Weight advice for moving from single HP100 to double LP85s?

[SaltyWombat]

I plan to get a twinset of Faber LP85s this summer. I currently dive a single Faber HP100. At first glance, I'll be losing approx 14 lbs from the HP100 and gaining approx 13 lbs back from the double LP85s. So there's a net loss of approx 1 pound. Am I right so far? If so, the total amount of lead I'll carry is approximately the same.

I'm under the impression I might need to move trim weights lower down on the cylinders or use a V weight.

I use a drysuit with 400 g undergarments. I'm 5'10" (177.8 cm). With my HP100, I dive with 4 x 5 lbs of lead, a 6 lb Halcyon SS backplate, and a 2 lb Halcyon STA.

Any advice on how I should distribute the weight? During a test drive with double AL80s in a pool, I was a little head heavy.

I hear it's common to switch to aluminum backplates when moving to twinsets. True?

 

[PfcAJ]

I bet you’ll be pretty good with no additional weight.

do a proper check to be sure though. 85s are great tanks.

 

[grantctobin]

I bet you’ll be pretty good with no additional weight.

do a proper check to be sure though. 85s are great tanks.

^this. If you’re not in Jet/Rocket/negative fins, you’re more likely to need a p-weight. I bet you’re within 2lb though.

 

[Jack Hammer]

I hear it's common to switch to aluminum backplates when moving to twinsets. True?

In warm water an aluminum plate is nice. In cold Lake Michigan water a steel plate allows you to carry less lead. Some is still needed. IIRC, when I dove steel double 100s with a BZ400 I used a SS plate with a 6# V-weight and 5# on my waist.

 

[tbone1004]

I plan to get a twinset of Faber LP85s this summer. I currently dive a single Faber HP100. At first glance, I'll be losing approx 14 lbs from the HP100 and gaining approx 13 lbs back from the double LP85s. So there's a net loss of approx 1 pound. Am I right so far? If so, the total amount of lead I'll carry is approximately the same.

I'm under the impression I might need to move trim weights lower down on the cylinders or use a V weight.

I use a drysuit with 400 g undergarments. I'm 5'10" (177.8 cm). With my HP100, I dive with 4 x 5 lbs of lead, a 6 lb Halcyon SS backplate, and a 2 lb Halcyon STA.

Any advice on how I should distribute the weight? During a test drive with double AL80s in a pool, I was a little head heavy.

I hear it's common to switch to aluminum backplates when moving to twinsets. True?

I'd strongly recommend against the 85's and instead get more of the FX100's unless you can 100% guarantee that you will always have access to cave fills. Low pressure steels are awful when filled to working pressure.
1x HP100 to a set of double 85's will likely be a wash but since you have that much lead on you, that is just extra reasoning to go with the FX100's that are about 3lbs each more negative than the 85's and you'll be able to take at least 10lbs of that lead off.

 

[mc42]

Between single and dual Faber HP100s using the same SS backplate I went from 24 down to 6 lbs. I'm using a 40lb wing.

If you're already head heavy, doubles are worse, certainly for me. With the tallish Thermo manifold it has been a battle finding good trim. I had to to move the bands up as high on the tank shoulders to offset them down, add tail weight with the V-weight pouch and make sure the BP is in the correct location (crotch strap and shoulder strap length).

Realistically, a couple of those 6 lbs in the V-weight are for trimming feet down, help offset the extra buoyancy from empty stages or to keep a little more air in my drysuit. The challenge is picking between good trim and being overweight. I'm probably slightly overweighted as a result.

I guess the LP85s might be a little more buoyant when empty, so maybe a little extra lead may be needed to keep them down. When you're first trying them out, you might start with 10lbs. I think that's what I used when I first tried a set of LP85s.

 

[Gone for diving]

find your tanks and do the math...
But remember... to add the weight of the bands, manifold. And second regulator..
That does add up fairly fast..
I would be surprised if you need any weight... depending on you drysuit underwear... and the amount of air you have in the suit..
As for trim jet fins. And drill a set of holes lower in the back plate that does help with shifting weight. And there are usually 3 grommets in your wing to play with...

Aluminum plate is for trying to save weight like traveling or doubles with a wet suit.
Sounds like you are trying to add weight so a SS plate is heavier..

 

[Dark Wolf]

I am head heavy using my 85's and AL plate, but with trim weights it works out well with thicker undergarments.

DW

ETA-It sounds as if we are pretty similar in height, I am about 175 pounds (give or take).

 

[Ayisha]

I'd strongly recommend against the 85's and instead get more of the FX100's unless you can 100% guarantee that you will always have access to cave fills. Low pressure steels are awful when filled to working pressure...

I find that LP tanks get better fills even without being cave fills, since many will at least go for 3000 psi/200 bar. It's the HP tanks that tend to get underfilled, very likely also to 3000 psi/200 bar, at least around here.

 

[tbone1004]

I find that LP tanks get better fills even without being cave fills, since many will at least go for 3000 psi/200 bar. It's the HP tanks that tend to get underfilled, very likely also to 3000 psi/200 bar, at least around here.

doesn't matter, in the case of the LP85 vs FX100 the water volume is the same so they hold the same amount of gas when filled to the same pressure. If you are going to get 3000psi fills, I'd rather it be in a FX100 where in the case of the OP you get buoyancy benefits while still retaining the potential of getting a full fill