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Hi Jon, "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." You make some good points Jon. Some of us have the extra time, and are willing to do the extra labor when funds are limited and we still want a reasonably safe submarine.
"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." Very true, but now you only have one head to attach, meaning you have one less circumference weld to worry about applying correctly. Also I have what I call a high H support ring design that if the three different basic components of each ring are cut into three sections and then the butt joints staggered, I think you could install them readily without cutting off one of the heads. The high H support ring design allows you to apply all the weld beads in relatively easy to see and work on areas, when compared to a T type stiffener being installed in a hull that has the heads already welded on. Here are some pictures of the concept I worked up some years ago. The model is I believe over kill in stiffener size and thickness, but you can see the idea in any case. http://www.frappr.com/?a=viewphoto&id=4001713&pid=10216832 You can also use the angle iron configuration like on the K-250 and add horizontal pieces of angle iron between the rings for extra strength in keeping the ring from ribboning when bending, as well as seriously strengthen the hull from collapsing in an accordion fashion between the stiffener rings. Not to mention a lot of extra collision protection. But as many of you know you can't get angle stock in A516 Gr 70, (or so I'm been told) so that's why someone might want to use a the high H design. Another option might be to install a mini version of the Euronaut's stiffeners, If you can find small I or H beams. 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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