Best way to match wing lift to back plate weight?

[CycleCat]

With an empty wing, about 500# in your tank, at 15', you should be.neutral. On a shore dive, I just place the excess weight in a game bag on the bottom, ...

I've tried a couple of stays, one put the tank too high off my back making it act awkward, the other wasn't noticable, so I don't use any. You might want to save your money for something else.

That is exactly what my wife and I worked on. Once we breather our tanks down to 500, we tested buoyancy. I think I can still shave 2#.

Good input on the single tank adapter. If I get one I will look for one that does not hold the tank up too high.

 

[halocline]

Don't buy a single tank adapter just because you need more weight. The STA was used back in the days when wings were originally designed for doubles and so did not have slots for the tank straps. Current small wings all have slots for the tank straps and most have some sort of tank stabilizer built in, making the STA completely unnecessary, and in fact they tend to move the tank away from your back, which most divers don't like. Of course there are always exceptions.

Probably you will want a steel plate. Many BP/W divers have a steel and AL plate if they routinely switch between cold and warm water and/or steel and AL tanks. If you want to spend money and you really need 24 lbs of lead with a 5mil suit and AL80, here's an idea. Get a steel tank! That'll help you unload some cash and definitely lower your lead use.

I'm having a little trouble imagining someone really needing 24 lbs in a 5 mil suit. Are you, how do I put this delicately, built for comfort? Is there any padding on your harness? If so, switch to just plain webbing and SS hardware. Even a AL plate with plain, one piece webbing harness and steel hardware should provide a little ballast, and a AL tank with a regulator is no more than 4lbs positive, even empty. So you should be able to knock off more lead. You can put your suit in a mesh bag, throw it in a pool, and start adding weights to the bag until the suit sinks. That's an interesting experiment if you have some free time someday. I bet a 5 mil suit sinks with around 12 lbs, but there's only one way to be sure.

When I use my AL plate with an AL tank in the ocean and a 3mil suit, I tend to need about 8 lbs of lead, and I put it on the tank straps. There are nifty little pouches specifically for that. You can slide the pouches up against the plate, one on each side of the tank, and it works pretty well. Lets say you got your weight down to 16 lbs, which should be easy, that's four 4lb weights, two of which could go on tank straps and two could go in pouches on your harness waistbelt. No need to get quick release pockets, if you really needed to drop those weights you could just take them out of the pockets and drop.

 

[CycleCat]

... here's an idea. Get a steel tank! That'll help you unload some cash and definitely lower your lead use.

I'm having a little trouble imagining someone really needing 24 lbs in a 5 mil suit. Are you, how do I put this delicately, built for comfort? Is there any padding on your harness? If so, switch to just plain webbing and SS hardware. Even a AL plate with plain, one piece webbing harness and steel hardware should provide a little ballast, and a AL tank with a regulator is no more than 4lbs positive, even empty. So you should be able to knock off more lead. You can put your suit in a mesh bag, throw it in a pool, and start adding weights to the bag until the suit sinks. That's an interesting experiment if you have some free time someday. I bet a 5 mil suit sinks with around 12 lbs, but there's only one way to be sure.

Right now tanks are the one thing I'm still renting and everywhere I rent has aluminum. I will definitely look at
getting steel if I ever buy my own.

I'm 5'10" and 200#, not slim but I would not describe myself as built for comfort either! I used the dive weight calculator here to find a starting point:
Estimated Diving Weight Calculator | DiveBuddy.com

I'll do that pool experiment and sink my wetsuit next chance I get.

 

[lowwall]

If I start piecing together another set I'm wondering how would be best to mix the pieces I end up with. If my next wing has more or less lift do I want to put the bigger lift on the heavier plate or just the opposite? I can see it working both ways.

Here's the scenarios:
-Warm water dive with 3 mil suit or less: Not a lot of buoyancy so lighter plate. Do I offset my lower buoyancy with the bigger wing or will the smaller one do?
-Cooler water with 5 mil or thicker suit (I will never dry suit dive): More buoyant so heavier plate. Since I already have suit-induced buoyancy will the lighter lifting wing suffice?
-Or do I have this all bass-ackwards and I should do the lighter lift with the lighter plate and heavier lift with the heavy plate?

This is kind of backwards.

Wing size is determined by the amount of lift required to compensate for the weight of the gas used during a dive and the difference in buoyancy for your wetsuit between the surface and the deepest part of your dive. You have to account for the wetsuit since it gets most of its buoyancy from tiny air bubbles trapped in the neoprene. These bubbles compress as you go deeper and so the suit loses buoyancy. A rough estimate is a loss of 2 to 3 lbs of buoyancy for each mm of suit thickness for a fullsuit.

So in your case of an AL80 and 5mm wetsuit, you want a wing with 15-20 pounds of lift: 4.5 pounds to offset the extra weight of the air in your tank and 10-15 to offset the loss of suit buoyancy. In the unlikely event that you really need 24 pounds of weight to be neutral at the safety stop, you'll want to look at upper end of the range since that suggests you are using a wetsuit with a lot of fabric. There aren't many 20# wings, so if you want the minimum drag I'd look at a 24 which will also cover you if you decide to use a larger tank. Do the same math for a 3mm suit and you'll find a 16# wing will suffice. For a 7mm, you'll want your 32#, especially if you'll be adding a hooded vest or other second layers.

Now let's look at weight. Weighting is determined by what you need to keep from popping to the surface at the end of a dive. It doesn't matter in terms of buoyancy (it might matter in terms of trim) whether that weight is in the form of lead weights, steel backplates, steel tanks, or the removal of buoyant material like neoprene or BCD padding. If you need any lead to be neutral at the safety stop, switching from an AL to SS backplate will mean you get to take off up to 5 pounds of that lead, no matter what wing you are diving.

The only time this breaks down is if your rig - BC and everything attached to it including integrated and trim weights - is so heavy that your wing won't be able to float it at the surface without you in it. This is rarely a problem with warm water and single tanks, but if it is a problem is you should consider making some of the weight non-integrated, i.e., put it on a weight belt or harness. This will make your rig easier to handle when you aren't wearing it and will help prevent you from being excessively buoyant if you are forced to take off your gear underwater due to an entanglement or other problem.

 

[halocline]

I'm 5'10" and 200#, not slim but I would not describe myself as built for comfort either! I used the dive weight calculator here to find a starting point:
Estimated Diving Weight Calculator | DiveBuddy.com

I'll do that pool experiment and sink my wetsuit next chance I get.

I tried that calculator and it told me I would need 16lbs in a 3 mil suit, double what I normally start with (and drop from there). I would just forget anything it says. Instead, do a weight check. If you strictly dive in salt water on vacation (I'm landlocked, so that also describes me) you can just spend some time in a pool and get pretty close, then adjust for salt water. One way is to submerge in a pool with your gear and a tank that has 500PSI in it, and just start handing off weights until you can no longer stay down. Then add 5 lbs, maybe 6, and you should be pretty close for salt water. I don't know how experienced you are as a diver, but most new recreational divers are taught to use too much weight.

Another thing you can try is the wetsuit sink as I mentioned earlier. Most humans that are not really overweight are more-or-less neutral or even negative. Your AL plate with simple webbing harness and no padding is slightly negative, and the tank is 4lbs positive empty (but that's without a regulator, so actually a little less). This means that whatever it takes to sink your suit, add 4 lbs to that and you should be fairly close. There's always some experimentation, but someone your size should definitely not need 24 lbs in a 5 mil. I guess there are always exceptions.

 

[happy-diver]

And the much sought after answer that remains unseen

SubGravity Stainless Steel Backplate, 6mm, 10.1lbs

 

[CycleCat]

I am a new diver with a dozen dives since cert, maybe a half dozen as a tourist before that. These last four dives were my first in salt water with my own gear. I think I'm just going to have to get back to New Mexico's Blue Hole or a deep pool and continue to tune my buoyancy. I think passing weights back and forth with 500PSI is going to be the best way. I tried the optimal buoyancy calculator here but I'm not sure it likes my Chrome OS on this laptop. I'll try it again from a desktop later.

 

[gqllc007]

Dive Rite SS weighs 6# 5oz , OMS SS weighs 4# 11oz....The xDeep Zen weighs closer to 9# I think....havent weighed it yet but the other two were weighed on a postal scale