Lift Bag Size

[markmantei]

I need to purchase a new lift bag, and I'm debating between a 50 and 100 lb lift bag. I will need this as I continue with tec training, but I also am thinking to use it as backup buoyancy for warm water dives where I am not diving dry (I know double bladder would be better, but I am not sure I will be doing enough diving in the configuration to justify the expense at this time).

My gut feeling is that 50lbs should be sufficient, but you can always have less gas in the 100lb bag if necessary.

Am I wrong to think that the 100lb bag is overkill and go with the 50?

 

[Herb-alaska]

my thought would be

the larger it is the less likely you will carry it. I also would want to make sure that the lift bag is dump able so that you can control the rate of ascent

If the 100 is small enough to carry and you can control the amount of gas in the bag then I would go with the 100 otherwise I would find one to fit both goals. 50 lbs of lift is a lot of lift for everyday use.,

 

[Doppler]

You should speak with your instructor... a liftbag may not be what he/she wants you to use (a DSMB is usually preferred).

In any event, 100 pounds is excessive. You will find it a challenge to stow away neatly.

You plan to use this as backup bouyancy? What events specifically do you expect to occur that would require almost 40 kilos of lift?

I have never needed backup buoyancy of any type... my experience may reflect good luck... or pre-dive kit inspection... but you should not need more that a couple of kilos if that... if you do, you are overweighted.

 

[Jared0425]

I have a 100 lift bag on my doubles. I have it strapped to the side. 50lbs is more than enough if you need to hang or shoot a line. I have mine in case I find something interesting or have multiple divers using it. If you hang it off your BC I find it in my way most of the time.
Jared

 

[decompression]

Mark, who are you taking tech training with (agency, instructor,shop)? You can pm me if you'd prefer. I think you might be missing some background info that could influence your decision on size of lift bag, a larger SMB and the thought of a double bladder BCD....

---------- Post Merged at 10:56 AM ---------- Previous Post was at 10:44 AM ----------

This is the required equip for TDI deco procedures course (I'll find my DSAT tec and UTD info in a bit);

Required Equipment
The following are required for this course:
The following equipment is required for each student:


1. 2.
3. 4.
5. 6. 7.
8. 9. 10.

Primary Cylinder(s). Cylinder volume appropriate for planned dive and student gas consumption. Decompression Mix Cylinder(s)

2. Cylinder volume appropriate for the planned dive and student gas consumption with
   submersible pressure gauge.
3. Labeled in accordance with TDI Standards.

Depth gauge and automatic bottom timer and I or dive computer. Regulator(s)

2. Primary and alternate 2nd stage required on all primary cylinders.
3. Submersible pressure gauges are required on all primary cylinders.

Buoyancy Compensator(s) adequate for equipment configuration. Jon-line and other rigging lines as dictated by site conditions. Ascent Reel with Lift Bag /Surface Marker Buoy.

2. Adequate for maximum planned depth.
3. Minimum of eleven (11) kg / twenty five (25) lb lift bag.

Oxygen Analyzer (may be supplied by the Instructor). Exposure Suit adequate for the open water environment. Underwater Slate.

Note-,"lift bag/SMB.....25 lbs lift min.....there are reasons behind this option. We can find the right one for you.

UTD Tech1/2 (padi also does not specify size)

• Backplate BC System SS or Aluminum Back plate w/ web harness and hardware
• Back inflate style wing.
  
• At least one depth-measuring device
• At least one time-keeping device
• Fins: non-split variety
• At least one cutting device
• X-notes or Wetnotes
• One spool with 100 feet of line
• One surface marker or lift bag
• Exposure suit appropriate for the environment you will be diving in
• Regulators & UTD Hose Configuration 5 or 7 ft. Primary Regulator Hose
• 22 or 24" Necklace Regulator Hose
• 24 or 26" SPG hose
• BC-mounted canister dive light w/ Goodman handle or long hose catch such as a knife pouch.
• Cylinders Double tank configuration (1 per day of diving)
• A single decompression bottle with a minimum of 40 cuft is required

Note; size of lift bag/SMB is not specified. This is where the instructor helps determine your needs depending on several factors (water conditions, exposure suit, focus of dive goals, current and future equipment etc).



I hope I've helped a little.

 

[flots am]

I need to purchase a new lift bag, and I'm debating between a 50 and 100 lb lift bag. I will need this as I continue with tec training, but I also am thinking to use it as backup buoyancy for warm water dives where I am not diving dry (I know double bladder would be better, but I am not sure I will be doing enough diving in the configuration to justify the expense at this time).

My gut feeling is that 50lbs should be sufficient, but you can always have less gas in the 100lb bag if necessary.

Am I wrong to think that the 100lb bag is overkill and go with the 50?

Bigger bags are more visible and give more lift but are more difficult to inflate at depth. Getting your 100LB bag to stand up on the surface would require making it nearly 33LB buoyant if you inflated it at 99', which is nearly impossible unless you're really fast and over-weighted.

Smaller bags are easier to inflate at depth but less visible on the surface. It's a compromise either way and is really your decision.

Redundant lift isn't really an issue with a drysuit, since you still have your BC. If you're diving hugely negative doubles with a thick wetsuit, you would be better off to rethink your configuration than hope you can wrangle your lift bag into making you buoyant during an emergency.

I have both the large and small Carter and have never sucessfully shot the large one and had it surface fully inflated.

flots.

 

[rongoodman]

I like the Halcyon bag, which has 80 lb of lift but still quite compact.

 

[nimoh]

I think there might be some confusion in this thread regarding surface marker buoys (SMB) and lift bags.

I carry two smbs. My 4', I can fill it half full with most of the air from my lungs, and so can deploy it from 30' without losing neutral buoyancy. If I were to get to the surface, and realize it wasn't enough to be visible, I would deploy my 6' smb on the surface.

A lift bag is for lifting, you tie it to something you want to lift and inflate it until the object is neutral. If the object is 50lbs negative, then you have plenty of time to fill the lift bag, since the object will hold it down until you have enough air in the bag. the lift bag also has a dump valve on top, so that you can spill air as necessary on the way up to maintain neutral buoyancy for the object.

 

[decompression]

I think there might be some confusion in this thread regarding surface marker buoys (SMB) and lift bags.

I carry two smbs. My 4', I can fill it half full with most of the air from my lungs, and so can deploy it from 30' without losing neutral buoyancy. If I were to get to the surface, and realize it wasn't enough to be visible, I would deploy by 6' smb on the surface.

A lift bag is for lifting, you tie it to something you want to lift and inflate it until the object is neutral. If the object is 50lbs negative, then you have plenty of time to fill the lift bag, since the object will hold it down until you have enough air in the bag. the lift bag also has a dump valve on top, so that you can spill air as necessary on the way up to maintain neutral buoyancy for the object.

Nice bit of info there, what's the confusion you see?

 

[nimoh]

Nice bit of info there, what's the confusion you see?

here is one example, not sure why you would need a 100lb lift bag to stand up on the surface, and not sure why you would need to make your SMB 33lb buoyant at 99'

Bigger bags are more visible and give more lift but are more difficult to inflate at depth. Getting your 100LB bag to stand up on the surface would require making it nearly 33LB buoyant if you inflated it at 99', which is nearly impossible unless you're really fast and over-weighted.