Manufacturing Materials for SCUBA
- Thread starter Dr. Vinny
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I've dove a fire fighter's scba fiber tank.
Felt really good until I added sufficient lead to get myself neutral. Found it awkward handling a significantly positively buoyant cylinder and harness underwater
Personally I prefer a cylinder swing weight to be negative to neutral rather than positive to even more positive.
Felt really good until I added sufficient lead to get myself neutral. Found it awkward handling a significantly positively buoyant cylinder and harness underwater
Personally I prefer a cylinder swing weight to be negative to neutral rather than positive to even more positive.
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Check your math. And your physics. 11 to 15 liters of air has a gross buoyancy of 11 to 15 kg (24 to 33 lbs). Subtract the weight of the air (depends on the pressure) and the weight of the tank and valve, and you have the net buoyancy of the filled tank. 200 bar steel tanks are pretty close to neutrally buoyant when empty; 232 bar tanks are somewhat negative (a couple of kilos) and 300 bar tanks are noticeably negative (5-ish kilos for a 12L). Cite: Faber Cylinders for Scuba Diving Catalogue
Even with a 12L or 15L 200 bar steel tank (which weigh some 12 or 15 kg when empty, or 15 to 18.5 kg when full), I need about 6kg of lead when I'm in a 5 mil WS. I see no reason whatsoever to shave more weight off the tank just to have to add the same amount of weight to my belt. Or adding that weight to my backplate, effectively making the rig just as heavy as it was whith a steel tank attached.
Now, if your rig is very negative to start with (I have the impression that some RBs are), lighter tanks may be an advantage. For diving normal OC scuba while wearing anything more than a rash guard, probably not so much. This seems like a solution in search of a problem to me.
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Dr. Vinny
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The amount of lead that anyone requires to dive properly is dependent on a number of factors (in addition to the type and size of tank that one uses.) The "physical" weight of a tank does not equal "buoyancy" weight. Attached is some valuable info on tank buoyancy characteristics. Also, in case anyone is really interested or curious, every 10 lbs in body fat will cost you an additional 1lb in lead to compensate- don't get me started on bone density-- LOL
The amount of lead that anyone requires to dive properly is dependent on a number of factors (in addition to the type and size of tank that one uses.) The "physical" weight of a tank does not equal "buoyancy" weight. Attached is some valuable info on tank buoyancy characteristics. Also, in case anyone is really interested or curious, every 10 lbs in body fat will cost you an additional 1lb in lead to compensate- don't get me started on bone density-- LOL
Tanks, I saved the PDF.
It's my understanding that Luxfer is only doing a Fiberglass composite and that wasn't the original question. I've already discarded this tank in favor of the more advanced materials, if available, or remain in "the dark ages".
It's also my understanding, from design efforts in Gov. contracting, the Carbon materials are easier to machine, would allow an extended inspection cycle and life cycle, are stronger and more durable than any of the materials used now.
I agree that the shops would have an issue with the higher pressures but if nothing is done we remain stagnant in technology, and, BTW, from my local shop, The Dive Station Orlando Fla., plug intended, the "Pressure's ON", pun intended, for the higher pressures from the Paintball and EMT folk at this time.
As far as all this titter about weight; divers have been adding and subtracting weight with ever changing mechanisms since ole Jacques-Yves Cousteau=US Divers and the Genesis of SCBA underwater with the original US Navy research.
From all the discussion it appears that "Norteamérica" isn't interested in this technology. It's also my understanding as mentioned on the original post that our Chinese friends are already in the biz with these new materials. Sooooo, is-we-is, or is-we-ain't. I would be nice to hear from Fabricantes de América del norte = North American manufacturers, por favor
.
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When you say "resin" I think Luxfer and fiberglass. For all intent and purpose a nonstarter. Do you have any design experience with the composites that are Carbon based?
About 15 years ago some Russian company came out with a "Titanium" scuba tank that could be filled to 10,000PSI and was very light AFAIR. It didn't go anywhere and was never introduced to the market in the free world.
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@Vincent B. Collins it's not that we are against the technology, there are plenty of composite cylinders in the market and the designs for them are continuing to get better and better. The issue is that the technology is not suitable for underwater pressure vessels at this point which is why they aren't being actively used by the mainstream.
Resin is required for all hard composites, it is what holds the woven, wrapped, braided, blown, pick a technology to use fibers in their place. Without it, the fabric structures themselves are largely useless because of distortion and how brittle most of these materials are. The resin chosen is just as complex as the fabric structure that it is binding together and will depend on what it's binding, what it's holding back, and what environment it will be living in. It is also extremely difficult and expensive to get perfect resin impregnation on a wrapped cylinder because it can't be pre-pregged like they do with most flat composites.
Regarding experience with composites that are carbon based. Yes I have quite a bit of experience with carbon based composites which is why I have been rather outspoken about my dislike of the choice of it in the SF2 rebreather and the Bonex DPV's where it is used solely as a "sexy" selling point as opposed to being an ideal material for the application *which from an engineering perspective, it is probably 4th or 5th on the list of appropriate materials for those applications*.
Carbon fiber is chosen when you need incredible rigidity and ultimate tensile strength in the thinnest possible product. Things like vanes in turbine engines, aerofoils, airframes, etc etc. are appropriate uses of carbon fiber. The downside of carbon fiber is that it is not a "tough" material. Toughness and strength are often used interchangeably but should not be. Strength is how much force an object can withstand ultimately. I.e. it takes 200lbs to pull it apart. Carbon is very strong compared to most materials. Toughness is the area under the stress strain curve. Carbon is not very tough. It loads quickly and breaks quickly which is why it shatters like glass. Pressure vessels need to have some give *you can't perform a hydrostatic test on a carbon cylinder because it will just sit there*. This is part of why their service life is so short, you can't reasonably test these vessels for anything other than "it doesn't explode at this pressure at this time" with a hydro and no one has the scanning equipment available to test them outside of basically the military
Resin is required for all hard composites, it is what holds the woven, wrapped, braided, blown, pick a technology to use fibers in their place. Without it, the fabric structures themselves are largely useless because of distortion and how brittle most of these materials are. The resin chosen is just as complex as the fabric structure that it is binding together and will depend on what it's binding, what it's holding back, and what environment it will be living in. It is also extremely difficult and expensive to get perfect resin impregnation on a wrapped cylinder because it can't be pre-pregged like they do with most flat composites.
Regarding experience with composites that are carbon based. Yes I have quite a bit of experience with carbon based composites which is why I have been rather outspoken about my dislike of the choice of it in the SF2 rebreather and the Bonex DPV's where it is used solely as a "sexy" selling point as opposed to being an ideal material for the application *which from an engineering perspective, it is probably 4th or 5th on the list of appropriate materials for those applications*.
Carbon fiber is chosen when you need incredible rigidity and ultimate tensile strength in the thinnest possible product. Things like vanes in turbine engines, aerofoils, airframes, etc etc. are appropriate uses of carbon fiber. The downside of carbon fiber is that it is not a "tough" material. Toughness and strength are often used interchangeably but should not be. Strength is how much force an object can withstand ultimately. I.e. it takes 200lbs to pull it apart. Carbon is very strong compared to most materials. Toughness is the area under the stress strain curve. Carbon is not very tough. It loads quickly and breaks quickly which is why it shatters like glass. Pressure vessels need to have some give *you can't perform a hydrostatic test on a carbon cylinder because it will just sit there*. This is part of why their service life is so short, you can't reasonably test these vessels for anything other than "it doesn't explode at this pressure at this time" with a hydro and no one has the scanning equipment available to test them outside of basically the military
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Of Course, but what I'm trying to get in an online discussion about are the materials, already used in Free World defense contracting and space exploration, and, in not so free worlds as you indicated, in which my "Packaging" brethren at the Lockheed Martin Corp. have sent into all manner of environments along with my gadgets. BTW, the Russians are good for cheep range ammunition. According to ???, I'd have to look it up again, these Carbon materials are superior in all categories than AL or Steel.
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except damage tolerance, which is very important in our world... tank that high of pressure goes boom in air, it's annoying and your ears will ring for a little while. Does that in the water? insta-death
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Ok, Finally, are you in engineering? From what you say, makes sense, there is a testing issue and the Gov., as far as civilian application is not providing guidance. For all intent and and purpose my information is of military origin so I suspect that was my confusion in why we haven't herd of this material for Civilian application. AND, I understand you aren't to keen on it for the rebreather. I haven' had a chance to work with that yet although my local Dive shop has one for training purposes. It would seem this would be a good application. Could you elaborate on your concerns.
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