Weighting for HP 119 vs AL80

[lemke]

Worthington's are ball busters. The most negative cylinders on the market.


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Which is why they are the only tanks I own!

 

[cephasiii]

I'm not surprised you didn't need any weight for a 119. They are heavy, try diving double 119's! Just make sure you can get to the service when the tank is full (at its heavest) and you will be fine.


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[raftingtigger]

I drop 10 pounds when I dive a HP100 instead of either a LP95 or AL80.

I came up with that by suspending a rigged tank over the dock side and using a luggage scale. When I put it into practice it worked just as expected.

What a tank weighs above the water and what it "weighs" in the water can be surprising. My LP95s (steel Faber) are the heaviest tanks I have above water, and are barely negative in the water. My HP100s are lighter than many of my tanks (above water), but add by far the most ballast in the water. Guess which ones I prefer to dive?

 

[kafkaland]

All kinds of air pockets and non water logged parts at first until you get down and get it all burped. The weight check at the end of the dive can be more accurate. I have a few different tanks and I started taking a sharpy and writing the weight I need on it instead of some mental reference to an AL80

Is there a good way to speed this up? I was recently diving in a relatively new, rented heavy 2-piece 7mm farmer John / jacked wetsuit, and had a hard time getting descending at all. Had to swim heads-down. But at the end of the dive I felt that I was correctly weighted, or, if anything, slightly overweighted. But the DM thought I was underweighted because of my initially difficulties getting down. Is there a good way to at least get all the air pockets out in the beginning? I didn't have that much difficulties with a dry suit - it seemed easier burping it than this wetsuit.

 

[johngayle]

I have lp 95s which are same size and weight as hp 119s and i use no weights at all with 3m or 5 mil wetsuit.

 

[MXGratefulDiver]

Worthington's are ball busters. The most negative cylinders on the market.

Not even close ...

- Worthington 120's are -2 lbs empty.
- Faber 120's are -7 lbs empty.
- Heiser 120's are -18 lbs empty.

... Bob (Grateful Diver)

---------- Post added July 12th, 2014 at 05:26 AM ----------

I drop 10 pounds when I dive a HP100 instead of either a LP95 or AL80.

I came up with that by suspending a rigged tank over the dock side and using a luggage scale. When I put it into practice it worked just as expected.

What a tank weighs above the water and what it "weighs" in the water can be surprising. My LP95s (steel Faber) are the heaviest tanks I have above water, and are barely negative in the water. My HP100s are lighter than many of my tanks (above water), but add by far the most ballast in the water. Guess which ones I prefer to dive?

It's helpful to remember that specifying the size of a cylinder says nothing about its buoyancy characteristics without also specifying the manufacturer and model of the cylinder. Buoyancy specs are all over the map when just looking at the size ... see the example above.

I own two AL80's ... a Catalina S80 and a Catalina C80 ... there's roughly 4 lbs difference in their buoyancy characteristics.

Also keep in mind that you're not weighting yourself to sink at the beginning at the dive ... you're weighting yourself to be able to hold a safety stop at the end of the dive. And therefore you should be performing your weight check with just your reserves (typically 500 psi) in the cylinder at the time of the weight check. If you weight yourself at the beginning of the dive, there is going to be a significant difference in the buoyancy of the cylinder by the time you need to do a safety stop ... due to the weight of the gas you're using up during the dive. For an '80 that's going to be about 6 lbs difference between full and minimum reserves. For a '100 it's going to be about 8 lbs. And for a '120 it's going to be about 10 lbs.

... Bob (Grateful Diver)

---------- Post added July 12th, 2014 at 05:29 AM ----------

Here's a useful chart ... it doesn't cover all the cylinders out there, but over the years I've found it to be reasonably accurate with respect to making buoyancy comparisons between the ones it does cover ...

Scuba Cylinder Specification Chart from Huron Scuba, Ann Arbor Michigan

... Bob (Grateful Diver)

 

[Scubanoobi]

Just for an update, I tried a weight check with my AL80 (15 feet at 500 psi) and the lowest weight I could go without floating up was 10 pounds. So about 10 pounds difference between the 80 and 119. According to the above website (which I checked before my initial post - and prompted my question) it should be about 6.5 pounds. I'll go with my weight check numbers.

 

[beanojones]

Just for an update, I tried a weight check with my AL80 (15 feet at 500 psi) and the lowest weight I could go without floating up was 10 pounds. So about 10 pounds difference between the 80 and 119. According to the above website (which I checked before my initial post - and prompted my question) it should be about 6.5 pounds. I'll go with my weight check numbers.

I have noticed about four pounds difference between XS Scuba 120's and most AL80s. And an 8 pound between XS Scuba 100's and AL80s.

I wonder if the XS Scuba 120's are Worthington 119's?

 

[MXGratefulDiver]

XS Scuba steel cylinders are built by Worthington, but the 120 is a 7.25 inch diameter cylinder, while the 119 is an 8.0 inch cylinder that is about 4 inches shorter than the 120. They have similar buoyancy characteristics although the 119 is a couple pounds heavier in terms of weight.

... Bob (Grateful Diver)