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Phanatic posted:It’s a well-understood problem and the standard way to prevent it is with cathodoc protection, where you bond in a chunk of metal with a higher electrochemical potential that will act as the anode in a battery and preferentially corrode. This has been well-understood and easily-incorporated for well over 100 years. Commercial practice is generally impressed current systems. Generally one sees those on ships rather than sacrificial anodes. Sacrificial anodes when they pop up are often inside of ballast holds or even (rarely) ballast tanks. Basically only smaller boats will have zincs on the hull. GD hosed up big. Edit also my personal opinion is that aluminum house on steel hull is dumb dumb dumb. Bar Ran Dun fucked around with this message at 16:37 on May 13, 2019 |
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May 13, 2019 16:34
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BrandorKP posted:Edit also my personal opinion is that aluminum house on steel hull is dumb dumb dumb. Why? (Don't say HMS Sheffield. Don't say HMS Sheffield. Don't say HMS Sheffield.)
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May 13, 2019 18:19
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Phanatic posted:Why? Without electrical isolation between the steel and aluminum, the aluminum hull acts as an anode to the stainless steel, resulting in aggressive galvanic corrosion. ... and the HMS Sheffield.
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May 13, 2019 19:40
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VideoGameVet posted:Without electrical isolation between the steel and aluminum, the aluminum hull acts as an anode to the stainless steel, resulting in aggressive galvanic corrosion. Yeah, if you don't do anything with it, but that hasn't been a problem in any navy ships with a steel hull and aluminum superstructure. The corrosion in the LCS wasn't of the aluminum superstructure coupled to a steel hull, it was of steel engine impeller housings coupled to an aluminum *hull*. I'd definitely agree that an aluminum hull is pretty dumb for a warship. But the LCS was a completely dumb idea at all levels. quote:... and the HMS Sheffield. Which did not have an aluminum superstructure.
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May 13, 2019 19:55
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Phanatic posted:Why? Yeah i just mean the mixing of the two in general. And galvanic corrosion is the biggest why. They have to goto great lengths to isolate the steel and aluminum to prevent it. Just mixing the two is bad news and potentially turns the ship into a battery. I'm not sure the maneuvering performance the navy shoots for is nessisary, given the nature of new threats to ships. Aluminum construction also contributes to the decline in institutional knowledge in the navy. Also aluminum melts/burns/weakens to cyclical stress differently than steel does.
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May 13, 2019 20:58
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evil_bunnY posted:Didn't the yard specifically warn against it and the guv' went all "gotta CUT CUT CUT"? It's much more likely that the contract was underbid and that that the contractor was told to cut costs to try and remain on budget. Someone somewhere noticed a big cost savings that wouldn't impact ability to meet requirements.
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May 13, 2019 22:47
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QuarkJets posted:It's much more likely that the contract was underbid and that that the contractor was told to cut costs to try and remain on budget. Someone somewhere noticed a big cost savings that wouldn't impact ability to meet requirements. Personally, I'd guess a bunch of mid-construction change and feature requests (iirc, this is where defense contractors actually make their money; the original bid is always a bit low).
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May 14, 2019 02:52
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gaj70 posted:Personally, I'd guess a bunch of mid-construction change and feature requests (iirc, this is where defense contractors actually make their money; the original bid is always a bit low). Some of the big shipyards have taken the navy to court over that. They brought in McKinsey and modeled what the change orders at the last second from the navy actually did to the work flow and costs. It rather dramatically increases both.
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May 14, 2019 02:57
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Failure to define requirements accurately up-front and making continual changes during execution is loving death, regardless of the field.
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May 14, 2019 03:10
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There were some good models of what under staffing for a big project does to a work force too. That's also as bad as one would expect.
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May 14, 2019 03:24
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Phanatic posted:Failure to define requirements accurately up-front and making continual changes during execution is loving death, regardless of the field. Once you start getting away from that.... it is really bad for both parties.
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May 14, 2019 05:23
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Yeah, so much of the money we're absolutely shocked at for public project overruns come from stupid little changes the happen as the project goes along, and so often the private contractors have planned for all this and basically have "trap cards" hidden in their contract to absolutely ream the public. Little things like setting a set price for a fixed amount of asphalt but then a little clause giving a innocent little formula for how much the asphalt will be charged at beyond that that ends up being 10x the price. Then when some politician or bureaucrat inevitably makes some changes or the contractor them selves gently caress something up, surprise, your million dollar road's minor change has doubled its cost. But it's no one thing. Don't trust anyone who says north american project bloat is just from one thing (ie those drat unions). It's a ton of things all coming together and resonating to make things spiral out of control. It's quite an awful situation because it's not something anyone can figure out how to actually fix and things just keep getting worse. I honestly don't know how long it can go on. Power plants, highways, subway tunnels, they should not cost remotely what they are currently ending up costing.
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May 14, 2019 05:33
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bawfuls posted:ok but what about aluminum? Surely that’s the relevant comparison no? Aluminum and steel frames of the same class are very similar in weight.
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May 14, 2019 06:37
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It is for the reason that the stresses on frame in a bike design prevent you from taking real advantage of aluminum strength to reduce weight, yes?
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May 14, 2019 16:55
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nepetaMisekiryoiki posted:It is for the reason that the stresses on frame in a bike design prevent you from taking real advantage of aluminum strength to reduce weight, yes? The lack of a fatigue limit (in AL) for one. Typically AL frames use larger diameter tubing to account for the lower tensile strength. This works well, but you also end up with a stiffer frame ... and some prefer the springiness of a steel bike.
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May 14, 2019 17:56
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nepetaMisekiryoiki posted:It is for the reason that the stresses on frame in a bike design prevent you from taking real advantage of aluminum strength to reduce weight, yes? nepetaMisekiryoiki posted:It is for the reason that the stresses on frame in a bike design prevent you from taking real advantage of aluminum strength to reduce weight, yes? Aluminum and steel are close in specific strength. If I wanted to hang something from a metal rod of a certain length, I’d have to use about the same mass of either material to do the job. The aluminum bar would be 70% larger in diameter because of its lower density, but the weight would work out the same. Likewise with pressure vessels. Aluminum and steel SCUBA tanks of the same capacity are similar in weight (with the edge going to steel). The aluminum tank needs walls more than three times as thick to bear the same pressure. Where aluminum spanks steel is when you have to have a solid part that resists bending. A sheet of aluminum will be three times thicker than steel for the same mass and area. An aluminum canoe and an aluminum‐skinned aircraft will resist bending and denting better than the steel alternatives. Thickness is a virtue when resisting bending. If the part doesn’t have to be solid, engineers can do something like use an I‐beam, which is thick in the dimension that matters and concentrates the material at the top and bottom where it does the most good. Designers of bicycles are free to use hollow shapes, so aluminum’s low density is of little consequence. They use big hollow tubes to resist bending, but there are no tricks to resisting tension. It all goes back to specific strength, and in that there is little difference between steel and aluminum.
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May 14, 2019 21:03
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Platystemon posted:It all goes back to specific strength, and in that there is little difference between steel and aluminum. What do moderate cyclical stresses do to steel vs aluminum? The answer, that's not a little diffence.
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May 14, 2019 21:15
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BrandorKP posted:What do moderate cyclical stresses do to steel vs aluminum? The answer, that's not a little diffence. If you’re stressing the thing real hard, they will both fatigue. If you’re not stressing them hard, aluminum is probably not going to reach its breaking point. Yeah there are exceptions for things that cycle frequently and do so over long periods of time, but I’m sceptical they apply to the typical bicycle.
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May 14, 2019 21:23
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Platystemon posted:If you’re stressing the thing real hard, they will both fatigue. quote:By continually applying loads to a material, in many cases loads way below the yield limit, you stress it and cause fatigue on it. ... So yes, aluminum can fail due to fatigue and continued stress cycles, but there is no fatigue limit as you can see on steel.  Note: I have broken (steel in fact) bike frames, most notably a Bob Jackson on a training ride when I was on the cycling team in college. Separated the downtube from the bottom bracket. VideoGameVet fucked around with this message at 21:33 on May 14, 2019 |
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May 14, 2019 21:31
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A million cycles is a lot. If the frame is being stress cycled every second in an eight hour workday, it takes a month to hit a million cycles. I’d be concerned about that if I were a serious mountain biker, but I don’t think road bike manufacturers are heavily overbuilding aluminum‐framed bikes for fear of fatigue.
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May 14, 2019 22:29
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Platystemon posted:Yeah there are exceptions for things that cycle frequently and do so over long periods of time, but I’m sceptical they apply to the typical bicycle. My brain is still thinking ships, and that's exactly the case with rolling motions.
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May 14, 2019 22:40
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Baronjutter posted:But it's no one thing. Don't trust anyone who says north american project bloat is just from one thing (ie those drat unions). It's a ton of things all coming together and resonating to make things spiral out of control. It's quite an awful situation because it's not something anyone can figure out how to actually fix and things just keep getting worse. I honestly don't know how long it can go on. Power plants, highways, subway tunnels, they should not cost remotely what they are currently ending up costing. In Finland alliance model has been successful in large construction projects in recent years. It's hard to pinpoint what exactly is done differently to traditional projects. The goal is also not lowest price but high quality and keeping the project in time and in budget. Alliance contracting: the way forward?
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May 14, 2019 23:06
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Platystemon posted:A million cycles is a lot. If the frame is being stress cycled every second in an eight hour workday, it takes a month to hit a million cycles. I got into cycling as a sport because at 14 I broke a Raliegh bike's frame and my mom managed to get the shop to replace that with a Peugeot PX10e in 1972. Sweet bike.
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May 15, 2019 00:52
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Saukkis posted:In Finland alliance model has been successful in large construction projects in recent years. It's hard to pinpoint what exactly is done differently to traditional projects. The goal is also not lowest price but high quality and keeping the project in time and in budget. Telling any contractor or consultant that you're not going to take the project away from them if they're not the lowest bidder, and stressing you'll get really upset about time or cost overruns, does wonders. Most contractors and consultants can estimate accurately, but they massage the numbers down until they win the project with the lowest bid. Then reality happens and it costs the originally expected amount, or more due to cost saving risks that don't pan out. Telling them they don't have to bullshit to win (and having them believe that) works wonders for any project.
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May 15, 2019 10:54
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Hey, bumping the thread cause I have a question: There was a back n forth in the dem primary thread that nuclear plants take forever to build but what I want to know is what if we reopened all the plants we closed? Like the Zion plant here in Illinois, for example.
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Aug 24, 2019 21:44
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HootTheOwl posted:Hey, bumping the thread cause I have a question: In most cases, nuclear plants are decommissioned because they've reached the end of their safe operating life. Decades of irradiation will weaken the steel and concrete to where they need to be replaced. Refurbishing the plants can cost hundreds of millions or billions of dollars and take a decade or more. Utilities are finding that solar, wind, and natural gas will provide more power in less time at lower cost than trying to restart the nuclear plants.
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Aug 24, 2019 21:53
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HootTheOwl posted:Hey, bumping the thread cause I have a question: Florida Power and Light has a license to build a new pair of nuclear units at Turkey Point, but has put a hold on the project, electing to wait and see what happens with the AP1000 units currently under construction and in early operation. More recently, they’ve filed to life-extend the existing pair of nuclear units at Turkey Point another twenty years, which would make them 80 years old at retirement, and the oldest units in the country.
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Aug 24, 2019 22:30
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HootTheOwl posted:Hey, bumping the thread cause I have a question: The Zion plant literally can’t be reopened, because last year they deconstructed the containment building. I don’t think there is anything left on that site except spent fuel storage. Also, in some cases permits for various things like water use, or pollution/waste discharge can expire if the plant is not operational. So they would have to reapply for those permits, and I am sure in a lot of cases they were grandfathered in to their processes as the EPA rules changed over time. So they would not be compliant with current laws/regulations and would require additional massive retrofitting to meet those new requirements.
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Aug 24, 2019 22:34
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HootTheOwl posted:Hey, bumping the thread cause I have a question: Continuing to operate old reactors is probably worse than opening new reactors or retiring all reactors because we're relying on reactors that have less safety and reliability compared to new designs, but keeping things the same is always easier than changing things, so here we are.
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Aug 24, 2019 22:35
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I'm trying to see the downsides of a federal heavy investment into modular liquid fluoride thorium reactors, and I'm not sure what I'm missing here.
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Aug 24, 2019 23:23
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Discendo Vox posted:I'm trying to see the downsides of a federal heavy investment into modular liquid fluoride thorium reactors, and I'm not sure what I'm missing here. Aside from the fact that LFTRs don't exist: https://en.wikipedia.org/wiki/Liquid_fluoride_thorium_reactor#Disadvantages
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Aug 24, 2019 23:25
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Dante80 posted:Aside from the fact that LFTRs don't exist: thanks yeah I've read the wikipedia article. I was looking for more in depth information that's up to date and less poorly cited. That section's a damned mess. Discendo Vox fucked around with this message at 23:39 on Aug 24, 2019 |
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Aug 24, 2019 23:27
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Nuclear energy has a major cost problem, and new nuclear energy technologies would not really reduce the cost of nuclear electricity. If you are ideologically committed to powering the United States on nuclear electricity, it would make more sense to just build more of the old nuclear technology.
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Aug 25, 2019 00:58
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CANDU has some cool stuff coming up, I'm holding out for it.
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Aug 25, 2019 01:06
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CommieGIR posted:CANDU has some cool stuff coming up, I'm holding out for it. Seriously? Can you link some info, Google is failing me. When CANDU/AECL were sold to SNC-Lavalin it seemed like the kiss of death.
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Aug 25, 2019 02:17
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Nocturtle posted:Seriously? Can you link some info, Google is failing me. When CANDU/AECL were sold to SNC-Lavalin it seemed like the kiss of death. I think it did kill the ACR series dead as a door nail, but they are still pitching sales with Argentina, China, and Britain as of right now. Who knows if they'll bite. I've kinda hitched my train to the modular reactor push for GENIII/GENIV, plus the hope that China is pursuing a MSR. At this point though, as the effects of climate change increase, I suspect we'll see an increasing trend in willingness to spend on nuclear projects to shift away from Coal/Gas/etc faster. It really is almost the only way we can kick our carbon addiction fast enough to do anything. At least I hope... CommieGIR fucked around with this message at 03:03 on Aug 25, 2019 |
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Aug 25, 2019 02:38
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Discendo Vox posted:I'm trying to see the downsides of a federal heavy investment into modular liquid fluoride thorium reactors, and I'm not sure what I'm missing here. The technical hurdles that need to be overcome for it to be commercially viable are large and will be expensive to implement. With the prices of solar and wind dropping so fast, there doesn't seem to be a significant case to be made for spending lots of money on it.
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Aug 25, 2019 03:05
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Deteriorata posted:The technical hurdles that need to be overcome for it to be commercially viable are large and will be expensive to implement. With the prices of solar and wind dropping so fast, there doesn't seem to be a significant case to be made for spending lots of money on it. Density is the problem: We don't have the energy storage yet to make Solar and Wind replace natural gas. Not fast enough. And for the required land needed to do so, regardless, it would be immense. We should use Solar and Wind wherever possible, but kicking the carbon habit means a highly energy dense source with a fairly tight footprint.
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Aug 25, 2019 03:12
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CommieGIR posted:Density is the problem: We don't have the energy storage yet to make Solar and Wind replace natural gas. Not fast enough. And for the required land needed to do so, regardless, it would be immense. On the other hand, solving the storage issue for wind and solar is a whole lot cheaper and more straightforward than figuring out how to make the thorium cycle work. Also, thorium isn't going to be able to replace natural gas for at least 20 years, anyway. Even if the technological problems were solved today, it would be at least a decade before any were built and generating energy.
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Aug 25, 2019 03:29
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CommieGIR posted:Density is the problem: We don't have the energy storage yet to make Solar and Wind replace natural gas. Not fast enough. And for the required land needed to do so, regardless, it would be immense. Land requirements for wind and solar are often vastly overblown by "experts" ignoring storage, demand response, etc and just flat calculating insane land use requirements by assuming that we need vastly more generation capacity than we do. Then the second complication is the varying types of land use. Impacted land use for renewables is pretty high, but disrupted land use is not. So take North Texas where you have wind turbines as far as the eye can see, that all counts as impacted land use. But only the area around the turbine (and the roads etc) are actually disrupted. The rest of the land is still active ag land. So this isn't just me saying stuff, here's a peer reviewed paper looking at 80% renewables: https://doi.org/10.1016/j.apenergy.2013.12.022 quote:This paper explores some of the implications of achieving such high levels of renewable electricity for supply chains and the environment in scenarios with renewable supply So if we exclude the land near wind turbines that is still being used for other purposes the land use impact of non-biopower at 80% renewables is around 13,100 km^2, add together the high end estimate for storage at 19,000 km^2 and you're still under the 49,000km^2 we have in major roads alone. Edit: Also we currently use 148,000 km^2 on corn for ethanol. So yeah. To the question of storage, well sure we don't have the storage capacity now, but we don't need any new technology. Building more storage isn't a problem for renewables, it is just part of the solution. Trabisnikof fucked around with this message at 03:44 on Aug 25, 2019 |
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Aug 25, 2019 03:34
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