how to choose bc's lift capacity?

I want to buy a bc, but don't know how to choose the lift capacity? I am planing to dive in California.

It would help if you provided a bit more info.

Are you planning to dive wet or dry ? If wet what thickness of suit ?

What about tanks ? Steel or Aluminium, singles or doubles ?

Thanks

If you do a search, the is a handy "ultimate wing lift calculator' on the board. It seems fairly accurate for my gear configurations. You might want to run you specific gear through it,

For Cali diving, regardless of wetsuit or drysuit, if you're probably weighted and diving single tank for fun (i.e. no harvesting or hunting), you wouldn't need anything more than 30-lbs lift. That is assuming you're correctly weighted and not crazily overweighted. That's the rule of thumb. The only way to truly calculate the weight is to know what your correct negative buoyancy value is for diving in SoCal coupled with the equipment (BC, tank, cannister lights, big ass blade, etc.) so that you can do a calculation with.

But generally speaking, the typical BC sold in scuba shops have plenty of lift. Probably too much at times. The only time you'd want to pick up a lift capacity is if you were to buy a wing to go with your backplate.

Over in the BC's forum you will find that Ultimate Lift Calculator as a 'sticky' at the top of the forum.

FWIW, I use a 30# wing with a 7mm wetsuit and an HP100 tank at Monterey.

Richard

Others have noted the stickey. IMHO, here are the three questions:

1. Can I float the rig, at the surface and, without me in it, at the heaviest?
You want to be able to take off your rig and have it float. So you can add up the net bouyancy of everything that will be attached to a fully inflated BC (full tank, reg, gauges, integrated weights, can lights, pocket items, etc.). Plan for what you might use down the road in terms of tank size, pony, etc. when you do the math. Personally, I would want to do this using probably less than 90% of the BC lift.

2. Can it adjust for my change in bouyancy under normal conditions?
With a shell drysuit, there should be no change in bouyancy as you go deeper (assuming you properly manage the suit and it is in working order). If it is a neoprene suit (wet or dry), you should account for lost bouyancy as the suit crushes. Then you need to add the difference in bouyancy between a full tank and an empty tank plus a bit extra. I doubt this gets you much (if any) above 30 pounds.

3. Can you get yourself positive in a worst case scenario?
If you dive dry, it might be a major drysuit flood with a full tank (at depth if your suit crushes; and at the surface in all cases). The most conservative scenario would be to have 100% of that lift from your BC with a bit of lift to spare. A less conservative approach would be to get to that lift using 100% of your BC plus some fraction of your ditchable weight.

When I dove dry, I opted for an approach that was all of my BC and 1/2 of my weight ditched. If I have a major drysuit failure, I am fine giving some weight to Neptune.

What would the math look like for this? I would first take my personal bouyancy (i.e., swimsuit w/no gear), add that to the bouyancy in my gear, add that to my weight belt. Lets say I am neutral. My gear at its heaviest is -12 and I wear 35 pounds. That means I need to have lift of 47 pounds (I am implicitly assuming that 100% of the suit lift is gone). If I were to dump half of my weight (17 pounds) plus my BC (36 pounds) that would equal 53 pounds -- more than enough.

Diving wet is a bit simpler. It is calculated at depth at the start of your dive. This is when you are most negative. You would add the lost bouyancy due to suit crush (suit bouyancy at depth vs suit bouyancy at the surface) plus the negative bouyancy of a full tank plus all of your other gear. Then you would add a reserve.

my weight is 180 lbs, planing to use single aluminum tank, and integrated weight bc, 7mm wet suit. I just got my certification, and when we where diving with instructor my weight belt was 24-26 lbs. And the issue that I have I already bought bc before thinking ahead, my bc has only 32 lbs lift capacity and probably not going be enough?

It is probably OK. Next time you dive, check you rig by itself and make sure it floats with a full tank and your lead in the BC. This is the most critical check since your 7mm suit provides tons of additional lift. Although lift of the suit it is reduced at depth, some is always still present at recreational depths. Most people tend to buy a BC/Wing with too much lift the first time around.

I see, ok I'll test it first before the dive Thanks a lot

Toshas79:

I want to buy a bc, but don't know how to choose the lift capacity? I am planing to dive in California.

Click to expand...

I like having enough extra lift to allow me to float a panicking diver with his head well out of the water, while I figure out what the problem is.

This works nicely while teaching and around infrequent divers.

The SCUBAPro Classic+, for example, has 66 Lbs of lift (thought it used to be 75?), which has always been enough to handle any problems that arise.

Terry