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Hello Ian, I'll order that book. Thank you for the heads up on it. You make some good points. The void area on the High H design requires good welds to seal, and if you want/need to insulate your sub you would need to fill it with urethane foam or the like, through drilled holes, and then cap them. Carsten thought it would be ok to have sealed in areas in the interior of the sub like my void and high rolled H beams outer surface, if you weld them properly. The idea for the high H stiffeners primarily came from a skilled metal fabricator relative of mine. A big part of the reasoning for that design was that one of the primary failure modes of I and H beams, is there loose edges bending in a wavy ribbon effect. So if you have an existing trailer built with I beams, and weld on metal plates the the vertical sides, making the I beam into a rectangle. You will have a much stronger frame. This is why you see Ford bragging about there fully boxed frames on there trucks. Instead of the channel type they used to use. The Euronaut's stiffener configuration is easier to install then the high H design, but you can't get the H beams in A516 as far as I know. Perhaps there are some other steel alloys available for H beams. In any case I think mild steel H beams will work great for a lot of applications. You can also space them closer if need be. This means more weight, but in a lot of cases you will need a lot of weight any ways. It's only the change in metacentric height with extra metal up high that gives me pause in doing that. In the same basic size and thickness of material of both the rolled H beams and the high H design. I would suspect that the high H configuration would be stronger and lighter. especially if you used A516 for the material in the high H stiffeners. I've seen one of Carsten's Euronaut drawings, that showed 8 horizontal H beam weldments spaced out around the hull, between the stiffeners. For some reason he chose not to install them. Perhaps it was cost and the extra weight up high. In any case your stiffener rings will be much stronger with those in place to stop the ribboning effect of the loose edges of the inside rolled ring. For my live aboard sub design, I had decided to change from the high H stiffeners to the rolled H beams like in the Euronaut, but with the horizontal weldments add and made out of T stock. This way It was far cheaper to not have to cut rings out of large sheets of A516, a lot less welding, easier to insulate and inspect, and easier to install and inspect the wiring and piping. I plan to do FEA analysis of a number of different configurations to get a better picture of what is going on in regards to failure modes and strength versus weight. For a angle iron stiffener configuration like in my K-250 I plan to install A-36 T stock horizontal weldments to restrict the angle iron stiffeners from ribboning. I could also use angle iron for the horizontal weldments, but I need the extra rib to lock in the infusion molded syntactic foam I plan to install. Regards, Brent Hartwig > Date: Tue, 22 Jul 2008 17:26:49 -0400 > From: irox@ix.netcom.com > To: personal_submersibles@psubs.org > Subject: Re: [PSUBS-MAILIST] Pressure hull framing options. > > > Hi Brent, > > I'm not going to discuss propane tanks, this is already done (many times!), > any thing I say is already in the archives (normal for many different people). > > However, I will discuss framing issues with you. If you want to do advanced > designs like this, I would highly recommend getting a copy of: > Pressure Vessels: External Pressure Technology > by Prof Carl T. F. Ross > > This will help you start to understand some of the math (reason) behind > different framing designs. It's a great book - although kind of bleeding > edge. Once you see what's going on for a simple framing solution, you'll > get an idea of how complex your is and figuring out the potential failure > modes is going to be tricky. > > Note, with most H beam, it is the side of the H the contacts the pressure hull, > like with an I beam it's the top or bottom of the I attached to the hull. > First understand the general reason for stiffener like this. It's really > making that part of the hull a small diameter (small diameter means more > pressure resistance), one side of the I attaches to the hull (lots of contact > area), the long part extends into the hull attaches the hull to the inner > ring - the inner can take more pressure than the hull, hence re-enforcing > that part of the hull. > > With your design, it looks like you have no plate attached to the hull, > so the legs of the H are weld straight to the hull metal. They extend > out, then before the end is a inner ring welded between the legs (the cross > bridge of the H). Before using this design over other you really need > to understand how that design is going to buckle and fail. Once you > understand how it can fail, you can do some simulation with different > designs, spacing, metals thickness, etc.. Then time to start building > some models on different scales and destroying them to verify your calculations > and research, you might have to revisit your calculations and simulations > to make some adjustments, then repeat destroying some models. > > Eventually your new design will be ready to use in a manned submersible, > and providing the original research/design/work was done correctly, then > it will not fail you. > > Also, how you inspect the section between the legs of your H, for > rust, leaks and the likes? > > I have a feeling you can loose one of the legs from the H and just have > an L bean with the same strength instead, saving you metal, time and money. > > Cheers, > Ian. > > -----Original Message----- > >From: Brent Hartwig <brenthartwig@hotmail.com> > >Sent: Jul 22, 2008 3:12 PM > >To: personal_submersibles@psubs.org > >Subject: [PSUBS-MAILIST] Propane Tank Hull Options > > > > > >Hi Jon, > > > >"Regarding your second point about materials. Whether it is true or > >not, people have suggested that the time, effort, and cost required tomodify a propane tank for sub-use, is ultimately more expensive thanjust ordering the parts and starting from scratch. Perhaps that isnot strictly true from the perspective of cash-out-of-your-pocket ifthe propane tanks have cost you nothing. However, it does seem to bethe general consensus. Therefore, the issue does not appear to bewhether a modified propane tank is better/worse than a similarraw design from a performance perspective, but rather that the propanemodification is definately worse from a time/labor perspective, andcertainly 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 theribbing, the quality of the robot welds are immaterial since theweak 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.orgTo: personal_submersibles@psubs.orgSubject: RE: [PSUBS-MAILIST] Yunk Yard Wars Submarine BuildingDate: 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 acrane into a relatively shallow area of water used for boat launchingat the marina, so that if there were a problem he would not be in dangerof 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 severetrauma. I interviewed both the mother of the deceased, and thesurvivor last year. Interestingly, the day prior to the accident theyhad performed an exact similar dive in the sub without incident, andther 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 > >of dives you perform in it. You can read about it athttp://www.psubs.org/accidents/seaker100.html > > > > > > > >> 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 tobe 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 aloneif you are serious about having expectations of diving and returningto the surface safely, consistently. At some point, you are going to > >have to assess the risk of failure associated with the design andmaterials 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 tomodify a propane tank for sub-use, is ultimately more expensive thanjust ordering the parts and starting from scratch. Perhaps that isnot strictly true from the perspective of cash-out-of-your-pocket ifthe propane tanks have cost you nothing. However, it does seem to bethe general consensus. Therefore, the issue does not appear to bewhether a modified propane tank is better/worse than a similarraw design from a performance perspective, but rather that the propanemodification is definately worse from a time/labor perspective, andcertainly 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 theribbing, the quality of the robot welds are immaterial since theweak 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 arean impediment to this group, then I strongly disagree with you. > > > >Jon > > > > > > > > > ************************************************************************ > ************************************************************************ > ************************************************************************ > The personal submersibles mailing list complies with the US Federal > CAN-SPAM Act of 2003. 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