Hull Form Design - Doing better than a floating brick
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- เผยแพร่เมื่อ 15 มิ.ย. 2021
- Today we look at some of the more important factors that need to be considered when deciding what hull form to use for warship construction and why there is no single right answer.
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Pinned post for Q&A :)
What was the rationale behind the differences in insignia, specifically the cuff rings, for the RN, RNR, & RNVR? Besides being able to call the RNVR the " Wavy Navy"...
Edit: And I know it was so you could tell at a glance who was which, but why was it considered so important to do so? The US Navy didn't have anything like it to distinguish the Annapolis grads from the ROTC grads (the functional equivalent of the RNR) or the wartime ninety-day wonders (the RNVR counterpart), so it seems to me that there was some snobbery involved.
Can we get the full 'Drach rants about German WW2 designs inefficiencies.' experience? With special focus on the Konigsberg class.
Maybe it's irrelevant, but is the boat tail bullet shape actually related to the hull form in any way? What is the effect of the transom stern if it was made to be concave, would it cause an even greater vacuum and vortex effects?
What was the budget for the Royal Navy/Navies throughout ww1 and how does it compare to the ww2 or the modern day naval budget
But bricks make wonderful weapons!
Everyone who's disappointed we didn't get the 84-hour version of this video raise their hand. XD
Well then there is part 2 and 3... then later the Unplaned part 4.. and the part 5 that didnt fit in part 5.. then part 6, 7 and 8 for upcoming questions
Give me the 84 hour video or Give me Death!
Soon:tm:
I want a 48 hour vid
🙋♂️
Being a Marine engineering student I completely agree, that anything above the basics is mind numbingly complex .
Marine engineering!!!??? I would love to ask you some questions about buoyancy to help debate against Flat Earthers.
@@mindbomb9341 I'd love to hear how the flat earthers perceive buoyancy.
@@mindbomb9341 why waste his time?
@@petermuller3995 Hahaha. That's a good question. I see Flat Earthism as a gateway conspiracy theory. By posting things against it, we can hopefully reduce the inflow of new members.
@@petermuller3995 I agree. I just engaged a flat earther in a TH-cam thread. I couldn't tell if he was serious facetious. Either way, it was a ridiculous experience. There's no correcting them online.
I think we can all agree floaty log was the peak of naval design.
LOL
Ah yes, nvel desin
Oh, please. Wooden slab was best. Floaty log is SO last epoch.
@@Deridus You are a fool for thinking wooden slab even compared to floaty log.
Awww man I _loved_ floaty log. Naval warfare in the Age of Hand Paddle was far more interesting than these later periods.
Everyone: Which would be better, thin and long, or short and wide?
Rear-Admiral Popov: R O U N D.
" K R U G "
-(КРУГ is circle in Russian.)-
I vote for a coricle
An expression of the Russian soul in steel - present a threat in all directions, while confusing the opposition as to where you're going next!!
Why aren't there more armoured coricles around, I wonder......(nod to Tom 😆). On another note, there was a 2018ish? attempt at a similar ice pack resistant arctic oil drilling rig/mobile island deployed off Alaska, didn't go well and ran aground on a real island. 🙄
R O T U N D
"Ahh, I see you are an Admiral of culture, as well..."
The Square Cube Law: it's why a 20" shell is a lot more than four-inches scarier than a 16" shell.
Before taking in other factors,the funniest being that no one knowing that your BB has the biggest fielded guns due to how well kept a secret it was until after the war is over.
As a practical example, the iowa's super heavy shells had around 18kg of bursting charge, the yamato's type 1 had 38kg. That's at least 2 times as scary lol
@@pedrofelipefreitas2666,one of the other factors was the fact that the Iowas' shells actually penetrated better at long distance due to the denser design of the fore end then the Yamatos' shell.
I feel insulted, my brick shaped boat floats just fine. Admittedly it isn't very fast... And it turns like, well... A brick... But other than that it works fine, sort of
but is it very good at blockading like a brick wall?
Oh you must have an Optimist.
For a brick, he sails pretty good.
I think it's a terrible shame to denigrate the floating brick despite its obvious advantages over the previous design, the non floating brick.
And the stability calculations are nice and easy.
Then there's all the fun you can have with SUBMERSIBLE hulls.
Back when the US began playing with nuclear powered submarines, they decided to build a little experimental boat, mostly full of batteries, to do some testing of what the handling characteristics of this new hull form called a 'body of revolution' would be like. The tank tests said it should be a very efficient hull form for a sub while underwater, which was where a nuclear powered sub was expected to spend almost all it's time while on patrol.
A body of revolution is one which is formed by taking a curve and rotating it about an axis. For the sort of curve you'd use for a hull shape, the result is sort of cigar shaped, and all cross sections of it are circles.
So, they build this test boat and take it out to do test maneuvering to see if it does anything strange.
Well, it did something strange, all right. The strange behavior was named the "Jesus Christ Factor," most likely due to someone saying that when it was discovered. One of the properties of a hull form that has all cross sections being circular is it has no hydro-dynamically preferred orientation in the water. They tried to pull a sharp turn (like you'd pull in combat to evade enemy anti-sub weapons) and discovered that when you turn sharply in a sub with this kind of hull form, it likes to snap-roll into a steep dive, in excess of 45 degrees down.
Now, snapping into a steep dive is fine and dandy when you WANT to do that, and could make for a nifty evasion maneuver, but most of the time you don't want to evade like that. It risks you hitting the sea bed or exceeding your crush depth. fortunately, it just needed a small rudder added to the back of the conning tower to prevent the boats from doing that.
USS Albacore.
Round hulls with the slab sided sail makes for an interesting ride on a surface transit in rough seas.
@@mikespangler98 Yup, the US Navy spent decades interested in any kind of round hulls with slavs.
Just reading this made me pucker up. Congratulations, you actually made me feel anxious... and very glad I am a Mountaineer, not a Mariner.
@@Deridus Testing out new vehicle designs can indeed be fun. Makes me glad I don't I'm not a pilot of flying, floating, or submersible craft.
@@evensgrey There are some things I am too chicken to do. I know my limits. That said... In a different life track, I'd love to be an experimental aircraft pilot.
When I was a young midshipman, we spent a month in a classroom wrestling with the concept of ship's stability. You nailed it in a matter of minutes. Well done Professor Drach.
When I was a young mid shipman it took a month to pound an hours worth of information into my head. Much easier for both of us these days I'm sure.
2:50
The chance to show the Russian round battleships on screen was missed here.
I had that thought too. But perhaps they are so out of the norm and were designed for such specialized circumstances, he thought it best not to include them to prevent them from being a distraction?
@@idaho_girl Oh, for sure.
It would have been a huge meme, but anyone not familiar with the joke (read: not following Drach for too long) would be completely out of the loop.
As a naval architect with more than 45 years of experience in hull design, this was a good video for non-technical people to help them understand the complexity and compromise that goes into every ship design.
On stability: roll acceleration is critical not only to equipment functionality but also to habitability. Too stiff a ship, roll period very short, and equipment, especially those located in high places can actually be broken off the ship, and people have trouble standing and moving around.
On speed/power: as a gross rule of thumb for every 3 knot increase in speed, double the shaft power. This rough approximation works throughout the speed range.
During my 12 years responsible for hull form at a major U.S. shipyard, it was common for us to go through dozens of iterations on the hull geometry (both commercial and naval auxiliaries ships) before we settled on one that met all of the requirements for speed, power, range, habitability, seakeeping, maneuverability, as well as sufficient volume to carry whatever was necessary to meet the mission requirements. Inevitably, the final hull was not ideal for any requirement, but always met, and often significantly exceeded, the contract specifications. Always a fun puzzle to crack!
On stability(habitability): I think some roll periods/accelerations are very detrimental to seasickness and such, so that also have to be considered.
So, question, albeit a silly one. Is a bathtub shape a valid hull design?
Does that doubling power for an extra 3 knots apply to those 10,000 gross ton catamarans made by companies like Incat that cruise at 40 to 50 knots, or is the equation different for big catamarans?
The soul of engineering is compromise.
@@philipwebb960 the art is how you put ten pounds into a five pound bag better than your competitor.
"since we're not going to make an 84hr run time video ..." ... wait, you're not? ... where did YT put the Down vote ...
There is, at the moment, one singular downvote on this video.
That is quite the antidrachinifelian response. I shall file a complaint with the Office of Consumer Dissatisfaction Bureau Department, at their Naval Affairs desk
I dunno, Patreon Drydock episode 583 has a good chance of being that long.
I would not be against the idea of an 84 hour video
Can concur, I have a shorter, fatter hull form, and I am quite slow. :)
USS Wasp?
Hydrodynamics: for when thermodynamics alone is no longer depressing enough on its own
Froude you, Geeky Boi! You need to _transform_ yo'self, and I know just _Laplace_ you can do it!
The only piece of garbage on the level of hydrodynamics is aeroelasticity. And I'm a week away from failing it.
@@andresmartinezramos7513 I'm sure they hadn't even invented aeroelasticity when I was in school. Good luck!
@@77thTrombone Thanks mate!
@@andresmartinezramos7513 Fourier series for DayZ!
*Reads title*
A wise Sergeant once said: For a brick, -he flew- she floated pretty good.
"Were it so easy" - A certain Swedish warship
also a certain russian repair(?) ship
@@seanarano4754 Do you see torpedo boats?
Trust me, he knows what the ladies like.
For a human you’d make a great shell
As a Naval Architect, I can say that this video is very good and covers pretty much every major concept in naval architecture (excluding all the math. There is a LOT of math). Very good summary of what naval architects think about when designing a a hull form.
Drachinifel: mentions a brick.
USS Monitor enters the conversation.
At least USS Monitor's turret was "maneuverable" as in it is forever spinning even in the depths of davy jone's locker and imitates a certain famous adorable seal...
@@ogscarl3t375 It did its job. How many vessels ever built can say that? And built in a nonce, at that. Never laugh at THE MONITOR. Monitors in general, laugh away until your gut splits, but NOT The Monitor.
Actually the Monitor's hull wasn't per se a brick. It was well tapered at both ends. Her issue was the complete absence of freeboard, along with flush grates in the deck for ventilation.
You rang?
Barges enter the conversation.
I can't believe you didn't go at least a tiny bit into the American stern, with its surfboard like qualities that got rid of the turbulence not by narrowing the stern horizontally, but tapering it vertically. THAT is where America got her fast battleships, even though prop design then became a problem for quite a while, due to cavitation, the boatman's nightmare.
But by narrowing it vertically, it made each fast battleship into a surfboard, not only not wasting its hp by burying its ass into the sea like any old displacement hull, but using that wasted hp to propel them even faster, by surfing their own wake, a phenomenon most experienced pleasure boat captains are familiar with. Transferring that concept to a battleship platform, given that almost all pleasure yachts at the time went for the traditional horizontal narrowing so the bow looked much as the stern, was indeed revolutionary.
It was really only achieved 100% with the Iowas, due to length limitations on the Washingtons and South Dakotas, but not mentioning it is sort of goofy, given that all modern warship and many commercial ships use the exact same technology, just tuned up a bit.
Funny you included the square stern, but not that. You do know only American Heavy Cruisers had that stern? Light cruisers had traditional round sterns, which were the beginning of the surfboard stern, although far simpler as they were so narrow. The fat battleship sterns came from this concept.
But I suppose you could go on forever on this subject. Kudos for a valiant charge at a complex subject and an extremely understandable presentation. I dare say you might have saved many lives by making Sunday sailors more aware of metacentric height alone! (Their eyes glaze over when the phrase is even mentioned, even though they own a million dollar yacht!)
I always click fastest on Drach's nerdy engineering videos. Boilers, steel formulation and now hull form. Excellent. I can pretend it's continuing professional development if anyone asks me.
Agreed. I can't wait for his video on propeller design.
Shell development
Be sure to check out Greg's Airplanes channel.
I strongly agree. I did not come here for flashy entertainment, I came here for education, in a no nonsense form with just a tad of dry humor. I don't often give strangers on the internet money... But Drach deserves it!
Currently sitting in my stateroom on the usns loyal watching this. Google the ship to see what happens when you care about sea keeping to the extreme. We barely roll at all in up to 12 ft seas... but out top speed in a sea state 0 is 6 knots
That is the epitome of brick
@@valhallastiger2960 Well, it's not meant to go fast. It's a passive SONAR surveillance vessel. I would think a slow top speed would be considered a desirable feature in such a ship. Passive SONAR doesn't really get along that well with fast travel through the water.
I do have to wonder how USNS Loyal managed a rated speed of 9.6 knots if she only makes 6 knots in a flat calm.
@@evensgrey i wasnt attacking the ship it just wasnt what i was expecting to see
Is it twin hull or single?
W I D E
@@evensgrey maybe when it was first commissioned it went 10 knots ( I doubt it) but she's not exactly a young girl anymore. If we really push it we could get 7 knots probably... but then the main engines would want a few weeks of R&R
Im reminded of a comment in "rebuilding the Royal Navy" (dk brown/G.Moore);
"It was said that you became a true propeller designer, when you ceased to think of a propeller as driving a ship, and started to think of the ship as a mere obstruction to the flow into the propeller"
It’s the Fairest Curve that drives the Sailors and the Naval architects Mad …and incompressible water becomes quite displeased when it is displaced …the Hydrofoil being the latest rage amongst kiters and windsurfers and dingy sailors..and Zippy ferry boat operators …. So Cool to watch ..
From what I can see, hydrofoils have seriously disappointed many operators that have tried them. Military hydrofoils (as the US Navy tried them) were an operational failure (they cost too much to operate to be justified by what they could do, making them fairly small vessels with the basic problem of battleships: They are astonishingly good for certain things, but you can accomplish the same jobs for less money in other ways).
It's difficult to use hydrofoils in the Atlantic, because the Atlantic tends to be fairly rough most of the time, and hydrofoils don't like rough waters. (It makes it hard to get up to the speed where the hydrofoils start being able to lift you hull out of the water, and a tall wave that hits your hull can really give your vessel a bad knock, so transitions can be quite nasty in more marginal sea conditions. I rode in a hydrofoil on Lake Ontario a couple of times about 40 years and, and half the time it was too rough for them to use their hydrofoils on nice, clear summer days. We get WIND in Ontario in the summertime. There have been attempts to restart a hydrofoil ferry between Toronto and some point on the Canadian side near the Niagara River, but they have previously fallen through, mostly because there's a very limited market for a marginally faster way to get to an area that has a fairly niche tourism industry built on wine and theater. There's now a rather amusing try at an electric hydrofoil ferry service, and they're making the cute claim of having no wake. The fact a hydrofoil disturbs the water less than a similarly sized conventional ship means a much smaller wake, but not NO wake.)
There are successful Mediterranean hydrofoil car ferries, but the Mediterranean is notable for being like the Pacific: It's usually really calm, except when it's really, REALLY not. It also has a huge advantage for a car ferry service that there's a number of big islands with large populations and lots of stuff to attract visitors who find it very useful to take their cars with them because those islands are that big, and there are these bodies of water that divide major countries on the northern coast from each other and can be much more quickly crossed on a fast ship than driven around.
@@evensgrey Exactly plus Foils are delicate… great if your on a Kite Board or small dingy … our Carrier routinely visited Naples Italy and they had those ferry’s zipping around on their Foils going to Capri .. but their is no way your getting a 60,000 ton carrier up on a Foil … yet … but even those new Zumwalt class are a big disappointment… plus they corrode to pieces … besides when your at sea the coolest thing is to go forward and watch the bow cutting trough the ocean ..
Short in coastal boats, the German Schnellebooten beat all. Their Diesels went from 800 to 1500 hp on the same displacement during the war, simply due to technological advancements. PT Boats and Vospers were very well in the south Pacific and the Med, but a handful of E-boats could kill a destroyer.
They could go over 60 knots in the North Sea by the end of the war, in almost any conditions. Displacement hulls and huge power plants fueled with diesel. Very tough nuts to crack.
@@georgesoros6415 Excellent Point …. I hope Drach does a E boat episode or episodes there is nothing out there about those fascinating craft ….cause pound for pound they and the u boats really did a lot of damage … if Germany had started the war with 300 E and 300 U boats … it might have gone somewhat differently….?
@@stephenrickstrew7237 It would be a hilarious sight to see. A carrier going almost 50 knots on several rows of hydrofoils. Certainly harder to torpedo lol. Would definitely be completely unviable on a battleship though, lol.
"Free board" comes from the first (and usually only) side plank tied on with cords to a dugout canoe. One on each side. They had them in Britain during the stone age.
side fact: transom stern. in modern merchant ships, it's there to keep the deck at full width all the way to the aft. To keep the speed up, we usually load/trim it so the transom stays OUT of the water. Just for those vortexes. because they drag ALOT.
The diagram with the center of gravity and center of buoyancy really helped me to visualize how and why ships roll over!
I appreciated the definition of the metacentric height. That is something that I somehow missed when I was casually looking for explanations of the stability of hullforms in the past.
Of course, if I had not been lazy and bothered to read a proper I likely would have gotten it. LOL
I certainly have to believe that copying a shape that is good for the performance you want is more likely to give good results than a random shape that just feels lucky.
If technology is completely static and uniform across nations, then that will eventually become true as everybody evolves toward the same optimum.
In reality the constraints were ever-changing and not uniform from one power to the next, and there was therefore strong incentive to innovate. In the days before tank testing (and more recently CFD/FEA) the only way to achieve that was to take some risks with new ship designs, and the marine architects' intuitions therefore played a role.
@@patrickchase5614
Are you sure you understand the meaning of the word "random".
@@calvingreene90 Yes, I do, and back in the day the designers did some remarkably "random" stuff (by modern standards) with their hull designs, often with disastrous consequences. I thought that was what you were alluding to and was trying to explain why.
Rear Admiral Popov would like you know your location....
R.I.P James D. Hornfischer
Oh he passed away!? Amazing writer. RIP.
Perfectly Timed, I shall listen to this whilst constructing vessels in From the Depths and this video will come in very handy. Thanks drach!
Wait, your crafts are not repulsed by both the air and the sea to sit at equilibrium between them?
Sometimes you want a boat and not a hovercraft.
I can't stop building spaceships bc my AI keep running me into every goddamn island it finds.
@@CharChar2121 Try adjusting the estimated turning circle, surprisingly it helps somehow?
When the aspect of stability is brought upp, the ship model Drach shows makes me, as a Swede, slowly blush ...
A feew more years of watching this chanel and i will be able to build my own navy!
Dry jokes to add to this subject from the channel "Not what you think"
The efficient bulbous bow on modern warship always looks like this, even when it's not excited.
My 50+yrs as an amateur historian of military aircraft is still going on,but until I came across one of your videos I knew nothing of ships.But I enjoyed that so much I subbed and devoured your information very quickly.So now I have 2 subjects to educate myself on and I am always stunned at the depth of your knowledge.Just wanted to thank you for your content.Deep and thorough.Excellent resource!
this is a concise and still interesting thumbnail sketch of a very complex subject. Congratulations on striking a good balance between complexity & brevity and giving an understandable overview of the issues & choices in warship hull design!!!
Many years ago I attended what I think was the first meeting of the historical group of the Royal Institution of Naval Architects, in the hope that I would learn something about the reasons behind ship designs. I concluded that it was a talking shop for academic historians to score debating points off one another, and never went again. Drach does a far better job all on his own!
Good sir: it's ALL about hydrodynamics. (Hull speed that is.)
*unless you use foils. And, then it's still about hydrodynamics*
😎🇺🇸
"Make it long, make it concave. What do you mean, rough seas?" - Designers of the -Coke bottle- Iowa Class
Lol
"Great hull design" - captain Larry
Its a pity David K Brown is gone. His books were the ones that got me into this stuff. He would have made a wonderful interview subject for you.
Hulls: The thing that makes your ship float. Except for swedish warships going on maiden voyages in 1628...
This is very similar to what we discuss in Aerospace when we look at stability for aircraft, so a very interesting video for me.
Was reading about this subject in a book earlier this week, 'Battleship, Design and Development 1905-1945 by Norman Friedman, rather a interesting subject and video, along with the boiler, propulsion and armaments videos previously posted.
Ok, I confess, I was More confused about how Hull shapes works after I listened to this at work then before. ;) Thats not a criticism, thats a a compliment on a well done 1 hour condensed video on a very complex subject. Maybe after I have listened to it about 10 times I will understand it. :)
ditto.
Go buy the simplest of watercraft. Own it for ten years. Then watch this again, and you will be eternally grateful to Drach.
I would love to see a similar discussion about submarine hullform designs... specifically about the physics of blunt cigar-shaped bows, and why they are better than sharpened prows, and why it wouldn't be even better to simply emulate the shape of a fast-swimming fish's head.
Me building ships in Kerbal Space Program: _hmm yes this shall aid me greatly in my endeavors_
And here I just thought more rockets was the solution to everything.
Very nice explained al lot of things about the hulls.
Thank you for this.
I would like to share my thoughts about sailing ships (42 minutes).
The propulsion of a sail is indeed high above the center of gravity.And it can push down the bow , especially from the mid mast.
But we have also sails far before resp after the point of gravity.
It is possible to lift the bow with the most front sails (like a spinnaker on a modern sailing boat).
The next following...It is not the sail pushing to the mast and the mast pushing the ship forward.
It's the rigging which bear the most (pulling) force to the ships hull.
For what I know about sailing: The mast is mostly to keep the sails high up above the ship .
no day where i'm not astonished about the effort people make to bring free accessible knowledge to the world
thank you
Maybe a video about the more famous tricks used to tickle the last knot of speed out of ships? Things like hydrofoils come to mind.
I worked on primarily Incat 74 and Incat 81 Fast Craft Cat passenger ferries. They are wave piercing catamarans and utilize hydrofoils to plane through the water. One of the weirdest quirks was you needed near full throttle to get up on the plane which depending on load for Incat 81 is anything from 14-20knts but once up you throttle back and continue to accelerate to cruising around 36knts. At top speed these things were far more efficient than plodding along at half speed. They were also remarkably nimble due to having 4 massive water jets that would turn instead of a screw driving water over a rudder. Think scaled up jet ski.
There are trade offs though. They're good when moving really slow or really fast but speeds in between are just weird. Trying to maintain a speed just in the threshold of coming up on the plane is extremely hard and forget about turning. "falling off the plane" as it's called sometimes feels like stalling a car. Then there's the fun of trying to reverse. Because it isn't an open screw you can't simply run it in reverse so instead they have what are called Buckets that drop down in front of the jets to redirect the water down and under the stern. Both types of Fast cats I worked on used to vibrate quite a bit trying to back up onto the berth and they'd struggle to reach a few knts while doing it. Hope my wall of text didn't bore you and you're having a great day 😉
@@MoA-Reload... Nah, didn't bore a bit. I once sailed on a foil yawl for a weekend and that was exiting, fun and scarily fast. Also steered a RHIB with waterjets once, made 40 knots in a calm sea.
@@JainZar1 I bet it was exciting. I was an RNLI volunteer for a bit too before moving away for work. Bombing along 20knts in a Severn class always felt far faster than 35-40 on the Incats due to the size difference. Can also confirm Severn class barrelling at you while you bob around in a liferaft is far less scary that watching Seacat Scotland come at you when you suddenly remember you were out on the lash the night before with everyone on the bridge 😂
@@MoA-Reload... Yeah, speed on a small boat is really something else. At the end of the weekend I was doing 20+ knots in the Laser I was sailing, absolutely crazy feeling.
@@MoA-Reload... Back about 40 years ago I had rides on a couple of different days on the oil hydrofoil service on Lake Ontario, on the Canadian side. Lake Ontario is a damn big freshwater lake, but quite small compared to most bodies of salt water. We get such strong winds in Ontario that half the time it was too rough for them to get up to hydrofoil speed. When they could, transitions were often unpleasant due to having to plow through parts of waves that were tall enough to reach the hull.
My grandfather on my fathers side built a small rowing boat in his youth, with his brother. Just before WW2. My grandfather said it was sturdy, and slightly worse handling then a half sunken log.
From a retired deck officer and sailboat captain, great job on a complex subject.
57:00 - Being longer and thinner can also hurt your speed directly if you take it too far. As the ship's aspect ratio increases, its surface-to-volume ratio also increases; if displacement is held constant, this translates into an increase in wetted area, which, in turn, increases the frictional drag on the hull as it moves through the water, _and_ the wetted area (which is directly proportional to the frictional drag) increases faster and faster as you keep increasing the aspect ratio. Past a certain point, going longer and thinner will actually _increase_ your overall drag, as the increase in wetted area will add more drag than you save by decreasing the ship's frontal area. (The balance between pressure drag and frictional drag is also important for aircraft, and is one of the big reasons why you don't tend to see a lot of airliners with enormously long, skinny fuselages, nor ones with stubby, bloated ones.)
"floats better than a brick" is similar to what was said about the space shuttle "glides better than a typewritter"
This is like a 3D balancing puzzle where you have 37 hanging platforms and 83 different weights that you need to distribute perfectly to complete the puzzle.
Oh, and some of the hanging bars push up on other bars, making it even more complex.
My friend, Howard Gradin, found a damage control chart on the USS Salem. It showed speeds for various engine and propeller conditions, ( ?Damaged shafts might be locked, creating drag. ) He was impressed by the increased power required to push the ship to its top speed versus something a few knots slower. Officially it had a 33 knot top speed. I do not know what her actual speed might be operationally. Atomic aircraft carriers have have rumored top speed in the 40 knot plus area. atomic power providing the insane grunt needed to push them to such classified speeds.
My friend reported seeing Green ( solid, non foaming) water was seen over the B ( higher front ) turret, in very heavy weather. This was on a auto loading 8" gun cruiser. Great work! .
Some nuclear submarines are rumoured to be capable of 70+kts submerged (Russian Alfa) because both the reactors are capable of delivering the power and the high pressure around the propeller prevents cavitation.
The down side is that it is VERY noisy due to vortex shedding.
This does however make them fast enough to out run a lot of torpedoes (other than the 200kt Russian Shkval).
Note the Shkval cannot be launched at above 50kts.
Brilliant photos and diagrams. Often I listen to rum rations and drydocks as audio-only podcasts, but I absolutely needed visual support on these relatively complex issues of buoyancy, gravity, righting moment etc Thanks.
Another great episode of 'naval history and morning coffee'
Thank you Drach!
I sit in my house and watch tugs on the Mississippi River. The barges they push are essentially hollow bricks.
32:28 if you assume you keep the same underwatervolume, a shalower draft is more stable:
BM (boyancypoint-Metacentre) = (Ixx)/(volume)
With a square hull:
BM = B / (12T^2) B=breete (with), T=tief (depth)
T stands under the division line so the larger the depth, the lower the stability
It was an interesting overhead photo around minute 34:00. You can see by the light cruisers moored with the CVL’s that they share a hull.
Ah yes for instance Cleveland and Princeton
I would love to see something like this about submarine design. I wonder how much it's like aircraft design, given that the fluid is all around instead of located in one area.
25:30 -ish: That sounds like the rocket equation to me. Just... on a warship.
Hello there friend
@@yobeefjerky42 hello
I get that reference I salute you! :-)
A hullform test tank, something that give you so much information when doing this.
I went into this video with the question about the flat vs pointy stern. Thank you for answering that, let alone in the last 5 minutes! 😂
So, it ALL depends ...
Great treatment of the subject. Amazing what was achieved before the advent of modern computational methods.
This makes me appreciate Scotty even more; just imagine the engineering shenanigans of a starship.
Especially when the idiots on the command deck keep demanding more power...
The only guy in a red shirt who's still alive.
Spaceship designers have it much easier, no air or water resistance, no buoyancy or metacentric height. Bricks fly quite nicely in space.
(But still have to worry about the thrust line relative to centre of mass as Drach said about sails vs engines. The Enterprise should pitch itself nose down into a roll with those off-axis nacelles.)
@@hughfisher9820 slightly angling the thrust exhaust so it goes through the centre of mass, and countering with manouvering engines of some description would make it possible to fly in a straight line. Less efficient, yes. But possible
But Scotty was the very model of a WWI engineering officer at Jutland, where Scots couldn't be line officers, by law, as incredibly stupid as that might sound, so they made up almost all the engineering officers in the RN. Their reputation was that the snotty brit captains would issue impossible orders, yet they would carry them out, just to get at the snotty bastards.
So Star Trek, always wanting to be inclusive, but realistic, made Doohan the engineering officer, which I fancy was entirely appropriate, just as Sulu was the typical Japanese WWII officer (quiet and respectful an competent) and Chekhov was the typical Russian officer Obeying orders but always questioning and troublemaking. And surly.
All because Whitehall thought Scotsmen too stupid to be line officers (but apparently not too stupid to beat back the Russian heavy cavalry at Sevastopol nor the Afghans at the Khyber Pass, dying to the last man nor a thousand other places.....
Yet when Beatty crapped himself at Jutland, he replaced Jellicoe.
Go figure that shit out.
very interesting and neat to learn more about why ships look like they do
Awesome video Drach!. The topics covered in this video are the prime focus of my department where I work, and you've done an outstanding job of distilling amazingly complex subjects down to their basics.
Drach, this was an outstanding video. While I can’t definitively say I got it all on the first pass, you definitely addressed and resolved some questions I’ve had.
Of particular note is the discussion of free surface effect. I’m not sure it’s worth a video on its own, but I’d like to learn more about this phenomena (which I first learned about after the loss of the “Herald of Free Enterprise”). While I always think of it as at its worst on ferries, I was wondering if the compartmentalization on warships nullified the effect; it seems like it reduces it but doesn’t eliminate the threat.
The runaway cycle of increasing displacement at 24:48 has a name: It's known as the "Iowa class"
Thanks for your videos - they are just great but I would like to point out that in case of Pensacola class the major reason behind placing triple gunhouse (not the turret - sic!) that high was that designers did inderstand that their bows would not have very much of buyoancy and they decide that the more guns would be higher the more guns would be drier (that's how Norman Friedman describes it in his magnificient book US Cruisers - An Illustrated Design history, p.123). If we look at the plans of these cruisers we can easily notice that difference between widths of the twin and the triple gunhouses is much less than difference between cross-sections of the ship in the places of theis respective installation. Moreover, the after part of tPensacola's is wider but the triples there were again placed above twins. So there was enough room to place triples in the bows lower (in it was showed initially in sketch design with four triple gun mounts). Finally - just remember HMS Dreadnought and her wind turrets P and Q))))
So sad that this misconception is so wide spread and so many people take it without logical fact checking
To get into a lock in the Panama we had to go full ahead! Bank Line.
Floaty log best design 👌
You can treat air as incompressible as well if you’re dealing with a subsonic plane
I more than half expected this to be about the Vasa. I am not disappointed.
"(...) you might make some compromises to another essential point: stablity." Vasa shows up. Liked.
22:07 thats more like capsizing than rolling Drach
i support it's still a running joke
But Drach, there are ships which can turn themselves upright again! Most Rescue-Cruisers of the German Seaborne Rescue Society are built to be able to save themselves from capsizing.
Yep, there's very specific and highly advanced engineering that goes into them, include absolute watertightness. :)
All the all weather RNLI lifeboats are self righting too and their design are nothing short of an engineering marvel. They also have the astonishingly good ability to maintain near their top speed regardless of sea state. Severn class tops out around 20knts in flat calm and they'll do that in just about anything you throw at it whereas boats similar size would be mad to even head out and larger ships can lose a hell of a lot of speed. So while Severn isn't that fast on paper, they designed her to achieve that speed in all weather's. Add in that they're remarkably good at taking much larger ships under tow plus some other party tricks as well you'll get why I claimed "engineering marvels" 😉
@@Drachinifel ......so....not the Vasa?
Lol.... And three minutes later, a beautiful model of her crash diving!
At a very different scale and purpose, monohull sailing yachts that are not strongly self-righting are considered to be dangerously deficient designs.
@@markhamstra1083 yup, yachts being self-righting to a heel of 100+ degrees is not too unusual.
This may be your best technical video ever. LOVED this.
While looking for general information about hull design relating to kayak hull shape and stability i happened upon this presentation. Very interesting topic and while i wasn't looking for such in depth information about large ships and certainly came away with more general knowledge about ship design. And of course now i know what i need to consider for my next kayak build with regards to gun placement!
As an aeronautics engineer, so someone who designs things moving through air, I can assure You that compressibility of air causes major problems, and it would be better if it weren't
It changing it density can get annoying but would take it over trying to move things through a non comparable fluid like water. You would just watch anything that tried to re enter the atmosphere explode like it just came from
Orbital speeds into the side of a mountain
Not half the headache viscosity causes! (Well, specifically, turbulent flows)
And in process industries compressibility effects of air is actually very useful (especially for turbocompressors)…
Really interesting video. I learnt a ton about buoyancy as well as hulls! Your thoughts on stability made me think of the modern (well 80s) supertankers which were certainly wider than tall.
Edit: We have seen wooden and metal warships. Lots of racing craft now are carbon fibre or fibreglass. Do you think we will see warships made of the same material & the effects thereof on hulls.
Some warships already made with fiberglass hulls. Plus Kevlar and similar protective sheets are made from polymers.
At 33:39 into the video there is a pic of ships layed up. There's a carrier there with 29 painted on the deck. USS Santee is her name and my uncle Ralf Kennedy served on her WWII. Video played on but for some reason I backed it up, googled the ship, and it was the Santee. Ralf passed a number of years back, these ships were disposable...nice to see a pic of her.
Absolutely amazing video thank you. Even though this is only the first video of yours I have seen I subscribed. I figure if you put half as much time and info in every other video you do it's worth watching. That was one of the most informative vids I ever seen on TH-cam. Thank u especially for such a difficult subject
Alternate title: Drach goes physics teacher!
Aren't you worried about someone asking for 84 hours course in patreon drydock?
There's already disappointed comments that want exactly that.
My comment thanks Drach for the short version.
I do not have 84 hours to spare.
Many thanks for this great video, Drachinifel, and in as simple as you can get in this broad and complex topic. So in short, it's all about compromises, there is no perfect hull form. The best design you can get would be one with the best compromise you're willing to accept. No wonder engineering is about getting the best compromise from what I've heard.
Oh, and I would like to know more on those other factors in hull design you mentioned, please.
Brilliantly done Drach
At 14.50 I was thinking about SS Waratah. Her hesitancy in righting a roll so worried one passenger (observing his bath water) that he left at Durban. The ship subsequently disappeared (1909).
Yes, but apparently he added, that he had been disturbed by visions he saw in dreams during the voyage of a man "dressed in a very peculiar dress, which I had never seen before, with a long sword in his right hand, which he seemed to be holding between us. In the other hand he had a rag covered with blood.
Modern submarine design is more complex than large aircraft.
Large aircraft get away with the flying brick design so long as you have enough power and wing area
I found this video really good! I’m glad TH-cam recommend it. You have a new sub! Really well explain with a d’inamicale and calm voice. Really enjoyable to listen and watch!
Operation Habakkuk - making the case for floating bricks everywhere ;-)
"why are you out of your port?" - some Mediteranian storm
Why has all the Rum gone ?
I love these dives in to a certain subject series
I've watched many and they're all great! Keep it up!
I'm studying hull design, for from the depts.
So, the tyranny of the rocket equation started with ship building, nice haha
Honestly, it probably started with water skins somewhere in Africa a few millenia ago.
William Crealock, one of the better naval architects and yach designers, started by designing missils...
that's a really nice vid - the explanation of the stability/roll of the ship was particularly good
Excellent as always, I was thinking about the copper the R.N. used to keep their hulls clean.
Lol, the photo at 29:00 .. The South Dakota class BB has the number 2 turret pointed back directly at the bridge of the store ship that is along side. One can imagine the Captain saying: "No, we will take ALL the chicken."
Regarding a difference with modern sailboats, the latest hydrodynamic factor mentioned is "Wetted Surface" which refers to how much hull is underwater. This is why modern racers usually have a dish-shaped hull which seems rather shallow for the size (the main hull having less draft and a little more beam, although the narrow wing style keel sticks down quite a bit, often with a big lead-weighted bulb at the bottom for added stability). This can extend the "Hull Speed" of a boat which is the maximum speed of a non-planing hull that can be achieved without exerting exponentially greater power. Such boats are not known for sea-keeping, and many long-range or family cruisers prefer more traditional full "Displacement" hull shapes for comfort and safety. Warships probably can't go that route, they need the volume and stability of a fuller hull. But I suspect if they did for some reason, they could get by with dramatically less horsepower for the same speed, and therefor much smaller engine and fuel spaces.
It is often said that the introduction of the Dreadnaught changed the entire landscape of naval warfare. But what exactly was so revolutionary about the dreadnoughts?
They up'ed the anty on the level of protection, speed and firepower way beyond anything floating at the time. Up until then ships had improved on one or the other. Dreadnought leapt ahead on everything all at once
The two main differences was guns (main and secondary batteries effectively meged into a single large gun calibre, instead of 4x12" in twin turrets + a bunch if 8 to 9 inch in casements Dreadnought had 10x12" all in turrets) and propulsion Dreadnought was the first Capital ship with turbines. The effect of this was she had more long-range firepower and was faster.
@@alanclague2333 not to mention the shift away from ramming
@@invadegreece9281 ironically Dreadnought's only victory was ramming a German U-boat. 😏
@@jefferyindorf699 yeah
Fascinating, accessible, and informative.