The cobwebs in my brain are just starting clearing to remember half of the Naval Engineering course from third year. Looks like I will have to watch this a few times.
I disagree… I didn’t enjoy this video. Maybe some pictures or diagrams would better explain the concepts to us outsiders. But I do love when a person gets 20 minutes to talk about something they’re passionate about. I love to get behind that!
Former captains of the Iowas always mentioned how surprisingly maneuverable they were, especially at higher speeds. They said that they had to warn smaller ships turning in a formation with them not to "turn inside" an Iowa-class ship's track because the Iowas could frequently out-turn the smaller ships and run the risk of cutting one in half.
@@philsalvatore3902 IIRC, the captain of the Missouri once warned his formation about that, but a destroyer pilot didn't listen and the Missouri took the flag pole off of the destroyer's fantail rigging.
We're so lucky to have Drach, who's been to NJ multiple times as Ryan and Drach seem to have become really good friends. What a treat to hear him get technical on the vibration issue.
As a Naval Architect and Marine Engineer with over 50 years of experience working in, on and around ships I think this conversation touches on a lot of issues but never really answers the question. The USN was well aware of the vibration issues associated with North Carolina and worked hard, as pointed out, to solve them. Until the advent of high speed modern computers Naval Architects of the 1930's could not solve the complicated hydrodynamic equations required to solve the vibration issues. Their only recourse was at sea experimentation. This they did and settled on the 4 bladed out board screws and the 5 bladed inboard screw design to move the vibration away from the cruising speed and below full speed. During towing tank testing for the IOWA design it was noted she had similar vibration issues primarily due to the skegs which were incorporated into the design to reduce drag from exposed propellor shafts and provide structural strength to the hull in the stern to support the #3 turret. Again the solution was to use different size propellers on the inboard shafts and outboard shafts. Another issue facing the designers, which is not mentioned here, is cavitation. The inboard screws are operating in the wake of the outboard screws (turbulent water) and are thus subject to cavitation at low RPM. In the 1930's propellor design was a black art (due to the lack of high speed computers) and propellors were designed by experimentation. But what was known was that if you increased the expanded area ratio of a propeller one would increase the RPM of the propellor before the onset of cavitation . Note that cavitation means vibration. The expanded area ratio is the area of all propeller blades divided by the propellor diameter. So bottom line; there are two different props on the IOWA class to eliminate cavitation and vibration while at the same time reducing hull drag. Also note that the SS United States also has a similar propeller arrangement and she holds the world speed record for a Trans-Atlantic crossing. The Lead Naval Architect for her design was William Gibbs who was also a member of the General Board headed by USN Captain Chantry which was responsible for the IOWA Class design.
The stern layout was most definitely a compromise using practical observation as a best estimate. I do not think any design from that era would be "better" unless by pure luck. Gibbs was a pretty clever guy and known for attention to details - I'm fairly confident that if improvements could have been made, they would have likely been in the next class (which was cancelled).
I wanted to add that a small Italian cruise ship on which the LCS-1 is based shattered that record in 1992 crossing the Atlantic in a little over two days and ten hours. She was denied the Blue Ribband because the organization that awards it refused to acknowledge the Italian ship was an "ocean liner". She was more of a pocket liner for private cruises, but one heck of a fast one!
@@tcoradeschi Yep! It applies in all cases across pretty much all fields. In history if you give a quick, categorical answer, it’s likely to be very, very reductive and incorrect.
What his description needs is an animation of the concepts he is talking about. I pictured everything he said, but I think the average person would be lost in the various phrases.
An "engineer" who has never used it. Drach only made a couple mistakes in his explanation, the water would be curling under the skegs giving the differential velocity vector, and resonance is fixed via structural rigidity or eliminating the differential velocity vector, and those skegs make the ship LESS maneuverable, not more as the thrust from the props give it the maneuverability. Otherwise good explanation by him with the obvious, you have to have a KEEL to drydock the ship and thus the skegs + survivability. The only true way to fix this would be to have drop down skegs for docking and propeller shaft tunnels which can be truly sealed. Neither of which is all that practical ultimately forcing one to be a slave regarding cost and practicality, thus the skegs.
@@virginiaorganbuilder my son and I went to the Victor. We drove a 1500 mile round trip to do it. It was a great time. Drachinifel is such a real guy to talk to. There were only about a dozen of us there. Everyone just joining in the conversation. One gentleman brought some very rare photos to share. My son (15) shared a battleship design he'd drawn and everyone discussed. He was thrilled. If you ever get the chance to do a meet up, it's very much worth the effort.
while you are out of the water, you should see if you can get someone to come in and do a complete 3d scan of the hull. you have the plans of how it should have been shaped, but how close to the plans is the reality? And once you have a good scan of the hull, it can then be put into a CFD program to test the various theories. As for a fresh Battleship design, there has never been a Battleship designed with computer support for the hull design, I'd bet that with a lot of computer design and optimization, the outer skin of the hull would gain quite a few subtle curves to manage the wake at high speed
What you’re talking about would be quite expensive and, thankfully, they’ve been very strategic with their spending on this project. While that would be nice to have I don’t see how it would benefit anyone or help the museum in its mission. Now if someone wants to foot the cost I’m sure they wouldn’t object.
@@cruisinguy6024 You're talking tens of thousands at the low end. Something that large could run into the six figure mark easy. When I was on C-130's we had guys come in to scan a gunship. Not the whole plane, just a handful of the antennas on the belly to update the model they already had. When we talked to them, they told us just to scan for a day was over ten grand. Though, most of the cost is in the second half importing and updating.
now we had CFD to aid on design of any shape interacting with fluids. Most of the issues plaguing ships like Mauritania, South Carolinas, or the Queen Mary rolling around could be avoided by today's simulation tech. You don't need to have the actual ship on sea trials, and wait several months to have a new screw designed, fitted and tested.
The Navy did extensive analysis of the vibration problems and the late-war and post-war reports from DTMB (David Taylor Model Basin, now NAVSEA Carderock) are available online for all three classes of fast battleship--North Carolina, South Dakota, and Iowa. The reports characterize the vibration as axial and discuss the measurements, analysis, model testing, and full scale testing performed.
@@OfficialUSKRprogram looked like he was using a drill to tighten something, counting along rows or whatnot to make sure he got em all. but that's a guess
BBNJ's, what I can only call, "ongoing love affair" with drach is probably the best thing ever. More reasons to get drak talking about ships is always going to get a like from me
Thank you so both for this well done and informative episode, fascinating info. In 1940, my father, who had a Doctorate in Mechanical engineering, was working at Electric Boat trying to improve the design for the hull and propellers for quieting the fleet submarine designs. Once the extreme prop vibrations on the North Carolina class became evident he was tasked by the Navy to help diagnose the problems and recommend solutions. I was unaware of his participation, partly because I wasn’t born until 1945, but the real reason was he and his team were sworn to secrecy as the Navy wanted both the problems and solutions to be secret. I didn’t know about this until upon his death in 1973 at his memorial a retired representative from the Navy informed us of his accomplishments. I respect the need for National Security but I certainly would have liked to know of his work especially since the Carolina Class were scrapped beginning in 1959!
Also worth remembering, that most designs were evolving improvements, from previous designs, and were done with pencil and paper and slide rules. Really amazing work
Talk about diving down the rabbit hole, but everything you talked about made sense. Maybe some baffles in the tunnel to slow the water would have helped, but that would me more drag as well.
Drach only made a couple mistakes in his explanation, the water would be curling under the skegs giving the differential velocity vector, and resonance is fixed via structural rigidity, and those skegs make the ship LESS maneuverable, not more as the thrust from the props give it the maneuverability. Otherwise good explanation by him
Been watching BSNJ and Drach's videos for years. This is absolutely one of the best I've ever seen. Super informative, and thought provoking. Thank you both for your continued collaborations!
*I get it. What he's saying is if you drove that ship through the snow. As they're many videos of R/C Boats being driven thru the snow and they perform quite well. In the cycled-through snow, there'd be much bigger piles left behind from the "Rooster Tails" in the inboard props grooves in the snow than the outboard props grooves. And there's the unequalized vibration.The P-51 Mustang used the **_"Meredith Effect"_** to turn aerodynamic drag from its radiator cooling ductwork into usable jet thrust increasing its top speed from 410 mph to 440.*
The whole water flow situation reminds me of the B-36 with it's pusher props mounted on the trailing edge of the wing. The air coming over the top of the wing is at a different speed that the air along the bottom. This led to a unique "muttering" sound.
@@philsalvatore3902 We don't get many 'Bears' where I live, but the old Avro Shackleton also had twin contra-rotating propellers, with a very harsh sound.
I believe there was some success on ocean liners by opposing the rotation of props. So basically reverse rotation of the inboard props or the outboard props. I dont remember if it was the Mauretania class or the Normandie where they tried this. Both had similar issues.
One of the most interesting videos about New Jersey, kudos. A typical solution to resonance is to stiffen the offending element to change its natural frequency to range that is outside the normal operating frequencies of the rotating elements. My father and his friends worked on the construction of the ship as welders. They all lived in a nearby Philadelphia neighborhood. Sometimes they commuted to Camden by auto when there were sufficient gas rationing stamps to operate one car occasionally.
A similar vibration effect is seen in wind turbines as each blade crosses in front of the column. Momentarily that blade loses some power causing the whole rotor to place unequal loads across the bearing and at a given frequency that happens to be near that of the column. The third blade in a wind turbine does not produce much extra energy it is there to offset the resonance by halving the rotational speed needed for two bladed sails whose needed rotational speed is well in the range of the severe resonance of the column. Perhaps the Titanic may had the solution with three propeller system and utilized a very pressure turbine to drive the middle shaft. However vibration problems are always a nightmare in these as the easiest solutions always interfere with the some other critical design feature.
Oooh boy you stirred the pot by mentioning the Titanic. Apparently she and her sisters went through several iterations of propellor layouts and blade counts. Apparently there’s still no clear consensus on what the configuration was for the Titanics fateful voyage.
@@cruisinguy6024 Err .... Yes. Seems there is no ideal configuration. Titanic had a neat engine efficiency configuration. When you are dealing with this level of power the amount of energy from even a small mid configuration can set everything a tremble.
To correct Iowa Class vibration problems (periodical publications have issues) I would model the hull using computational fluid dynamics software to experiment with different stern configurations including a transom stern and test different kinds of propellers with skewed blades, along with Prairie and Masker to see of bubbler systems affect vibration.
A transient vibration occurring at distinct speeds within its range suggests to me that the Holland tunnel could be equipped with some sort of active flaps or rotatable eccentric cylinders that would minorly reshape the tunnel enough to rapidly "skip" the harmonic causing the vibration by preferably transferring it to a previously attained speed. Anyway, I greatly appreciate both of you on sharing your wealth of knowledge regarding the history of naval vessels. Fantastic.
The fluid dynamics are so complicated, the only way to “solve” the vibration issues would be to take a Time Machine with a pretty decent data center, along with the software back to 1940. Even then, there may not be a perfect solution given the Panama Canal constraints.
I agree. It's chaos back there and there are probably complex cavitation effects from the washes of the outboard propellers that are contributing factors as well.
@@BlueSpruce2 I barely know my arse from a hole in a ground and once Drach started describing the interaction of the outboard water from the stuff shooting out from the hull tunnel I immediately thought of the mess coming off of those propellers. Like wouldn't they just be shooting pure turbulence at the inboards?
Because the propeller shafts are not level but are angled downwards somewhat, (right?) so are the propellers. This results in more pitch in the propeller blade while rotating downwards (in this case the outboard blades on the inboard propellers) and less pitch in the blade rotating upwards (their blades on the inboard side). If the inboard propellers were swapped, then there would be the greater pitch on their inboard sides where the faster moving water is instead of where they are now in the slower water. Of course the shafts would have to be rotated in the opposite direction from what they do now.
Very interesting and informative. When Mighty Mo got to 30 knots, there was an obvious vibration in her stern. Even so, with eight burning and four turning, moving at that speed was exhilarating!
Watching this my mind went in a different direction. As a Sonar technician with an ASW rating I can see the different number of blades on the propellers rendering a technique of ASW ineffective. I do not feel I can be more specific because of the confidential of the subject, but I cannot imagine trying to use the technique against the New Jersey.
That's funny you say that because the Midway class had much the same hull as an Iowa class, the same propulsion and props and sonar operators I was familiar with told me they were both noisy and had an instantly recognizable acoustic signature.
I agree with the suggestion of getting rid of the Panama Canal requirement. There are shipyards on both coasts, they could build 2 or 3 for the Pacific and the same for the Atlantic and just rotate within their own ocean
Canal was expanded. At the time the Iowas were built the canal was 110 ft wide and allowed the passage of Panamax ships. The expanded waterway began commercial operation on June 26, 2016. The new locks allow transit of larger, Neopanamax ships, up to 160 ft wide.
It’s not really an issue for large Navy carriers these days. For example the USS George Washington is on her way to Japan by way of the Magellan Strait
I was on the USS Trenton lpd 14 and when I tell you I thought that ship was going to come apart at flank speed (only 20 kts on that old turd) I never felt a ship shake like that before. I was on the aft gun mount on the fantaile and I thought the back end of the ship was going to break off from the vibrations. I've also been on modern destroyers and they also shake at certain speeds. I think it's just a problem that's going to be there so long as physics are what they are.
Great vid!!! But..... The burning question is what the guy on the lift is doing?!? Waving what looks like a drill at a prop? Inquiring minds want to know!
Great conversation, thoughts for Alex, what about spray deflectors on bow to move water into tunnel area, other thoughts are done after laid, flat plate on top of tunnel, similar to E-boats and Fairmile D stern. To knock water to props and similar hysocat, trim plane across bottom of skegs. I wonder if David Taylor center ever worked on fix or was busy with development projects.
Great video guys!!! That was very fascinating listening to all the different theories on what could possibly cause the vibration. Very informative, and really makes you think….
Without testing, I'm inclined to think that the turbulent water from the outboard propellers when mixed with the mostly laminar flow of the water in the tunnel is going to produce vibration. You might have been able to use some sort of water divider system (a skeg between each of the propellers, for instance) to keep each prop in its own, relatively constant, water stream. Alternatively (and this wouldn't work for those propellers on that beam), you could mount your props horizontally rather than in echelon, so the turbulence wouldn't travel from one prop to another.
What Drach seems to be describing is vortex shedding off the skegs because of the unequal velocities inside the Holland Tunnel and outside. If the vortex shedding frequency is near a characteristic frequency of the prop then it can result in a resonant interaction that will vibrate the stern. The vortex shedding frequency and the prop frequency are dependent on the speed of the ship and the rpm of the prop respectively so that is why the vibration only shows up at certain speeds.
It would be my guess , that the rez frequencies are hull deformation, or skeg flexing . There is a lot of stored energy in that hull . Prop pulse , yea , if you get everything just right , hard to stop. At the beginning of the prop tunnel , the shape should be arched at the beginning , ovel shaped , then move to a open bottom box shape.
I started learning about the Pacific War in 1965 when I read all 15 volumes of Samuel Eliot Morison. I've seen all 300 Drydocks and many episodes of Battleship New Jersey. And I still learned so much from this episode. And this is something you simply can't cover in a book or in a classroom. Being under the ship makes it so much easier to understand. Should we be thinking of Drach as the "Bono" of Naval history?
I am a little confused by Drach's comment regarding the Venturi effect.around 7:40 in the video. I would think with increasing cross sectional area, the speed of the water would be lower and not higher. Of course this is not a fully enclosed volume, so maybe some additional factors come into play?
Yes. As the volume increases, the velocity of the water decreases and pressure rises. Anyone who has tuned carburetors knows this. The narrow venturi in a carb throat causes the intake air to speed up, and as it speeds up pressure drops. That pressure drop is what pulls fuel up from the float bowl, through the needle jet and into the air stream where it is atomized.
@@physicsphirst191 I was surprised to hear an engineer make that mistake, but that video was like trying to do math on Excel real time during a Teams meeting O_O Your boo-boos and brain farts are there for all to see and, um, enjoy.
@@philsalvatore3902 He didn't use many engineering terms to describe the phenomenon... such as static pressure, dynamic pressure, skin friction, drag, pressure recovery, drag coefficient, flow separation, Bernoulli's equation, angle of attack, etc, and I don't think it was because he didn't want to baffle the audience. It was gibberish to me, and I'm an engineer, so I think the lay audience was mislead.
Learning every day! Drach has answered a lot of questions that I didn't know existed. For prop-vibes, try an IOM ferry: I out my bike on the centre-stand for the crossing out to the TT one year. When I rode it off, the stand had broken from the vibes, and one half was clattering on the ground.
Fairing the insude of the Holland Tunnel to reduce the rise in height as the tunnel transitions to the stern would reduce the volume of water at greater velocities versus the outboard side of the skegs. You could today's run effective FEI modeling analysis to obtain similar computer generated results. In essence a 3D equivalent to a "water" version of a wind tunnel. Ideally lowering the exterior hull while retaining the aft hull rise. Along with applying new prop technologies an overall reshape of the tunnel with newer prop design might well be appropriate for this ship and otherks smilar in design and build. Anyway just a thought considering fluid dynamics of water transiting down the hull.
I didn't know of the vibration issues. Drach's explanation though long was extremely interesting. I had no idea of the physics behind water movement and forces the ship generates while in motion. Thank you
There will either be a dead zone at the back of that tunnel, or it will be drawing serious amounts of water under the skegs, causing lateral vortices. Either way, a couple of veins in a similar form as the skegs (but narrower and tapered) maybe 2/3 the length of the tunnel would probably help with uniformity of flow to the props.
The main vibration excitation in the modern passenger cruisers and most other ship types as well is propeller blade cavitation, creating major load pulses at blade frequency. While Drachinifel makes many valid points, that phenomenon has certainly existed in battleships also and should have been mentioned at least as a very possible trembling elephant in the room 🐘
thanks for the collabaration video, it was a pleasure to listen. To Ryans question, what would we do to reduce vibrations. I see two approaches: 1. with the overall geometry fixed because of panamacanal and docking etc, we could still alter the properties of the surfaces. Like a noisy room with hard surfaces, by adding absorbing materials to the surface you can alter the acoustic behaviour of the whole room. alternative you may alter the flow of the water near the surfaces by materials anlog to a Golfball or sharkskin. there is a lot of develpment in this field ongoing in the aviation industrie. 2. changing the symetrical layout of the "Tunnel" to a asymetrical. We are used to prefer symetrical solutions for our constructions, but this is a risky aproach in fields where resonances are occuring. May be shorten one side or/and altering the curve of the hull on the other
Drachinifel: "Well, I don't know where this expert is, but..." 😆 It was such a satisfying experience seeing the engineer explain problem solving challenges encountered in battleship hull design. This was a great video. And shot under the actual battleship too! Not just a recorded webinar. Such a satisfying watch for a subscriber to both channels. 😁👍
William Froude is the man who conducted thousands of test tank experiments and formulated hydrodynamic theories that still form the basis of our understanding today - resonance can be astonishingly destructive when one cycle builds on another and can quickly get out of control
Reminds me of an episode concerning former german truck-maker Krupp. They had an issue with drive-shafts breaking and tried to solve it by reinforcing the shafts, but they kept breaking. Until they realized that the shafts broke because of vibrations interfering. The solution was making the shafts weaker, i.e. lighter, so their own frequency was higher, and interference occurred at speeds that the trucks never achieved. Keep that in mind if you ever prepare a vintage Krupp truck for drag racing. As a solution for New Jersey's vibration issues, I suggest mounting balancer-shafts like they use in motorcycles to cancel out vibrations (shame really, since vibrations are an essential part of the classic motorcycle experience). A silly solution, I know, but explicitly you asked us laypeople for a solution to a problem that experts have had difficulty with for decades, so what did you expect?
As to Ryan's closing question, 'what would I do', the only thing that comes to mind for me is perhaps a series of cuts in the skegs allowing water to flow from outboard through to inboard, to equalize the internal pressure volume as the cheerfully-named 'Holland Tunnel' expands. But that introduces drag and structural integrity questions that might make it a null gain, if not worse.
There's reasons why the NoCal and Washington weren't sent into the frontline, even though they went into service pre Pearl Harbor, and one of them is vibration, they finally solved it in mid 1942 iirc. Also the USN learned from this and made sure it won't happen with the Iowas
One thing I heard about on some new ships is that they are using offset props. There are 2 versions of offset props, the first being that the blades are not evenly spaced. The other way is that not all the blades are the same length. You can have symmetrical or asymmetrical offset. For symmetrical, if you imagine a 4 bladed prop, blades 1 & 3 will be 20 meters across. Blades 2 & 4 will be 25 meters across. For Asymmetrical, blade 1 will be 15m long, blade 2 will be 10m long, blade 3 will be 7.5m long, however will be weighted to balance against the 15m blade, and the 4th blade will be 10m again.
Great to see Drach and hear his analysis. I had never heard about this issue before, but I now notice something that he brought my attention to. I'm an F1 fan, and a mechanical engineer. In Formula 1 racing, they use ground effect to provide aero down force. The floor, undersides look like the "Holland Tunnel" on Battleship New Jersey. The theory is that the velocity of the air in the venturi (the tunnel) is much higher than on the sides of the floor. That creates a vacuum below the flow from the tunnel. Obviously no "ground effect" here but the same theory I would think. I didn't run any calculations, but with accelerated flow through a venturi, flow can "choke", that is, when no additional flow can pass through the venturi no matter how fast the object is moving through a fluid. I wonder if "choking" is a problem here, or do you need to be going much faster for that to happen? By the way Drach, I am a subscriber and enjoy your commentary and analysis.
Ryan and Drach - the collaboration the world never knew it could have, but the one that we all so desperately wanted.
@@frankbarnwell____ohio checking in lol
Wasn't the first time, and let's hope it's not the last! Always a treat.
Yeah not the first time. Highly recommend watching Drach climb to the top of New Jersey and overcome his Vertigo. It's a fantastic video!
@@iwantmyvanback not for poor Drach lmao
Maybe the CIA is reinstating her! Don’t tell anyone
Massive props to Ryan and Drach! 😝
And over them😂
I see what you did there
Excellent!
Best comment ever.
Angry up vote
You knew Drach wasn't going to miss the opportunity to get a look under her.
He was scheduled to lead a series of the drydock tours.
@@craigf6277That would be fantastic!
Shame it wasn’t a hovercraft
He's been to the top. Had to make a journey to see the bottom
He 's a dirty boy looking under her skirt, but he is our dirty boy. Excellent communication and learning in this one.
I love watching Drach answer a question with a long, rambling, multi-faceted, explanation. It scratches all the itches in my brain. Haha.
More isn’t less, I love it too.
The cobwebs in my brain are just starting clearing to remember half of the Naval Engineering course from third year. Looks like I will have to watch this a few times.
🥰
He’s a very good explainer.
I disagree… I didn’t enjoy this video. Maybe some pictures or diagrams would better explain the concepts to us outsiders. But I do love when a person gets 20 minutes to talk about something they’re passionate about. I love to get behind that!
Former captains of the Iowas always mentioned how surprisingly maneuverable they were, especially at higher speeds. They said that they had to warn smaller ships turning in a formation with them not to "turn inside" an Iowa-class ship's track because the Iowas could frequently out-turn the smaller ships and run the risk of cutting one in half.
Any link or an example of this?
I've read that too.
@@philsalvatore3902 IIRC, the captain of the Missouri once warned his formation about that, but a destroyer pilot didn't listen and the Missouri took the flag pole off of the destroyer's fantail rigging.
We're so lucky to have Drach, who's been to NJ multiple times as Ryan and Drach seem to have become really good friends. What a treat to hear him get technical on the vibration issue.
As a Naval Architect and Marine Engineer with over 50 years of experience working in, on and around ships I think this conversation touches on a lot of issues but never really answers the question. The USN was well aware of the vibration issues associated with North Carolina and worked hard, as pointed out, to solve them. Until the advent of high speed modern computers Naval Architects of the 1930's could not solve the complicated hydrodynamic equations required to solve the vibration issues. Their only recourse was at sea experimentation. This they did and settled on the 4 bladed out board screws and the 5 bladed inboard screw design to move the vibration away from the cruising speed and below full speed. During towing tank testing for the IOWA design it was noted she had similar vibration issues primarily due to the skegs which were incorporated into the design to reduce drag from exposed propellor shafts and provide structural strength to the hull in the stern to support the #3 turret. Again the solution was to use different size propellers on the inboard shafts and outboard shafts. Another issue facing the designers, which is not mentioned here, is cavitation. The inboard screws are operating in the wake of the outboard screws (turbulent water) and are thus subject to cavitation at low RPM. In the 1930's propellor design was a black art (due to the lack of high speed computers) and propellors were designed by experimentation. But what was known was that if you increased the expanded area ratio of a propeller one would increase the RPM of the propellor before the onset of cavitation . Note that cavitation means vibration. The expanded area ratio is the area of all propeller blades divided by the propellor diameter.
So bottom line; there are two different props on the IOWA class to eliminate cavitation and vibration while at the same time reducing hull drag. Also note that the SS United States also has a similar propeller arrangement and she holds the world speed record for a Trans-Atlantic crossing. The Lead Naval Architect for her design was William Gibbs who was also a member of the General Board headed by USN Captain Chantry which was responsible for the IOWA Class design.
Wow. Great input!
The stern layout was most definitely a compromise using practical observation as a best estimate. I do not think any design from that era would be "better" unless by pure luck. Gibbs was a pretty clever guy and known for attention to details - I'm fairly confident that if improvements could have been made, they would have likely been in the next class (which was cancelled).
Fascinating read. Thank you.
I wanted to add that a small Italian cruise ship on which the LCS-1 is based shattered that record in 1992 crossing the Atlantic in a little over two days and ten hours. She was denied the Blue Ribband because the organization that awards it refused to acknowledge the Italian ship was an "ocean liner". She was more of a pocket liner for private cruises, but one heck of a fast one!
I kind of want a shirt with a picture of Drach on it that says “Not entirely” on the front and “Yes and no” on the back.
King of qualified answers.
Warning: degreed engineer turned project manager: the correct answer is ALWAYS “it depends”
@@tcoradeschi Yep! It applies in all cases across pretty much all fields. In history if you give a quick, categorical answer, it’s likely to be very, very reductive and incorrect.
I think "In and of itself" is a close second
I want one that has ship silhouettes with the caption, "ships that ran aground in their own waters club"...
When things are much of a muchness, what're you supposed to do?
Remember, Drach is an engineer by training, so his input and knowledge is beyond the layman!
What’s a layman?
@@CaymanIslandsCatWalks a layman is an untrained person in some subject.
100%
What his description needs is an animation of the concepts he is talking about. I pictured everything he said, but I think the average person would be lost in the various phrases.
An "engineer" who has never used it. Drach only made a couple mistakes in his explanation, the water would be curling under the skegs giving the differential velocity vector, and resonance is fixed via structural rigidity or eliminating the differential velocity vector, and those skegs make the ship LESS maneuverable, not more as the thrust from the props give it the maneuverability. Otherwise good explanation by him with the obvious, you have to have a KEEL to drydock the ship and thus the skegs + survivability. The only true way to fix this would be to have drop down skegs for docking and propeller shaft tunnels which can be truly sealed. Neither of which is all that practical ultimately forcing one to be a slave regarding cost and practicality, thus the skegs.
Took the tour last weekend, and even got to meet Drach and chat with him for a while. Fantastic! And if you don't have your tickets yet- HURRY!
Jealous!
Were you at the Victor?
@@jarodstrain8905 I wish! Just saw him at the merch table.
@@virginiaorganbuilder my son and I went to the Victor. We drove a 1500 mile round trip to do it. It was a great time. Drachinifel is such a real guy to talk to.
There were only about a dozen of us there. Everyone just joining in the conversation. One gentleman brought some very rare photos to share.
My son (15) shared a battleship design he'd drawn and everyone discussed. He was thrilled.
If you ever get the chance to do a meet up, it's very much worth the effort.
Love it when these two collaborate.
Yes indeed...still think it would be fun to watch them play Battleship on the Battleship New Jersey.
What other vids did they colab on?
Always a blast to see Ryan and Drach together
while you are out of the water, you should see if you can get someone to come in and do a complete 3d scan of the hull. you have the plans of how it should have been shaped, but how close to the plans is the reality? And once you have a good scan of the hull, it can then be put into a CFD program to test the various theories.
As for a fresh Battleship design, there has never been a Battleship designed with computer support for the hull design, I'd bet that with a lot of computer design and optimization, the outer skin of the hull would gain quite a few subtle curves to manage the wake at high speed
Would have to been done after the 80s when computers were able to do this
What you’re talking about would be quite expensive and, thankfully, they’ve been very strategic with their spending on this project.
While that would be nice to have I don’t see how it would benefit anyone or help the museum in its mission. Now if someone wants to foot the cost I’m sure they wouldn’t object.
@@cruisinguy6024 You're talking tens of thousands at the low end. Something that large could run into the six figure mark easy.
When I was on C-130's we had guys come in to scan a gunship. Not the whole plane, just a handful of the antennas on the belly to update the model they already had. When we talked to them, they told us just to scan for a day was over ten grand. Though, most of the cost is in the second half importing and updating.
now we had CFD to aid on design of any shape interacting with fluids. Most of the issues plaguing ships like Mauritania, South Carolinas, or the Queen Mary rolling around could be avoided by today's simulation tech. You don't need to have the actual ship on sea trials, and wait several months to have a new screw designed, fitted and tested.
@@1986arseny I really wonder what generative optimizations would do.
And I have to wonder about the Ford class carriers and their hull efficiencies
The Navy did extensive analysis of the vibration problems and the late-war and post-war reports from DTMB (David Taylor Model Basin, now NAVSEA Carderock) are available online for all three classes of fast battleship--North Carolina, South Dakota, and Iowa. The reports characterize the vibration as axial and discuss the measurements, analysis, model testing, and full scale testing performed.
Glad you could get a chance to see her in dry dock Drach.
I hope it filled a bucket list item for you. I know it would for me.
The guy in the scissor lift is my hero 😂
How many people watching this video checked their phones too? lol
what the genuine fuck was he doing? lol
@@OfficialUSKRprogram looked like he was using a drill to tighten something, counting along rows or whatnot to make sure he got em all. but that's a guess
Like how he's working in a shipyard, but wearing shorts.
Looks like he was using a battery drill to tighten the prop shaft.
BBNJ's, what I can only call, "ongoing love affair" with drach is probably the best thing ever. More reasons to get drak talking about ships is always going to get a like from me
Engineers and Curators and Historians, Oh My! A very interesting conversation…Thx Ryan and Drach!
Thank you so both for this well done and informative episode, fascinating info. In 1940, my father, who had a Doctorate in Mechanical engineering, was working at Electric Boat trying to improve the design for the hull and propellers for quieting the fleet submarine designs. Once the extreme prop vibrations on the North Carolina class became evident he was tasked by the Navy to help diagnose the problems and recommend solutions. I was unaware of his participation, partly because I wasn’t born until 1945, but the real reason was he and his team were sworn to secrecy as the Navy wanted both the problems and solutions to be secret. I didn’t know about this until upon his death in 1973 at his memorial a retired representative from the Navy informed us of his accomplishments. I respect the need for National Security but I certainly would have liked to know of his work especially since the Carolina Class were scrapped beginning in 1959!
Also worth remembering, that most designs were evolving improvements, from previous designs, and were done with pencil and paper and slide rules. Really amazing work
Talk about diving down the rabbit hole, but everything you talked about made sense. Maybe some baffles in the tunnel to slow the water would have helped, but that would me more drag as well.
Drach only made a couple mistakes in his explanation, the water would be curling under the skegs giving the differential velocity vector, and resonance is fixed via structural rigidity, and those skegs make the ship LESS maneuverable, not more as the thrust from the props give it the maneuverability. Otherwise good explanation by him
yeah.,., that rabbit hole was the holland tunnel it seems
Been watching BSNJ and Drach's videos for years. This is absolutely one of the best I've ever seen. Super informative, and thought provoking. Thank you both for your continued collaborations!
*I get it. What he's saying is if you drove that ship through the snow. As they're many videos of R/C Boats being driven thru the snow and they perform quite well. In the cycled-through snow, there'd be much bigger piles left behind from the "Rooster Tails" in the inboard props grooves in the snow than the outboard props grooves. And there's the unequalized vibration.The P-51 Mustang used the **_"Meredith Effect"_** to turn aerodynamic drag from its radiator cooling ductwork into usable jet thrust increasing its top speed from 410 mph to 440.*
The whole water flow situation reminds me of the B-36 with it's pusher props mounted on the trailing edge of the wing. The air coming over the top of the wing is at a different speed that the air along the bottom. This led to a unique "muttering" sound.
The Cessna Skymaster with its twin push-pull propellers makes a very distinctive sound.
@@gordonrichardson2972 TU-95 Bears with their counter rotating props also have a distinct sound.
@@philsalvatore3902 We don't get many 'Bears' where I live, but the old Avro Shackleton also had twin contra-rotating propellers, with a very harsh sound.
@@gordonrichardson2972 True. Our battle group had the mandatory Bear visits crossing the Pacific in a region known as "the Bear box".
I believe there was some success on ocean liners by opposing the rotation of props. So basically reverse rotation of the inboard props or the outboard props. I dont remember if it was the Mauretania class or the Normandie where they tried this. Both had similar issues.
One of the most interesting videos about New Jersey, kudos. A typical solution to resonance is to stiffen the offending element to change its natural frequency to range that is outside the normal operating frequencies of the rotating elements. My father and his friends worked on the construction of the ship as welders. They all lived in a nearby Philadelphia neighborhood. Sometimes they commuted to Camden by auto when there were sufficient gas rationing stamps to operate one car occasionally.
A similar vibration effect is seen in wind turbines as each blade crosses in front of the column. Momentarily that blade loses some power causing the whole rotor to place unequal loads across the bearing and at a given frequency that happens to be near that of the column. The third blade in a wind turbine does not produce much extra energy it is there to offset the resonance by halving the rotational speed needed for two bladed sails whose needed rotational speed is well in the range of the severe resonance of the column. Perhaps the Titanic may had the solution with three propeller system and utilized a very pressure turbine to drive the middle shaft. However vibration problems are always a nightmare in these as the easiest solutions always interfere with the some other critical design feature.
Oooh boy you stirred the pot by mentioning the Titanic. Apparently she and her sisters went through several iterations of propellor layouts and blade counts. Apparently there’s still no clear consensus on what the configuration was for the Titanics fateful voyage.
@@cruisinguy6024 Err .... Yes. Seems there is no ideal configuration. Titanic had a neat engine efficiency configuration. When you are dealing with this level of power the amount of energy from even a small mid configuration can set everything a tremble.
The guy in the background on the scissor lift having to pretend to be busy for 14 minutes straight lol
Love the smile face under the last block on the keel.
Love this. A lot of thought provoking discussion. Drach knows his stuff and always enjoy his point of view.
Hooray for Drach!
To correct Iowa Class vibration problems (periodical publications have issues) I would model the hull using computational fluid dynamics software to experiment with different stern configurations including a transom stern and test different kinds of propellers with skewed blades, along with Prairie and Masker to see of bubbler systems affect vibration.
A transient vibration occurring at distinct speeds within its range suggests to me that the Holland tunnel could be equipped with some sort of active flaps or rotatable eccentric cylinders that would minorly reshape the tunnel enough to rapidly "skip" the harmonic causing the vibration by preferably transferring it to a previously attained speed.
Anyway, I greatly appreciate both of you on sharing your wealth of knowledge regarding the history of naval vessels. Fantastic.
The fluid dynamics are so complicated, the only way to “solve” the vibration issues would be to take a Time Machine with a pretty decent data center, along with the software back to 1940.
Even then, there may not be a perfect solution given the Panama Canal constraints.
I agree. It's chaos back there and there are probably complex cavitation effects from the washes of the outboard propellers that are contributing factors as well.
@@BlueSpruce2 I barely know my arse from a hole in a ground and once Drach started describing the interaction of the outboard water from the stuff shooting out from the hull tunnel I immediately thought of the mess coming off of those propellers. Like wouldn't they just be shooting pure turbulence at the inboards?
Because the propeller shafts are not level but are angled downwards somewhat, (right?) so are the propellers.
This results in more pitch in the propeller blade while rotating downwards (in this case the outboard blades on the inboard propellers) and less pitch in the blade rotating upwards (their blades on the inboard side).
If the inboard propellers were swapped, then there would be the greater pitch on their inboard sides where the faster moving water is instead of where they are now in the slower water. Of course the shafts would have to be rotated in the opposite direction from what they do now.
This is a great collaboration, love hearing the physics of Iowa class! So interesting!
Two guys just bein dudes talkin about what they love... what a great thing to sit down with a cup of coffee to ( or spot of tea)
Very interesting and informative. When Mighty Mo got to 30 knots, there was an obvious vibration in her stern. Even so, with eight burning and four turning, moving at that speed was exhilarating!
Watching this my mind went in a different direction. As a Sonar technician with an ASW rating I can see the different number of blades on the propellers rendering a technique of ASW ineffective. I do not feel I can be more specific because of the confidential of the subject, but I cannot imagine trying to use the technique against the New Jersey.
That's funny you say that because the Midway class had much the same hull as an Iowa class, the same propulsion and props and sonar operators I was familiar with told me they were both noisy and had an instantly recognizable acoustic signature.
I agree there noise signature made them easily recognizable. I was referring to the passive technique of turn counting.
Drach throwing down some real vital engineering knowledge. Love you both!
Very Very interesting Ryan & Drach. Much food for thought
Welcome back to the US Drach. I hope you are enjoying your stay.
Fantastic discussion, so much involved in ship design. Remember this was designed in the 1930's and 40's with slide rules!
The best combo period
I agree with the suggestion of getting rid of the Panama Canal requirement. There are shipyards on both coasts, they could build 2 or 3 for the Pacific and the same for the Atlantic and just rotate within their own ocean
This. And expand the canal at the same time.
Canal was expanded. At the time the Iowas were built the canal was 110 ft wide and allowed the passage of Panamax ships. The expanded waterway began commercial operation on June 26, 2016. The new locks allow transit of larger, Neopanamax ships, up to 160 ft wide.
It’s not really an issue for large Navy carriers these days. For example the USS George Washington is on her way to Japan by way of the Magellan Strait
Even in WW2 didn’t have enough for 2 oceans
Had to move them back and forth as needed
That were the low water issue comes from?
Now wider so need more?
Is it deeper?
I was on the USS Trenton lpd 14 and when I tell you I thought that ship was going to come apart at flank speed (only 20 kts on that old turd) I never felt a ship shake like that before. I was on the aft gun mount on the fantaile and I thought the back end of the ship was going to break off from the vibrations. I've also been on modern destroyers and they also shake at certain speeds. I think it's just a problem that's going to be there so long as physics are what they are.
Good Video learned a lot. Would like to see more videos like this.
Great vid!!! But..... The burning question is what the guy on the lift is doing?!? Waving what looks like a drill at a prop? Inquiring minds want to know!
Thank you! It's bothering me so much, I have no idea what buddy is actually accomplishing
@@matthewkramer7089 using a heat gun to dry the epoxy.
Not wear much safety gear
Great conversation, thoughts for Alex, what about spray deflectors on bow to move water into tunnel area, other thoughts are done after laid, flat plate on top of tunnel, similar to E-boats and Fairmile D stern. To knock water to props and similar hysocat, trim plane across bottom of skegs. I wonder if David Taylor center ever worked on fix or was busy with development projects.
Wow! A combination of my 2 favorite ship oriented channels. Great video!
Great video guys!!! That was very fascinating listening to all the different theories on what could possibly cause the vibration. Very informative, and really makes you think….
Without testing, I'm inclined to think that the turbulent water from the outboard propellers when mixed with the mostly laminar flow of the water in the tunnel is going to produce vibration.
You might have been able to use some sort of water divider system (a skeg between each of the propellers, for instance) to keep each prop in its own, relatively constant, water stream. Alternatively (and this wouldn't work for those propellers on that beam), you could mount your props horizontally rather than in echelon, so the turbulence wouldn't travel from one prop to another.
Hell yeah! I love Drachinifel making a cameo! His extensive knowledge of all things warship amazes me.
BEST dry dock video to date! Great work Ryan, thanks @Drachinifel!
Excellent commentary
Fascinating!
And I appreciate the collaborations.
What Drach seems to be describing is vortex shedding off the skegs because of the unequal velocities inside the Holland Tunnel and outside. If the vortex shedding frequency is near a characteristic frequency of the prop then it can result in a resonant interaction that will vibrate the stern. The vortex shedding frequency and the prop frequency are dependent on the speed of the ship and the rpm of the prop respectively so that is why the vibration only shows up at certain speeds.
It would be my guess , that the rez frequencies are hull deformation, or skeg flexing . There is a lot of stored energy in that hull . Prop pulse , yea , if you get everything just right , hard to stop. At the beginning of the prop tunnel , the shape should be arched at the beginning , ovel shaped , then move to a open bottom box shape.
I started learning about the Pacific War in 1965 when I read all 15 volumes of Samuel Eliot Morison. I've seen all 300 Drydocks and many episodes of Battleship New Jersey. And I still learned so much from this episode.
And this is something you simply can't cover in a book or in a classroom. Being under the ship makes it so much easier to understand.
Should we be thinking of Drach as the "Bono" of Naval history?
The best two Naval Ship experts on TH-cam
WOW, more about the Washington BB-56 than I ever knew. Thanks Drach and Ryan!
I am a little confused by Drach's comment regarding the Venturi effect.around 7:40 in the video. I would think with increasing cross sectional area, the speed of the water would be lower and not higher. Of course this is not a fully enclosed volume, so maybe some additional factors come into play?
Absolutely correct. That area of the hull is a diffuser, where the flow is decelerated to match the external flow and reduce drag.
Yes. As the volume increases, the velocity of the water decreases and pressure rises. Anyone who has tuned carburetors knows this. The narrow venturi in a carb throat causes the intake air to speed up, and as it speeds up pressure drops. That pressure drop is what pulls fuel up from the float bowl, through the needle jet and into the air stream where it is atomized.
@@philsalvatore3902 Thank you. There's a lot of pseudoscience in this thread.
@@physicsphirst191 I was surprised to hear an engineer make that mistake, but that video was like trying to do math on Excel real time during a Teams meeting O_O Your boo-boos and brain farts are there for all to see and, um, enjoy.
@@philsalvatore3902 He didn't use many engineering terms to describe the phenomenon... such as static pressure, dynamic pressure, skin friction, drag, pressure recovery, drag coefficient, flow separation, Bernoulli's equation, angle of attack, etc, and I don't think it was because he didn't want to baffle the audience. It was gibberish to me, and I'm an engineer, so I think the lay audience was mislead.
I love props in general but those are awesome, just size, wow, picture them churning through the ocean firing the guns. God bless America 🇺🇸
Learning every day! Drach has answered a lot of questions that I didn't know existed. For prop-vibes, try an IOM ferry: I out my bike on the centre-stand for the crossing out to the TT one year. When I rode it off, the stand had broken from the vibes, and one half was clattering on the ground.
Fairing the insude of the Holland Tunnel to reduce the rise in height as the tunnel transitions to the stern would reduce the volume of water at greater velocities versus the outboard side of the skegs.
You could today's run effective FEI modeling analysis to obtain similar computer generated results. In essence a 3D equivalent to a "water" version of a wind tunnel. Ideally lowering the exterior hull while retaining the aft hull rise. Along with applying new prop technologies an overall reshape of the tunnel with newer prop design might well be appropriate for this ship and otherks smilar in design and build.
Anyway just a thought considering fluid dynamics of water transiting down the hull.
I didn't know of the vibration issues. Drach's explanation though long was extremely interesting. I had no idea of the physics behind water movement and forces the ship generates while in motion. Thank you
There will either be a dead zone at the back of that tunnel, or it will be drawing serious amounts of water under the skegs, causing lateral vortices. Either way, a couple of veins in a similar form as the skegs (but narrower and tapered) maybe 2/3 the length of the tunnel would probably help with uniformity of flow to the props.
The main vibration excitation in the modern passenger cruisers and most other ship types as well is propeller blade cavitation, creating major load pulses at blade frequency. While Drachinifel makes many valid points, that phenomenon has certainly existed in battleships also and should have been mentioned at least as a very possible trembling elephant in the room 🐘
Low cavitation skewed props with the right number of blade might have helped, but engineers of that era hadn't figured out skewed props.
Fascinating !! Well done, Gentlemen, thank you !!
I saw both of you guys on Saturday may 25th and got to go under the ship very cool experience checked off my bucket list
No way! I knew he'd be there!!
Holy smokes I know that voice... pretty cool seeing a face with it.👍👍👍
Good video thank you , very informative , great job 👍🇬🇧❤️🇺🇲
Thank you Ryan and Drach, love it when you two talk ship
Unique stern design to get satisfactory TDS depth about the wide triple turret barbette and weight restrictions and speed requirements.
What a very informative video, thanks to you both for sharing this knowledge.
What a collaborative treat!!! Thank you Ryan and Drach!!
In aviation, we balance props. Even the smallest imbalance can be noticeable. Did the military balance their props?
Awesome, thanks!
Love this Thanks!
Would it be possible to speed up or slow down the flow of water by installing some kinda adjustable hydrofoil in-between the skeggs ???
thanks for the collabaration video, it was a pleasure to listen.
To Ryans question, what would we do to reduce vibrations. I see two approaches:
1. with the overall geometry fixed because of panamacanal and docking etc, we could still alter the properties of the surfaces. Like a noisy room with hard surfaces, by adding absorbing materials to the surface you can alter the acoustic behaviour of the whole room. alternative you may alter the flow of the water near the surfaces by materials anlog to a Golfball or sharkskin. there is a lot of develpment in this field ongoing in the aviation industrie.
2. changing the symetrical layout of the "Tunnel" to a asymetrical. We are used to prefer symetrical solutions for our constructions, but this is a risky aproach in fields where resonances are occuring. May be shorten one side or/and altering the curve of the hull on the other
Drachinifel: "Well, I don't know where this expert is, but..." 😆 It was such a satisfying experience seeing the engineer explain problem solving challenges encountered in battleship hull design. This was a great video. And shot under the actual battleship too! Not just a recorded webinar. Such a satisfying watch for a subscriber to both channels. 😁👍
William Froude is the man who conducted thousands of test tank experiments and formulated hydrodynamic theories that still form the basis of our understanding today - resonance can be astonishingly destructive when one cycle builds on another and can quickly get out of control
Super interesting! Thanks for the video.
Great explanation of how it all works and the complexity of the design issues
Ryan, Drach... Love you both.
It's more complicated than what is explained, but these are the basics, and I appreciate you both in this Video.
You guys are both studs!
Absolutely fascinating! Never knew dry docking would be so interesting - you're doing a great job Ryan and thanks to Drach too.
widening the inside of both scags to match the curve of the outboard sides.
utility fascinating , Physics and engineering, explained so perfectly. We all can learn from this , Thanks Ryan
That lucky gentleman who gets to listen to the live premiere of the episode while working on a battleship prop.
Reminds me of an episode concerning former german truck-maker Krupp. They had an issue with drive-shafts breaking and tried to solve it by reinforcing the shafts, but they kept breaking. Until they realized that the shafts broke because of vibrations interfering. The solution was making the shafts weaker, i.e. lighter, so their own frequency was higher, and interference occurred at speeds that the trucks never achieved. Keep that in mind if you ever prepare a vintage Krupp truck for drag racing.
As a solution for New Jersey's vibration issues, I suggest mounting balancer-shafts like they use in motorcycles to cancel out vibrations (shame really, since vibrations are an essential part of the classic motorcycle experience). A silly solution, I know, but explicitly you asked us laypeople for a solution to a problem that experts have had difficulty with for decades, so what did you expect?
I really love seeing an engineer explain. Great analysis.
As to Ryan's closing question, 'what would I do', the only thing that comes to mind for me is perhaps a series of cuts in the skegs allowing water to flow from outboard through to inboard, to equalize the internal pressure volume as the cheerfully-named 'Holland Tunnel' expands. But that introduces drag and structural integrity questions that might make it a null gain, if not worse.
Absolutely terrific video! Great collaboration!
Awesome. Thank you for this info, both of you. Outstanding job.
There's reasons why the NoCal and Washington weren't sent into the frontline, even though they went into service pre Pearl Harbor, and one of them is vibration, they finally solved it in mid 1942 iirc. Also the USN learned from this and made sure it won't happen with the Iowas
One thing I heard about on some new ships is that they are using offset props. There are 2 versions of offset props, the first being that the blades are not evenly spaced. The other way is that not all the blades are the same length. You can have symmetrical or asymmetrical offset. For symmetrical, if you imagine a 4 bladed prop, blades 1 & 3 will be 20 meters across. Blades 2 & 4 will be 25 meters across. For Asymmetrical, blade 1 will be 15m long, blade 2 will be 10m long, blade 3 will be 7.5m long, however will be weighted to balance against the 15m blade, and the 4th blade will be 10m again.
Great to see Drach and hear his analysis. I had never heard about this issue before, but I now notice something that he brought my attention to. I'm an F1 fan, and a mechanical engineer. In Formula 1 racing, they use ground effect to provide aero down force. The floor, undersides look like the "Holland Tunnel" on Battleship New Jersey. The theory is that the velocity of the air in the venturi (the tunnel) is much higher than on the sides of the floor. That creates a vacuum below the flow from the tunnel. Obviously no "ground effect" here but the same theory I would think. I didn't run any calculations, but with accelerated flow through a venturi, flow can "choke", that is, when no additional flow can pass through the venturi no matter how fast the object is moving through a fluid. I wonder if "choking" is a problem here, or do you need to be going much faster for that to happen? By the way Drach, I am a subscriber and enjoy your commentary and analysis.
Very well explained, it looks like the tunnel under a race car