I used to be a professional merchant marine deck officer, and one thing that drove me freaking crazy was on the Coast Guard exams, if you wanted to get a math question exactly right, which was important because of the way the tests worked, you had to take any number with a decimal point, round it to the 4th place, and keep going.... however, when you had to use nautical miles, if you wanted to get the answer exactly correct, you had to consider 1 nautical mile to be 6080 feet. 1 nautical mile is not 6080 feet. It is 6076 feet. Apparently, it was critical that I kept decimal places accurate enough that I needed to go down to the nearest 1/10,000th of any incriment, but when we were doing nautical miles, it was completely A-OK to be a full 4 feet too long. That's more than an entire meter... That's a whole 0.0658 of a percent off... I'm supposed to be accurate to the nearest 1/10,000th, and 6080 feet in a nautical mile is off by 2/3rds of 1/10th of a percent. That's a much larger amount of "rounding error" and it makes me mad still, 13 years later.
Oh man, I absolutely despise when tests require you to use bad information and/or have an incorrect “right” answer. I can appreciate it still bothering you after all those years.
oh man, Dutch merchant navy here, we'd do meters. But yeah I can feel your furiation. We where pushed with the same need for accuracy tho, but did not have an outdated definiation for a nautical mile.
Never been a sailor or in a military unit so forgive me that the I was ignorant about how good at math you needed to be to be a good sailor! I still remember high school boys declaring they would have no use for math in the real world! I am totally impressed!
@@julieenslow5915 Yeah, I knew those guys. I am an engineer so using math is second nature. When I watch people struggle trying to figure gas mileage, percentages or simply add scores in a card game it really pains me. Have a friend with advanced degrees in business who is in upper management with that big mouse outfit in Orlando. He wanted so bad to be a part of the innovation and design bunch but got passed over for his lack of math skills. He actually went back to school to pick up the knowledge he needed and landed his dream job. Math, we use it everyday.
'Chip logs' on old sailing ships had another interesting quirk. One leg of the three ropes wasn't tied directly to the 'chip' but attached with a wooden peg tied to the line. After taking the reading, the sailor could give the line a sharp tug, pulling the peg loose. This allowed the chip to turn edgewise and the sailor could then pull it back in quite easily. Reinsert the peg into the chip and ready to go again.
I love how we get a back room look on how you guys do research with the battleship and rediscover these small hidden gems. It really puts into perspective how easy it is to lose knowledge. Thanks for keeping it safe
The EM Log sensor sounds like an open channel magnetic flow meter. The salt water passes through a magnetic field and generates a current in a wire loop. The current is proportional to the velocity of the water passing by. This is a very common flow meter in the process industry.
Very interesting. Though i would imagine if you had different kind of saltwater (less or more salt leading to more or less resistance) you would also get different readings for same velocity of water passing by, though, proportionally to the resistivity of water... Right?!
But he did say when going from one body of water to another they would have to recalibrate for salinity so basicly you would check the salinity and change the range of the sensors accordingly to get a accurate speed reading
My favorite videos are the ones where you go to places that haven’t been painted/ renovated. I went aboard the USS NC also many times the guys got to know me. One day they took me deep in the ship where few people get to go. It was the best experience I have ever had on a museum ship. It was incredible, you could feel the pulse of the ship. I will come to NJ some day and take the tour.
The Nautical mile was originally defined as the meridian arc length corresponding to one minute (1/60 of a degree) of latitude, which is way easier to calculate where you are on a globe without the need for complicated conversions (such as from "yards" or "feet").
And a kilometre was the metric equivalent being 1/40000 of the circumference of the Earth. Which is where gradians comes in with 400 gradians for a full circle… (The measurement was a bit out so the length of a kilometre was a bit out because the Earth isn’t a sphere).
@@allangibson8494 nautical miles and meters are fundamentally different measures. The SI meter is a linear distance measure, they just mistakenly tried to define it by the earth's circumfrence. A true nautical mile is a sort of angular unit for positional navigation and is always one minute of angle regardless of the local radius of the earth(meaning a nautical mile is not a fixed distance). There are some false nautical miles that have been subsequently defined for use with speed calculations, which are averaged linear-distance equivalent units. I suppose its sort of how people tend to mix units of force and mass because they happen to be conveniently interchangable for every day tasks on earth's surface. But none the less a pound is a unit of force and kilogram a unit of mass.
@@mytech6779 The nautical mile and meter have exactly the same origin - the physical dimensions of the earth. The base angular dimensions were differently defined however. Nautical miles use ninety degrees in a right angle with sixty minutes in a degree. Kilometres originally were defined by one hundred gradians in a right angle with one hundred kilometres in a geometric gradian. The SI metre deviates from this because it was soon realised that the earth both wasn’t dimensionally precise enough and inconveniently sized to be used as a reference unit but the French did use kilometres in that way for navigation into the 1950’s with a reference meridian at Paris. Historically both the pound and kilogram have been used interchangeably for both force and mass. I have worked with equipment calibrated in kg/cm2 as the unit of pressure (which is conveniently close to one atmosphere) but the variable nature of gravity makes precise repetition of calibration measurements hard in different locations (hence the switch to newtons per square meter (Pascals and kiloPascals).
@@allangibson8494 You have a fundamental misunderstanding of the difference in the use of circumfrential distance and angles. Degrees or Gradians are irrelevent to that fundamental difference. Circumfrence is dependent on radius, degrees of angle are independent of radius.
@@mytech6779 I have a fundamental knowledge of the HISTORY of metrology. The history doesn’t define the present but does help you understand how we got to where we are now and why things are the way they are. The last three centuries have been a chase for higher precision and repeatability. Our units of measurement have gone from being defined by the size of human body parts and grains of wheat to fundamental and universally reproducible constants.
We had a speed indicator on the bridge of the Dixie next to the Navigators chart table. It was always fun to watch our speed increase during the mid watch just before reaching a port and especially on the way home from deployment. The Snipes would turn up the RPM's thinking we'd get into port quicker but not thinking we would adjust our speed the next morning. I don't ever remember entering port ahead of time.
Nope, we would crank on the turns and wind up floating around killing time till our stated time. Didn't want to catch those wives saying goodbye to their boyfriends! :)
Never happened. If you watched the Log the speed would swing +/- 2 knots. we assumed that this was because the salinity of the water would very. normally the pit sward equipment was in the forward gyro space and was the responsibly of the IC gang. I was an was IC2.
@@jimnunn9232 Raising and lowering the pit sword. What a FINE incentive for a junior sailor to work on quals so that he had a legit reason to be on watch elsewhere while entering/leaving port.... IC2 (also)
On cargo ships our speed was worked out on departure for arrival time. Extra revs were added to make up for losses during the voyage. We slowed down or sped up to get there at the correct time. Except for the Ariake which always made up for lost time on departure. The shippers loved her. The big white ship always arrived a day early.
Never happened on my ship. We all knew that we had a schedule. If we arrived early, we would just do circles until our scheduled arrival. No point in adding extra heat and workload to the engine room watch standers for nothing. I was an EOW.
Interesting stuff. I have a small collection of Walker Taffrail Logs, a technology somewhere between the chip log and the E-M. You tow a "turbeller", a torpedo shaped fish with skewed fins that spins as it moves through the water. This spins the rope that's towing it. A meter mounted on the Taffrail counts the revolutions and translates that to distance traveled. Some old timers still use them.
The pit sword on a ship is the equivalent of the pitot tube on an aircraft. Both air and water are fluids you can use the same type of device to measure the speed.
I actually had two speed sensors on the little flats skiff I owned several years ago. One was a pitot tube type that came with the boat and had an indicator mounted on the dash. The other was a small "water wheel" attached to the depthfinder probe and read out via the depthfinder screen. Why two? The wiz-wheel was very sensitive, but did not work well once you were up in a plane. The pitot tube was not accurate at low speeds, but worked fine at planing speeds.
Yeah, the same is true for pitot-based airspeed indicators on airplanes. They're typically useless at taxi speeds. This is why the "airspeed alive" check is done during the takeoff run, rather than during the various checklists that are run before taking off like nearly every other system check.
The differential pressure generated by ram pressure has a square root relationship to speed. Double the speed gives four times the pressure. That basically makes them useless at less than 10% of maximum scale.
When I was a junior rating one of my duties was to do rounds at night. I had to check about 20 compartments got various things, one was the EM log compartment. I had to look down to see if there was much water in it. Sometimes the senior ratings would put a note on the inside of the hatch to make sure we were opening it - it had about 8 clasps which took ages to undo!
Lol, I get instantly Ill just thinking about that video of you crawling through the gun barrel. Like chills that won’t go away, and now I have to distract myself.
Nothing like archeology! Warships are cities--and until taken out of service, warships are almost organic with modifications, repairs, upgrades, and a human crew making use of "unused spaces" for some function that the crew needed or wanted. How many dead cables are left on the Battleship New Jersey? My limited experience with aircraft and vehicle wiring harnesses is that when a cable bundle is no longer used, it generally is too much hassle to remove and gets left in place. There has to be old cables to those speed sensor probes that ran to several locations in the New Jersey through armored decks and bulkheads.
It depends on when the jobs are done , if it's during a shorter upkeep usually the redundant cable is taken out to the bulkhead bland and made safe or to a junction box if it's a change of equipment . If it's a refit and main runs are disturbed then a lot of redundant cables are taken out and the glands may be reused .
I greatly enjoy your videos. Your intricate understanding of so huge and complex a machine as a battleship, brings me new knowledge with each program. But not without envy. How did land this plum of a job? In any event, I have been a lifelong fan of the great ships, and I eagerly await each new edition of your videos.
Between the knotted line and electronics was the Taffrail Log. The taffrail is the railing around the stern of a ship. The log is attached to the rail and counts rotations of (what looks like) an elongated propeller towed on a long braided line. A dial on the log indicated distance traveled in knots and tenths. Also known as a Patent Log. It was still used as late as the 1950s on older merchant ships. Some people that sail long distances still use them because there's no power requirement.
What you show lashed to the bulkhead is commonly known as the "pit sword". The sensing elements are actually the two round Monel buttons located in the bottom fiberglass portion. Signals from the Pit Sword would generally go to the head-end equipment in the IC Shop, then be transmitted as synchro signals to the indicator locations via the Distribution/ACO side of the Main IC Switchboard. One of the main drawbacks of the system is that all it can sense is the speed through the water at that point. If you are making 10 knots good against an 8 knot current, the Log will indicate 18 knots. I don't recall ever needing to adjust the system for varying salinity, most likely because the indicators were ignored in favor of the SatNav system which could give you a real-time display of the actual speed through the water. Pity for the FNG, as he was the one who was detailed to stand by in the bowels of the ship waiting for the word to be passed to "Raise/Lower the Pit Sword". Ours had its own little enclosed trunk in the Cargo JP-5 Pumproom, and was located 1 deck below the grates with the trunk hatch at grate level. You had to open the hatch and climb down into the trunk, where there was a grate almost large enough to stand on while cranking it up or down. Really close quarters unless you were very skinny. IC2
@@stanants8566 One would hope that the QMs were using the SatNav tools to VERIFY their plotted course on the charts, not DETERMINE it. When you get right down to it, can't spoof a paper chart and a pencil. When all else fails, There is always the two ensigns with a sextant out on the bridge wing arguing about what star they are looking at... Personally, I didn't really care, as i was just along for the ride. As long as both gyros continued to be north-seeking, stable, and in agreement with one another, my main concern was that the coffee pot was full and the ashtray empty. Sounds lazy, but if the PMS was done properly, everything pretty much just worked reliably. The exception was the MK 19 master gyrocompass system, who's accuracy was generally excellent but could suffer from a weak/failing tube. Yep, tubes. The MK 19 Control cabinet contained dozens of them. "12AX7" is permanently embossed upon my memory, even after 32 years. The further north we went, the better the chance that we would start going through tubes. We actually had the box of spare tubes bungied to the top of the cabinet. I was on the USS Kansas City (AOR-3), a Replenishment Oiler. They were somewhat anal about gyro accuracy. It's almost like we routinely sailed around with ships on both sides at a 200 foot separation or something. Fun times. IC2
A nautical mile is 1.151 or so miles, but the distance wasn't designed to be "simpler" to measure, but because it corresponded to 1 arc minute of latitude. 60 arc minutes equals 1 degree of latitude. This unit made it much easier to plot a course on a map, both tracking forward from a last known location with direction and speed, but also as a way of measuring / anticipating time as you can set your compass and project forward by 12 or 24 hour increments to your intended destination or waypoint. 15 knots, for instance, is 6 degrees of latitude per day, by setting the compass to 6 degrees of latitude from the map scale, you can plot how far in both distance and time you are from your destination, without doing any complicated conversions or maths. Actually pretty ingenious. The modern nautical mile is a little different, I think it's an average distance of degrees of latitude and longitude at the equator, because the earth isn't perfectly round. But it still plays a similar purpose.
Fun to see all the former IC electricians chiming-in here! Anyone else do their time back in the early-1970's? Back then, Interior Communications electricians had what seemed like several hundred pieces of equipment. The underwater log was only one of many. I never saw or heard of a sword raised or lowered for any reason other than PMS (Planned Maintenance). I suppose each ship may have had some different procedures, but breaking-off the sword in shallow water? The sonar domes and the screws and rudders protrude farther than that fiberglass sword. I don't even remember where ours was located on DDG-5! The one I really can envision nearly 50 years was on USS Puget Sound (AD-38). It was located in a pump room, four or five decks down, below the mess decks. On the bottom of the ship, duh... A long climb down the ladder, with cargo nets at every level to catch you if you fell. Really cold down there at the bottom!
I used to do wireline in the oil fields. We had a tool that we pretty much always used called a Casing Collar Locator (CCL). Simply put it was two magnets with the same poles facing each other, N/N or S/S. Between hem a coil of copper wire. With the poles of the magnets facing each other makes the flux field push out radially around the tool. If any mass, like the collars of pipe connections, pass through the field it would induce a current on the coil that then went up the cable to the surface. Why bring this up? I am wondering, and kinda guessing, if the EM probe works in a similar manner but at a more sensitive level.
So, I gather it’s a little bit more complicated than throwing a rope over the side and timing how long it takes to pass a given number of knots in said rope.
Hello Ferrari.... Well I think it's all the same really. In fact, I think we should go back chucking a rope over the side. We would get more exercise for one thing! But I did not know that much effort was spent on this. As noted, a major factor was turret range finding. A sobering thought.
I watched some video that said they measured "knots" back in sailing ship days by tying a rope full of knots, throwing it over and counting to 30 and seeing how many knots passed by in that time.
3:59 a NM is 6076.115 feet, or exactly 1852 meters, which is 1 minute of arc on earth (the distance you travel above the ground around earth's equator when you move 1 minute east or west). I worked in nav for too long to not compulsively correct that lol
The problem with the EM log is that it measures the velocity of the water past the log. If you are fighting a 5 knot current while making 5 knots good, the darn thing will read 10 knots. Sometimes, nothing works as well as accurate sightings, a good chart, and a sharp pencil.
@@aleasley94 had our sea valve jammed open could raise lower but not remove. The sword burned out prior to Decommissioning so was Pakistan’s issue when they bought the ship.
A common means on a sailboat is to use a "paddle wheel" through a hull opening. I suppose that wouldn't work on the battleship, for the reason you stated in the video about erroneous results due to the water flowing over the hull. I suppose in today's ships they likely use the GPS facility to determine boat speed, as commonly done in recreational boating.
The problem is that there is a boundary layer next to the hull where friction drags the water along with the ship. On small boats, the boundary layer is quite thin, but still you mount the paddle transducer close to the bow for best results. On a battleship sized hull, the boundary layer can be quite thick, so the transducer needs to extend several feet down to be in undisturbed water.
Early warships used a turbine wheel on a cable thrown over the stern. The turbine spun the cable and then you had a mechanical speedometer convert the rotational movement to a speed indication and a counter for distance traveled (just like a car).
@aserta for tactical situation the propulsion plant needs the through water speed to get the best results because that's what's at the intakes and that's what the screw and rudder are experiencing
Ahem, the "rounded" Nautical Mile is 6080 feet, or ±1 minute of arc at the Equator. (The precision value is like 6079.23'from memory) . Using 6/5 to convert to Statute Miles works, but /6 is a tad closer (just harder math). The 6000 foot "nautical mile" is a convenience for gunnery, and comes from the 1000 fathom unit the Royal Navy called a Cable. You did leave yourself another video, though. One of the uses for the Pelorus is to read a precise bearing from the ship to some other known point. Most ships have more than one Pelorus. So, the Quartermast takes out a chart, and marks off a measured distance on that chart. From the chart, the QM than strikes off the bearings to known points ashore. So, when the two bearings match the start point, you start the stopwatch, and let it run until you hit the next set of bearings. Which creates a "measured mile" independent of currents, tides, RPM or the like.
I add 10%; then add half that value again. If you don't care about precision, it's simple and fast. Someone says 85 knots. Add 8.5; add 4.25. Or split it into easier parts: add 8, add 4; then add .5 and .25.
In the 80’s, when doing manual aircraft navigation, a quick reference for distance in nautical miles was to span the distance on a chart using a plotter/compass and then lay that along the nearest latitude line and count the minutes on the line, a minute of degree approximating a nautical mile
"Ahem, the "rounded" Nautical Mile is 6080 feet, or ±1 minute of arc at the Equator. (The precision value is like 6079.23'from memory) ." If you're wanting to be pedantic, that's somewhat incorrect in multiple ways. In the mid 19th century, both the US and UK officially adopted the Clarke ellipsoid as the basis of the nautical mile. The UK officially adpoted 4 significant digits and the US adopted 5 digits. That's 6080 feet in a UK nautical mile and 6080.2 feet in a US nautical mile. The US then diverged again by adopting a new standard of exactly 1852 metres in a nautical mile in the 1950s and that works out to 6076.1154 feet. This is the nautical mile used in basically every modern measurement from aviation to shipping. Since the Iowa class was built in the 40s and had multiple refits, I'm guessing that it used both the old US standard and the modern international standard in different places. For example, the targeting computers would have relied on the old standard but any installed modern radars would have the new standard built in. I would also be willing to bet that this caused some confusion in some specific areas until people got used to it but it just mostly didn't really matter. TBH, I doubt that origin story too. It just seems natural to conveniently round to 6000 where that level of precision is unnecessary.
Just as a forewarning, be careful whenever entering a space like the pitsword pit, or really anything that requires removing a lot of bolts to get to. If you have to go through that much effort to get in there, it's not meant for someone to regularly be there, which means it probably doesn't have any air circulation. When air is left in a sealed compartment on a ship for a long time, the oxygen is slowly pulled out of the air as the steel oxidizes, which leads to the space being a low oxygen environment. Sailors and mariners have and still do die from asphyxiation after entering confined spaces like that without proper breathing apparatuses.
Coming from an aeronautical background, it's interesting to compare this with how speed is measured on airplanes. The concern he's describing at 4:52 - accurately but without knowing the term - is boundary layer, that a layer of water is dragged along the ship's surface, so to get an accurate speed measurement the probe must be long enough to be outside the boundary layer. The boundary layer gets thicker further back on the ship, so it would make sense to have this apparatus as far forward as possible. Airplanes usually have it fairly close to the side of the plane, but have it as close to the nose or leading edge of the wing as feasible, in some cases even sticking out forward from the nose. The earlier "sword" style he describes uses a pressure differential very similar to an airplane pitot tube. I wonder why they switched from that to this electromagnetic style? Perhaps holes on the earlier stile tended to get clogged? That tends to be less of a problem on aircraft that aren't flying through seaweed or silt, but airplanes can have them ice over or be clogged by insects building nests in them - this (or forgetting to remove protective covers) has caused numerous crashes, most famously Air France 447 (the A330 that fell into the Atlantic).
Lord Ryan you keep coming up with Interesting Items , we do not worry that you will run out of Topics . That Ship is Huge ! As a Reward I offer you a Vacation from your Ship and I suggest something completely different as a Video . Could you do a Video on BB 16 , the lay out of the Guns looks Wild .
nice to see the & hear how speed was measured, but what's the indicator itself look like? , were there multiple indicators so say, the engineers & the captain would know their speed? or just the gunnery computer?
The control cabinet for the EM log coverts the signal from the EM log to a proportional fractional rotation of a shaft connected to a Synchro Transmitter. Synchro Transmitter is electrically connected to a Synchro Receiver in a Synchro Signal Amplifier, which in turn drives a much larger Synchro Transmitter. Signal from the Synchro Signal Amplifier goes to the ACO/Signal Distribution side of the IC Switchboard, where it is distributed by way of rotary switches to displays containing Synchro Receivers all over the ship. When all is working properly, moving the shaft of a Synchro Transmitter 90 degrees will cause the shafts of all Synchro Receivers connected to it to also rotate 90 degrees. This is how much of the IC gear operates...Gyro repeaters, rudder angle, shaft speed, lee helm, helm, etc. (For the helm, there is a Synchro Transmitter attached to the wheel, and a Synchro Receiver attached to the spool valves on the rudder hydraulics.)
7:18 The "wing-shape" is not at all obvious from the single angle we're presented with. Only after it was pointed out (and some squinting) did the color/lighting gradients slightly show. Great video anyway.
I wonder, was "pit sword" just a shortened version of pitot. A pitot tube is a way of measuring flow using the difference between the static pressure and dynamic pressure.
8:00 I’m not sure that they knew what they were getting into with the Texas. I’m guessing that they could only guess at the condition of several areas and only really got an idea when it entered dry dock. At least with NJ divers can get underneath.
It sounded like it was so bad in areas they knew they had to replace whole sections of hull plating. It's probably harder to estimate what truly needs replacing on NJ and what is still in good condition
@@kumaflamewar6524 The Texas doesn’t seem to have a clear scope of work. I asked about it but didn’t get a real answer. They knew areas were bad but seems like they have a price point on what they can spend on the repairs. So Fix stuff until a particular pot of mis expended?
Question: during the sea trials it was rumored that bb-62 hit a speed of 38 knots, is this true and would it be possible to do again during a service career if it is true?
Could it be 38 kn “land speed” going with a current? Just like a normal subsonic airliner can fly apparently faster than Mach 1 if you measure land speed if you fly with a jet stream. A few years back such a manoeuvre even got a brief news mention when a flight across the Atlantic was the fastest since Concord.
It happened before Vietnam. The ship was the lightest displacement ever of an Iowa in service. With the WWII, Korea or 80’s dispersant it would have been slower
i wonder if during the mothball period before the 80s they became inoperative on one ore more of the battleships? due to age and them no longer being in regular use might have caused someone to say to heck with it and they were replaced with the EM Log. also, the improved accuracy of teh EM Log might have been seen as major plus for shore bombardment on stationary land targets.
The problem with all of those older methods is that they only measure your speed relative to the surrounding water. If the water itself is moving, as with a current, your actual speed over the ground (just like airspeed when flying) isn't necessarily the same.
SINS - Ship's Inertial Navigation System. Used on subs. No sats. Very accurate gyros, accelerometers, quite a bit of computing power, and more than a bit of classified magic. Described at a rather high level in the PARS for IC2. No details, as it is a classified system. I knew what it was and very broadly how it worked. Nothing more, as we didn't have one.
Imagine what bulb maintenance looks like on an active ship with 24/7 vibration. Also, some of those yellow emergency lights contain lead/acid batteries which require maint and occasional charging. Ditto for the larger versions carried in the repair lockers. It could really suck being the low guy in the EM Shop pecking order... When I first got to the ship, I had 60 6V lead-acid batteries to test and fill. (120 VDC Backup for PBX and the Master/ Aux Gyrocompass systems.) At least mine were all in one space.
Each of the methods is measuring the speed of the ship through the water, not over the ground. You touched on the need to account for the movement of the water several times but it's very important especially in areas with a lot of current and the higher latitudes (more tide). Have you done a video on ship navigation over the years of her life? Would love to see one
A very good point. Before GPS the only way to calculate speed and distance over land would be through plotting locations of the ship, measuring the distance travelled and and dividing by the time that it took to travel that distance. I believe that now days GPS can be used to give an accurate measure of speed over land.
@@garygreen7552 Correct. Problem is that GPS can be spoofed, jammed, or outright taken out. There is still a place in modern navigation for good sightings, an accurate chart, and a sharp pencil.
@@kevincrosby1760 Anything electronic can be screwed up by bad guys. I also understand that the Navy and the Coast Guard are again teaching navigation using a sextant, a chronometer and paper charts. However ships are using electronic charts and GPS as a primary way of navigating. A side note, Drachinfel, a channel on RUclips, has a video on early iron hulled ships used by the British East India Company. He noted that the captains of those ships discovered that the iron hull affected the magnetic compasses used at the time.
@@garygreen7552 I wasn't aware that they stopped. I can remember in the late 80's a gaggle of midshipmen out on a bridge wing with a sextant arguing over which star was which. You also mentioned the age-old issues with a magnetic compass. That is actually the purpose of the iron balls found on the mag compass pedestal. They are adjusted to compensate for the hull of the ship. Biggest problem with a mag compass is that they show Magnetic North, while charts are oriented to True North. Nav charts are generally marked with the Deviation in degrees between True and Mag North. Failing to make the required adjustment has put more than one ship on the reef. Even worse, it has been the probable cause of "Controlled flight into terrain" a few times. Hitting a reef can be survived, flying a jet into the side of a mountain, not so much. To make life exciting, the Magnetic Poles are actually moving, so the published Deviation may not be correct if you don't have new charts.
Who here is ex-USN and caught the flickering light on the left at 1:16 and winced. "Hey, you got any bulbs? How about starters? Maybe the ballast is just bad?"
I personally believe the Statute Mile, or land mile as Ryan calls it, should be replaced by the Nautical Mile even when on land. I feel we should do this mostly to annoy people. Call it the Universal Mile, or the UniMile. I love videos like this which cover less often discussed aspects of the ships. Often it's fun just to watch where all Ryan gets to as he moves about the ship to discuss things. Sometimes you're looking at something behind him and wondering what the heck is that thing? Then one or two more videos later, he tells you what it is, and while he's doing that you see this weird thing behind him, and it sets the whole cycle into repeat. Hope you get a firm date for the drydocking soon.
A nautical mile is not 6000 feet. It's one minute of arc in latitude, 1/(60*90) = 1/5400 of distance from the equator to the north pole,1851.58 m. More recently they rounded it to the nearest meter, to get to 1852 meters. ~6074ft by the old definition or ~6076 by the new. In any case not 6000.
so this pit sword or EM log, passes through 3 layers of the bottom steel. how would they have been able to pull it up and into the ship, and get the hatch closed against the pressure of the sea trying to flood the ship? you said that it wasnt something that was left in place so it was obviously installed and retracted on more than one occasion... you mention 'falling through a pit of death in the deck'. when my dad was in the Navy (boiler technician 3rd), they lost all power and lights while switching from ship power to shore power (or vice versa) and he turned to head up to the light from the task he was on and stepped into a 'pit of death' on a grated catwalk. a fellow sailor had pulled up the grating to work on his task and never replaced it. he tore up his knee, ruptured 4 vertebrae in his back, damaged a kidney and dislocated a shoulder. he spent 30 days on his back in the base infirmary, unable to move.
The pitsword has a sea valve at the bottom and a packing gland at the top. When it is raised the sea valve is closed. When the sea valve is opened and the pitsword lowered the packing gland is adjusted to keep out the water. You will probably have a bit of water come in around the pitsword while being raised and lowered, as you need to back off the packing gland a bit to allow movement. However, not much, and it only takes 2 or 3 minutes to actually raise or lower...assuming that you are strong enough to crank it that fast.
The Pit Log operates on the Bernoulli principle or Bernoulli's Law which basically describes a relation between pressure (static and dynamic) and flow speed. I wouldn't call it "less sophisticated" as this principle is still the way to measure the speed of aircraft, the instrument is called a pitot tube. "Pit Log" is probably short for "Pitot Log", which is named after the gentleman who invented it: Herni Pitot.
I had someone who worked for me that was stationed on the New Jersey and he said that they did not have sonar because they would have had to break through the hull to install it. So a sub had to shadow it wherever it sailed. Is that true?
Nautical mile has nothing to do with the distance in feet. A nautical mile was originally defined as the meridian arc length of one minute of latitude. (So if you sail 1 degree straight north, that's 60 nautical miles.) It has since been redefined to exactly 1,852 meters. (This works out to 6,076 + 44/381 feet)
What's that red painted framework between you and the camera at the end of the video? It looks as though it held something pretty sizeable at one time.
Given they have barely done more than discuss it, I'd guess a good few years yet. It took Texas several years to get a dry dock sorted, and that's when it was known she was an urgent case with the danger of sinking....
Wow, there is devices crammed into everything on these ships, and someone used to be trained to operate them. I wonder if there ever was a complete, compiled User´s Manual for an Iowa-class battleship, and how that would look like. Probably a couple of cabinets.
I wonder why they went from two measuring devices to one? If there's one thing that I've learned about battleships from this channel, it's how much they value redundancy. For a piece of equipment that is so critical for fighting the ship, it seems odd that they didn't have two installed, especially as they already had the openings in the bottom of the ship.
I am a retired US merchant marine officer. Such precision with my USCG tests down to 1/1000 of a knot or nautical mile was never required. Accuracy needed was never more than a tenth, for anything. A nautical mile is defined as 1/60 of a degree of latitude.
Modern Speed Logs still are retractable. This is more so they can be retracted before the ship is moved into drydock than anything else. Also because they can measure both longitudinal speed and transverse speed, so they also need to aligned to the ship, also acomplished at the through hull.
I was given a tour of that space last year and i thought that tube looked like it was for measuring speed. But when i asked the tour guide he had no idea what i was talking about.
Attempting to explain to junior officers the difference between EM LOG speed (speed through water) and GPS-derived speed (speed over ground) was a major part of being a Combat Systems Officer of the Watch on a DDG.
There were times that I thought that being Duty IC was comprised mainly of responding to "burned out light bulb" calls to instead educate junior deck officers on the wonders of the little knob marked "DIM". With practice, I learned to do so without insinuating that the gyro repeater wasn't the only "dim bulb" on deck. I did however get in a bit of trouble once on a "distorted mic" call, when I suggested to the BMOW that the mic would be just fine if he wasn't trying to give it a instead of holding it a few inches away from his mouth.
I used to be a professional merchant marine deck officer, and one thing that drove me freaking crazy was on the Coast Guard exams, if you wanted to get a math question exactly right, which was important because of the way the tests worked, you had to take any number with a decimal point, round it to the 4th place, and keep going.... however, when you had to use nautical miles, if you wanted to get the answer exactly correct, you had to consider 1 nautical mile to be 6080 feet. 1 nautical mile is not 6080 feet. It is 6076 feet. Apparently, it was critical that I kept decimal places accurate enough that I needed to go down to the nearest 1/10,000th of any incriment, but when we were doing nautical miles, it was completely A-OK to be a full 4 feet too long. That's more than an entire meter... That's a whole 0.0658 of a percent off... I'm supposed to be accurate to the nearest 1/10,000th, and 6080 feet in a nautical mile is off by 2/3rds of 1/10th of a percent. That's a much larger amount of "rounding error" and it makes me mad still, 13 years later.
Oh man, I absolutely despise when tests require you to use bad information and/or have an incorrect “right” answer.
I can appreciate it still bothering you after all those years.
oh man, Dutch merchant navy here, we'd do meters. But yeah I can feel your furiation. We where pushed with the same need for accuracy tho, but did not have an outdated definiation for a nautical mile.
Never been a sailor or in a military unit so forgive me that the I was ignorant about how good at math you needed to be to be a good sailor! I still remember high school boys declaring they would have no use for math in the real world! I am totally impressed!
@@julieenslow5915 Yeah, I knew those guys. I am an engineer so using math is second nature. When I watch people struggle trying to figure gas mileage, percentages or simply add scores in a card game it really pains me. Have a friend with advanced degrees in business who is in upper management with that big mouse outfit in Orlando. He wanted so bad to be a part of the innovation and design bunch but got passed over for his lack of math skills. He actually went back to school to pick up the knowledge he needed and landed his dream job. Math, we use it everyday.
@@julieenslow5915 - spherical trig for the win! My dad was a merchant captain. I learned celestial navigation using his sextant from WW2
'Chip logs' on old sailing ships had another interesting quirk. One leg of the three ropes wasn't tied directly to the 'chip' but attached with a wooden peg tied to the line. After taking the reading, the sailor could give the line a sharp tug, pulling the peg loose. This allowed the chip to turn edgewise and the sailor could then pull it back in quite easily. Reinsert the peg into the chip and ready to go again.
That is so smart yet so obvious
I love how we get a back room look on how you guys do research with the battleship and rediscover these small hidden gems. It really puts into perspective how easy it is to lose knowledge. Thanks for keeping it safe
The EM Log sensor sounds like an open channel magnetic flow meter. The salt water passes through a magnetic field and generates a current in a wire loop. The current is proportional to the velocity of the water passing by. This is a very common flow meter in the process industry.
Very interesting. Though i would imagine if you had different kind of saltwater (less or more salt leading to more or less resistance) you would also get different readings for same velocity of water passing by, though, proportionally to the resistivity of water...
Right?!
That would also change the ships buoyancy. It will change with salinity fluctuations. Effecting the drag of the ship. Works for it or against it? IDK?
I think magnetic based detonators had this sorts of issue, if I remember correctly Mk 14 torpedo's issue was partly because of it?
But he did say when going from one body of water to another they would have to recalibrate for salinity so basicly you would check the salinity and change the range of the sensors accordingly to get a accurate speed reading
EMF=BlvsinTheta
My favorite videos are the ones where you go to places that haven’t been painted/ renovated. I went aboard the USS NC also many times the guys got to know me. One day they took me deep in the ship where few people get to go. It was the best experience I have ever had on a museum ship. It was incredible, you could feel the pulse of the ship. I will come to NJ some day and take the tour.
The Nautical mile was originally defined as the meridian arc length corresponding to one minute (1/60 of a degree) of latitude, which is way easier to calculate where you are on a globe without the need for complicated conversions (such as from "yards" or "feet").
And a kilometre was the metric equivalent being 1/40000 of the circumference of the Earth. Which is where gradians comes in with 400 gradians for a full circle… (The measurement was a bit out so the length of a kilometre was a bit out because the Earth isn’t a sphere).
@@allangibson8494 nautical miles and meters are fundamentally different measures. The SI meter is a linear distance measure, they just mistakenly tried to define it by the earth's circumfrence. A true nautical mile is a sort of angular unit for positional navigation and is always one minute of angle regardless of the local radius of the earth(meaning a nautical mile is not a fixed distance). There are some false nautical miles that have been subsequently defined for use with speed calculations, which are averaged linear-distance equivalent units.
I suppose its sort of how people tend to mix units of force and mass because they happen to be conveniently interchangable for every day tasks on earth's surface. But none the less a pound is a unit of force and kilogram a unit of mass.
@@mytech6779 The nautical mile and meter have exactly the same origin - the physical dimensions of the earth.
The base angular dimensions were differently defined however.
Nautical miles use ninety degrees in a right angle with sixty minutes in a degree.
Kilometres originally were defined by one hundred gradians in a right angle with one hundred kilometres in a geometric gradian.
The SI metre deviates from this because it was soon realised that the earth both wasn’t dimensionally precise enough and inconveniently sized to be used as a reference unit but the French did use kilometres in that way for navigation into the 1950’s with a reference meridian at Paris.
Historically both the pound and kilogram have been used interchangeably for both force and mass. I have worked with equipment calibrated in kg/cm2 as the unit of pressure (which is conveniently close to one atmosphere) but the variable nature of gravity makes precise repetition of calibration measurements hard in different locations (hence the switch to newtons per square meter (Pascals and kiloPascals).
@@allangibson8494 You have a fundamental misunderstanding of the difference in the use of circumfrential distance and angles.
Degrees or Gradians are irrelevent to that fundamental difference.
Circumfrence is dependent on radius, degrees of angle are independent of radius.
@@mytech6779 I have a fundamental knowledge of the HISTORY of metrology.
The history doesn’t define the present but does help you understand how we got to where we are now and why things are the way they are.
The last three centuries have been a chase for higher precision and repeatability. Our units of measurement have gone from being defined by the size of human body parts and grains of wheat to fundamental and universally reproducible constants.
We had a speed indicator on the bridge of the Dixie next to the Navigators chart table. It was always fun to watch our speed increase during the mid watch just before reaching a port and especially on the way home from deployment. The Snipes would turn up the RPM's thinking we'd get into port quicker but not thinking we would adjust our speed the next morning. I don't ever remember entering port ahead of time.
Nope, we would crank on the turns and wind up floating around killing time till our stated time. Didn't want to catch those wives saying goodbye to their boyfriends! :)
Never happened. If you watched the Log the speed would swing +/- 2 knots. we assumed that this was because the salinity of the water would very.
normally the pit sward equipment was in the forward gyro space and was the responsibly of the IC gang.
I was an was IC2.
@@jimnunn9232 Raising and lowering the pit sword. What a FINE incentive for a junior sailor to work on quals so that he had a legit reason to be on watch elsewhere while entering/leaving port....
IC2 (also)
On cargo ships our speed was worked out on departure for arrival time. Extra revs were added to make up for losses during the voyage. We slowed down or sped up to get there at the correct time. Except for the Ariake which always made up for lost time on departure. The shippers loved her. The big white ship always arrived a day early.
Never happened on my ship. We all knew that we had a schedule. If we arrived early, we would just do circles until our scheduled arrival. No point in adding extra heat and workload to the engine room watch standers for nothing.
I was an EOW.
Interesting stuff. I have a small collection of Walker Taffrail Logs, a technology somewhere between the chip log and the E-M. You tow a "turbeller", a torpedo shaped fish with skewed fins that spins as it moves through the water. This spins the rope that's towing it. A meter mounted on the Taffrail counts the revolutions and translates that to distance traveled. Some old timers still use them.
Excellent video again Ryan. It's so important that the museum keeps history alive. Thanks a lot.
Man videos like this one really demonstrate how huge, and dense these ships really are!
I'm learning more battleships everyday , than I thought I would Great video👍
It's especially interesting to me because I do not care about ships, navies, et al..... or so I thought .... too cool ...
The pit sword on a ship is the equivalent of the pitot tube on an aircraft. Both air and water are fluids you can use the same type of device to measure the speed.
An excellent comparison.
Ah that’s what I expected. Thank you for explaining
Also used to measure airflow in ducts. Called an Annubar by Rosemount Inc.
I can't wait for Big J to get some needed drydock time! What kind of timeline do you guys think? A year or two? 5 years from now?
I actually had two speed sensors on the little flats skiff I owned several years ago. One was a pitot tube type that came with the boat and had an indicator mounted on the dash. The other was a small "water wheel" attached to the depthfinder probe and read out via the depthfinder screen. Why two? The wiz-wheel was very sensitive, but did not work well once you were up in a plane. The pitot tube was not accurate at low speeds, but worked fine at planing speeds.
Yeah, the same is true for pitot-based airspeed indicators on airplanes. They're typically useless at taxi speeds. This is why the "airspeed alive" check is done during the takeoff run, rather than during the various checklists that are run before taking off like nearly every other system check.
The differential pressure generated by ram pressure has a square root relationship to speed. Double the speed gives four times the pressure.
That basically makes them useless at less than 10% of maximum scale.
Great video Ryan! Always enjoy learning about New Jersey.
Great video! Love the random things you guys find to open up on camera 👍
Thanks for keeping up all these videos, can’t wait until I get a chance to visit!
Very interesting bit of info. Who would've thought as to how speed was calculated in this manner. But it does make sense. Thanks for posting.
I dig the Captains beard, Ryan.
You've earned it!!
When I was a junior rating one of my duties was to do rounds at night. I had to check about 20 compartments got various things, one was the EM log compartment. I had to look down to see if there was much water in it. Sometimes the senior ratings would put a note on the inside of the hatch to make sure we were opening it - it had about 8 clasps which took ages to undo!
First time I heard that you were on the Taney Museum! As a retired USCG Cutterman, that’s awesome.
This man had the greatest job on earth.
As always, very interesting content. Thanks!
Lol, I get instantly Ill just thinking about that video of you crawling through the gun barrel. Like chills that won’t go away, and now I have to distract myself.
Nothing like archeology! Warships are cities--and until taken out of service, warships are almost organic with modifications, repairs, upgrades, and a human crew making use of "unused spaces" for some function that the crew needed or wanted.
How many dead cables are left on the Battleship New Jersey? My limited experience with aircraft and vehicle wiring harnesses is that when a cable bundle is no longer used, it generally is too much hassle to remove and gets left in place. There has to be old cables to those speed sensor probes that ran to several locations in the New Jersey through armored decks and bulkheads.
It depends on when the jobs are done , if it's during a shorter upkeep usually the redundant cable is taken out to the bulkhead bland and made safe or to a junction box if it's a change of equipment . If it's a refit and main runs are disturbed then a lot of redundant cables are taken out and the glands may be reused .
Ryan covered this in a previous video. They did leave a lot of unused cable in place.
I greatly enjoy your videos. Your intricate understanding of so huge and complex a machine as a battleship, brings me new knowledge with each program. But not without envy. How did land this plum of a job? In any event, I have been a lifelong fan of the great ships, and I eagerly await each new edition of your videos.
Between the knotted line and electronics was the Taffrail Log. The taffrail is the railing around the stern of a ship. The log is attached to the rail and counts rotations of (what looks like) an elongated propeller towed on a long braided line. A dial on the log indicated distance traveled in knots and tenths. Also known as a Patent Log. It was still used as late as the 1950s on older merchant ships. Some people that sail long distances still use them because there's no power requirement.
1:44 There's another fluorescent light for Ryan to change.
Came here to make the same comment. Looks like the bulb is going out. Or the ballast.
@@shaun3423 With that orange glow, I was thinking ballast too.
Just the cathode on the lamp, just disconnect that end to save the balast. Just a word of warning that end gets very very hot.
Anyone else hoping Ryan get to ride on New Jersey when they tow her to dry dock. That would be an epic video.
Did you notice the fluorescent light is sending morse code messages... LOL
Another fun episode Ryan. Thankyou
As an EM had to go into the pit sword compartment to raise and lower the pitometer. On my ship it was behind #1 boiler.
Was an IC was our job, EM’s were too busy standing switchboard watch
6:34 - Gotta love that "untill" typo; it sure adds that extra bit of the human ell-ement to the sign.
I was part of the ceremonial decommissioning crew for the USCGC Taney while I was stationed at the Yard in Curtis Bay. Pretty cool old ship!
What you show lashed to the bulkhead is commonly known as the "pit sword".
The sensing elements are actually the two round Monel buttons located in the bottom fiberglass portion. Signals from the Pit Sword would generally go to the head-end equipment in the IC Shop, then be transmitted as synchro signals to the indicator locations via the Distribution/ACO side of the Main IC Switchboard.
One of the main drawbacks of the system is that all it can sense is the speed through the water at that point. If you are making 10 knots good against an 8 knot current, the Log will indicate 18 knots. I don't recall ever needing to adjust the system for varying salinity, most likely because the indicators were ignored in favor of the SatNav system which could give you a real-time display of the actual speed through the water.
Pity for the FNG, as he was the one who was detailed to stand by in the bowels of the ship waiting for the word to be passed to "Raise/Lower the Pit Sword". Ours had its own little enclosed trunk in the Cargo JP-5 Pumproom, and was located 1 deck below the grates with the trunk hatch at grate level. You had to open the hatch and climb down into the trunk, where there was a grate almost large enough to stand on while cranking it up or down. Really close quarters unless you were very skinny.
IC2
When The Sat Nav didnt catch a bad bird and send us off to some place in the Desert .
ET3 ;)
@@stanants8566 One would hope that the QMs were using the SatNav tools to VERIFY their plotted course on the charts, not DETERMINE it. When you get right down to it, can't spoof a paper chart and a pencil.
When all else fails, There is always the two ensigns with a sextant out on the bridge wing arguing about what star they are looking at...
Personally, I didn't really care, as i was just along for the ride. As long as both gyros continued to be north-seeking, stable, and in agreement with one another, my main concern was that the coffee pot was full and the ashtray empty.
Sounds lazy, but if the PMS was done properly, everything pretty much just worked reliably. The exception was the MK 19 master gyrocompass system, who's accuracy was generally excellent but could suffer from a weak/failing tube.
Yep, tubes. The MK 19 Control cabinet contained dozens of them. "12AX7" is permanently embossed upon my memory, even after 32 years. The further north we went, the better the chance that we would start going through tubes. We actually had the box of spare tubes bungied to the top of the cabinet.
I was on the USS Kansas City (AOR-3), a Replenishment Oiler. They were somewhat anal about gyro accuracy. It's almost like we routinely sailed around with ships on both sides at a 200 foot separation or something.
Fun times.
IC2
Excellent. Thank you for posting this.
A nautical mile is 1.151 or so miles, but the distance wasn't designed to be "simpler" to measure, but because it corresponded to 1 arc minute of latitude. 60 arc minutes equals 1 degree of latitude. This unit made it much easier to plot a course on a map, both tracking forward from a last known location with direction and speed, but also as a way of measuring / anticipating time as you can set your compass and project forward by 12 or 24 hour increments to your intended destination or waypoint. 15 knots, for instance, is 6 degrees of latitude per day, by setting the compass to 6 degrees of latitude from the map scale, you can plot how far in both distance and time you are from your destination, without doing any complicated conversions or maths. Actually pretty ingenious.
The modern nautical mile is a little different, I think it's an average distance of degrees of latitude and longitude at the equator, because the earth isn't perfectly round. But it still plays a similar purpose.
Fun to see all the former IC electricians chiming-in here! Anyone else do their time back in the early-1970's? Back then, Interior Communications electricians had what seemed like several hundred pieces of equipment. The underwater log was only one of many.
I never saw or heard of a sword raised or lowered for any reason other than PMS (Planned Maintenance). I suppose each ship may have had some different procedures, but breaking-off the sword in shallow water? The sonar domes and the screws and rudders protrude farther than that fiberglass sword. I don't even remember where ours was located on DDG-5!
The one I really can envision nearly 50 years was on USS Puget Sound (AD-38). It was located in a pump room, four or five decks down, below the mess decks. On the bottom of the ship, duh... A long climb down the ladder, with cargo nets at every level to catch you if you fell. Really cold down there at the bottom!
I used to do wireline in the oil fields. We had a tool that we pretty much always used called a Casing Collar Locator (CCL). Simply put it was two magnets with the same poles facing each other, N/N or S/S. Between hem a coil of copper wire. With the poles of the magnets facing each other makes the flux field push out radially around the tool. If any mass, like the collars of pipe connections, pass through the field it would induce a current on the coil that then went up the cable to the surface.
Why bring this up? I am wondering, and kinda guessing, if the EM probe works in a similar manner but at a more sensitive level.
Good investigating
So, I gather it’s a little bit more complicated than throwing a rope over the side and timing how long it takes to pass a given number of knots in said rope.
Hello Ferrari.... Well I think it's all the same really. In fact, I think we should go back chucking a rope over the side. We would get more exercise for one thing! But I did not know that much effort was spent on this. As noted, a major factor was turret range finding. A sobering thought.
I watched some video that said they measured "knots" back in sailing ship days by tying a rope full of knots, throwing it over and counting to 30 and seeing how many knots passed by in that time.
I thought for sure Ryan would have been under the deck grate and into that confined space!
3:59 a NM is 6076.115 feet, or exactly 1852 meters, which is 1 minute of arc on earth (the distance you travel above the ground around earth's equator when you move 1 minute east or west). I worked in nav for too long to not compulsively correct that lol
The problem with the EM log is that it measures the velocity of the water past the log. If you are fighting a 5 knot current while making 5 knots good, the darn thing will read 10 knots.
Sometimes, nothing works as well as accurate sightings, a good chart, and a sharp pencil.
Or when you move 1 minute north or south anywhere on the planet.
At 12:15 in the video, what is the rack in the foreground? Looks like it is for holding barrels?
The technology and infrastructure of the ship never ceases to amaze me. No wonder why we owned the oceans. God bless America!
On a Gearing Destroyer in EM log was behind #1 boiler, got hot lowering and raising.
On the Leahy Class,it was behind 1B Boiler. Also seen broken ones removed because someone forgot to call down to have it raised..
@@aleasley94 had our sea valve jammed open could raise lower but not remove. The sword burned out prior to Decommissioning so was Pakistan’s issue when they bought the ship.
Awesome! Thanks.
No tiny paddle wheel on stick like my WaveRunner?
Adore the vids, thank you.
A common means on a sailboat is to use a "paddle wheel" through a hull opening. I suppose that wouldn't work on the battleship, for the reason you stated in the video about erroneous results due to the water flowing over the hull. I suppose in today's ships they likely use the GPS facility to determine boat speed, as commonly done in recreational boating.
The problem is that there is a boundary layer next to the hull where friction drags the water along with the ship. On small boats, the boundary layer is quite thin, but still you mount the paddle transducer close to the bow for best results. On a battleship sized hull, the boundary layer can be quite thick, so the transducer needs to extend several feet down to be in undisturbed water.
Military is about redundancy, so... it's possible that they still have a bare bones method in use to double check.
Early warships used a turbine wheel on a cable thrown over the stern. The turbine spun the cable and then you had a mechanical speedometer convert the rotational movement to a speed indication and a counter for distance traveled (just like a car).
@@aserta and for when extensive E-War is in play where GPS could be jammed or spoofed.
@aserta for tactical situation the propulsion plant needs the through water speed to get the best results because that's what's at the intakes and that's what the screw and rudder are experiencing
Ahem, the "rounded" Nautical Mile is 6080 feet, or ±1 minute of arc at the Equator. (The precision value is like 6079.23'from memory) .
Using 6/5 to convert to Statute Miles works, but /6 is a tad closer (just harder math).
The 6000 foot "nautical mile" is a convenience for gunnery, and comes from the 1000 fathom unit the Royal Navy called a Cable.
You did leave yourself another video, though. One of the uses for the Pelorus is to read a precise bearing from the ship to some other known point. Most ships have more than one Pelorus. So, the Quartermast takes out a chart, and marks off a measured distance on that chart. From the chart, the QM than strikes off the bearings to known points ashore. So, when the two bearings match the start point, you start the stopwatch, and let it run until you hit the next set of bearings. Which creates a "measured mile" independent of currents, tides, RPM or the like.
I add 10%; then add half that value again. If you don't care about precision, it's simple and fast.
Someone says 85 knots. Add 8.5; add 4.25. Or split it into easier parts: add 8, add 4; then add .5 and .25.
In the 80’s, when doing manual aircraft navigation, a quick reference for distance in nautical miles was to span the distance on a chart using a plotter/compass and then lay that along the nearest latitude line and count the minutes on the line, a minute of degree approximating a nautical mile
Could off, been a few years and I’m saying that from memory
Awesome
"Ahem, the "rounded" Nautical Mile is 6080 feet, or ±1 minute of arc at the Equator. (The precision value is like 6079.23'from memory) ."
If you're wanting to be pedantic, that's somewhat incorrect in multiple ways. In the mid 19th century, both the US and UK officially adopted the Clarke ellipsoid as the basis of the nautical mile. The UK officially adpoted 4 significant digits and the US adopted 5 digits. That's 6080 feet in a UK nautical mile and 6080.2 feet in a US nautical mile. The US then diverged again by adopting a new standard of exactly 1852 metres in a nautical mile in the 1950s and that works out to 6076.1154 feet. This is the nautical mile used in basically every modern measurement from aviation to shipping.
Since the Iowa class was built in the 40s and had multiple refits, I'm guessing that it used both the old US standard and the modern international standard in different places. For example, the targeting computers would have relied on the old standard but any installed modern radars would have the new standard built in. I would also be willing to bet that this caused some confusion in some specific areas until people got used to it but it just mostly didn't really matter.
TBH, I doubt that origin story too. It just seems natural to conveniently round to 6000 where that level of precision is unnecessary.
Just as a forewarning, be careful whenever entering a space like the pitsword pit, or really anything that requires removing a lot of bolts to get to. If you have to go through that much effort to get in there, it's not meant for someone to regularly be there, which means it probably doesn't have any air circulation. When air is left in a sealed compartment on a ship for a long time, the oxygen is slowly pulled out of the air as the steel oxidizes, which leads to the space being a low oxygen environment. Sailors and mariners have and still do die from asphyxiation after entering confined spaces like that without proper breathing apparatuses.
This is a hazard Ryan has talked about several times, but reminders are always wise.
Coming from an aeronautical background, it's interesting to compare this with how speed is measured on airplanes. The concern he's describing at 4:52 - accurately but without knowing the term - is boundary layer, that a layer of water is dragged along the ship's surface, so to get an accurate speed measurement the probe must be long enough to be outside the boundary layer. The boundary layer gets thicker further back on the ship, so it would make sense to have this apparatus as far forward as possible. Airplanes usually have it fairly close to the side of the plane, but have it as close to the nose or leading edge of the wing as feasible, in some cases even sticking out forward from the nose. The earlier "sword" style he describes uses a pressure differential very similar to an airplane pitot tube. I wonder why they switched from that to this electromagnetic style? Perhaps holes on the earlier stile tended to get clogged? That tends to be less of a problem on aircraft that aren't flying through seaweed or silt, but airplanes can have them ice over or be clogged by insects building nests in them - this (or forgetting to remove protective covers) has caused numerous crashes, most famously Air France 447 (the A330 that fell into the Atlantic).
learning more battleships everyday 😀😀😀
Lord Ryan you keep coming up with Interesting Items , we do not worry that you will run out of Topics . That Ship is Huge ! As a Reward I offer you a Vacation from your Ship and I suggest something completely different as a Video . Could you do a Video on BB 16 , the lay out of the Guns looks Wild .
nice to see the & hear how speed was measured, but what's the indicator itself look like? , were there multiple indicators so say, the engineers & the captain would know their speed? or just the gunnery computer?
The control cabinet for the EM log coverts the signal from the EM log to a proportional fractional rotation of a shaft connected to a Synchro Transmitter. Synchro Transmitter is electrically connected to a Synchro Receiver in a Synchro Signal Amplifier, which in turn drives a much larger Synchro Transmitter.
Signal from the Synchro Signal Amplifier goes to the ACO/Signal Distribution side of the IC Switchboard, where it is distributed by way of rotary switches to displays containing Synchro Receivers all over the ship.
When all is working properly, moving the shaft of a Synchro Transmitter 90 degrees will cause the shafts of all Synchro Receivers connected to it to also rotate 90 degrees. This is how much of the IC gear operates...Gyro repeaters, rudder angle, shaft speed, lee helm, helm, etc. (For the helm, there is a Synchro Transmitter attached to the wheel, and a Synchro Receiver attached to the spool valves on the rudder hydraulics.)
It's amazing how on Iowa class you had cutting edge tech for the time and next to in a humble chip log, known to mariners for ages.
Most excellent.
Neat seeing whats on the other end im use to just looking down right next to shaft rpm and reactor total power and not really thinking any farther
Fascinating.
The beard is coming in nicely, Ryan.
Ryan's beard RULES!
7:18 The "wing-shape" is not at all obvious from the single angle we're presented with. Only after it was pointed out (and some squinting) did the color/lighting gradients slightly show.
Great video anyway.
I wonder, was "pit sword" just a shortened version of pitot. A pitot tube is a way of measuring flow using the difference between the static pressure and dynamic pressure.
8:00 I’m not sure that they knew what they were getting into with the Texas. I’m guessing that they could only guess at the condition of several areas and only really got an idea when it entered dry dock. At least with NJ divers can get underneath.
It sounded like it was so bad in areas they knew they had to replace whole sections of hull plating. It's probably harder to estimate what truly needs replacing on NJ and what is still in good condition
@@kumaflamewar6524 The Texas doesn’t seem to have a clear scope of work. I asked about it but didn’t get a real answer. They knew areas were bad but seems like they have a price point on what they can spend on the repairs. So Fix stuff until a particular pot of mis expended?
I grew up 500 miles away from the ocean, never wanted to go anywhere near it... watch one video and now I suddenly want to go explore a battleship 😂
Looks like a couple more fluorescent tubes to swap
Question: during the sea trials it was rumored that bb-62 hit a speed of 38 knots, is this true and would it be possible to do again during a service career if it is true?
No 38 knots is to high of a speed the fastest NJ Achieved was 35.2 knots.
Heres a video about that ruclips.net/video/J4Dp-TOAyho/видео.html
Could it be 38 kn “land speed” going with a current? Just like a normal subsonic airliner can fly apparently faster than Mach 1 if you measure land speed if you fly with a jet stream. A few years back such a manoeuvre even got a brief news mention when a flight across the Atlantic was the fastest since Concord.
@@DrBovdin that would have been 38 mph not knots. Kts Is used only in the water
It happened before Vietnam. The ship was the lightest displacement ever of an Iowa in service. With the WWII, Korea or 80’s dispersant it would have been slower
i wonder if during the mothball period before the 80s they became inoperative on one ore more of the battleships? due to age and them no longer being in regular use might have caused someone to say to heck with it and they were replaced with the EM Log.
also, the improved accuracy of teh EM Log might have been seen as major plus for shore bombardment on stationary land targets.
Happy 2023! Still the same belt from 2019!
When Ryan was Showing where the probe was mounted, there was a light that needs replacing over on the left of the screen.
The problem with all of those older methods is that they only measure your speed relative to the surrounding water. If the water itself is moving, as with a current, your actual speed over the ground (just like airspeed when flying) isn't necessarily the same.
It's interesting to the trottleman all that matters is over water speed to navigation all that matters is over land speed
Interesting , Thank You . Have you ever heard of SINS? Satelite information Navigation System ?
SINS - Ship's Inertial Navigation System. Used on subs. No sats. Very accurate gyros, accelerometers, quite a bit of computing power, and more than a bit of classified magic.
Described at a rather high level in the PARS for IC2. No details, as it is a classified system. I knew what it was and very broadly how it worked. Nothing more, as we didn't have one.
looks like you have another light bulb to change
Or a bad starter/ballast.
@@gambit3le Most likely. I
Imagine what bulb maintenance looks like on an active ship with 24/7 vibration. Also, some of those yellow emergency lights contain lead/acid batteries which require maint and occasional charging. Ditto for the larger versions carried in the repair lockers.
It could really suck being the low guy in the EM Shop pecking order...
When I first got to the ship, I had 60 6V lead-acid batteries to test and fill. (120 VDC Backup for PBX and the Master/ Aux Gyrocompass systems.) At least mine were all in one space.
Ahh the pit sword. I remember raising and lowering it on the ships I was stationed on.
You need to replace a florescent lite in the back of the room.
Each of the methods is measuring the speed of the ship through the water, not over the ground. You touched on the need to account for the movement of the water several times but it's very important especially in areas with a lot of current and the higher latitudes (more tide). Have you done a video on ship navigation over the years of her life? Would love to see one
A very good point. Before GPS the only way to calculate speed and distance over land would be through plotting locations of the ship, measuring the distance travelled and and dividing by the time that it took to travel that distance. I believe that now days GPS can be used to give an accurate measure of speed over land.
@@garygreen7552 Correct. Problem is that GPS can be spoofed, jammed, or outright taken out. There is still a place in modern navigation for good sightings, an accurate chart, and a sharp pencil.
@@kevincrosby1760 Anything electronic can be screwed up by bad guys. I also understand that the Navy and the Coast Guard are again teaching navigation using a sextant, a chronometer and paper charts. However ships are using electronic charts and GPS as a primary way of navigating. A side note, Drachinfel, a channel on RUclips, has a video on early iron hulled ships used by the British East India Company. He noted that the captains of those ships discovered that the iron hull affected the magnetic compasses used at the time.
@@garygreen7552 I wasn't aware that they stopped. I can remember in the late 80's a gaggle of midshipmen out on a bridge wing with a sextant arguing over which star was which.
You also mentioned the age-old issues with a magnetic compass. That is actually the purpose of the iron balls found on the mag compass pedestal. They are adjusted to compensate for the hull of the ship.
Biggest problem with a mag compass is that they show Magnetic North, while charts are oriented to True North. Nav charts are generally marked with the Deviation in degrees between True and Mag North. Failing to make the required adjustment has put more than one ship on the reef. Even worse, it has been the probable cause of "Controlled flight into terrain" a few times. Hitting a reef can be survived, flying a jet into the side of a mountain, not so much.
To make life exciting, the Magnetic Poles are actually moving, so the published Deviation may not be correct if you don't have new charts.
Who here is ex-USN and caught the flickering light on the left at 1:16 and winced. "Hey, you got any bulbs? How about starters? Maybe the ballast is just bad?"
I personally believe the Statute Mile, or land mile as Ryan calls it, should be replaced by the Nautical Mile even when on land. I feel we should do this mostly to annoy people. Call it the Universal Mile, or the UniMile.
I love videos like this which cover less often discussed aspects of the ships. Often it's fun just to watch where all Ryan gets to as he moves about the ship to discuss things. Sometimes you're looking at something behind him and wondering what the heck is that thing? Then one or two more videos later, he tells you what it is, and while he's doing that you see this weird thing behind him, and it sets the whole cycle into repeat.
Hope you get a firm date for the drydocking soon.
Nah, go SI and adopt the kilometer eventually. You guys are 200 years late to the party😂
@@peterkoch3777 I categorically refuse, because that's what the so-called international community wants. 😉
@@Sanderford so it is pure stubborness? Guess why they will never give up the land mile😂
@@peterkoch3777 Also we went to the Moon using statute miles. 😉
@@Sanderford yes, and ruined a mio $$$ space probe by mixing miles and km.
A nautical mile is not 6000 feet. It's one minute of arc in latitude, 1/(60*90) = 1/5400 of distance from the equator to the north pole,1851.58 m. More recently they rounded it to the nearest meter, to get to 1852 meters. ~6074ft by the old definition or ~6076 by the new. In any case not 6000.
So, is that going to be the next confined place Ryan crams himself into?
I thought for sure Ryan would have been under the deck grate and into that confined space!
so this pit sword or EM log, passes through 3 layers of the bottom steel. how would they have been able to pull it up and into the ship, and get the hatch closed against the pressure of the sea trying to flood the ship? you said that it wasnt something that was left in place so it was obviously installed and retracted on more than one occasion...
you mention 'falling through a pit of death in the deck'. when my dad was in the Navy (boiler technician 3rd), they lost all power and lights while switching from ship power to shore power (or vice versa) and he turned to head up to the light from the task he was on and stepped into a 'pit of death' on a grated catwalk. a fellow sailor had pulled up the grating to work on his task and never replaced it. he tore up his knee, ruptured 4 vertebrae in his back, damaged a kidney and dislocated a shoulder. he spent 30 days on his back in the base infirmary, unable to move.
The pitsword has a sea valve at the bottom and a packing gland at the top.
When it is raised the sea valve is closed. When the sea valve is opened and the pitsword lowered the packing gland is adjusted to keep out the water.
You will probably have a bit of water come in around the pitsword while being raised and lowered, as you need to back off the packing gland a bit to allow movement. However, not much, and it only takes 2 or 3 minutes to actually raise or lower...assuming that you are strong enough to crank it that fast.
What an interesting video! For me I cannot survive within the bowels of the ship due claustrophobia.
The Pit Log operates on the Bernoulli principle or Bernoulli's Law which basically describes a relation between pressure (static and dynamic) and flow speed. I wouldn't call it "less sophisticated" as this principle is still the way to measure the speed of aircraft, the instrument is called a pitot tube. "Pit Log" is probably short for "Pitot Log", which is named after the gentleman who invented it: Herni Pitot.
I had someone who worked for me that was stationed on the New Jersey and he said that they did not have sonar because they would have had to break through the hull to install it. So a sub had to shadow it wherever it sailed. Is that true?
A bit off topic. Could you fire up the auxiliary diesels, are they also intact and preserved?
When were you at the Taney? I think we did a BSA overnight in 2012.
Nautical mile has nothing to do with the distance in feet. A nautical mile was originally defined as the meridian arc length of one minute of latitude. (So if you sail 1 degree straight north, that's 60 nautical miles.) It has since been redefined to exactly 1,852 meters. (This works out to 6,076 + 44/381 feet)
I always thought NMs were 1.5 miles, thanks for the correct figure as 1.15 vs 1.5 make a big difference at long distance equations.
What's that red painted framework between you and the camera at the end of the video? It looks as though it held something pretty sizeable at one time.
Fire bottle holder. In my time onboard there would have been two bottles of Halon in the rack.
Nice work. Ryan mentioned dry docking plans. Any idea on the timeframe for dry docking? Definitely want to make a visit before.
Given they have barely done more than discuss it, I'd guess a good few years yet. It took Texas several years to get a dry dock sorted, and that's when it was known she was an urgent case with the danger of sinking....
Wow, there is devices crammed into everything on these ships, and someone used to be trained to operate them. I wonder if there ever was a complete, compiled User´s Manual for an Iowa-class battleship, and how that would look like. Probably a couple of cabinets.
I wonder why they went from two measuring devices to one? If there's one thing that I've learned about battleships from this channel, it's how much they value redundancy. For a piece of equipment that is so critical for fighting the ship, it seems odd that they didn't have two installed, especially as they already had the openings in the bottom of the ship.
The deeper tech is interesting. :)
I am a retired US merchant marine officer. Such precision with my USCG tests down to 1/1000 of a knot or nautical mile was never required. Accuracy needed was never more than a tenth, for anything. A nautical mile is defined as 1/60 of a degree of latitude.
It’s official name among sailors is “pit sword”
Making turns for 32 knots.
Maneuvering, aye!
But measured speed it 27 due to ships load, hull conditions and mother nature!!
@@johnchilds6471 - and slippage
Modern Speed Logs still are retractable. This is more so they can be retracted before the ship is moved into drydock than anything else. Also because they can measure both longitudinal speed and transverse speed, so they also need to aligned to the ship, also acomplished at the through hull.
I was given a tour of that space last year and i thought that tube looked like it was for measuring speed. But when i asked the tour guide he had no idea what i was talking about.
Attempting to explain to junior officers the difference between EM LOG speed (speed through water) and GPS-derived speed (speed over ground) was a major part of being a Combat Systems Officer of the Watch on a DDG.
There were times that I thought that being Duty IC was comprised mainly of responding to "burned out light bulb" calls to instead educate junior deck officers on the wonders of the little knob marked "DIM". With practice, I learned to do so without insinuating that the gyro repeater wasn't the only "dim bulb" on deck.
I did however get in a bit of trouble once on a "distorted mic" call, when I suggested to the BMOW that the mic would be just fine if he wasn't trying to give it a instead of holding it a few inches away from his mouth.
@@kevincrosby1760 That was the nice thing about being an ET2... I had no problem telling other 2nds and below when they were dumb.