Question (more like advice): Weighting moving from AL 80 to HP 100

[Librarybarry]

Friends,

As the title says, I'll be switching to a HP 100 on my next charter dives, and only have experience with AL 80's.
I know this advice has been sought before. I've read a few of the suggested "Is this topic being discussed" when input the title, as well as searched keywords, and found that based on the empty weight of different manufacturer's tanks there usually a drop of 5-7lbs (and this may well be the answer). I know that rsingler's Optimal Buoyancy Computer may help me get the answers, and when I have time to read the user's manual and weigh my gear, I plan to do so.

I'm new (30 dives in quarries, springs, and a few ocean charters), and I guess just looking for validation of what I found (drop 5-7 lbs from last ocean dive) as a starting point for how much weight to drop when switching from an AL 80 to a HP 100 -- exact same gear as I wore on a dive last weekend, same general area off the coast, but maybe a little deeper.

I appreciate anyone who can provide a bit of advice, and do not wish to start a conflict about different manufacturers, tank density/vol/etc.
Thanks

 

[inquis]

If it's a Faber HP100, yes drop 5 lb of lead from what you used with an AL80.

 

[NW Dive Dawg]

Sounds to me like you're on the right track... I'd probably start with the 5lbs since you can compensate for a couple lbs heavy but it sucks to be at your safety stop and a couple lbs too light. You'll love the HP100's! I know I love mine and not just for the buoyancy factor..... I like that they are noticeably shorter than an AL80.... Just for reference, here's a pic of 2 of my HP100's next to my emergency O2 which is an AL80.

 

[tursiops]

It depends on what kind of AL80 and what kind of HP100.
The AL80 empty weight (with valve) runs from +4.4 to -0.2, depending on tank. the two most common (Luxfer and Catalina) are 4.4 and 4 lbs positive, respectively.
The HP100 empty weight (with valve) runs from -1 to -1.3 to -7.3 lbs, depending on tank. The Faber 100 is the heavy one, the PST tanks are the light ones.
So the added (empty) weight in the water could be as little as 0.8 lbs or as much as 11.7 lbs.

This info is from SCUBA Cylinder Specifications – Huron Scuba, Snorkel & Adventure Travel Inc. PADI 5 star IDC in Ann Arbor, MI.

 

[RIHappyDiver]

It depends on what kind of AL80 and what kind of HP100.
The AL80 empty weight (with valve) runs from +4.4 to -0.2, depending on tank. the two most common (Luxfer and Catalina) are 4.4 and 4 lbs positive, respectively.
The HP100 empty weight (with valve) runs from -1 to -1.3 to -7.3 lbs, depending on tank. The Faber 100 is the heavy one, the PST tanks are the light ones.
So the added (empty) weight in the water could be as little as 0.8 lbs or as much as 11.7 lbs.

This info is from SCUBA Cylinder Specifications – Huron Scuba, Snorkel & Adventure Travel Inc. PADI 5 star IDC in Ann Arbor, MI.

For some reason, the only Faber 100 that is referenced on Huron’s list is the M series, which I used to own. It is a BEAST, both in and out of the water. The Fabre FX series has an empty weight (with valve) of -0.59. And it is much easier to manage than the M series.

@Librarybarry, we did this same exercise with my wife this past weekend. I made the assumption (Yea, I know) that the 80’s that she has used in the past were at the 4.4 ish weight. 5# was a perfect change for her. Now, to @tursiops point, it wouldn’t hurt to call the charter and ask which HP100 they’re using, and call the previous charter and ask which AL80 they use.

Have a great dive!

Erik

 

[scubadada]

I take off 4 lbs. Do a weight check at the end of the first dive. You won't be too far off.

 

[RGDiver]

Personally I think the HP 100 is the best tank overall that you can dive with for various reasons. I find that it sits perfectly on my back and makes buoyancy as simple as it gets. Steel tanks don't become flotation devices like aluminum ones do near the end of the dive either, so keep that in mind. It's a shame it's hard to get steel when traveling. For me I drop about 6 pounds of weight in salt and won't need any weight in fresh.

 

[L13]

Assuming the same valves:

The Faber HP-100-HDG is -0.59 lbs, the Luxfer AL80 is +4.40 lbs, and the Catalina AL80 is +4.1 lbs (all empty). So net is 4.69 to 4.99 lbs, or 5 lbs as @inquis said. (the other HP100's can be as much as 6 lbs more negative)

 

[Librarybarry]

I really appreciate the advice of everyone who responded. I figured I was on the correct path, but wanted to be sure. I believe I will take @RIHappyDiver 's suggestion and ask the charter if there is a particular HP100 that is used most often and adjust from there using the chart @tursiops linked.

Thanks again, everyone.