your exposure suit, and the weight you carry in EXCESS of that which is required to be neutral at 10ft or at the surface (this is the subject of much discussion)with an empty tank or near empty tank plus an appropriate factor of safety.
Based on your description you would probably need to lift to offset 6# of gas and maybe 4# for suit compression. So, if you are perfectly neutral you would theoretically need only 10# of lift. Doubling your actual lift capabilty would result in a minimum of 20#. The 36# Pioneer would allow you to overweight by 9# and still have a F.O.S. of 2.
This analysis didn't make sense to me when I first had it presented to me - I had previously thought you needed to have enough lift to offset the change in gas weight + suit compression + weight carried.
Hope this helps - good luck with your new purchase.
Paul
NickR
Registered
Thanks for the info. I have decided to go for an Oxycheq package.
Cheers
Nick
Cheers
Nick
reubencahn
Contributor
ocpaul:
How did you arrive at 4 lb for suit compression?
ocpaul
Contributor
It was just a quick guess based on memory. I'm sure some research on the Board will reveal methods of determining loss of bouyancy due to suit compression.
Paul
Paul
Scubaroo
Contributor
I don't know why suit compression calculations come into play when determining lift. Ignoring suit compression, you need enough lift to offset the weight of the gas in a full tank, and the weight of your weightbelt (and backplate if used), and any other negative items you might be carrying, like a camera, sling tank(s), reel, heavy canister, etc depending on what sort of diving your'e engaged in. It's implicit that some of the weight on your belt is already being used to counter the buoyancy of your wetsuit on the surface, assuming you're diving wet.
You need enough lift so that at the beginning of a dive, you can counter your full tanks and your negative weight at depth, where it is safe to assume that your wetsuit has lost *all* inherent buoyancy, because it's being crushed. Dive a 7mm suit to 40m/130' and see how buoyant it is - it's a lot more than 4lb lost.
You need enough lift so that at the beginning of a dive, you can counter your full tanks and your negative weight at depth, where it is safe to assume that your wetsuit has lost *all* inherent buoyancy, because it's being crushed. Dive a 7mm suit to 40m/130' and see how buoyant it is - it's a lot more than 4lb lost.
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