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Hello Jon, > How many people have died in 1 ATM and/or ambient propane tank sub? "I don't know, but I do know the facts surrounding a couple of engineering
students who built what they considered a safe sub, but in which one of
them died. The other fortunately survived the ordeal, but suffered severe
trauma. I interviewed both the mother of the deceased, and the survivor last year. Interestingly, the day prior to the accident they had performed an exact similar dive in the sub without incident, and ther e fore assumed that the sub was safe for shallow-depth diving. Funny how you can't determine the safety of a sub by the number
First I don't see the Seaker 100 as being any thing like a propane tank sub other then it's experimental in nature and the pods might be small propane tanks. I had read those articles some time ago, except the PDF file with pictures was new to me. Now that I've seen the pictures and the data about them using temporary show acrylic domes blown out of 1/4" acrylic, I think I better understand the problems. First 1/4" acrylic blown into a dome is a fair bit thinner then 1/4" in some areas. Not to mention that 1/4" acrylic used for such a large dome is very fragile in terms of what external hydrostatic pressure it can take. So regardless of whether they hit one of the windows with some thing, they shouldn't of done a live test until the thick acrylic windows they ordered arrived and were installed properly. Also there are no window protect bars of any kind.
On top of all that, the acrylic windows have a lot of bolt holes drilled into them. Of which I've been told Stachiw does not requimend. One reason for this I suspect is that when you drill acrylic, it's easy to drill it to fast and/or with the wrong bit and put in small cracks inside the holes. Karl Stanley's C-BUG had viewports with holes drilled in the acrylic like his mentor's sub Nekton Delta. One seriously cracked at far less then the depth it was supposed to be able to take, and had taken many times before. Perhaps this was because of a crack started in one or more of the drilled holes. This was long before he scuttled the sub. But might be a reason he did in the end.
Also on Karl's Idabel the first configuration of his bottom flat viewport was with holes drilled in the acrylic. It cracked at depth, but didn't completely fail. But it sure scared the passengers half to death. He said the failure was due to a design flaw. He changed the viewport to a none drilled acrylic type.
Engineering students built the Dennoch propane tank sub and it worked.
Here is some Dennoch data from PSUBs.org.
"PRESSURE HULL - Made of 3/8-inch thick steel, the 288 gallon cylinder began life as a propane tank. Extensive bracing has been added to strengthen the openings necessary to convert the tank into a submarine. The hull is theoretically capable of withstanding depths in excess of 1000 feet, although several other elements of the submarine have limits of less than half that depth." "What did he say about using 55-gallon drums?"
I don't know. I'll keep reading. ;)'
Regards, Brent Hartwig From: jonw@psubs.org To: personal_submersibles@psubs.org Subject: RE: [PSUBS-MAILIST] Yunk Yard Wars Submarine Building Date: Tue, 22 Jul 2008 01:14:49 -0400 Brent,
> Can a reasonably safe ambient or wet, oil drum submarine be designed
> and built? I believe there are lots of options. The Chinese oil drum > submarine builder will likely put his sub in shallow water for testing > and see he needs a lot more keel weight before he even gets into it. > He can add more weight to the wheel assemblies and/or a keel of some > sort below the hull. The RV Needlefish had the same basic metacenter > problem, and Bill found that out without ever diving it. Bill owned a very large and successful marina, and had almost unlimited
resources available to him. Bill tested his sub by lowering it from a
crane into a relatively shallow area of water used for boat launching at the marina, so that if there were a problem he would not be in danger of entrapment and drowning. His sub was connected to the crane at all times.
> How many people have died in 1 ATM and/or ambient propane tank sub? I don't know, but I do know the facts surrounding a couple of engineering
students who built what they considered a safe sub, but in which one of
them died. The other fortunately survived the ordeal, but suffered severe
trauma. I interviewed both the mother of the deceased, and the survivor last year. Interestingly, the day prior to the accident they had performed an exact similar dive in the sub without incident, and ther e fore assumed that the sub was safe for shallow-depth diving. Funny how you can't determine the safety of a sub by the number
> I have literature in my K-250 paperwork that has the George
> Kittredge saying that you can build your whole K-250 sub out > of A-36 mild steel and be just fine. He did say how ever that > A516 Gr 70 is a great upgrade. Here is the quote. What did he say about using 55-gallon drums?
> Designing a $2,000 US 1 ATM sub that anyone in the world could find
> the same materials for the same price, is not likely. When one has > the need and/or desire to construct a inexpensive sub, it's not > always about getting new products cheaply, but usually about found > objects that are very cheap or even free. To build those same > objects brand new would be in many cases very expensive. I have two > used, but solid nice 500 gallon propane tanks with half hemisphere > heads that I got for free from a neighbor. Should I not use them for > a 1 ATM sub because they are not made of new A-516, they have a > little bit of rust on them, and they smell funny? You talk about cost as if safety is a constant that doesn't have to
be accounted. It's not, and has to be built into the cost of the sub. You can't base your design and fabrication on cost of materials alone if you are serious about having expectations of diving and returning to the surface safely, consistently. At some point, you are going to have to assess the risk of failure associated with the design and
materials you have chosen. Regarding your second point about materials. Whether it is true or
not, people have suggested that the time, effort, and cost required to
modify a propane tank for sub-use, is ultimately more expensive than just ordering the parts and starting from scratch. Perhaps that is not strictly true from the perspective of cash-out-of-your-pocket if the propane tanks have cost you nothing. However, it does seem to be the general consensus. Therefore, the issue does not appear to be whether a modified propane tank is better/worse than a similar raw design from a performance perspective, but rather that the propane modification is definately worse from a time/labor perspective, and certainly from the chemical "smell" inherent in propane tanks. > The heads are robot welded with three passes. Most of us can't weld
> even close to that good. Besides I would likely have to cut one end > off to install the ribbing unless I cut the ribbing into three > sections. I'm sure you realize that once you cut the end off to install the
ribbing, the quality of the robot welds are immaterial since the weak link is now the the weld you made to reattach the end. > One thing that this group needs to be reminded of from time to time,
> is that the synergy of experiences and combined brain power of this > global group, is incredible, if not impeded. If you are suggesting that people who have an interest in safety are
an impediment to this group, then I strongly disagree with you. Jon
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