Diving Without BCD

[aquacat8]

A steel 72 holds about 5 lbs of air weight. During the time it goes from full to empty the diver can use lungs combined with suit cooling and bubble contraction/suit squeeze to counter the affects of the buoyancy swing of the tank. This can become automatic with practice so it seems there is no swing, but there is. I could use a big steel 120 too of I wanted, I’d just have to adjust for the added weight of the tank and be sure to weight myself accordingly. Bug divers love those big tanks because they normally cover a lot of ground and use a lot of gas. They are considerably heavy at the start of the dive and gear their weighting so they can be about neutral breathing normally at the end of the dive. They are not the least concerned about hovering in a skydiver position because they are always on the move going up over things, looking in holes, grabbing bugs, inverted, upside down, right side up, reaching under ledges, chasing ones that wiggle away. Skydiver hovering is a BC thing (and a skydiving thing) just like you’d never see a freediver hovering in a skydiver position. They are about as polar opposite to cave divers as you could ever get. Some use a dive trackers to find their way back to the boat.

I never thought of suit cooling changing buoyancy before... having a bag full of bugs might too perhaps?

 

[aquacat8]

This picture is of my buddy, Wayne, and me back in 1965 or so. You can see two different backpacks. The one I am wearing is almost identical to the one shown in post #7. My buddy's backpack is very similar to the Freedom Plate that @Eric Sedletzky makes today. (Here is where I will insert a shameless plug to be at the top of Eric's list when he makes another run of them) Frankly, if you could get one of Eric's plates, I think it would be perfect for what you want to do. The tanks that we are using are steel 72's. We usually weighted ourselves to be neutral at whatever depth we planned to be. That would mean using a little less weight when deeper in order to compensate for wetsuit compression, but we would have to swim down the first bit. When using the rig in this picture, I don't remember wearing any lead. I don't remember the straps being uncomfortable either; however, at that age we were also bulletproof.

Best of luck.


View attachment 457368

Super cool pic!

 

[Michael Guerrero]

I might, but I’m afraid of being banned.

Let's hope that's an exaggeration. SB is about sharing ideas, isn't it?

 

[Michael Guerrero]

The straps look like they might be uncomfortable on bare skin.

Do yourself a favor and wear a rash guard. If you want smooth skin get a wax.

 

[Eric Sedletzky]

I never thought of suit cooling changing buoyancy before... having a bag full of bugs might too perhaps?

Yes, as the gas bubbles in the suit cool they also get smaller and lose some buoyancy, so as your tank empties and gets lighter your suit gets heavier and helps offset the swing.
Bugs really aren’t that heavy underwater. Scallops are though if you take them with the shell.
Betting on either one as part of your dive plan concerning weighting is kinda risky IMO. However there are still rocks.

 

[Eric Sedletzky]

Let's hope that's an exaggeration. SB is about sharing ideas, isn't it?

You’d think, but I’ve seen a few posters thrown off scubaboard for reasons that were never explained. I don’t remember anything rude or nasty from the banned posters, just a bit controversial. I’ve seen way worse offenders and those people are still around, so I don’t know what to think anymore.

 

[Bob DBF]

They always want to lump us into the vintage section even though there is a BRAND NEW movement towards minimalist diving that is differe

At least us old Pharts in vintage understand and respect what you are doing. I don't think what is being done is BRAND NEW, but the approach may be. In any event it is back to SCUBA basic.

You’d think, but I’ve seen a few posters thrown off scubaboard for reasons that were never explained. I don’t remember anything rude or nasty from the banned posters, just a bit controversial.

They never explain. I miss some, not so much others, but I think you are safe since you are reasonably polite and and are helpful rather than confrontational. Of course being open minded we may have missed some egregious faux pax.


Bob

 

[REVAN]

Hello All!

I am interested in doing some diving this summer with no BCD and a lightweight, minimal gear setup.

I enjoy exploring the coast snorkeling and freediving, and I'm competent with basic open water scuba diving. I would like to bridge the gap with a small, basic scuba system that I can comfortably haul a long distance from my car for shallow water summer diving.

My plan is to dive shore entry, shallow (35 ft or less), in warm water with no wetsuit or a thin shorty. For those familiar with San Diego, think Children's Pool and similar. I have aluminum luxfer 50s and 63s that I plan to use. I've practiced controlling my buoyancy on previous dives using my lung volume, but never witthout a BCD or wetsuit on.

Does anyone have any tips on how to get my weighting dialed in? Any recommendations for tank harness? So far I've been looking at a plastic backpack (Trident), a back plate and harness, , or a back inflation travel BCD with the wing removed (weight integration would be nice).

IMO: The big difference is that BC divers always error on the side of more weight, a diver without a BC will plan for what is statistically realistic.

Example: In calculating the weight of air in a tank, BC divers are taught to use unrealistic assumptions to get the most weight possible. They usually assume that the air is chilled to zero degrees C while at full tank pressure (which is actually about 10% overfull, if I remember right). They also assume they will be diving with the tank completely empty and plan to have enough weight to stay down in that condition.

A diver without a BC will want to plan better than that. I plan to be neutral with 500 psi remaining and at 15 feet depth with the suit I'm wearing and with shallow but comfortable breathing. If the tank is below 500 psi, I want it to be hard to stay underwater, because I should be up by then. If I really need to stay down for decompression reasons, I'll kick to stay down (it will only be a couple pounds delta, so easy to compensate when you are pointed the right way). I never plan a decompression dive without a BC, but want to now how to deal with the situation if everything is going bad for some reason and I must deal with the fallout. So, be comfortable with holding a depth station in the inverted position so that you aren't learning it for the first time in an actual emergency.

I think the no-BC diving is actually easier with a wetsuit than none at all. With a wetsuit, it will be easier to stay on the surface, especially at the beginning of the dive. You will need to kick to get down from the surface, but as a freediver, you will be used to that.

Keep track of how much weight you use on each dive and how your buoyancy was at the beginning of the dive at the surface and at depth, and also at the end of the dive at your safety stop. Iterate to get the best comfort overall. It should only take a few dives to get the weight dialed-in to something comfortable and close to optimum. If you are finding it hard to hover off the bottom at depth, you have too much lead. If you can't stay below 15 feet at the end of the dive, you don't have enough. If you are finding it hard to meet both conditions, you probably need to work on you structured breathing skills. Either that, or your tank is too big for your lung capacity to compensate, but that should not be an issue for the tank sizes you are planning to use. I dive AL80s all the time, and I find it easy to compensate for that.

 

[REVAN]

PS - this is a handy reference to get tank buoyancy characteristics for different tank sizes. Different tank manufacturers may vary slightly from this in absolute weight, but the deltas will be the same.

https://www.catalinacylinders.com/wp-content/uploads/2017/03/SCUBA-.-SCBA-.-Spec.2-11-15color.pdf

 

[Paladin]

'cept people still dive these and they are available new.View attachment 457217

I do. Along with my 1959 Aqua Lung DA Aquamaster double hose.