Comments by "Keit Hammleter" (@keithammleter3824) on "Oceanliner Designs"
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Mike claimed twice (at beginning and near the end) that growler or iceberg ice is harder than rock. That is very hard to accept. Such ice is somewhat harder than the ice you make in your fridge, because it has been compressed and contains no air bubbles. But iceberg ice is very pure H2O - you can melt it and drink it. Thus standard engineering tables are valid - the standard figure for ice well below freezing is 5 MPa. Iceberg ice has a compressive strength upwards of 5 MPa to an estimate of about 8 MPa deep inside the berg. Effectively the ship is hitting 5 MPa.ote
Stone has a compressive strength of 30 to 50 MPa depending on type (ref UKCSA).
Alternatively, you can look at the Mohs scale, which measures scratch resistance. Ice has a Mohs hardness of 2, whereas most rock is in the range 6-8. Note that the Mohs scale is sort of logarithmic, so 6 is not 3 times as hard as 2; it is about 12 times.
Or you can look at the Vickers hardness, which is an indentation test. Ice is 1.5 to 2 Vickers. Stone is not easy to measure on Vickers, but typically exceeds a few hundred. Even limestone, very soft by stone standards, exceeds 100 Vickers.
Some people think that since ice holes steel ships, it must be hard. This is not so. Icebergs hole ships because the volume of ice is such that the inertia of the iceberg means that the ice in contact has nowhere to go. Although steel has a strength upwards of 250 MPa, its only thin, so there is little inertia in it and it can move out the way.
Its the same as if you dive into water from a great height - water has a compressive strength of zero - but you can be bruised or even seriously injured, because at the speed you hit the water, the water you hit doesn't have time to get out of the way.
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I imagine it's much like emergency evacuation of a multi-story building, only worse. I was at one time a fire warden on my floor of a 20 story office building. We had a fully developed evac plan which we rehearsed. The first time we announced that there would be a drill in 2 day's time. On the day it went reasonably well, we got the whole building evacuated in 15 minutes. The fire warden team then held a meeting and we discussed lessons learnt. We then, a few weeks later, held another pre-announced drill. It went real smooth, we got everybody out in the target time of 12 minutes.
A few months later, we decided to have an unanounced drill. We got the city fire brigade to help make it realistic - they turned up with their truck sirens going. The drill was shambles. Some people panicked. Some people refused to leave their desks. Some cleared out without getting clearance from their warden. It took over 30 minutes to clear the building. And buildings don't tilt or fill with water. Our evac plan involved the phased entry of staff on each floor entering the stair wells so that the maximum number of people could be in the stair wells with gaps between groups of people so that there was no bunch-ups or congestion. It worked perfectly in the pre-announced drills, but not in the unannounced drill.
But I've worked in other buildings that made that look really good. In a 7-story building, an evac drill was so badly run that it took 40 minutes to clear the building - wardens trying to control people with load hailers with flat batteries didn't help. In that same building, when a fire alarm was triggered, big fans automatically pressurised the stairwells so that fire on any floor would not enter a stairwell. Trouble was, women found the stairwell doors unexpectedly hard to open due to the pressure and panicked.
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That men could outlive the burning of a candle is not as surprising as it might seem. In server (computer) farms, which are installed in windowless secure rooms, they don't typically use normal water sprinkler fire suppression, as water on electronic devices just makes fires worse. Instead they use gas fire suppression.
Gas fire suppression relies on the fact that the human body keeps its blood at saturation oxygen levels at all times, therefore breathing depth cannot be controlled from oxygen level. Instead, the body adjusts breathing based on the blood carbon dioxide level, which is normally very low, as is the level of CO2 in the atmosphere - its basically only a trace.
This means that you can halve the level of oxygen in the room, and provided you double the concentration of CO2, everybody breathes just fine, though their ability to perform intense exercise would be diminished. But at half oxygen level, most flames go out. I once witnessed a test gas dump in a computer room. I did not have any discomfort, though I did automatically breath a bit deeper.
A similar system is used to put out flightdeck electrical fires in aircraft.
People have trouble on high mountains where the oxygen pressure is reduced, because the CO2 level is also reduced, so the body exhales CO2 more easily, and thus compensates in the wrong direction and blood oxygen level falls.
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@PsRohrbaugh Submarines have been made with tanks open to the sea at the bottom. Submarine range is limited by how much fuel they can carry, and is never really enough. By venting some fuel tank space to sea, the fuel can be blown out by compressed air, which is nice to have if you have been depth charged and nothing works properly and you are otherwise going to sink to the bottom and die. Having valves instead of just holes is not good as they might seize. Or you can just push out some fuel, pushout some floatable junk via the torpedo tubes, and sneak off, hoping the enemy thinks he has holed you hull and you are finished.
Note that submarines have always run on regular diesel fuel, which has a specific gravity of 0.875, less than big ship bunker fuel with SG 0.95. So the chance of mixing due to rough weather is a lot less.
I don't think surface ships had fuel tanks open to sea.
You may be thinking of the World War 2 construction of British warships, particularly aircraft carriers. These were built with a "third skin" outside the armoured hull. The third skin was open to the sea via vent holes at the bottom. The idea is that enemy torpedoes would be detonated on striking the third shin, and relatively harmlessly blow the water out between the third skin and the hull. The space was never used for fuel.
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@rock-t3d2k With typical glacier ice, entrained rock, whether rock/dirt powder or large boulders, is on the bottom of the glacial thickness, which is typically 300 to 2,000 metres. This bottom layer containing entrained matter soon melts off, so by the time the bergs get near ships, there is no entrained/captured rock. Certainly not the growler ice that were the broken up remains of a glacier berg that hit the Explorer.
In any case, any entrained rock dust or small boulders would merely abrade a ship's hull and no hole it, as the ice substrate would not hold it in place against the locallised stress.
Note that ice is not a true solid. It is a plastic, this means that anything heavy trapped in it slowly migrates to the bottom. Rock is typically 8 times heavier. Thus the rate at which icebergs loose entrained rocks is faster than the rate of melting would suggest, especially the larger the rock size, since mass goes up faster with size than does surface area.
The sculpting of landscape by glaciers took place over millions of years.
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A minor error by Mike: He said the engines were diesels started with petrol. Actually, the design called for compressed air starting, as was common with marine diesels. However the compressed air system was not going to delivered in time for the scheduled flight, so they fitted a small "pony" engine to start each propulsion engine, just as a small 2-cyl engine was used to start Caterpillar tractor engines prior to the 1970's. An electric starter motor system as used in cars, adequate to start the diesels at altitude, would have been much heavier. As with the Caterpillar, the small pony engine was a gasoline unit. Had the R101 not crashed, when the compressed air starting system arrived, the gasoline pony engines would have been removed.
Mike erred in using a DC3 as yardstick. The DC3 first flew 6 years after the R101 - due to rapid progress in aircraft technology, really a different era.
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To large extent, the arguments presented do not make sense. At 5:13: "Launching lifeboats is dangerous for passengers, so let's not worry about having enough lifeboats." That's replacing risk of death with certain death. Later in the video: Using lifeboats to escape in is dangerous due to weather and sea conditions. So let's just use lifeboats to make multiple trips back and forth between the doomed ship and the rescue ship. Yeah, sure. If it's dangerous to make one trip in a small open boat, it's dangerous to make several trips.
Also stated in the video: The Titanic had safety features e.g., watertight compartments, radio, so that it should float long enough for rescue vessels to arrive. That makes some sense, but not a lot. What if it is caught in a heavy storm that delays lifeboat launching? What if it is not operating in a heavily used sea lane?
Oceanliner Designs says Harland and Wolfe were not seeking to cut costs and were keen on safety. But what is very clear here is that it is a classic case of legal requirements (lifeboat capacity related to hull size) not keeping place with advances in technology - allowing prvate industry to skimp on what they provide.
In a more ideal world, Harland & Wolfe would have said to themselves "We are legally required to provide x lifeboat capacity. But we are building a ship that is outside the passenger capacity parameters anticipated by the Board of Trade. Therefore we should honour the INTENT of the requirement, not just the literal words of the rule."
But of course, being a profit making company building for another profit making company, that's just what they did not do.
Never mind the excuses. Harland and Wolfe in combination with White Star are at fault, for not providing a means by which everyone could be rescued, even under ideal conditions.
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@DerpyPossum : Your last sentence: "They did everything they could ....." is very clearly wrong. It's wrong because the sister ship Olympic underwent a major refit as a result of the Titanic loss. The refit was driven partly by loss of public confidence in the Olympic class, and partly because of crew industrial action. Further, the third ship of the same class, had major design changes during its construction, again because of the Titanic loss.
If they could do it after the accident, they could have done it before - the only thing stopping them was competitive pressure and lack of ethics. This is self evident.
Asking "what if" in regard to safety is a standard ethical requirement of professional engineers, and has been since before Titanic. As I explained, it is not part of BoT ethics - such boards cannot anticipate technical innovation, such as the advent of 50,000 tonne liners carrying 3,300 people.
Your smartphone analogy is not a good analogy because under no circumstances can smartphones be lethal - unless you use one to batter someone to death, and that would clearly be criminal action.
A better analogy is airliners. When Boeing started to make jumbo jets, they asked "what if" in a formal process called FMEA (Failure Mode Effects Analysis) and that told them if the flight control cables failed the airplane would crash and all people would die. So their triplicated the control system with separate routing. There was no legal requirement to do so. They did it anyway, because their engineers were professionals. Unfortunately, Douglas only complied with industry norms, and several Douglas plane-loads of people died.
Lastly, as I said before, the concept of using lifeboats as ferries between ships on the open sea came from the industry, not the BoT. You are wrong there. The BoT just accepted it, until the Titanic accident showed they could not.
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Mike seemed to represent the 1958 movie A Night To Remember as pretty good. I saw this movie about 45 years ago, and at that time I thought it was good but not that good. Mike caused me to watch it again.
It's not that good. There is too much emphasis on the Titanic being supposedly unsinkable - dialog from the owner, the captain, passengers all stating that it can't sink. This unsinkable nonsense arose from newspaper articles tizzed up by second rate journalists. NOBODY in the shipping industry would have believed any ship could be made unsinkable, certainly not the builders and certainly not ship's officers.
There are too many obvious bloopers that distract your attention and ruin the intensity of the story. Possibly the movie was badly edited. dining room floors go from level to a 10 degree tilt then back to level again, then back to tilt again in consecutive scenes, then suddenly go to 20 degrees. Some events seem to be out of sequence.
A scene showing the Titanic from a distance showing the front going down at about 500 mm per second. That's way WAY too fast.
People in lifeboats some distance away from the ship were shown as hearing the band. There was no way that could happen. No amplification back then - the racket of all those people trying to yell their way into the boats would mean they couldn't hear the band either.
The movie did not show the ship breaking apart and the stern consequently, having risen up, falling back down then rising up a second time. This is understandable, as it wasn't not conclusively established that that the hull spilt until after the wreck was discovered.
Interestingly, when the berg is sighted, the movie has officer of the watch give an order "Full Astern Both" (engines - note that the centre engine was not reversible and would be automatically stopped by an order to reverse both). There has been ongoing differing views as to whether the order was to reverse engines, or was to stop them, including by Ocean Liner Designs - who as I recall thought it was an order to stop.
An order to stop both makes absolutely no sense, as the iceberg was too close to stop before hitting it - their only chance was to steer around it. Ordering Stop Both would kill rudder authority and make steering around the berg impossible. Inertia of the ship would simply keep it travelling until it hit the berg head on. We know it almost succeeded in going around the berg.
An order to reverse both would not save them, but is understandable as the officer had only a few hours on Titanic and most likely reacted automatically with an order correct for the ship he had last served on - which had no centre turbine. Titanic had only one rudder, so ordering Astern Both would not kill rudder authority but would seriously weaken it.
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I'm sorry, Mike, but you still have this in quite a mess, and added errors that were not in your engines video.
1. You have omitted the presence and important role of the feedwater heaters. They result in considerable coal saving. I have explained feedwater heating in another post to this video. Refer that post or the Shipbuilder Olympic class Special Edition June 1911 page 63.
2. You have re-stated that the steam pressure into the turbine as 9 Lb/in^2 absolute. I showed in another post to this video that a pressure that low could not be employed - it would result in too low a turbine exhaust temperature and thus cause condensation to water in the later blades of the turbine. This would result in loss of power and rapid turbine blade failure and thus would never have been allowed. Refer that post or the US DoE Steam Turbine Calculator.
3. At 5:51 you said that the "[double bottom] ... stood about 5 feet above the keel." This will mislead many if not most people, as the bottom of the double bottom is in contact with the sea - there is no projecting keel as there is in a sailboat.
4. (Minor error) At 6:23 you said feedwater needs to be topped up from the distilling plant due to evaporation and contamination from grease etc. Evaporation is basically what a boiler does - evaporation loss should not occur as nowhere in the system is water in contact with the atmosphere. The main causes of loss of feedwater are:- a) the need to blow down each boiler and clean the fire tubes periodically, b) leaks via imperfect seals; c) operator error in turning valves etc. The need to shut down each boiler in turn to clean it is why more boilers were provided than necessary for the steam consumption of the various engines and auxiliaries.
Many ships continually drained off a small amount of feed water and dumped it into the sea to prevent contaminant buildup, instead of doing boiler blow-downs as frequently, but I don't specifically know if the Olympic class did this.
5. At 9:15 thereabouts you stated that condensation in the steam pipes meant a need for steam separators. Separators were required anyway, because the steam from a continuous-flow boiler such as the Scotch boiler used in Titanic can only be wet steam, as there has to be liquid water in the boiler. To get dry steam, you would have to heat the water above the boiling point at the working pressure - that would mean no liquid water could be in the boiler to boil. Steam pipes were lagged (insulated) and condensation in the steam pipes should be minimal. This is why superheating has to be done after the boiler and not within it.
6. At 9:16 you stated that superheating heated the steam "high above the condensation temperature". That's true, in steamships generally, but it is a misleading statement. It misses the point. Superheating is not about adding lots of heat, it is about heating a liquid above the CRITICAL POINT TEMPERATURE (for H2O, 374 C or 705 F). This may or may not be well above the boiler temperature. For a boiler pressure at almost the critical point pressure (3200 Lb/in^2 for H2O) the temperature would be raised only slightly.
The critical point of a substance is the the combination of temperature and pressure that determines whther the substance can only exist as a pure gas or not. Raise it above the critical point temperature and it can only be a gas, regardless of how low the pressure is, so long as the pressure is below the critical point pressure. Superheated steam obeys the kinetic gas laws and thereby increases steam engine efficiency. Superheated steam can only be dry steam, as you have realised.
7. In the indicator diagram you showed at 13:24, you shaded the area below 14.7 Lb/in^2 absolute, and it looks like covering 1/3 the graph. You claimed that it means you get 1/3rd the power in the steam by operating below atmospheric pressure. THIS IS NOT SO. That would mean the top of the graph is at 2 atmospheres pressure. It appears from the hard to read numbers that the vertical scale is logarithmic, not linear. So the top of the graph is not 2 atmospheres, it is 10 atmospheres. In any case, Titanic's steam pressure was 14.6 atmospheres.
The turbine was able to contribute 1/3 of the total shaft output power not because there was 1/3 the energy still left in the steam, it was because turbines are about 4 times more thermodynamically efficient that reciprocating engines.
8. You claimed at 13:32 that the turbine "would actually assist the main engines by drawing steam through them. Clearly that is ridiculous. If the reciprocating engine exhaust steam went straight to the high vacuum of the condensers, a greater expansion could be designed for in the reciprocating engines and they would both be more efficient AND produce more power. The turbine is an impedance to the recip engines, not an aid. The recip engines without a turbine could produce not as much efficiency and power as the whole hybrid system, but more than they did in Titanic never the less.
9. At 13:50 you state that the condenser vacuum is created by the cooling of the steam. Clearly that is nonsense. A condenser is in essence a pipe through which the steam goes through, with cold water on the outside on the pipe to carry away the heat. In Titanic, the condensers were a very great number of pipes receiving the steam in parallel, but the principle is the same. Whatever is the pressure at one end of the pipe must be pretty much the same as at the other end. What creates the vacuum is the feedwater pumps drawing the condensed water out. Sure, a volume of steam condenses to a much small volume of water, but that isn't what creates the vacuum. If it wasn't for the pumps, the water wouldn't get sucked out and you would have no vacuum.
10. At 14:34 you stated that James Watt's engine ran purely at a vacuum. This is not so. Only the condenser was operated at a vacuum (about 0.1 atmosphere) by spray cooling. Steam pushed the working piston up. (Later Boulton and Watt used double action). Steam pressure in Watt's engines was about 7 to 10 Lbs/in^2 above atmospheric.
Possibly you were thinking of Newcomen's engine, in which steam at minimal pressure was admitted to the cylinder, than a jet of cold water condensed the steam within the cylinder, allowing atmospheric pressure on the top of the piston to push the piston down.
Newcomen engines were absolutely dreadfully inefficient, partly due to minimal steam pressure and partly because a lot of steam was wasted warming the cylinder up again at every stroke. When I was at university, the technicians had built a Newcomen engine about 1.5 metres high - it had so little power it couldn't overcome it's own friction.
11. At around 16:35 you compare Titanic's coal consumption (600 tones per day) with the roughly similar size Lucitania (1000 tonnes per day), stating that it showed Titanic's power plant was ver efficient. That is not a valid conclusion. Titanic cruised at 21 knots, Lucitania cruised at 24 knots. The power required to overcome drag rises as to the cube of speed, so with all other things equal, we should expect Lucitania to need 600 x (24/21)^3 i.e., 895 tonnes. But all other things might not be equal. It would take a lot of research to get a definitive answer.
12. At 17:23 you stated that Titanic's powerplant was "engineering genius". Hardly. Harland & Wolf tried the hybrid reciprocating/low pressure turbine configuration only once before (in 1909), and never went back to it. No other ship builder tried it. The fact is, a pure turbine installation is FAR more efficient. The reasons why the Olympic class got the hybrid system is that Harland & Wolf had a large skilled and semi-skilled workforce that made reciprocating engines in house and all relevant patents had expired. To use turbines they would have had to purchase them, so using reciprocating engines saved White Star capital expense, and delayed the point at which H&W had to start laying people with obsolete skills off.
Titanic's plant was competently designed but very much a compromise imposed by business constraints. The turbine was not used in an optimal way and could only be used when proceeding ahead at full cruising speed or close to it.
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@JedRothwell You have repeated a claim that has been made since the tests were done. But if you read the actual NIST report, the sulphur level was excessive by the standards of the day. There was a claim that over the decades, the iron could have absorbed sulphur from the sea, but this was shown to be insignificant.
However, NIST found that sulphur wasn't the main problem - it was just a contributing factor. The rivets contained really excessive amounts of slag from a bad manufacturing technique, which seriously weakened them. Hence plates parted from the hull from the shock propagating along the hull - plates that the iceberg had not hit.
Since NIST is a US agency with a world-wide reputation for scientific expertise and rigor, if NIST says the rivets were defectively made, then as far as I am concerned, the rivets were defectively made.
Slag inclusions is a problem that has been known about ever since man has been making cast iron and wrought iron. Long before Titanic. As a competent shipyard, they should have been testing samples of rivets, but evidently didn't or didn't do enough.
Harland & Wolf were a bit dodgy back then, focused on saving costs. It has been found in old records that they knowingly put cheap rivets in parts of the hull they thought should see less stress. Which was where the berg hit.
You can download the NIST report from their website.
See summary at https://www.nist.gov/nist-time-capsule/nist-beneath-waves/nist-reveals-how-tiny-rivets-doomed-titanic-vessel
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