johnn
Regular Diver
Posts: 10
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Post by johnn on Aug 17, 2023 14:58:03 GMT -8
I'm about to jump in the pool with my new-to-me Double-hose and have some questions about tanks and weighting. Before I have a chance to appear more foolish than I already do, a few questions. My understanding that 'back-in-the-day', the only tanks commonly available were steel LP72's. And the real-men of those halcyon days just strapped the tank to a minimalist backplate and handled the buoyancy with their lungs. So give this as a backdrop, a LP72 swings between about -5 lbs to 0 lbs I'd like to use this setup in warm water, which means travel (I live in the PNW) which means AL80's are the only thing likely to be available. For my gear, I have a 'new' minimalist backplate something like this: i.ebayimg.com/images/g/PwEAAOSwBX1h016O/s-l500.jpgAn AL80 swings between 1.4 negative to 4.4 positive. Do I just add a bit of lead to compensate for it being a floater at the end of the dive, or should I try and get my 19# wing attached to the backplate? I've not tried to sink my fat ass (but I rarely need a wetsuit) without a tank attached to it recently, but with an AL80 and aluminum backplate I need about 6 lbs not counting my regs. Opinions and guidance are most welcome! |
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Post by SeaRat on Aug 18, 2023 9:22:39 GMT -8
I dive both the single steel 72 and the AL 80, and I don't see much difference between the two. I'd do a weight check on your next dive, and weight yourself so that at the beginning of the dive, you are at eye level vertical at the beginning of a dive, on a full breath. You should be good to go with that.
It sounds like you're diving without a wetsuit, so the weight check should be good for about any depth you dive. The BCD was developed so as to compensate for compression of the wetsuit neoprene at depth (I had something to do with those studies) in the 1970s through the 1990s. But without a wetsuit, there is on change in buoyancy change, so the weight check should be enough with you.
Concerning the double hose regulator, mount that minimalist backpack as high up on the tank as possible, so that the double hose regulator sits between your shoulder blades. One common mistake is to have the double hose regulator too high, so that it is away from the center of your lungs. This makes the regulator breathe harder.
John
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Post by nikeajax on Aug 18, 2023 15:53:04 GMT -8
My understanding that 'back-in-the-day', the only tanks commonly available were steel LP72's. And the real-men of those halcyon days just strapped the tank to a minimalist backplate and handled the buoyancy with their lungs. So give this as a backdrop, a LP72 swings between about -5 lbs to 0 lbs If'n ya wanna see real he-man diving action from the old days, look for the original version of "Mermaids of Tiburon": en.wikipedia.org/wiki/Mermaids_of_TiburonThey later turned it into a soft-core porno, which I found boring actually: but all the same Diane Webber is super nice to look at, like Betty Page beautiful  Anyway, George Robotham only used a tank, only straps, no weights... Jaybird |
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johnn
Regular Diver
Posts: 10
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Post by johnn on Aug 22, 2023 8:25:57 GMT -8
They later turned it into a soft-core porno, which I found boring actually: but all the same Diane Webber is super nice to look at, like Betty Page beautiful Anyway, George Robotham only used a tank, only straps, no weights... Jaybird Props to the ladies for swimming in those cold waters. Yes a boring movie |
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Post by duramax on Aug 23, 2023 18:48:16 GMT -8
John, Here is my first dive with an Argonaut Kraken with AL i550 computer, Scuba Pro backpack (similar to what you have posted) with rubber strapping and a steel HP80, 12 lb of lead with a XCel semi-dri 8/7/6mm. No BC and also note the free diving fins, (the only way to fly). When I dive this configuration I am able to control my buoyancy at 20 ft by breathing. Will be slightly negative at depths greater than 50ft. But I can swim with no problem. I am working on a rig using the www.subseasports.com/shop?store-page=Vintage-SCUBA-Backplate-p468949518 and an AL Rogue wing (12 lb of lift not sure it is still available) if I am required to dive with a BC. I also think this configuration will move the regulator closer to my back. The ScubaPro Pack adds some thickness and the handle loop limits how low I can move the tank. RK |
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Post by vance on Aug 23, 2023 19:28:58 GMT -8
Hi,
Sorry, but the link doesn't work.
Fixed and working.
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Post by duramax on Aug 23, 2023 19:41:07 GMT -8
Try again
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Post by mackintoshman on Aug 23, 2023 20:30:09 GMT -8
They later turned it into a soft-core porno, which I found boring actually: but all the same Diane Webber is super nice to look at, like Betty Page beautiful Anyway, George Robotham only used a tank, only straps, no weights... Jaybird Props to the ladies for swimming in those cold waters. Yes a boring movie |
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Post by mackintoshman on Aug 23, 2023 20:38:02 GMT -8
Jaybird, I watched the mermaids of tiburon. Mr. gangster I mean Sangster was funny. I need to go full circle on this. you need to watch voyage to the bottom of the sea. season 3 ep.19 the mermaid. also what regs do they use and what is that chrome canister on there tanks.
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Post by SeaRat on Aug 30, 2023 17:45:16 GMT -8
John, Here is my first dive with an Argonaut Kraken with AL i550 computer, Scuba Pro backpack (similar to what you have posted) with rubber strapping and a steel HP80, 12 lb of lead with a XCel semi-dri 8/7/6mm. No BC and also note the free diving fins, (the only way to fly). When I dive this configuration I am able to control my buoyancy at 20 ft by breathing. Will be slightly negative at depths greater than 50ft. But I can swim with no problem. I am working on a rig using the www.subseasports.com/shop?store-page=Vintage-SCUBA-Backplate-p468949518 and an AL Rogue wing (12 lb of lift not sure it is still available) if I am required to dive with a BC. I also think this configuration will move the regulator closer to my back. The ScubaPro Pack adds some thickness and the handle loop limits how low I can move the tank. RK What a very nice little video. Thank you for sharing it. John |
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Post by herman on Oct 29, 2023 15:41:02 GMT -8
Several thing come to mind.
First off, get a proper BC/backpack. You want to keep the DH as close to your back as possible, most modern BC's don't including many steel/aluminum BPs, esp those with a ridge down the middle. Most do not hold the tank and reg close enough to your back or allow the reg to be set low enough. The more common plastic backpack (blown ones) of old that are an inch or so in thickness are not suited for DH use, they are too thick and usually don't allow proper placement of the reg. Your best option is a Kam EZ or similar single layer BP. These are one layer, about 1/4 inch thick and will allow the reg to be placed better.
With the proper BP, next is weighing. It really doesn't matter if you are using a steel 72 or AL 80, the swing on both is close enough to 4 lbs (you almost never suck one dry). The actual buoyancy is not really critical since you will be adjusting your weight for the tank and other gear, the swing from full to empty is what is important. Since the total swing is 4 lbs, I weight for the middle, IE, 2 lbs heavy at the beginning of the dive and/or 2 positive at the end and dead on neutral mid dive. That leaves me with +2 and -2 lbs to deal with, a fairly easy amount to deal with using lungs alone. You can always grab a rock if you need a little more during the dive. Getting down at first can be a little challenging since all the gear is full of air but that comes out pretty fast. This is assuming no wetsuit or at least one of the older ones that are not as susceptible to buoyancy changes, I wear a shark skin fleece if I can, they are neutral.
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Post by surflung on Jan 18, 2024 12:39:52 GMT -8
Generally speaking... It's my understanding that the original steel "72" was really about 65 cf at 2250 psi and reached 72 psi at 10% over or 2475 psi. The reason I mention this is because the present day aluminum "63" is said to have almost the same buoyancy characteristics as the original steel 72 (aka 65). And, you can rent a present day aluminum 63 from most dive operators. Here's a USD 72 Description from the 1963 catalog...  "Should sink slowly when full. +1.7 lbs positive when empty will float". And, I looked up the buoyancy of an aluminum 63... Full is -2.4 lbs (sinks slowly?) 500 psi + 1.7 lbs (floats) Just as Herman says... Swing is 4.10 lbs. I downloaded the 1963 USD catalog from the Vintage Double Hose website, courtesy of the late Bryan Pennington. |
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Post by SeaRat on Feb 9, 2024 18:14:06 GMT -8
The buoyancy characteristics you state are for salt water. For freshwater, the steel 72 is still a bit negative when empty.
Yes, the steel 72 is actually not 71.2 cubic feet until it is overfilled by 10%, if it still has its "+" sign. Here's the calculation:
71.2 ft3 / 2475 psi = X / 2250 psi
X = (71.2 ft3 / 2475 psi) x 2250 psi
X = 64.7 ft3
So at its rated pressure of 2250 psi, the "71.2 steel tank" is actually at 64.7 cubic feet. Most of the steel 72s still in use, including mine, don't sport the "+" sign on the hydro, and so they don't have a true 71.2 cubic feet, but rather the 64.7 cubic feet, or as stated above, 65 cubic feet (rounded). If the above figures are used for 72 cubic feet at 2475 psi, the calculation comes out to 65.45 psi at 2250 psi, or as stated above, rounded to 65 cubic feet.
John
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