Switching from Jacket bcd to Backplate/Wing??
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Hmmmm...not sure what your on about here lad. I don't use a back-inflate ( my Zeagle ) to teach because it tends to force me forward on the surface, thus requiring me to continuously forward fin to remain vertical during surface yak time. As to trim u/w - I have no issues that way with my current doubles kit ( I use the drysuit for primary buoyancy, I can lift the heavy twins off my lower back for comfort...). The extra lift in the wing will be handy if my suit integrity fails.
Best,
DSD
Deep South Divers
Contributor
Using an 80 lb wing is annoying... It's big and floppy most of the time, causing a lot of drag. God forbid you try to dive in a current with it. If you actually use the wing a little at depth to become neutral, then your partial bubble is all over the place, too.. Up, down... Tacoing the tank... It would create a very unstable rig that was "opinionated," and difficult to balance.
At the surface, it's even worse if you inflate it fully... It's certain to push the diver face-forward.
Now... If he actually NEEDS 80 lbs of lift, then he's diving entirely too negative. This can be tested by diving to the bottom with full tanks at the beginning of the dive. If he can't swim that rig up without any gas in the wing, then he's diving too negative, and changes will have to be made to correct for it. Option A would be to reduce the amount of weight he's carrying. Option B - if that isn't enough - would be to change gear to lighten the load (ie change to three AL80s rather than two 130s). Option C would be to at least make the weight ditchable so you could ditch at depth and swim up. Warning, though... This is the worst option because it requires that the diver has the wherewithal to ditch and attempt to control an uncontrolled ascent... A bad situation caused by wearing too much weight and having too big a wing in the first place... Which there are other issues with as well (see above).
Any bladder - wing or BC - that is used was originally designed to only compensate for the change in buoyancy of the tanks as they empty and to compensate for the change in buoyancy of the wetsuit as it compresses at depth. 130 cubic feet of gas is roughly 10 pounds of negativity... That is, the difference between a 130 cuft tank full and a 130 cuft tank empty is about 10 pounds. Two of them would be 20 pounds' difference. Add compression of wetsuit, which might be another 10 pounds, and you've got 30 pounds of max buoyancy swing from full to empty including compression at depth. Anything more in the wing is overkill, but it's always nice to have another 10 pounds to float on at the surface.
...So a 45 pound wing would work nicely for this rig. If the diver needs more than that, then he's overweighted and suffering in a variety of ways.
DeepSeaDan, open your PADI OW manual and read the first few pages on how to weight yourself properly. Follow the instructions to the letter... Get in the water with your rig, empty tanks. At the surface, take a full breath, deflate the wing... You should float at eye level, looking dead ahead. If you don't, tune your weights to do so. If you can't take off enough weight, then it's time to start lightening your rig... Aluminum plate, aluminum tanks, smaller, more modern battery canister... Whatever it takes.
Diving and needing 80 pounds of lift to be neutral is dangerous. If you have a wing failure (hole) or an OOA at depth, and if you can't drop the weight that you've been diving with that you never needed in the first place, you'll drown if you can't swim it up. A good friend of mine perished this way. He was wearing 128 lbs of lead at the time and was wearing a 65 pound wing. It all worked fine for 20-something years like that (apparently he needed 63 pounds of lead to be neutral in the first place, which is just shocking - I assume that this was not really the case and he was swimming up the difference at the end of the dive) until one day he irresponsibly ran out of gas. His weight was unditachable (most of it on a weight belt with suspenders UNDER his BC - and much of it literally thrown down his wetsuit) and so... There was nothing he could do but lose consciousness and drown.
Don't let this happen to you. Yes, it was an extreme case, but the story is true. Diving properly weighted improves EVERYTHING... Including your chances of diving again the next day instead of attending your own funeral. In a box.
At the surface, it's even worse if you inflate it fully... It's certain to push the diver face-forward.
Now... If he actually NEEDS 80 lbs of lift, then he's diving entirely too negative. This can be tested by diving to the bottom with full tanks at the beginning of the dive. If he can't swim that rig up without any gas in the wing, then he's diving too negative, and changes will have to be made to correct for it. Option A would be to reduce the amount of weight he's carrying. Option B - if that isn't enough - would be to change gear to lighten the load (ie change to three AL80s rather than two 130s). Option C would be to at least make the weight ditchable so you could ditch at depth and swim up. Warning, though... This is the worst option because it requires that the diver has the wherewithal to ditch and attempt to control an uncontrolled ascent... A bad situation caused by wearing too much weight and having too big a wing in the first place... Which there are other issues with as well (see above).
Any bladder - wing or BC - that is used was originally designed to only compensate for the change in buoyancy of the tanks as they empty and to compensate for the change in buoyancy of the wetsuit as it compresses at depth. 130 cubic feet of gas is roughly 10 pounds of negativity... That is, the difference between a 130 cuft tank full and a 130 cuft tank empty is about 10 pounds. Two of them would be 20 pounds' difference. Add compression of wetsuit, which might be another 10 pounds, and you've got 30 pounds of max buoyancy swing from full to empty including compression at depth. Anything more in the wing is overkill, but it's always nice to have another 10 pounds to float on at the surface.
...So a 45 pound wing would work nicely for this rig. If the diver needs more than that, then he's overweighted and suffering in a variety of ways.
DeepSeaDan, open your PADI OW manual and read the first few pages on how to weight yourself properly. Follow the instructions to the letter... Get in the water with your rig, empty tanks. At the surface, take a full breath, deflate the wing... You should float at eye level, looking dead ahead. If you don't, tune your weights to do so. If you can't take off enough weight, then it's time to start lightening your rig... Aluminum plate, aluminum tanks, smaller, more modern battery canister... Whatever it takes.
Diving and needing 80 pounds of lift to be neutral is dangerous. If you have a wing failure (hole) or an OOA at depth, and if you can't drop the weight that you've been diving with that you never needed in the first place, you'll drown if you can't swim it up. A good friend of mine perished this way. He was wearing 128 lbs of lead at the time and was wearing a 65 pound wing. It all worked fine for 20-something years like that (apparently he needed 63 pounds of lead to be neutral in the first place, which is just shocking - I assume that this was not really the case and he was swimming up the difference at the end of the dive) until one day he irresponsibly ran out of gas. His weight was unditachable (most of it on a weight belt with suspenders UNDER his BC - and much of it literally thrown down his wetsuit) and so... There was nothing he could do but lose consciousness and drown.
Don't let this happen to you. Yes, it was an extreme case, but the story is true. Diving properly weighted improves EVERYTHING... Including your chances of diving again the next day instead of attending your own funeral. In a box.
Deep South Divers
Contributor
The problem with your Zeagle at the surface isn't the location of the bladder (buoyancy)... It's the location of the center of buoyancy relative to your center of gravity.
There's two ways to resolve the issue, which I demonstrate with a diagram at http://www.deepsouthdivers.org/old/bc.html . You can move the center of buoyancy (which you can't do with a BC - the wings are affixed, so you've opted to use a horse collar) or you can move the center of gravity.
Moving the center of gravity back so that it's in line with your center of buoyancy is easy... There's two ways. One is that you can move weight off of your belt and into the trim pockets of your Zeagle. If I remember, Scott makes a maximum of 6 pounds able to be added to the trim pockets. The reason why he limits it to six pounds is to simulate the effect of a stainless steel backplate. The second way - which has the additional advantage of added stability for your tanks - is to ditch 6 pounds of lead off of your waist and actually add a stainless steel backplate to your Zeagle.
All of this, of course, assumes that you have first done the weighting exercise that I outlined above and already have the AMOUNT of weight nailed down.
If you still have an issue with "faceplanting," then use a weight trim pocket on your tank cam band to move your center of gravity even further back... And/or use a wing that has the lift that you need, and only the lift that you need (+- 10 or 15 pounds) so that the problem isn't so dramatic. This has the additional advantage of being more streamlined, too, and a lot easier to dive without any control issues.
Deep South Divers
Contributor
Using your drysuit as primary buoyancy creates the problem of bubble location even worse than oversized wings do... If you tilt up or down while diving, the bubble runs from your shoulders to your feet and throws the whole concept of being in control out the window... ESPECIALLY if you are using steel 130s and needing to compensate for 30 pounds of buoyancy swing! That's a 30-pound bubble traveling from your shoulders to your feet and back again... Why do that when you have a wing that keeps the center of buoyancy closer to your center of gravity?
One of the keys to diving dry is to avoid using your drysuit as inflation, and minimize the amount of gas that you have in the suit... "Just enough to keep the squeeze off," as they say. What drysuit course recommends the practice of using your drysuit as buoyancy control?
...Not that it couldn't be used in an emergency - assuming that the emergency wasn't an OOA - but why do that when you've got a BC?
For that matter, why use a BC if you're using the drysuit for buoyancy?
One of the keys to diving dry is to avoid using your drysuit as inflation, and minimize the amount of gas that you have in the suit... "Just enough to keep the squeeze off," as they say. What drysuit course recommends the practice of using your drysuit as buoyancy control?
...Not that it couldn't be used in an emergency - assuming that the emergency wasn't an OOA - but why do that when you've got a BC?
For that matter, why use a BC if you're using the drysuit for buoyancy?
Aqua-Andy
Contributor
SSI teaches using the drysuit for buoyancy. When using an Aluminum 80 I use the drysuit for all buoyancy, but when diving doubles I use the BC for buoyancy and the suit just for squeeze.
1. I can't recall a dive when I found my wing "annoying", & when enjoying a casual drift down the St. Lawrence, it acts as a bit of a "sail" - I like that.
2. I don't use any weights, the 130's are sufficient negativity.
3. Deep South Diver: Try not to be condescending. Try to stay calm.
4. I never use my 130's with anything but my dry-bag; if the bladder fails, my suit is my ticket up. Conversely, if my suit fails/floods, it's nice to have sufficient lift to surface easily/safely.
5. I like my kit. It works well for me.
DSD
Deep South Divers
Contributor
What? To quote "Teller" from http://www.scubaboard.com/forums/basic-scuba-discussions/324515-drysuit-buoyancy-5.html : "SSI says to only add enough air in your dry suit to avoid the squeeze and then add air to your BCD as needed. I have tried both ways and I find it easier to control the air in my BCD rather than in my dry suit."
I can't imagine any agency recommending the use of a drysuit's inflator and dump as buoyancy control, for the reasons I've mentioned... That it places the center of buoyancy and center of gravity far apart, which creates a situation whereby trim and attitude is impossible to control. Can you cite a specific reference?
As I previously mentioned, my solution to the Zeagle problem was/is...wait for it...a front flotation bcd!! Perfect for teaching. Simple fix. Works for me. Works just fine u/w as well.
All is good.
DSD
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