BP/W HP100 vs AL80 weighting

[Mouth Breather]

I have spent some time searching but didn't find any threads with this particular question. I'm looking into replacing my jacket bc with a bp/w and have seen a <cough> couple recommendations for DSS, which seems a solid choice after a lot of reading. I am looking at the kydex plate & Torus 26 wing, solely based on buoyancy estimates.

Using the wing lift calculator often linked on SB, I entered the two extremes I could possibly be in. I used 10# head weight, -1 for DSS kydex plate, -1 for a light or other stuff (camera, hunting gear etc).

AL80 with 5mm: Used 3lbs/mm for the suit, so +15, guessed +6 at depth. Tank -1.4/+3.4 full/empty. Need lift is ~15lbs, need lead is ~16lbs.
HP100 with skin: No positives here, end up 20lbs negative at the beginning and -2.6lbs at "3m end". Sheet calls for 20lbs of lift.

These are some pretty massive differences. It makes me think that either the spreadsheet is wrong (as I'm using it anyway) or my current jacket (Aqualung axiom) is VERY buoyant as with a HP100 and a well-crushed 2mm I still carry about 4lbs. In a skin/shorts and an AL80 I carry about 10lbs.

So...I feel like my choices are:

SS backplate, abandon the HP100s...hate that idea. Love my steel!
I was going to say kydex instead of ss but at -20 at the beginning of the dive, this is a no-go. I need some more buoyancy to make this work. At 6' 175lbs my body isn't providing it.

Those of you with experience in BP/W rigs or similar situations...what would you suggest that keep me near neutral in both situations?

 

[tbone1004]

the delta of 4lbs to 10lbs is about right for a HP100 to an AL80 if using the same suit depending on the HP100. Worthingtons the delta is closer to 8lbs, Fabers about 4lbs.

Personally I would stay with steel plate and the hp100 and just dive the 2mm most of the time. You'll be a few pounds heavy but that isn't the end of the world since it is a single steel tank and you should be able to kick it up.

 

[Wookie]

I wear 14 lbs of lead in a poodle jacket with an al-80. With a Stainless plate and 18# wing and a steel hundred I wear no lead. Both are with a 3 mil wetsuit.

 

[stuartv]

Something ain't right. The buoyancy swing from start to end of dive, with a 100 should be more like 8#, not 18.

Unless you are saying 20 # negative at the start AT DEPTH, and 2.4 negative at 3m End... Maybe that's what you meant and I just misinterpreted on my initial read through.

 

[Eric Sedletzky]

If you're going from a poodle jacket with an 80 to a steel plate with a steel 100 then you'll drop
5 lbs with the plate
4 lbs with steel tank
And maybe 3-5 lbs from ditching the jacket. They can have that much inherent buoyancy.
So you could get rid of 12 to 14 lbs from what you use now, that is if you are properly weighted, you might even be able to go more.

 

[Wookie]

Something ain't right. The buoyancy swing from start to end of dive, with a 100 should be more like 8#, not 18.

Unless you are saying 20 # negative at the start AT DEPTH, and 2.4 negative at 3m End... Maybe that's what you meant and I just misinterpreted on my initial read through.

Was that at me? No, you did not read it right.

 

[stuartv]

Was that at me? No, you did not read it right.

No, the OP's 3rd paragraph.

 

[The Laconic]

Using the wing lift calculator often linked on SB...

Which reminds me, I want to do some calculations too, but I can't find this thing anywhere, just a link from 2009 or so that's broken. Can anyone point me in the right direction?

 

[Mouth Breather]

@The Laconic I found a better one in this post.

@stuartv You're right, I accidentally typed in the pre-dive weight of 20lbs, which includes "head weight".

Using the newer sheet, I'm -14 on descent and -6 at a 10ft safety. With a 26lb wing, I'd be filling it up to keep my head above water at the start. I shared the spreadsheet with these numbers if you want to take a look: LINKY

With my jacket BC and the HP100, I normally wear my 2/3 and 4-6lbs. That means the jacket must be about +6 all by itself. Seems high.

 

[stuartv]

That sounds better.

My thoughts:

- Maybe you are coming up with +6 on your BC because you are not normally getting ALL the air out of it?

- +15 # of bouyancy for a 5mm seems on the high side, but I don't really know. OTOH, having a 26# wing for diving single tanks with a 5mm seems reasonable. I dive my Hog 23# wing with a SS BP, HP120 (steel) tank, and my 3/2 suit with no problems (and no lead added). But, I haven't tried that setup with my 5/4 suit. If I were diving a single 100 or 120 and needed the 5/4, I might use my bigger (30#) wing that I have, just to be safe. I think my 23# Hog might be pushing the limits of safety (and for no good reason since I have a bigger wing).

If you're shopping for your first wing and you're trying to figure out what to buy, I would suggest looking at:

DGX Gears Single Tank Wing - 25# lift, $199
DGX Gears Single Tank Wing | Dive Gear Express®

or

Deep6 30# Wing - 30# lift, $250
Deep 6 30 LB Single Tank Wing - Buoyancy

25 # might not be enough with your 5mm. You really need to measure your suit's actual buoyancy to figure it out for sure. Probably, though. If you're weighted right, then with an HP100, you'd be about 8# negative at the surface at the start. That gives you plenty of wing capacity to keep your head well out of the water if you're floating before you start the dive. At the bottom (at the start), you'll be negative by 8# plus however much you lose from suit crush. If the suit loses 14# (which seems like way more than what a 5mm would actually lose), then you're 22# negative and a 25# wing still has 3# capacity to spare. And, at the start, your rig would be something like 18 or 19 # negative - assuming SS BP, no lead on the rig, and an HP100 that is -9.5 when full. So, again, a 25# wing would be enough.

But, it all really depends on: How buoyant is your suit, really? Personally, I would calculate based on losing 75% of that, at 130'. And, how negative is your actual tank? My HP100s are about -9.5 when full, but other brands are different. And, are you going to hang any lead that you need on your rig, or wear it on a weight belt? If you hang it on your rig, then that makes it that much heavier for your wing to float your rig, if you need to take it off in the water.

Disclaimer: I have not used either of those wings I linked. Those are just the ones I would be considering if I needed a new single tank wing for use with a 5mm suit.