BCD Lift

[Teller]

I am looking at the new Nomad LT on the DiveRite website and they say the largest cylinder you can use with that rig are Faber 85s due to it only having 25lbs of lift. Faber 85s are -3.80 lbs when full. I prefer Faber 95s which are -5.37 lbs full. I get the concept of putting on all my gear with full tanks and making sure I can float on the surface but what I am wondering is how to really determin how much lift I need. The 95s are only another 2lbs negative. Can the rig really not support the extra weight or is DiveRite just trying to play it safe? What if I dove AL80s which are -1.6lbs ful (catalina)? Does that mean that the rig could support up to four AL80s or more?

 

[DivemasterDennis]

While I am not sure of the reasons for the manufacturer's stated limits, I am sure of this: I would use any piece of diving equipment only within the bounds of the manufacturer's specifications. They state those limits for a reason.
DivemasterDennis

 

[jonnythan]

Lift required is primarily a factor of quantity of gas carried and exposure suit.

 

[chrpai]

While I am not sure of the reasons for the manufacturer's stated limits, I am sure of this: I would use any piece of diving equipment only within the bounds of the manufacturer's specifications. They state those limits for a reason.
DivemasterDennis

Seems like an arbitrary statement though while ignoring other variables. It's probably put in place for people who wouldn't understand what I'm about to write next:

I'd ignore the statement and do the standard balanced rig calculations. If the math works out, then dive it. If not, get a bigger wing.

 

[ADeadlierSnake]

Keep in mind that your BC needs to be able to lift you AND your partner (at full tanks, and with all your weight) in the event of an emergency. For instance, if you ever have a tox event, or go unconscious for whatever reason, your buddy needs to be able to use YOUR wing to lift both of you out of the water. If he/she used their own BC to do this, it would be incredibly full, and in the event that they dropped you, they would now have an uncontrolled ascent. Now two people are in danger. The dive on top (your buddy) stays slightly negative while using your wing for buoyancy on the way up.


Refer to this:




I have not taken Tech1 yet, so I do not have formal training on this. I am explaining this to the best of my understanding. If I got anything wrong, someone please correct me, because I would hate to be doling out false information.

The point is that you should have a balanced rig though

 

[eelnoraa]

Keep in mind that your BC needs to be able to lift you AND your partner (at full tanks, and with all your weight) in the event of an emergency.

This isn't a correct way to determine wing lift.

25lb for double LP95 seems to be a bit on the low side. What exposure suit?

 

[Teller]

I understand all the reasons why you should have a balanced rig and I know how to conduct a check to see if my rig has enough lift. I just want to understand how someone can say this cylinder will work but that one wont.

 

[chrpai]

I understand all the reasons why you should have a balanced rig and I know how to conduct a check to see if my rig has enough lift. I just want to understand how someone can say this cylinder will work but that one wont.

Well, absent a detailed explanation from someone who was involved in writing it, I'd assume a group of people debated / edited the content and came up with something dummed down. I know that's how it happens at my work.

 

[ADeadlierSnake]

This isn't a correct way to determine wing lift.

Can you elaborate?

 

[freewillie]

I was alway under the assumption that a BC should have enough lift to offset how much weight you added to your rig. Normally I dive 7 mm wetsuits with hood, gloves, and booties using about 20 lbs. My lift for the BC should be able to handle at least 20 lbs lift but if has a greater capacity then I would have extra margin to offset additional weight if required such as adding negatively buoyant steel tanks.

I would assume relative light lift capacity 25 lbs manufacturer recommends a lighter tank due to limited lift. You would have to add up how much weight you're diving with in addition to your tank and see if it is comfortably under 25 lbs. The closer to the limit the less of a "cushion" you have for lift.