I just completed the confined water portion of my OW cert class.
It seems that the normal procedure for getting properly weighted results in the diver being negatively buoyant, when the BC is empty and the tank is full, by something like 6 to 10 pounds, maybe? Whatever the amount is, it's not a big amount.
I've been reading up on dive equipment to help me better understand the stuff I'm being issued to use and also to help know exactly what I want when I eventually get around to buying gear. In reading, I've seen that the BP/W setup is popular here. And that wings are generally rated from anywhere around 20'ish to 40 or so pounds of lift.
My question is, why would anyone ever need a wing with 40 pounds of lift? If you're weighted to be roughly negative 10 pounds buoyant, it seems like 40 pounds of lift from a wing would be overkill?
Is it because 40 pounds of lift at the surface is that much less at deep depths? I'm up to speed on the chemistry and physics involved, I'm just too lazy to do the math.
Is it so that you have enough lift to carry things up from the bottom?
Thanks for any help.
So a real question exists, as to what exposure suits you will wear....and how cold is the water you will dive most often in....
Here in S FlA, coldest we normally get is low 70's or sometimes high 60's.....Summer can be 85 degrees... My wife, who gets cold very easily, has a semi dry 7/8 by Aqualung, which is so hot she cant use it till the water is 70 degrees or colder....I think it would be very good for 50 to 55, and I have no idea how much colder it would be good for....the thing is, she uses a max of 24 pounds of lead, including the Stainless steel backplate/along with a steel 100. This is her January /February gear for the BHB Marine park, in 20 foot max depths, with her needing to be quite heavy for macro photogrphy of Nudiebranchs on the bottom. If she was doing an ocean dive in this suit, she would probably change to around 15 pounds of lead. Her Halcyon Wing is a 30 pound wing, and she would never consider the much larger drag of the bigger wings, and the de-stabilizing influence of using a monster wing, great big bubble of air inside, and ridiculous amounts of lead to compensate ( which is what many new divers actually do, as their instructors find it easier/quicker/expedient, to throw 20 pounds too much weight on them-- so they don't have to learn how to properly dump their BC for descent. This seems to be the norm in many large , high volume classes....
With her 5 mil Aqualung semi dry, which she just went to this weekend... ( water 79 degrees) Sandra is using 6 pounds of weight on a belt, plus her steel backplate....and a 30 pound lift wing.
And, in ocean dives, you really DONT want to be 10 pounds too heavy...certainly never 10 pounds too heavy at the end of the dive with 750 psi in the tank--this would mean you are way too heavy for the whole dive, and having to fight with a huge air bubble inside the BC, that is constantly growing or shrinking on depth changes, and drastically altering your buoyancy....and screwing up your trim....
You want the tiniest air bubble possible inside the wing/bc....Best case at 70 feet down, you have this tiny little bubble you pushed in to it at the bottom, to get dead neutral.....( and if you were wearing lycra, far better still would be NO Air in the wing at all, because your buoyancy does not change from surface to bottom, and you can run neutral on the bottom the first 3/4ths of the dive with this no air in bc balance....as the tank gets more buoyant as it nears 1000 psi, you should be coming up anyway, and you can just apply a tiny amount of swimming force to counteract the tiny pull up the tank will offer as you approach the end of the dive....holding the stop just means some lazy finning with a slight push down during it.
We don't want any more weight than we need!!! Which is another reason we go with 30 pound lift or less BC's, in Florida.
I myself use the Halcyon 18 pound lift wing, whether using an 80 Aluminum, or a HP 120 for a 110 to 115 foot foot max depth dive, like the Castor....
[video=youtube_share;qHFkQrPtlJM]http://youtu.be/qHFkQrPtlJM?list=UUsM5Za9Kc3DbP7Qo3-Zmz9w[/video]
PLEASE WATCH ONLY AT 1080P--( gear icon lower right of player bottom)
This shows Sandra with her 30 pound lift Halcyon wing and 6 pounds of weight ( plus the backplate--she has the huge camera and the freediving fins)..and our dive buddy Bill Mee with a 30 pound halcyon wing ( Halcyon 30 pound wing, no added weights to backplate--just it's 6 pounds plus reg)..Bill has the bright Surface marker buoy clipped to his side... and is in-shot several times in the vid. You can see he needs very little air in the wing to be dead neutral---to just hang effortlessly in a horizontal position while watching big marine life..
The idea is to never have your BC causing you to work overtime to control it....we adjust ours at the bottom, and then pretty much have little to do with it until we are on our way up to the surface.....With too much weighty and a big BC, every time you go up or down 15 feet you would be turning on the elevator
When Sandra's screaming through her reg alerted me to the Manta Ray about 50 feet above us, I was able to swim fast and shoot, without any noticeable nonsense out of my wing getting too much lift---nothing I could not easily compensate for with fins.....OBVIOUSLY I needed both hands on the camera, and would not have wanted to have to pull a hand off the camera to deflate the wing with....it was easy to ignore, by design. Wings and BC's are not supposed to be elevators...they are there ONLY so that you can be neutral when you want to be....swimming is what gets you up to the surface, not an elevator