No BCD diving...

[halocline]

If you're a new diver in the market for any sort of BC, I'd advise you to just go right for the freedom plate from ZKY, it's one of the best deals around. (Despite his shameless self-promotion!) It's super versatile, and if you decide at some point that you don't want it, it would be a easy to sell for practically what you paid for it because they're hand made and have limited availability.

I've seen the new trident plastic backplates, and the old ones specifically for vintage diving, and none of them are even close.

 

[Eric Sedletzky]

You mean due to the AL80s' larger diameter I assume. I see from the Scuba Cylinder Specification Chart from Huron Scuba, Ann Arbor Michigan that the 72 cu. ft. cylinders from back in the day are 6.9 inches in diameter. That means I'd have to be careful because most modern cylinders have a larger diameter. Good to know. Thanks for pointing out that.

Now that I think about it this brings me back to my original question. Given that most BCs produced in the past few years do work with larger diameter cylinders is it still reasonable to try to slice n' dice an existing older BC to extract the backpack and webbing? And if that might work do I need a size large (I'm 6 ft, 190 lbs, 44 inch chest, 38 inch waist) BC or could I deconstruct a size small or medium BC? In other words does the backpack component of modern BCs vary with regard to the size of the BC?



Good point. Today while snorkeling I experimented maintaining neutral buoyancy. I was diving in the Atlantic wearing a nylon bathing suit and rash guard shirt under my 3mm shorty wetsuit (a Deep See model with sleeves chopped at the bicep), a pair of ScubaPro Jet Fins large (the more buoyant model with the lightning on the label), a mask and snorkel, and a 7 pouch weight belt loaded with 4X3lb Sea Pearl lead pounches.

I attained neutral buoyancy by hanging vertically in the water, inhaling fully, and holding my breath. As long as I held my breath my head was just touching the water line and the top of my snorkel was above the water's surface. When I exhaled I sank to the bottom fairly quickly. The water was 10-12 feet deep so it didn't take long to touch bottom.

I concluded that I was neutrally bouyant with 12 lbs weighting. Is there something else I should consider to determine neutral buoyancy?

I think your idea of getting an old poodle jacket and stripping it down is kind of strange. Regular BC's are all sewn together as a unit. Many of them don't really have a pack or plate in them per say. They might have a rigid plastic component that holds the tank, but it wouldn't really be a back pack that you could remove and use. You still have sewn shoulder straps that are all part of the bladder, which is part of the waist securing system. Once you start cutting away on the thing you're not going to have anything useable. You still have the issue of a cumberbun, chest clip, waist clip, adjustable pull rings for the shoulders, etc. The whole concept is so far away from what a true backpack/plate is the two really don't relate.
The whole idea would be like trying to make a unibody car into a full frame car, the two are totally different.

Personally I think trying to do that would be a waste of time and money even if it's cheap because in the end you will not have anything useable.

 

[captain]

If you find aback pack with a nylon cam band it should work with any size tank. The ones with metal bands were mostly sized for steel 72 but some also will fit AL80's

 

[captain]

You mean due to the AL80s' larger diameter I assume. I see from the Scuba Cylinder Specification Chart from Huron Scuba, Ann Arbor Michigan that the 72 cu. ft. cylinders from back in the day are 6.9 inches in diameter. That means I'd have to be careful because most modern cylinders have a larger diameter. Good to know. Thanks for pointing out that.

Now that I think about it this brings me back to my original question. Given that most BCs produced in the past few years do work with larger diameter cylinders is it still reasonable to try to slice n' dice an existing older BC to extract the backpack and webbing? And if that might work do I need a size large (I'm 6 ft, 190 lbs, 44 inch chest, 38 inch waist) BC or could I deconstruct a size small or medium BC? In other words does the backpack component of modern BCs vary with regard to the size of the BC?



Good point. Today while snorkeling I experimented maintaining neutral buoyancy. I was diving in the Atlantic wearing a nylon bathing suit and rash guard shirt under my 3mm shorty wetsuit (a Deep See model with sleeves chopped at the bicep), a pair of ScubaPro Jet Fins large (the more buoyant model with the lightning on the label), a mask and snorkel, and a 7 pouch weight belt loaded with 4X3lb Sea Pearl lead pounches.

I attained neutral buoyancy by hanging vertically in the water, inhaling fully, and holding my breath. As long as I held my breath my head was just touching the water line and the top of my snorkel was above the water's surface. When I exhaled I sank to the bottom fairly quickly. The water was 10-12 feet deep so it didn't take long to touch bottom.

I concluded that I was neutrally bouyant with 12 lbs weighting. Is there something else I should consider to determine neutral buoyancy?

You need to do the buoyancy check with all the gear you plan on diving with not just snorkeling gear.

 

[Eric Sedletzky]

I know of a way you could set up a tank with a harness without any plate or pack at all.
You might need to re-read this a few times to fully understand the directions but here goes:

To do this you will need:
2 - cam bands/buckles - plastic or stainless buckles, doesn't matter.
1 - Hog harness kit - which includes 12 ft 2' webbing, 4 D-rings/keepers, crotch strap, waist band buckle.
3 - extra keepers
2 - extra D-rings

Set your tank on a bench so it's up at working height.

Take the length of webbing and slide one keeper on it and push the keeper all the way to the center of the webbing. Fold the webbing in half so the keeper is dangling in the middle. With the webbing folded in half, lay it vertically against the tank so the fold and keeper are at the bottom about half way down or slightly past the middle of the tank. While you're holding the webbing in place against the tank, place a cam band around the top of the tank (pre threaded) and place it right at the base of the shoulder (the part that starts to curve in wards towards the neck) and snap it down. Make sure the valve opening is facing towards the center of the webbing. Next, take two D-rings and keepers and thread them onto the other cam band so the cam buckle is in the back and the two d-rings are about 5" to 6" appart both set up on the cam band the same as you would set them up on a harness. These will be what you thread the webbing through for your shoulder to waist straps. Place this cam band w/ d-rings around the tank and position it right above the fold of webbing which should hang down below the cam band about an inch (with the single keeper on it. This keeper BTW is where you will loop the crotch strap through). The two cam bands should be abaout 11" or 12" appart on the tank with the webbing held tight against the tank. Take the two lengths of webbing and kind of pull them apart with quick tugs to form a V. This will be where the webbing goes over your shoulders. The two D-rings on the lower cam band should be spaced evenly from the center of the verticle webbing and each D-ring should be on the side or towards the sides of the tank.

You can also place a D-ring /keeper on each shoulder position at this time if you wish.

Next, thread each shoulder strap through the d-rings that are placed on the lower cam strap. These become your waist straps. leave enough webbing for the shoulder straps so when you pull the straps straight up you have about 1 foot between the top of the webbing and where it comes out from under the top cam band. This should give you enough shoulder room.

After you have threaded the webbing through the waist strap d-rings that are attached to the lower cam band, you can place another D-ring/keeper about 3"- 4" forward of the lower cam band D-ring. This will prevent the shoulder webbing from loosening up beyond a certain point. That certain point is determined by where you place the D-ring on the waist strap. By looping the webbing around the D-ring that is attached to the lower cam band, it allows the webbing to slide and therefore be adjustable for your shoulder tension, kind of a nice feature.
You can place as many D-rings as you wish along the waist strap, but with the list I gave you you will have used up all six thus far.

Next, thread the crotch strap through the keeper that is hanging down right below the bottom cam band on the tank and adjust it accordingly. On most crotch straps the design is such that you simply run the waist strap through the loop on the end of the crotch strap and when you release the waist buckle the crotch strap falls away.

Last, place the weight belt buckle so it's right hand release and Voila!, you have a basic tank to body harness, all for around $100 bucks.
No BC, no plate, just a harness that puts the tank directly on you. Absolute minimalism in it's rawest form.

 

[herman]

.........Good point. Today while snorkeling I experimented maintaining neutral buoyancy. I was diving in the Atlantic wearing a nylon bathing suit and rash guard shirt under my 3mm shorty wetsuit (a Deep See model with sleeves chopped at the bicep), a pair of ScubaPro Jet Fins large (the more buoyant model with the lightning on the label), a mask and snorkel, and a 7 pouch weight belt loaded with 4X3lb Sea Pearl lead pounches.

I attained neutral buoyancy by hanging vertically in the water, inhaling fully, and holding my breath. As long as I held my breath my head was just touching the water line and the top of my snorkel was above the water's surface. When I exhaled I sank to the bottom fairly quickly. The water was 10-12 feet deep so it didn't take long to touch bottom.

I concluded that I was neutrally bouyant with 12 lbs weighting. Is there something else I should consider to determine neutral buoyancy?

Sounds like you still have way to much lead; your objective is to be neutral with 1/2 filled lungs, not fully filled. Think of it this way, if you are neutral with 1/2 filled lungs you have additional positive buoyancy when you inhale and additional negative buoyancy when you exhale, this gives you the control you need. While diving, as you inhale and exhale your instantaneous buoyancy swings between some positive to negative values with the average buoyancy of neutral. By changing your inhale or exhale volume and/or breathing cadence your average buoyancy can be increased or decreased allowing easy control for depth changes. An average male has about 12 lbs (+/- a few depending on body size) of lift capacity due to lung volume so doing the check with filled lungs you are in the +6 to 8 lb range overweighed. You should shoot for neutral with about 1/2 filled lungs, floating about eye level and make sure you are not fining. Finning is an instinctive reaction and most don't realize they are doing so. I suggest you cross your ankles to make sure you are not fining. You also need to realize when you exhale the decent should be a SLOW easy drop and it should take a few seconds to start. If you are instantly dropping hard and fast you are overweighed. Same goes for the accent, it should start slow and accelerate, not take off quick. I agree with the Captain on weighting with your gear on for several reasons. First off, the gear does change your buoyancy, I can tell about 2 lbs of difference between 2 different regs I have and when you do the weight check after you descend you need to inhale to start you accent, kind of hard to do that on a snorkel. Plus it's just safer with a ready source of air available. And finally, buoyancy changes should be slow and deliberate, not quick and fast. It takes time to start the body moving when a change in buoyancy is made. This is most likely the hardest thing to teach someone about buoyancy SLOW DOWN AND WAIT FOR IT.

 

[Nemrod]

I attained neutral buoyancy by hanging vertically in the water, inhaling fully, and holding my breath. As long as I held my breath my head was just touching the water line and the top of my snorkel was above the water's surface. When I exhaled I sank to the bottom fairly quickly. The water was 10-12 feet deep so it didn't take long to touch bottom.

I concluded that I was neutrally buoyant with 12 lbs weighting. Is there something else I should consider to determine neutral buoyancy?

You are probably over weighted. You should be positive at the beginning requiring swimming down until suit crush depth, about 15 feet, where you will go slightly negative and as you deplete your air reserves and return to the surface be once again positive. This is why, we swim down, we swim around and then we swim back up.

If diving in just a swim suit then your buoyancy swing will be less due to no suit crush, you can adjust accordingly.

You should endeavor to dive in a horizontal condition, not vertical.

N

 

[RhatsaRuck]

I think your idea of getting an old poodle jacket and stripping it down is kind of strange.

That's an extremely tactful response. I'd paraphrase the philosopher Forrest Gump: strange is as strange does.

Regular BC's are all sewn together as a unit. ...

Lots of great info deleted to save space

...

Personally I think trying to do that would be a waste of time and money even if it's cheap because in the end you will not have anything useable.

I appreciate the info. I hadn't investigated the construction of modern BCs until you mentioned this. After looking at some units I see your points.

 

[RhatsaRuck]

Sounds like you still have way to much lead; your objective is to be neutral with 1/2 filled lungs, not fully filled. Think of it this way, if you are neutral with 1/2 filled lungs you have additional positive buoyancy when you inhale and additional negative buoyancy when you exhale, this gives you the control you need.

... other great info removed ...

Gotcha! That makes perfect sense. And I can see where I'd want my lungs to be 50% filled when I'm diving at depth. That allows fine control over buoyancy while I'm exploring near sensitive sites (e.g. coral, obstructions, silty bottom, etc.).

You also need to realize when you exhale the decent should be a SLOW easy drop and it should take a few seconds to start. If you are instantly dropping hard and fast you are overweighed. Same goes for the accent, it should start slow and accelerate, not take off quick.

Great point. More technique to practice.

I agree with the Captain on weighting with your gear on for several reasons. First off, the gear does change your buoyancy ...

...And finally, buoyancy changes should be slow and deliberate, not quick and fast. It takes time to start the body moving when a change in buoyancy is made. This is most likely the hardest thing to teach someone about buoyancy SLOW DOWN AND WAIT FOR IT.

This reminds me of playing Lunar Lander-type simulations years ago. When you're traveling in low gravity and you fire your thruster engines it takes a few seconds for the effects to be felt. If you continue to fire the engines the effects unexpectedly accelerate - you learn this pretty quickly.

There's no better low gravity situation on earth than being underwater.

Thanks for the great feedback.

 

[RhatsaRuck]

I know of a way you could set up a tank with a harness without any plate or pack at all.
You might need to re-read this a few times to fully understand the directions but here goes:

...

Voila!, you have a basic tank to body harness, all for around $100 bucks.
No BC, no plate, just a harness that puts the tank directly on you. Absolute minimalism in it's rawest form.

Now that's a DIYers good time!

Thank you for all the feedback.