Vintage Buoyancy and "Floaty" Tanks

[SurfLung]

- We've all seen Mike Nelson swimming straight and level with twin tanks, no wet suit, and even wearing a weight belt... Well, my first set of twin tanks were aluminum 50's. I didn't have much fat on me then but, even with a full 1/4 inch wet suit and no weight belt, I would sink with those tanks on and HAD to wear a horse collar inflatable vest to even out my buoyancy.
- Discussion around modern divers favors modern steel tanks because they are more negative than aluminum. I'm currently almost neutral with an aluminum 50 and no wet suit. But my high pressure steel 80 which is almost the same dimension is WAY Heavy. With my wetsuit on, I start sinking at 10 feet depth... With no weight belt.
- I'd much rather the tank be as close as possible to neutral and control my buoyancy with weights... Which are much more consistent than using air in a BC. Why doesn't this make sense to modern diving technique?
- Judging from the 1963 USD Catalog (below), a "Floaty" tank was a desired characteristic... Much like what I'm preferring from my experiences above.

- BTW... I just scored a beautiful set of Twin 38s like the bottom picture, only a year earlier when they were 38s.

[8dust]

I vaguely remember a video a while back of someone of us doffing and donning a set of vintage triples that looked floaty enough to serve as a life raft . can't picture who it was, and I haven't had the pleasure of diving any myself, but they do seem to have fit well within your theory...

[antique diver]

- We've all seen Mike Nelson swimming straight and level with twin tanks, no wet suit, and even wearing a weight belt... Well, my first set of twin tanks were aluminum 50's. I didn't have much fat on me then but, even with a full 1/4 inch wet suit and no weight belt, I would sink with those tanks on and HAD to wear a horse collar inflatable vest to even out my buoyancy.

Surflung, the steel 38's from that era are significantly lighter in the water than the steel 72's, and of course than most of the modern steel Scuba cylinders that I know of. As Mike did, I had/have to wear weights with my 38's as well. The USD steel (1800 psi) 53's had similar characteristics to the 38's, and I only kept a set of those Butt-Floaters briefly back in the early 70's. As irritating as the floaters were/are, I found twin 72's to be too negative for me with no BC or suit.

BTW, I think your Avatar is great!

[Nemrod]

Vintage divers are a conflicted bunch. They are told they want negative steels. What they really want are tanks with the characteristics of steel 72s which are fairly close to neutral for singles and for doubles sufficiently neutral positive to account for the manifold.

Current "technical" diving technique and even sport diving depends upon negative tanks to offset the need for large weight loads to sink a drysuit or 7mm heavy suit (and todays large diameter divers). Distributing the weight between a tank(s), plate, weight belt/harness and weight attached to the plate is more comfortable and practical way to sink a drysuit. At depth the drysuit can share duty with the wing to compensate.

This is not the technique divers who are vintage themselves were taught when we learned to dive and to manage our buoyancy. To some degree, we depended upon the tanks going enough neutral or positive to assist the return to the surface at the end of the dive and weight to assist sinking in the beginning. The Rubatex did not compress nearly as much as modern wet suits do and remained warm and buoyant even at depth. We swam down, we swam around and then we swam back up.

You know, really, without a Rubatex suit and fairly neutral tanks like steel 72s it is nearly impossible to vintage dive techniques. Aluminum 50s, 64s and 80s, in singles configurations do fine for the tanks, but modern wetsuits, mostly not and dry suits are not really vintage, well, maybe if you fill them with water.'

Nem

[antique diver]

....You know, really, without a Rubatex suit and fairly neutral tanks like steel 72s it is nearly impossible to vintage dive techniques. Aluminum 50s, 64s and 80s, in singles configurations do fine for the tanks, but modern wetsuits, mostly not and dry suits are not really vintage, well, maybe if you fill them with water.'

Nem

Good Nem... you have defined the differences that cause me to dive "Vintage Style" with one type of steel "tank", and dive in modern open water and cave configurations with an entirely different "cylinder" type (and of course, configuration).

Also, your reference to the old drysuits reminded me of why I called them "dampsuits"

[SurfLung]

- The Twin 38's I bought were full of air at 1800 psi! Markings on top show no hydro test since they left the factory in 1961. Cripes! (Interesting Side Note: Sea Hunt Jerry said you shouldn't breathe such air because if there was corrosion (oxidation) inside, there may not be any actual oxygen content left in that air and you could black out from anoxia.)
- Okay so, before I let the air out, I weighed these full tanks. Then when they were empty I weighed them again. The difference was 5.8 lbs of air when full. The USD catalog said they were 3.6 lbs buoyant when empty (fresh water) so I figure adding 5.8 lbs would make them 2.2 lbs negative when full.
- A single aluminum 50 is 2.7 lbs negative when full and .5 lbs positive when empty (3.2 lbs of air) but that's in sea water... So in fresh water it would be more negative. I am almost neutral with one of these 50s and no wet suit.
- Hard to believe these twin tanks could be less negative than a similar sized single 50. I hope this proves true in actual diving... If so, it's exactly what I've been looking for!
- P.S. The USD catalog was referring to twin 42s. I'm assuming 42s are 1880 psi while 38s are 1800 psi... And the tanks themselves are the same? If so, that would make them the same buoyancy when empty.

[SurfLung]

The Perfect Diving Buoyancy?

- I dove my Twin 38s four times last weekend at Fortune Pond. With a 3mm wetsuit and 3mm hooded vest, I think the suit compression was kept to a minimum. Buoyancy with just the tanks and wetsuit was significant. Adding 3 lbs helped. Adding another 3 lbs got it almost there for the first dive.
- For the second dive, I added 1 lb for a total of 7 lbs on the weight belt. That seemed to do it... Just slightly sinking on exhale at the surface. I wore 7 lbs for the remaining 3 dives.
- All four dives were a fairly deep test of buoyancy... With maximums from 80-98 ft. At the maximum 98 foot depth, I was noticeably more negative than positive. But the last 1/3 breath of an inhale would start me floating slightly.
- PLEASE NOTE: Photos by SwimJim

[SurfLung]

- P.S. The USD catalog was referring to twin 42s. I'm assuming 42s are 1880 psi while 38s are 1800 psi... And the tanks themselves are the same? If so, that would make them the same buoyancy when empty.

- Actually, this statement is totally wrong. The 1800 psi USD tanks are close to 42 cf when filled to 10% over working pressure. I now have a set of Sportsways twin 42s which Basic Scuba says are really 38s at the 1880 working pressure stamped on their necks. They only reach 42 cf when pumped to 10% over the 1880 working pressure. It looks like USD was responding to a sales claim by Sportsways. An earlier USD catalog referred to them as 38s but used the same illustration. The USD 38s and Sportsways 42s are NOT the same tanks at different pressures.
- I posted a comparison of USD and Sportsways twin sets "38s vs 42s" in the Tanks and Valves forum. Suffice it to say, there's quite a huge difference in buoyancy between these two systems. The USD 38s (set) is only 2.4lbs negative when full. The Sportsways 42s (set) is 7.9 lbs negative when full (I weighed them both underwater).


Left: USD "Twin 38's" ad. Right: USD "Twin 42's" ad. (Note the same Item Number)

[SurfLung]

Can't Do It With 5mm Suit...
- All of this great neutral buoyancy vintage style diving I've been doing has been with a 3mm suit. Yesterday I tried setting up a similar profile with a 5mm suit and the heavier 42s...
- I was neutral with 10 lbs on the surface but very sinky at 25 ft. depth.
- I settled on 6 lbs for 25 ft and was neutral. But coming up a mere 5 ft to 15 ft depth and I was already getting floaty... Geez what a pain.
- This 5mm suit is a very nice, BARE brand semi-dry wetsuit... But it must compress a heck of a lot as depth increases. I don't see how I can comfortably dive it without a BC.
- I checked with the Wet Wear wetsuit company... There's no more Rubbatex but they say they have their own formula that has similar low compression characteristics. I talked to them about a low compression 3mm suit... That might be the perfect compromise... Less compression will mean a warmer suit as well as more consistent buoyancy... Now to come up with the money for a custom suit!

[Chris]

Here in Oregon you dive a 7mm suit or dry suit. Before getting my dry suit I used to use a WBC(weight belt compensator) mostly because I watched my causing jam his knee into a broken bottle at the bottom so I wanted to stay neutral all the time no matter what tank I'm on. Now I have a dry suit so I no longer us a bc. I know how much weight I need on each of my different tanks So I only need to keep the suit from crushing me on the way down and I stay mostly neutral. I am a bit light at the end though but still manageable. I have been seeing Mike Nelson swimming at an incline in many of the episodes so he is a bit heavy and trying to compensate. It looks tiring trying to swim in two directions at once. I guess I'm not really vintage, but I do try to dive my modern equipment to vintage standards.

[Nemrod]

I would not use Mike Nelson who was a fictional character in a silly television show that was largely filmed in the confined waters of Silvers Springs with acting doubles as a documentary on vintage diving methods. Most of the gear shown in the programs, masks and fins in particular were hardly of pool toy quality and the techniques shown including knife fighting, underwater hand swimming etc. are laughable, then and now.

Yes, the venerable steel 72 and the very similar aluminum 63/80 do just fine and are an advantage to the vintage equipment diver. We depended upon that end of dive buoyancy assisting our return to the surface and our staying there on the surface for the swim back in.

Furthermore, as a recent thread on sb demonstrates, non-ditchable weight, be it in a tank or plate, is asking for trouble and especially so for vintage equipment divers who may not have any means of supplying buoyancy other than ditching weight.

I wouldn't especially apply Mike Nelsons skin diving methodology to a modern drysuit which is no more vintage equipment than a poodle jacket either.

Nem

[Chris]

Yah, I guess just because I'm using my grandpas double hose with no bc that doesn't automatically make me a vintage diver. Not knowing what a poodle jacket is I have to assume it was meant as criticism for entering the vintage community with a dry suit. However, when the alternative is sore shoulders, freezing in 45 degree water, and having to stand on my shoes while trying to get out of my stiff 7mm in a urine soaked public restroom I will accept your criticism and hide in shame at the bottom of my favorite lake and think about what I have done to the vintage community. My previous comment was merely to tell Surflung Why I don't let myself be negatively buoyant at the beginning of my dive. Nothing to do with saving the environment like those newly certified divers are taught, it just doesn't take much effort to run a piece of glass through your knee if you even slightly settle on the bottom.

[Nemrod]

Yah, I guess just because I'm using my grandpas double hose with no bc that doesn't automatically make me a vintage diver. Not knowing what a poodle jacket is I have to assume it was meant as criticism for entering the vintage community with a dry suit. However, when the alternative is sore shoulders, freezing in 45 degree water, and having to stand on my shoes while trying to get out of my stiff 7mm in a urine soaked public restroom I will accept your criticism and hide in shame at the bottom of my favorite lake and think about what I have done to the vintage community. My previous comment was merely to tell Surflung Why I don't let myself be negatively buoyant at the beginning of my dive. Nothing to do with saving the environment like those newly certified divers are taught, it just doesn't take much effort to run a piece of glass through your knee if you even slightly settle on the bottom.

1. My post above was not specific to you or a response specific to you.

2. No, I have a drysuit and I am saving for another, it is not a criticism of your using a drysuit, only the same thing I have said over and over is to be careful mixing equipment and methods that are from different eras, it can result in unexpected problems. The example I gave or started to give is of using a very negative tank to sink bouyant exposure suits (wet or dry) and not having a BC (because again, a BC is not really vintage excpet maybe a horsecollar, maybe) and not being able to ditch enough weight to become buoyant/swim up, just saying.

3. A poodle jacket is a long used term for the jacket type BCs that have the fluffy interiors in particular and has nothing to do with a drysuit and is not a vintage device. Being as this is the vintage forum though neither drysuits or BC jackets (aka poodle jackets) are really a vintage equipment subject.

4. I can understand, as it is, I hate being cold and I would be wearing a drysuit with you. Double hose or not, I would rig for ditch-able weight and as is current methods, I would split weight up on various places including using negative tanks. But, again, that is not really vintage diving technique.

5. And all of this is why we have that other forum for modern diving with double hose regs, . And being as I am a Moderator, I am simply providing a friendly reminder to try and discuss modern gear with dh in the appropriate forum. Lest we awaken the Vintage Hose Patrol who can be every bit as punitive as the PadI Snorkel Patrol You really do not want your hoses cut now do you

So chill, it is all good.

Nem

[Chris]

Oh, sorry. I understand now. My broken glass example would have worked just fine without my plug on dry suits and still made sense.

[luis]

3. A poodle jacket is a long used term for the jacket type BCs that have the fluffy interiors in particular and has nothing to do with a drysuit and is not a vintage device. Being as this is the vintage forum though neither drysuits or BC jackets (aka poodle jackets) are really a vintage equipment subject.


So chill, it is all good.

Nem

Well, actually, drysuits predate wetsuits...
Some were different materials... but even our wetsuits (and even our new hoses) are different material.

In the 60's the Unisuit was around, made out of neoprene, but other drysuits date back to WW-II.

Even valves in the drysuits date to the 50's. The Unisuit of course had valves similar to the most modern valves, but even Cousteau (and US Divers) had "constant volume" drysuits designs in the 50's.

None of them were popular in the Caribbean... and I am guessing they were not popular in Kansas either...