HOW MUCH LIFT FOR COLD WATER

[sarahlee]

Hello Divers,

Ive seen a lot of posts about this - its a little confusing when I try and compare it to my specific situation.

I am getting a backplate and wing rig, and want to know how much lift in my wing i'll need.

I am looking at a 28# wing - i dive a 8mil with hood - at my deepest and i usually never go past 95ft. - usually i do a lot of shore diving around 30ft. for the deeper dives I'm using a steel 80 or 73.

what do you think ...?

ms lee

 

[northernone]

Sounds good to me. I've been satisfied with the lift of a #18 for a 7/14mm suit with a single tank.

The amount of material in your wetsuit to compress could be a factor. I'm 6'2" 180lbs. A larger bodied person takes more wetsuit material and there's a larger buoyancy change as it compresses.

Regards,
Cameron

 

[rhwestfall]

the recommendation is that you need the amount of lift to support your rig (by itself) at the water surface with a full tank.

 

[northernone]

Sounds good to me. I've been satisfied with the lift of a #18 for a 7/14mm suit with a single tank.

The amount of material in your wetsuit to compress could be a factor. I'm 6'2" 180lbs. A larger bodied person takes more wetsuit material and there's a larger buoyancy change as it compresses.

Regards,
Cameron

Just noticed your profile pic. Disregard my question regarding wetsuit size.

Getting a properly weighed rig you should be very comfortable with the lift provided by a #28.

 

[rhwestfall]

For a reference point, we typically use 30# (28-32 depending on manufacturer) wings here in the Great Lakes for single tank diving in our cold waters.

 

[northernone]

the recommendation is that you need the amount of lift to support your rig (by itself) at the water surface with a full tank.

I'd be cautious with that advice depending on the size of diver and thickness of wetsuit. Wetsuits need from between 3lbs and 40lbs compensation for 100ft dive, depending on build. Rough estimate 1lb of standard neoprene needs 3lbs compensation.

Rig alone might give a ballpark coincidentally for the average suit and body type of your area?

I see you know cold water diving.

 

[sarahlee]

hey thanks for all the great info - you guys rock ;-)

 

[cool_hardware52]

Hello Divers,

Ive seen a lot of posts about this - its a little confusing when I try and compare it to my specific situation.

I am getting a backplate and wing rig, and want to know how much lift in my wing i'll need.

I am looking at a 28# wing - i dive a 8mil with hood - at my deepest and i usually never go past 95ft. - usually i do a lot of shore diving around 30ft. for the deeper dives I'm using a steel 80 or 73.

what do you think ...?

ms lee

Any BC needs to offer enough lift to do two things:

1) Float your rig at the surface with a full cylinder. The typical BP&W "rig" will include the backplate, harness, regulator, full cylinder, and any additional ballast attached to the rig (vs worn by the diver in on a belt or in a weight harness)

2) Offer enough lift to compensate for the maximum possible change in buoyancy of your exposure suit. It's possible for almost all suits, wet, dry, shell, neoprene etc to lose all the buoyancy they start with. Wetsuits can be crushed until they are a solid block of neoprene and drysuits can fail and be unable to trap any gas. Both are extreme circumstance, but your suit can't lose more buoyancy than it starts with.

Which ever number is larger dictates minimum required wing capacity.

For cold water diving it's almost always the buoyancy of the diver's suit that dictates minimum required lift.

When is the minimum not enough? IMO a properly weighted diver should not need more than what I listed above, however uncertainty about the exactly buoyancy of your suit, or future suits can make erring a bit on the larger capacity side worth considering.

OTOH if you want to use the same wing for warm and cold water diving selecting the smallest wing that meets the requirements above can be a reasonable choice.

Tobin

 

[rhwestfall]

neutrally buoyant at 15' means no air in your bladder. That means you have the full capacity of the bladder to offset compression of exposure protection...

Balanced Rig

 

[Akimbo]

How Much Lift for Cold Water?... The simple answer, because I'm a very simple guy, is no less than it takes to be neutral in the water with full cylinders at your safety stop. Figuring that out is an educational exercise but you can't beat actually verifying your "best guess" in the water.

... i dive a 8mil with hood - at my deepest and i usually never go past 95ft...

The displacement of your suit x 8mm thick is a big variable. A young teenager versus a 6'4 football player can be more than 3x the volume. A more useful way for anyone to help you figure it out is to start with the weight you use now and make small adjustments for the backplate/BC change.