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Posted: 6/29/2023 1:25:38 PM EDT
[#1]
Quote HistoryQuoted: I have to wonder if the kid had time to work his Rubik's Cube. I hope he had time to jam it down Cap'n Rush's throat. |
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Posted: 6/29/2023 1:26:57 PM EDT
[#2]
Quote HistoryQuoted: I get the impression from the pre-incident media interviews that this guy was working hard to raise his and the company's profile, so you've got to give him credit for that. Mission accomplished. @scuba_steve - his company's profile couldn't get much higher - in a very low sorta way! |
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Posted: 6/29/2023 1:29:17 PM EDT
[#3]
Quote HistoryQuoted: This is interesting. And I have not given it much thought. With an implosion, there is a chance the camera/storage card survived. About a zero percent chance a suddenly destroyed camera would be able to save the last video file. Anyone with a dash cam with a battery that died knows what I mean. |
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Posted: 6/29/2023 1:30:41 PM EDT
[#4]
Quote HistoryQuoted: I do wonder about the dropping ballast thing. How does anyone know if this happened with no communication? Was Cameron saying this as a way to enforce his belief the sub was dangerous or did the mother ship actually know they dropped ballast and relay this through the deep sea dive community? Word was that they had an automated system that alerts the mother ship when ballasts were dropped in case of an emergency. There was some talk about it with some of the people in the know. Cameron and Ballard obviously had some contact with people that were on the recovery efforts or possibly the mother ship. I cannot find the video where they talk about it. Like the Fog of war things get lost in the noise and there is no telling if this is true or not at this point. Would like to see what it says once the investigation is concluded. |
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Posted: 6/29/2023 1:42:58 PM EDT
[#5]
Quote HistoryI wish people would stop trying to model it in Solidworks FEA. It's nowhere near accurate. It can't model the fibers and resin holding it together. It's getting treated as a homogeneous material with forces distributed through it, because they are modeling it as a solid piece. |
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Posted: 6/29/2023 1:48:07 PM EDT
[#6]
Quote HistoryQuoted: I’m not convinced it was the glue failure that caused the implosion. Just like the viewing window or the 17 bolts holding the cap on, the underwater pressure would’ve been squeezing both end caps onto the tube, holding them in place against the carbon fiber hull tube. I’m still thinking it was the carbon fiber itself that was the failure point, and the glue let go during the implosion. Perhaps the forces of the end caps pressing on the tube contributed to it. The failure of the carbon tube itself would rip the glue connection off the Ti. Weak spot in the structure would be the halfway between the end caps. The tube most likely crushed in at that point and the crush popped the glue bond loose. Or the glue bond failed over repeated dive cycles which allowed water intrusion leading to a failure. That staining on the ring will be very telling. I am sure some smart engineer will examine the wreckage and figure it out. |
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Posted: 6/29/2023 1:53:09 PM EDT
[#7]
Everything they've recovered so far is in remarkably good shape considering the amount of energy that was released.
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Posted: 6/29/2023 1:53:45 PM EDT
[#8]
Y'all dont hate me for noticing it, but that video of them jbwelding on the endcaps to the toiletpaper tube. All I see there are some 50yr old white men.
 The diversity hires must have been out inspiring the local youths at the time. |
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Posted: 6/29/2023 1:53:51 PM EDT
[#9]
You ever stand on a beer can and ever so slightly touch the side? I wonder if they bumped into some debris and something similar happened. Gnarly to think about honestly.
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Posted: 6/29/2023 2:01:33 PM EDT
[#10]
Quote HistoryThat is exactly what I was attempting to describe. |
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Posted: 6/29/2023 2:10:04 PM EDT
[#11]
  The oceangate facebook is still open    |
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Posted: 6/29/2023 2:12:44 PM EDT
[#12]
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Posted: 6/29/2023 2:13:05 PM EDT
[#13]
the CF squeezed in and separated itself from the titanium caps. Im sure CF and titanium react differently at those depths its amazing the glue held together as long as it did.
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Posted: 6/29/2023 2:14:44 PM EDT
[#14]
Quote HistoryQuoted: the CF squeezed in and separated itself from the titanium caps. Im sure CF and titanium react differently at those depths its amazing the glue held together as long as it did. I wouldn't even go 100 feet down with anything that was glued together. I want welds and/or graded bolts. |
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Posted: 6/29/2023 2:24:58 PM EDT
[#15]
Quote HistoryQuoted: I wouldn't even go 100 feet down with anything that was glued together. I want welds and/or graded bolts. Grading doesn't making them good. Taco Bell uses grade Z beef. The grade just lets you know how bad it is.
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Posted: 6/29/2023 2:25:52 PM EDT
[#16]
Quote HistoryQuoted: Grading doesn't making them good. Taco Bell uses grade Z beef. The grade just lets you know how bad it is. Quote HistoryQuoted: Quoted: I wouldn't even go 100 feet down with anything that was glued together. I want welds and/or graded bolts. Grading doesn't making them good. Taco Bell uses grade Z beef. The grade just lets you know how bad it is.  |
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Posted: 6/29/2023 2:44:48 PM EDT
[#17]
I've two questions:
In the video realwar posted, the mangled carbon fiber images came from where? Not recovered remains? Correct? @realwar Secondly, it is not really know if the ballast was dropped or blown away is it? I'm just trying to keep this all straight in my head. Thanks. edit: I wonder if dropping the ballast, if they did do that voluntarily, would or could have precipitated the final failure? |
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Posted: 6/29/2023 2:46:30 PM EDT
[#18]
OceanGate Expeditions is still advertising $250,000 trips to the Titanic wreckage.
https://oceangateexpeditions.com/tour/titanic-expedition/ |
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Posted: 6/29/2023 2:48:11 PM EDT
[#19]
Quote HistoryQuoted: I've two questions: In the video realwar posted, the mangled carbon fiber images came from where? Not recovered remains? Correct? @realwar Secondly, it is not really know if the ballast was dropped or blown away is it? I'm just trying to keep this all straight in my head. Thanks. The pictures shown at the tech talk was a 1/3 scale model they used for pressure testing. |
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Posted: 6/29/2023 2:52:52 PM EDT
[#20]
Thank you.
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Posted: 6/29/2023 3:01:08 PM EDT
[#21]
Quote HistoryQuoted: The failure of the carbon tube itself would rip the glue connection off the Ti. Weak spot in the structure would be the halfway between the end caps. The tube most likely crushed in at that point and the crush popped the glue bond loose. Or the glue bond failed over repeated dive cycles which allowed water intrusion leading to a failure. That staining on the ring will be very telling. I am sure some smart engineer will examine the wreckage and figure it out. Quote HistoryQuoted: Quoted: I’m not convinced it was the glue failure that caused the implosion. Just like the viewing window or the 17 bolts holding the cap on, the underwater pressure would’ve been squeezing both end caps onto the tube, holding them in place against the carbon fiber hull tube. I’m still thinking it was the carbon fiber itself that was the failure point, and the glue let go during the implosion. Perhaps the forces of the end caps pressing on the tube contributed to it. The failure of the carbon tube itself would rip the glue connection off the Ti. Weak spot in the structure would be the halfway between the end caps. The tube most likely crushed in at that point and the crush popped the glue bond loose. Or the glue bond failed over repeated dive cycles which allowed water intrusion leading to a failure. That staining on the ring will be very telling. I am sure some smart engineer will examine the wreckage and figure it out. Failure point “should” be the halfway point, unless it was a carbon fiber flaw. Carbon fiber isn’t one solid piece like a piece of metal. It’s a bunch of strands wrapped around each other and is essentially held in place with resin. That means a flaw could’ve been anywhere within the carbon fiber tube, such as a trapped air bubble, or piece of a contaminate, or a portion of the pre-impregnated resin that went been bad from age, etc. Edit: The more talk about all the potential issues, the more I realize just how hard it is to grasp all of the forces involved. IMHO, Stockton Rush was thinking above his actual knowledge level just by using a unbraced cylindrical tube for those depths, no matter what material he picked. |
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Posted: 6/29/2023 3:03:06 PM EDT
[#22]
They didn't understand the precise poof-point of that submersible.
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Posted: 6/29/2023 3:28:04 PM EDT
[#23]
Quote HistoryI didn't realize there was so much science behind Fleshlight designs. |
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Posted: 6/29/2023 3:32:21 PM EDT
[#24]
Quote HistoryQuoted: OceanGate Expeditions is still advertising $250,000 trips to the Titanic wreckage. https://oceangateexpeditions.com/tour/titanic-expedition/ I'm surprised they don't have a "Well shit" message on their home page. ...and that they haven't been hacked yet. |
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Posted: 6/29/2023 3:35:46 PM EDT
[#25]
Quote HistoryQuoted: OceanGate Expeditions is still advertising $250,000 trips to the Titanic wreckage. https://oceangateexpeditions.com/tour/titanic-expedition/ Well, you can't argue with this claim on their site: 
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Posted: 6/29/2023 3:39:11 PM EDT
[#26]
Quote HistoryQuoted: I wish people would stop trying to model it in Solidworks FEA. It's nowhere near accurate. It can't model the fibers and resin holding it together. It's getting treated as a homogeneous material with forces distributed through it, because they are modeling it as a solid piece. Quote HistoryQuoted: I wish people would stop trying to model it in Solidworks FEA. It's nowhere near accurate. It can't model the fibers and resin holding it together. It's getting treated as a homogeneous material with forces distributed through it, because they are modeling it as a solid piece. plus they're fucked up the plot scaling, so that it looks like a pretty benign loading. it should be solid red all over |
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Posted: 6/29/2023 3:47:21 PM EDT
[#27]
Quote HistoryQuoted: That makes sense from the pics. The window seemed similar to other submersibles. I still can't comprehend why carbon fiber would be used. From reading and videos I believe Rush may have been envisioning his company as the gatekeeper to a world full of inexpensive, off the shelf, carbon fibre submersibles. His idea wasn't primarily to dive the Titanic. That just funded his ,research" and got the name out there. For him, the goal was to actually make a deep diving CF submersible or die trying. |
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Posted: 6/29/2023 3:55:19 PM EDT
[#28]
Quote HistoryQuoted: OceanGate Expeditions is still advertising $250,000 trips to the Titanic wreckage. https://oceangateexpeditions.com/tour/titanic-expedition/ |
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Posted: 6/29/2023 4:01:34 PM EDT
[#29]
Quote HistoryQuoted: From reading and videos I believe Rush may have been envisioning his company as the gatekeeper to a world full of inexpensive, off the shelf, carbon fibre submersibles. His idea wasn't primarily to dive the Titanic. That just funded his ,research" and got the name out there. For him, the goal was to actually make a deep diving CF submersible or die trying. Quote HistoryQuoted: Quoted: That makes sense from the pics. The window seemed similar to other submersibles. I still can't comprehend why carbon fiber would be used. From reading and videos I believe Rush may have been envisioning his company as the gatekeeper to a world full of inexpensive, off the shelf, carbon fibre submersibles. His idea wasn't primarily to dive the Titanic. That just funded his ,research" and got the name out there. For him, the goal was to actually make a deep diving CF submersible or die trying. We were discussing this earlier. He spent a lot of time talking about OceanGate as an affordable, as in not millions of dollars, deep sea expeditions to encourage deep sea research as he couldn't be an astronaut in his earlier life. He's originally an aerospace guy who had dreams of NASA. There was also a 501c3 OceanGate Foundation with huge plans for all kinds of deep sea stuff. OceanGate Expeditions was their Bahamas registered company for tourism stuff, they still called it "research" as tourists were "mission specialists" who did research while tourism Quite a bit of his earlier expeditions were not full price. He was offering free or low cost trips to "influencers" and other influential people to get the word out and grow his company. He had 4 more CF submersibles in the works to grow the company. He only had 3 subs, now 2. But he talks like its this massive deep sea company with multiple subs, is why he was so hellbent on making a bunch of cheap CF subs. They were really only active in the late 2010's and had a lot of setbacks to the deep stuff, majority of it was 1,000 foot or less stuff |
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Posted: 6/29/2023 4:01:38 PM EDT
[#30]
Quote HistoryQuoted: You ever stand on a beer can and ever so slightly touch the side? I wonder if they bumped into some debris and something similar happened. Gnarly to think about honestly. Is standing on beer cans a normal thing in Michigan? |
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Posted: 6/29/2023 4:05:30 PM EDT
[#31]
Quote HistoryQuoted: From reading and videos I believe Rush may have been envisioning his company as the gatekeeper to a world full of inexpensive, off the shelf, carbon fibre submersibles. His idea wasn't primarily to dive the Titanic. That just funded his ,research" and got the name out there. For him, the goal was to actually make a deep diving CF submersible or die trying. Quote HistoryQuoted: Quoted: That makes sense from the pics. The window seemed similar to other submersibles. I still can't comprehend why carbon fiber would be used. From reading and videos I believe Rush may have been envisioning his company as the gatekeeper to a world full of inexpensive, off the shelf, carbon fibre submersibles. His idea wasn't primarily to dive the Titanic. That just funded his ,research" and got the name out there. For him, the goal was to actually make a deep diving CF submersible or die trying. then he achieved his goal |
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Posted: 6/29/2023 4:11:59 PM EDT
[#32]
Theres been some discussion into the transportation of the sub to diving sites. Pulled behind the ship on a platform that was subject to days of being pulled thru stormy seas and the way the frame tied down to this platform and is tied to the end caps and could have subjected the ends of the hull to stresses and possible deformity of the end caps area where it meets the CF hull combined with everything else
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Posted: 6/29/2023 4:21:07 PM EDT
[#33]
Quote HistoryQuoted: From reading and videos I believe Rush may have been envisioning his company as the gatekeeper to a world full of inexpensive, off the shelf, carbon fibre submersibles. His idea wasn't primarily to dive the Titanic. That just funded his ,research" and got the name out there. For him, the goal was to actually make a deep diving CF submersible or die trying. He had hopes to contract deals with the oil and gas companies after developing a reputation from its dives to see the Titanic wreckage. He said they spend about $16 billion a year on submersible robots to service oil and gas platforms. He was hoping to eventually land billion dollar deals with them. He knew the Titanic expeditions would eventually slow down so this was his main goal. |
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Posted: 6/29/2023 4:21:48 PM EDT
[#34]
Quote HistoryQuoted: Theres been some discussion into the transportation of the sub to diving sites. Pulled behind the ship on a platform that was subject to days of being pulled thru stormy seas and the way the frame tied down to this platform and is tied to the end caps and could have subjected the ends of the hull to stresses and possible deformity of the end caps area where it meets the CF hull combined with everything else That's a good point. Plus, the barge was 2 barges somehow connected. But even in this picture you can tell it's no very rigid as the barges are making a V shape as I highlighted using a line in the picture. That was probably putting a lot of stress on the sub depending on how they attached it to the barge.  Attached File |
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Posted: 6/29/2023 4:27:27 PM EDT
[#35]
Food for thought:
Rush isn't the first guy in human history to die trying. He's also not the first guy to take others down with him. |
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Posted: 6/29/2023 4:31:03 PM EDT
[#36]
Quote HistoryQuoted: That's a good point. Plus, the barge was 2 barges somehow connected. But even in this picture you can tell it's no very rigid as the barges are making a V shape as I highlighted using a line in the picture. That was probably putting a lot of stress on the sub depending on how they attached it to the barge. https://www.ar15.com/media/mediaFiles/167167/2023-06-29_15_20_24-oceangate_barge_-_Go-2868004.JPG That thing weighed 21,000 lbs. I bet that ties down pictured pulling on the rear titanium end cap isn't helping that glue. |
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Posted: 6/29/2023 4:35:50 PM EDT
[#37]
If the implosion was after they dropped ballast but before actually seeing the wreck then they definitely knew it was coming.
Given how intact the back part of the sub is I wouldn't be surprised if they can get video and telemetry off of the thing. Would be wild to watch. |
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Posted: 6/29/2023 4:40:46 PM EDT
[#38]
Quote HistoryQuoted: Theres been some discussion into the transportation of the sub to diving sites. Pulled behind the ship on a platform that was subject to days of being pulled thru stormy seas and the way the frame tied down to this platform and is tied to the end caps and could have subjected the ends of the hull to stresses and possible deformity of the end caps area where it meets the CF hull combined with everything else Flexing of the platform and how rigidly they attached the Titan to it is a very valid concern. However, the ends caps wouldn’t just pop off once deeply submerge if the glue joint was compromised. They could’ve been held with silly putty as long as it stayed together until submerging. Once it is deeply submerged, the water pressure is going to press the titanium end caps to the carbon fiber tube, just like how they got away with just 17 bolts to hold the end caps onto the rings. I found that thinking of the Titan as an extreme vacuum chamber helps me to grasp the forces involved. The rings or end caps aren’t going to pop off if there’s vacuum holding them on. |
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Posted: 6/29/2023 5:01:44 PM EDT
[#39]
Quote HistoryQuoted: He had hopes to contract deals with the oil and gas companies after developing a reputation from its dives to see the Titanic wreckage. He said they spend about $16 billion a year on submersible robots to service oil and gas platforms. He was hoping to eventually land billion dollar deals with them. He knew the Titanic expeditions would eventually slow down so this was his main goal. Quote HistoryQuoted: Quoted: From reading and videos I believe Rush may have been envisioning his company as the gatekeeper to a world full of inexpensive, off the shelf, carbon fibre submersibles. His idea wasn't primarily to dive the Titanic. That just funded his ,research" and got the name out there. For him, the goal was to actually make a deep diving CF submersible or die trying. He had hopes to contract deals with the oil and gas companies after developing a reputation from its dives to see the Titanic wreckage. He said they spend about $16 billion a year on submersible robots to service oil and gas platforms. He was hoping to eventually land billion dollar deals with them. He knew the Titanic expeditions would eventually slow down so this was his main goal. Why would they want to use his glued together subs when they could get perfectly good deep sea ROVs that didn't have required a ziplock bag shitter next to the front view hole |
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Posted: 6/29/2023 5:07:28 PM EDT
[#40]
Quote HistoryQuoted: Flexing of the platform and how rigidly they attached the Titan to it is a very valid concern. However, the ends caps wouldn’t just pop off once deeply submerge if the glue joint was compromised. They could’ve been held with silly putty as long as it stayed together until submerging. Once it is deeply submerged, the water pressure is going to press the titanium end caps to the carbon fiber tube, just like how they got away with just 17 bolts to hold the end caps onto the rings. I found that thinking of the Titan as an extreme vacuum chamber helps me to grasp the forces involved. The rings or end caps aren’t going to pop off if there’s vacuum holding them on. Quote HistoryQuoted: Quoted: Theres been some discussion into the transportation of the sub to diving sites. Pulled behind the ship on a platform that was subject to days of being pulled thru stormy seas and the way the frame tied down to this platform and is tied to the end caps and could have subjected the ends of the hull to stresses and possible deformity of the end caps area where it meets the CF hull combined with everything else Flexing of the platform and how rigidly they attached the Titan to it is a very valid concern. However, the ends caps wouldn’t just pop off once deeply submerge if the glue joint was compromised. They could’ve been held with silly putty as long as it stayed together until submerging. Once it is deeply submerged, the water pressure is going to press the titanium end caps to the carbon fiber tube, just like how they got away with just 17 bolts to hold the end caps onto the rings. I found that thinking of the Titan as an extreme vacuum chamber helps me to grasp the forces involved. The rings or end caps aren’t going to pop off if there’s vacuum holding them on. It wasn't just the end caps popping off into the hull that was the concern, it was the constant motion of the seas while towing it on those 2 barges tied together so putting stresses and moving around the Ti end caps to the carbon fiber would otherwise damage it not as it was new ever so slightly so that at 6,600 psi there wouldn't be much wiggle room that when those end caps would put the stresses on already possible weakened every so slightly ends of the hull |
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Posted: 6/29/2023 5:20:26 PM EDT
[#41]
I still don't understand why you wouldn't run at least 2'' titanium or steel rings all the way down the CF to prevent it compressing in the middle [especially] because as it pushes in, the stresses on the glued area to the end caps would be immense.
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Posted: 6/29/2023 5:29:33 PM EDT
[#42]
Quote HistoryQuoted: I still don't understand why you wouldn't run at least 2'' titanium or steel rings all the way down the CF to prevent it compressing in the middle [especially] because as it pushes in, the stresses on the glued area to the end caps would be immense. From what everyone has said, the CF/epoxy matric was, for all practical purposes, no advantage over a straight epoxy, in terms of compressive strength. So I don't understand why he bothered with the CF in the first place. Just make the whole thing out of thicker Ti. *shrug* On a different note.... You guys who've been aboard real submarines at depth - do the hatches leak? A sub at 1000' will have ~440PSI on the hatch seal. And in contrast to these really deep-diving things, a conventional sub doesn't have a finely machined seal between hull and hatch. They have a swing-shut metal cap that gets bumped, corroded by seawater, kicked, probably gouged when men and gear are going in and out.... Do regular submarine hatches leak? How do they seal? |
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Posted: 6/29/2023 5:51:10 PM EDT
[#43]
Quote HistoryQuoted: From what everyone has said, the CF/epoxy matric was, for all practical purposes, no advantage over a straight epoxy, in terms of compressive strength. So I don't understand why he bothered with the CF in the first place. Just make the whole thing out of thicker Ti. That statement, or similar ones, have been made over and over in here but not by anyone who has a background in composite structures. If it were true there wouldn’t be a bunch of commercial and military aircraft flying around with composite upper wing skins. It handles compressive loads just fine. It’s also very resistant to fatigue and has a long track record of being successfully bonded to titanium. However all of those feats are only possible if you pay old white guys to figure out how to implement it properly. I think in the end the ignorant GD material scientists will be proven correct, in a sense, but not for any of the reasons they think. |
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Posted: 6/29/2023 5:54:53 PM EDT
[#44]
Another dumb question:
If lets say, it was the window that failed, would the fact that it protruded away from the curvature of the front titanium plate, thus giving the sea pressure more force to exert on it? I'm noticing other deep see vehicles having a flat front to their windows, not to mention much smaller openings. |
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Posted: 6/29/2023 6:17:36 PM EDT
[#45]
Quote HistoryQuoted: Flexing of the platform and how rigidly they attached the Titan to it is a very valid concern. However, the ends caps wouldn’t just pop off once deeply submerge if the glue joint was compromised. They could’ve been held with silly putty as long as it stayed together until submerging. Once it is deeply submerged, the water pressure is going to press the titanium end caps to the carbon fiber tube, just like how they got away with just 17 bolts to hold the end caps onto the rings. I found that thinking of the Titan as an extreme vacuum chamber helps me to grasp the forces involved. The rings or end caps aren’t going to pop off if there’s vacuum holding them on. Why concentrate on the end caps? The pressure would have been squeezing the tube too, with the middle theoretically being the weakest part since its further away from the end caps that could support the tube better at the ends. So my thought is, the implosion in the tube could have produced enough force to blow the ends out. |
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Posted: 6/29/2023 6:29:33 PM EDT
[#46]
Quote HistoryQuoted: From what everyone has said, the CF/epoxy matric was, for all practical purposes, no advantage over a straight epoxy, in terms of compressive strength. So I don't understand why he bothered with the CF in the first place. Just make the whole thing out of thicker Ti. *shrug* On a different note.... You guys who've been aboard real submarines at depth - do the hatches leak? A sub at 1000' will have ~440PSI on the hatch seal. And in contrast to these really deep-diving things, a conventional sub doesn't have a finely machined seal between hull and hatch. They have a swing-shut metal cap that gets bumped, corroded by seawater, kicked, probably gouged when men and gear are going in and out.... Do regular submarine hatches leak? How do they seal? Two nicely machined surfaces with one having a small oring/gasket. We had hatch covers that get installed while they are open to prevent damaging them when passing through or moving equipment. Prior to closing they get wiped down and inspected, and then watched as they are closed to ensure nothing falls on the seating surface. Then then get tightened down which is just a ring(or dogs that are just fingers) that rotates to interface with lugs on the opposite side so it can't come loose. There was an inner and outer hatch, so 2 separate sealing surfaces that would get closed and inspected separately. I don't recall ours ever leaking. Like you said, it's a significant pressure which seats them pretty well. One of the things we had to do after shipyard was at one of the hatches which involved checking it shut while at test depth. We were warned to not go crazy when checking it shut because of compression, and we would potentially have to come back down to loosen it up since it could be too tight to reopen once we surfaced. Behind Rickover is the upper hatch cover with gasket around the middle of the ring and near his waist is the flat hatch ring. This doesn't seem to have a cover on the bottom, which could be due to recently opening the hatch and not installing it yet or not using them at the time. 
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Posted: 6/29/2023 6:38:50 PM EDT
[#47]
Quote HistoryQuoted: From what everyone has said, the CF/epoxy matric was, for all practical purposes, no advantage over a straight epoxy, in terms of compressive strength. So I don't understand why he bothered with the CF in the first place. Just make the whole thing out of thicker Ti. *shrug* On a different note.... You guys who've been aboard real submarines at depth - do the hatches leak? A sub at 1000' will have ~440PSI on the hatch seal. And in contrast to these really deep-diving things, a conventional sub doesn't have a finely machined seal between hull and hatch. They have a swing-shut metal cap that gets bumped, corroded by seawater, kicked, probably gouged when men and gear are going in and out.... Do regular submarine hatches leak? How do they seal? Dive bell hatches are sealed with an O-ring. Typically 3/8” diameter 70 or 90 durometer buna-n. The o-ring stands proud enough of the ring groove to deal with minor surface damage. Surfaces are preferable SS clad, but not all are. Of course, this is for internal pressure, not external, but the idea is the same. ETA, lip seals are often used also, but those can be a bit of a pain. If the sealing surface is damaged to the point it will not pass the leak checks, you call in the experts to re-machine things, Which can be a bit spendy. Of course, most leaks are caused by o-ring damage. |
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Posted: 6/29/2023 7:15:57 PM EDT
[#48]
Quote HistoryTalk about a shitty FEM That doesn’t even model the boundary condition properly in any way |
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Posted: 6/29/2023 7:32:09 PM EDT
[#49]
Quote HistoryQuoted: Because it was a flat cylinder. No end domes to wrap a helical wrap around. Still wouldn’t have made a difference in this application. The shape is not the only reason why you wrap in the way they did In a pressure vessel (thin wall) you have two main sources of stress, which are hoop and loop stress, as shown in the image below. As sigma L (loop) and sigma H (hoop)  Attached FileThe reason they laid 0 and 90 deg plies down was for hoop and loop stress. Now in the case of this pressure vessel you also have compressive forces being applied be the domed ends which probably lead to a buckling failure mode. I’m not up on my thick wall math but I suspect that because the wall is thick you have bending forces involved now too. 45s on outer skins can help prevent global buckling and layering of 0,90,45,-45 plies can create a material known as quasi-iso or quasi-isotropic. Basically since carbon fibers are, well fibers, their properties are not symmetric. Unlike most metals where if I take a cube and apply a force on any one side it responds the same way, with anisotropic materials like composites the response depends on the orientation. Making a structure Quasi iso can be nice to simplify math and prevent unexpected failure modes since the material now behaves much closer to an isotropic material, though not perfectly. The “45s” on a dome are acting as zeroes and 90s because they are on a domed surface. I’m still surprised they had absolutely no 45s or didn’t go quasi iso because while it theoretically makes your material usage more efficient it can lead to some unexpected failure modes. Also since the whole thing is under compression global buckling seems like it would have, or should have, been a considered failure mode. Your paintball canister almost certainly also has 90 and 0 plies because they are so necessary for the hoop and loop stress failure modes of the main cylinder. |
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Posted: 6/29/2023 7:40:23 PM EDT
[#50]
Quote HistoryQuoted: plus they're fucked up the plot scaling, so that it looks like a pretty benign loading. it should be solid red all over I could model it in fibersim but it would be a waste of my time without knowing a lot more about the exact details of their ply schedule. Odds of random YT channel picking some random CF property built into SW… very high. |
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