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I used a 40lb Halcyon Eclipse when I dived in the UK...complete with steel 15l and 3l tanks, umbilical torch etc. I never used the full capacity.
From your stated configuration, you will be borderline with your requirement. Having said that, your weighting seems pretty heavy.
Underwater, with the correct weighting, you shouldn't need to add much air to the wing - only a couple of lbs too offset the weight carried to compensate for the increasing bouyancy of your tank as the dive progresses. So, in theory, the only requirement is for surface support.
This is why I am having doubt. Everyone I spoke to, said that I am over weighted. I want to test it out, but I cannot until I get everything together. And once I tested it in water, I don't think I can return the 30lb for a 40lb.
Can come one, if possible, tell me for sure I would be OK with 30lb??? BTW, I am 5'6", no more than 140lb.
First, I'm happy with 30lbs, steel backplate, 15L steel tank, two first stages on a H valve and 6.5mm suit. Because my tank is very heavy (18 kg empty), I only use 3kg of weights.
You are using AL tanks. They are slightly negative when full, and very buoyant when empty. My 30lbs wing floats easily a 15L steel tank, with two first stages on it, so your AL should not be an issue for floating the rig.
The second purpose of the wing is to compensate for wetsuit buoyancy loss with depth plus the air your are carrying at the begining of the dive. You carry about 2.71 kilograms of air in AL 80.
The only unknown is the buoyancy of your wetsuit. Enter with the wetsuit (plus gloves and boots) in water - without the scuba rig, and establish its weighting (how much weight is required so with average-filled lungs you float, and you sink when you exhale. In my case this value was 8-9kg. Added with 3.6kg of air, it meant 12.6 kg (27lbs), so the 30lbs wing was enough. Keep in mind that your wetsuit will never lose it's full buoyancy (only drysuits could do this), so this value is already on the safe side.
I think you'll be fine with the 30lbs. If you want to be sure, find out your wetsuit weight.
I just order my first bq+w setup. SS back plate 30lb wing. Now I have doubt, I wonder if 30 will be good enough, or should I call and change to 40 for more margin. Can cold water driver comment?
Here is what I have been diving with: AL80, 7mm farmer john + 7mm jacket. 20lb weight belt. SeaQuest ProDQ BCD with 10lb intergrated.
Will I be OK with 30lb wing? What if I decide to take a smaller camera (canon G9 in underwater housing) and a small light with me (UK SL4 or similar). Would I still be OK? How about with a steel tank?
Should I call and switch to a 40lb wing?
You'll probably be fine with the 30 lb wing. The wing has to do two things; float your rig without you in it, and compensate for a total loss of buoyancy of your wetsuit plus the weight of your gas, assuming you're weighted properly.
Okay, so in your case lets assume that your wetsuit has about 20lbs buoyancy. It almost certainly has less, but since you're using 30 lbs total with an AL80.... anyhow, a very liberal estimate of buoyancy needed for that is 20lbs, plus 6 for the BP, maybe another 4 for the reg, camera, light, and there's your 30 lbs. You're not wearing that weight on the rig, so no problem floating it, and in an absolute worst case scenario at depth with your gear and a full tank you'd only need 30lbs if your wetsuit lost every pound of it's buoyancy, which of course it can't do unless you take it off and let it float away.
The 40 lb wing might float you a bit higher on the surface if that's important to you, but I bet you'll enjoy diving with the 30 lb wing more; it will vent quicker and easier and be a little more streamlined. There's probably not that much difference to be honest.
op, try this. it was posted by tsandm, so if you need to search it that might help you find the original post.
take your suit & lots of lead to a pool. put the suit on the bottom around 6 or so feet & start putting lead on it. when it stays down, you have a rough idea of the inherent buoyancy in the suit.
but if you're comparing your weight belt needs with your bc to what you'll need with your new stuff, then don't worry. 30# of lift will be fine. you'll lose the lead needed to sink the bc (you can do the pool test with it, too) and the lead on the belt that will now be your plate & sta (if you have one). i bet your weight belt requirements will shrink by about 10 pounds.