Why Are Bows That Shape?
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- Опубліковано 7 лип 2022
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In this video, we take a look at why the bow of ships is shaped the way it is.
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"one thing all bows have in common, however, is that they're all at the front of the ship."
can't argue with that
@@kirkhamandy You could always tow it outside of the environment in that situation
You are not wrong :D
@@kirkhamandy Well, that's not very typical, I'd like to make that point.
Ah yes, the floor is made of floor
There’s also the so-called “Great Lakes bow”, which can be found on some of the very largest iron ore freighters on the Great Lakes. It’s semicircular. The ore freighters move slowly enough that their wave making resistance is small and skin friction becomes a much more significant factor. They are also limited in length by the Poe Lock. The semicircular bow enables them to minimize the wetted surface area while also maximizing the available displacement within the constraints of the locks.
Yeah, he didn't mention wake reduction. Wakes are a major source of energy loss. Energy spent kicking up a a bow wave is not spent moving the ship forward. Military ships tend to be sharp, they produce more wake at cruising speed but let the ship move at higher top speed. An important consideration when being shot at. The more rounded bows of civilian ships, esp cargo vessels don't have nearly the same top speed but they waste less energy in the wake.
They also have flatter bottom increasing the buoyancy to carry heavier loads and less resistance when using the bow and stern thrusters when docking or navigating rivers.
I've also heard the waves can get so large for the depth that the troughs can ram you into the floor. It makes sense to place yourself as high in the water as possible to minimize that.
@@themekahippie991 That sounds like stories I've heard about Saginaw Bay.
Yea Great Lakes are a whole other deal with ships it seems
The Iowa class fast battleships have such a fine bow, that the first hull sections are actually negatively buoyant.
The bow by itself would just sink.
Also why the bow is completely unarmored. Damage to the bow has such minimal impact to buoyancy that the weight added by armor would be far more than any added by flooding.
That's really, really funny. They're beautiful ships, and those bows look downright regal and majestic. Never occurred to me that they were actually kind of a tradeoff.
@@acomingextinction They were a significant tradeoff, they even narrowed the torpedo protection for Nr 1 turret, to get that little bit more speed.
I often think of the Iowas as South Dakotas, that went six knots faster.
Those six kts required almost 200 feet in length, 12000t of additional displacement and 80% more horsepower.
Well.. Cut the bow off of any ship and it would sink. Ships are not designed in a way that any random arbitrarily chosen relatively small part of the ship would be buoyant by itself. Rather, it's the other way around; When that part loses it's buoyancy, the rest of the ship can still keep everything afloat. Of course this doesn't mean smaller parts can never stay afloat, but it is more of an exception to the rule.
Comment edited slightly to weed out people whining about it even though I corrected the error in the later comment. People can't be bothered to read that far before throwing out their knee-jerk-reactions FFS.
@@anteshell During WW2 several destroyers survived being cut in half and there have been quite a few instances of bows being torn off and the ship surviving.
Warships have an advantage here with being compartmentalised and more watertight bulkheads.
Now I want to know why the stern of ships are so different, cut-off like in cruise ships while tapered in ww2 battleships.
Speed and efficiency. They started with transoms in early sail for military, stylistic and construction reasons, then changed to counter sterns on clippers in the 19th century because they were more streamlined and therefore more efficient, then cruiser sterns in the 1930s because they lengthened hull length and were more efficient, then transoms (again) in the 1970s because they reduced squat and were actually the most efficient at speed.
The transom stern is just above the waterline. The ship is still streamlined below the waterline. Transom sterns are much easier to construct and don’t really have higher resistance than the old cruiser sterns except in extremely rough sea conditions. People just hadn’t realized that in the past. There’s no point in hydrodynamically designing a part of the ship that won’t be in the water.
I guess I’m an incurable Titanic nerd, but I think the kind of stern it had is the most elegant.
@@martinamaggioni8124 u6uu66pu66u67pup766uup6p6uu6
edit:ive heard of butt dialing someone but ever heard of pocket commenting?
Pointy stern goes faster. Flat stern steers better. Round stern is good (but not best) at both.
And of course wider means more useful deck space, multiplied by number of decks. All the machinery for rudders and props takes up useful space, if not in the stern then further forward.
It's worth pointing that even things designed for absolute maximum speed underwater (like torpedoes or submarine launched ICBMs) have rather blunt, rounded bows/noses. In fact, making these noses more pointy would slow them down, due to greater wetted area and greater skin drag.
The big cargo ships have a blunt bow and as much as Casual Navigation wants it to be all about cargo space it isn't.
If you check the speed vs range data for the Bering 65 motor yacht, this blunt bow yacht can be built so that it gets nearly 15,000 Nautical Miles per load of fuel. The blunt shape is a fuel efficient shape not just a space maximization shape.
Also note with torpedos the circular shape also helps significantly with packing the most amount of explosives towards the front end of the torpedo giving it the greatest chance of critically damaging a ship
Subs also have a rounded bow due to the sonar. You can get a much greater radius around your sub with a rounded bow instead of a pointy one. The downside of that round bow; expensive and complex to produce. Which is why the new British subs have such a funny looking bow; flat plates are easier to produce, and it's set in a dome shape to allow maximum sonar coverage.
Submarines also need to resist high water pressure. Any sharp edges will generate a stress concentration and be more likely to break. That's why things that have to resist high pressures are always round
@@finlaymcewan It’s true. I’m a chubby guy and don’t get stressed.
2 other items, a flared bow helps reduce the amount of water that ends up on the deck in severe weather, as well a very fine bow can be weak and prone to plunging in heavy seas. The Iowas suffered from this and could not maintain their high speed in rough weather.
True, for pleasure boats reducing spray and plunging bows inundating passengers is not a good thing for sales or comfort. Another item in racing boats generally are rules. Good or bad, to win you have to start by building to rules and sometimes that affect the bow.
We're concerns about submerged collision damage so instrumental in the development of the flared now? My understanding is that it was adopted to keep water of the deck in high sea states as vessel speed & stability increased. I have a hard time imagining that a reduction/avoidance in underwater damage during a collision was anything but a nice side effect of the new design, instead of a driving design concern
True... It was a design necessity to keep the deck dry. Collisions between ships in a head on approach is now rare if you factors are not included.
The way the flared bow is built is much more expensive than a plumb or straight or a tumblehome bow. The amount of steel to bend and form the bow is an expensive art of skill on its own. Compared to a straight bow, thick underwater plates require little shaping to form the bow. And a straight bow has a more linear power vs speed ratio compared to a bulbous flared bow. The latter has a narrow range of specific speed to capitalize the bulb while at different speeds, its just a drag maker. The straight bow is more friendly on speed changes and a very linear ratio of fuel consumption at different speeds. Thats they are starting to pop back from the past as volatile fuel prices can be detrimental to any shipping company. The bulbous bow ones needs a nose job everytime they want to change optimal cruising speeds..
No bow is truly straight. Even "straight" bows from the turn of the last century had a huge amount of flare side on and were very curved. The only two straight bits in this traditional design were the stem above the waterline, and the waterline itself. Every other aspect plate and line always curved.
we are concerns indeed
Don’t forget that some of the first dedicated war ships that we know of were the ramming ships used by the Greeks with what amounts to a tumblehome bow that terminates at a reinforced hull breaker.
The evolution of bow design is very old. It’s kinda hard to say what the first bow really were.
One thing to consider when talking about sailboats is that many sailboats were designed withe the IOR rating system in mind. A system which gave boats a handicap rating based on their design and was popular in the late 20th century.
IOR was extremely flawed and one of its quirks is that it measured length of waterline instead of overall length. This drove designers to design bows with a huge amount of rake, the idea being that as soon as your boat heels your waterline length increases making you go faster, without increasing the rating.
On the flip side, a practical and economical sailboat owner will often want a squarer bow. Cargo space being one concern, but another is that many costs of owning a sailboat are driven by the total length, regardless of the waterline length. Docking spaces especially can be expensive, and the cost goes by total length.
@@DanStaal From a strictly performance POV you want to keep weight out of the ends while allowing as much waterline length as possible. Displacement hull speed is dependent on waterline length.
Could we get a video on the old sailing ship designs? The rounded hull segment was interesting, I never realized they needed ballast to stay upright as compared to modern day ships that had their buoyancy much helped by hull design.
He's spoken often about the instability inherent with that design but it stuck around for a long time. I want to know why. What advantage did it have over other designs?
@@franzfanz working with wood, I'd assume not only was it easier to achieve with wooden construction but also doable in a structurally strong way.
Also, a lot of weight was carried far up with heavy guns and the obvious very strong forces introduced from the tall rigging and the wind pushing against the sails.
Some countries like the dutch built their ships hulls a bit more boxy, and merchantmen in general were a bit more boxy, to maximise cargo hold space vs draft.
But that always made these ships somewhat bobbing like a cork in the seas, which was pretty undesirable for gunnery and thus ships of war. Those needed to be stable enugh to sail around the world and to self right, but not so stable as to be a bobbing cork, making it unusable as a platform for guns
Also these are sailing vessels, so they have very tall masts, regardless of the hull design they would need a heavy keel to keep the ship upright either way
@@velianlodestone1249 I think this is a big part of it, along with the sails on said masts having a sideways force, which causes a major moment arm trying to capsize the vessel. To counteract this sailing vessels need to have either a heavy keel (most larger monohulls), very wide beam (smaller sailing skiffs like Sunfish - relative to their draft their beam is immense) or multiple hulls.
I second this! I assume it is because of purpose (cargo types for merchant vessels, and speed, maneuverability, and combat capability for pirate and military ships, etc.), aesthetics and beliefs of their era if ever albeit unlikely variable, way of propulsion (as they primarily use wind for sailing), construction materials, and technological limitations.
For any person of the future, please inform me for such video as yt notifications work in mysterious ways.
The understanding of Physics when applied to all sorts of different ships is just beautiful to me. The same goes for knowing how Physics is applied to vehicles that work on land and especially air.
its so interesting how there are so many valid bow design choices. Each one has its usage and ship type. The diversity is not seen so often in other areas. I never really thought much about ships from engineering perspective (I am mostly interested in aerospace) but ships fascinates me a little now thanks to this channel.
after certain speeds, the air becomes as viscous as water, so it becomes vert simular at that point. except the whole flying part
@@alexzanderroberts995 we also consider aerodynamics in high speed boat desing. İn some hydrofoil desings the hull is completely out of water
For a bit of military background on this, the tumblehome design of bow used to be very common on warships, but it was discovered that when a ship with a tumblehome design was damaged and started to take on water it had a greater chance of sinking due to the greater volume at the bottom of the ship, meaning a lot of buoyancy would be removed in the case of flooding. This is one of the reasons you stop seeing new tumblehome design ships after WW1 up until the recent failed Zumwalt class of Destroyers.
Aaah. French predreadnought design. Some of the *greatest*, hilariously bad and wonkily designed vessels. I love them.
@@5peciesunkn0wn it wasn't even just the French, a lot of different nations toyed around with the idea.
@@Sturmischer The Russian designs were by the French. Most of the nations that went with Tumblehome pre-dreads were inspired by...the French. Since second biggest naval power.
well, the Zumwalt failed for a multitude of reasons; the hull probably had nothing to do with it. we arent firing shells at each other anymore, and NO hull design will survive a direct hit from a modern anti-shipping missile...a direct hit from a single Brahmos missile, or equivalent, WOULD sink even the Gerald R. Ford without any issue, whatsoever.
@@nikoc8968 I wasn’t implying the Zumwalt failed because of the hull design, just stating that it was a Tumblehome design. The Zumwalt’s main reason for being a failed design was they tried to implement too many untested technologies at once into a single design.
I have the impression that the straight bow of modern sailing yachts is also just fashion coming from race yachts that have a vertical bow due to "box" rules in racing that favor a longest waterline within a box shape leading to a vertical bow, just like overhang in more classical yachts, that were based on rules in which waterline length was penalized so they tried to always reduce it leading to large overhang. This then also became fashionable for non racing yachts...
Different racing rules over the decades have produced some extremely seaworthy, beautiful yachts, and some really crappy sailboats..
IIRC the backwards sloping stern of many sailboats are a legacy of the IOR rules which measured length at the deck level. So by extending the hull behind the end of the deck they got a longer waterline length (and thus higher hull speed). So in effect it was working around the rules, that then became fashion as non-racing leisure yachts adopted the same design.
Another reason for modern yacht to use a plumb bow v the steeply raked bows of some years ago, is it increases the waterline length and so hull speed. Now you’ve covered that as well 🙂
You're polite to say 'another reason'. The brief sailing yacht section was his least accurate in my opinion and potentially more extrapolation than research. For example what he called the 'raked' bow isn't generally the one seen as providing more accommodation, he didn't mention your relatively well known LOA vs LWL point and he didn't appreciate the historic impact of yacht racing rules on design evolution.
Those X-Bow tugs are supposed to be really stable and just truck through the heaviest seas. Apparently they were inspired by Viking longships
I think the biggest takeaway is that “size is only one element” very important to remember
The vertical bows of modern sailboats are designed to maximize the waterline at the expense of comfort. Foiling race boats have inverted "wave piercing" bows to avoid pitching up. Some older sailboats had long overhangs both bow and stern because of a set of complex rules of measuring the waterline. Effective waterline on 10 degrees heel was substantially longer than static.
Finally a new video. I’ve been watching all the old videos while I wait
The "nose" of a submarine has nothing to do with pressure. It's literally just a fairing cover over the sonar dome to minimize drag and it's not even watertight. The sonar dome is the pressure boundary, though there is a watertight door at the rear of the dome that is normally rigged for dive while underway. At least on first-flight 688's
I deeply appreciate you sneaking in a smiley face at the two minute, six seconds mark.
"Tumble home" is the name for a ship design feature where, in cross section, the ship is widest at about the waterline and narrower at the gunwale. The name for the narrow bow profile which protrudes farther forward at the waterline than at the forepeak, is "inverted bow". This is an evolution from "axe bow", "axe-box", and "leadge bow", which all have basically vertical stems, but similarly narrow cross sections.
Tugboats have pretty cool bows.
You'll mention something about it when you eventually come to your senses and make that tugboat video we're all waiting for.
I do want to cover tugs.. Its on my list...
I did not know youtube couldreport upload times in seconds
Great video. I sailed a lot in my childhood, and noticed how my dads boat, with its square bow, cut into the waves while the nearby banana bowed hobie cats would bounced up and down.
It’s great to get a more detailed explanation and see the larger scale applications of the same principles
The bow one sees on the submarine is flooded. There is a spherical or horseshoe shaped acoustic sensor array in that flooded space. The shape of the submarine’s bow is to accommodate that sensor array and provide the flow you describe. Wgen you see a submarine you’re only seeing its outer jacket, not the inner pressure container that looks much like a propane tank.
but the flooded bow moves with the ship, so the surface pushing away water will be the "outer jacket", the bow. it would make absolutely no sense to let water ciculate in and out, so the bow one sees is indeed the bow that needs to produce as little drag as possible while accommodating the sonar. so what are you trying to say?
This has nothing to do with drag generated by the shape of the bow...
@Dirty Eddy It has, because the sonar array (and torpedo tubes) are what pushed the submarine bow design that way. They could have other shapes but this is the most adequate for the task of the vessel.
@@moteroargentino7944 the same is applicable for ship bow design and the required width of the ship for stability and cargo capacity which was disclaimed in the video. The accommodation of sonar array is bs as wider submarines with side by side pressure hulls have a different width thus bow shape etc. again, sonar array accommodation has little to do with drag for bow design. The bow could've been pointy instead of rounded while accommodating for the sonar…. Hydrodynamics call for rounded regardless of the sonar.
@@lIlIlIlIlIlIlIlIlI The video specifically talks about _why are ship's bows shaped that way_ . Drag is always a factor be it on the surface or below it. Submarines have that shape as a compromise between low drag/noise & volume for equipment.
The first submarines had ship-like bows as they spended most of their time on the surface due to power limitations. In the 50's, the first nuclear submarine (USS Nautilus) was launched and had a semi-pointed bow, which proved to be so noisy that *deafened the submarine's own sonar* . Then the USS Albacore was built as a diesel research experimental submarine with a teardrop hull design that showed to be faster, quieter and more maneuverable, but less stable on the surface. Around the same time, the Soviet Union launched their first nuclear submarine (K-3 Leninsky Komsomol) equipped with a rounded bow that gave it a lot more of space for equipment.
Submarine bow shapes have been studied and the results showed that conic and fish-like bows had the lowest drag coefficient and noise generation. Hemispheric designs generate more drag but not turbulence like ship-like pointy bows. Then came the conclusion: sonar is *essential* for a submarine, as is it's eyes and ears. There's always the need to fit the biggest and better sonar possible in the bow, and that requires _space_ , to the point that in the USS Tullibee they removed the torpedo tubes from the front and placed them on the sides, just to make room for a bigger sonar that allowed it to perform long range hunter-killer missions.
Out of curiosity, the newer cruise ships all seem to be heading towards the Parabolic Ultra Bow - what's the main design aspects of it that allows the stated "reduction in fuel consumption" through "gained hydrodynamic efficiency" the yards seem to be marketing on?
Yeah, a lot of them like Celebrity Edge, Scarlet Lady, Norwegian Prima, AIDAnova, MSC World Europa, Costa Smeralda, and a lot more to cone seems to have that kind of a reverse bow.
7:11 He says "speed" with such intense resentment
I'm an amateur in this Field , but it's been very interesting and thought-provoking. You've encouraged me to learn more! Thank you!
Love me some boat dumpy 0:13
Bro 💀
Sus
@@holvingar4375 sus
I've always wondered why ocean liners of the late 19th-early 20th Centuries, such as Titanic, nearly universally had vertical bows, while modern cruise ships pretty much universally have flare bows. This video addressed it to some degree, but not fully. I get the sense vertical bows ride better on rough seas by having no change in waterplane area with depth while flare bows have an increase in waterplane area that would cause more pitching - I'd think this would make the vertical or rake bow better for passenger comfort. The flare bow has more internal volume, and given how modern cruise ships are constructed to maximize volume for their dimensions I could see that being a higher priority. Is the danger of causing damage to another ship below the waterline a major decision factor? Most ships now have bulbous bows, which I'd think might cause the same problem, though they are blunt so maybe not as bad as a sharp edge. On such note, are bulbous bows designed as crumple zones, designed to crush and absorb energy with minimal damage to the rest of the ship and - if hitting another ship - minimize damage to the other ship? Sort of like a car's bumper? That would actually make a lot of sense.
I think you kind of answered your first question yourself - you're comparing ocean liners to cruise ships, which is kind of an apples and oranges thing. Cruise ships, since they're all about passenger comfort, will try to avoid adverse weather as much as possible. However, should that be unavoidable, they'll want a ship that can ride it out, which the flared bow is good for. We must also remember that cruise ships are comparatively light - they have these huge superstructures, but they're mostly empty space, not full of, say, cargo or something else heavy. As such, they have a rather low displacement for their overall volumetric size. And to conserve fuel, they want that displacement to be as hydrodynamically efficient as possible. So a nice, pointy, streamlined hull shape, but with a flared bow to handle eventualities. (Also, a flared bow gives more deckspace for even larger superstructures.)
@Retired Bore True, good point. The largest ships are a lot larger now, that could also be a factor - waves are smaller relative to their colossal size, while smaller ships are more sturdy. We have to keep in mind that ships like Titanic would be fairly small by modern standards.
Bulbous bow is engineered in order to create the wave forward. That allows for greater efficiency of the hull.
@@jinksomiabodyart3189 So you and Retired Bore are saying that the bulbous bow is a newer design that performs better than the old vertical bows of older ships? An interesting thing I've noticed is that early ships with "bulbous bows" were sort of a combination of the vertical and bulbous, with the vertical bow leading edge, but having it wider below the water line and very narrow at the water line some distance back. Almost like a modern raked bow/bulbous bow but with a plate of steel between the bulbous bow and hull above. You could also have the bulbous bow project out in front of a vertical bow, sort of like a "ram bow" that some WWI-era warships had. But as the name suggests that can be dangerous having the ship project further forward below the waterline than above, and warship ram bows more often accidentally sank friendly ships than enemies. A bulbous bow I'd think could be designed to crush or break away in a collision, but just being strong enough to withstand pounding through waves in a storm would mean it could still do a lot of damage. So overall I don't think a bulbous bow and vertical bow are necessarily mutually exclusive, couple ways of having both. So I suspect there are other reasons for this change.
@Retired Bore It also causes a wave to form at a more-forward location so that it's trough will "cancel out" the crest of the main bow wave, thus reducing the amount of energy wasted on making waves and even increasing the speed which can be attained.
Tumblehome is such a great word, a perfect mix of descriptive and silly.
5:48 Middle to the left. Man really put a smiley face there and thought we wouldn't notice
It's not simply the fact that he used the word "dumpy", it's the hesitation and intonation with which he used it that makes me crack the hell up.
Absolutely fascinating. I have always liked ships (my dad was in the Navy), but I barely thought about this stuff. I wished I'd gotten a degree in naval engineering. My dad probably would've paid for my education.
One for your best video in the series and a must-have primer/explainer for any playlist.
This channel keeps surprising me with how interesting navigation is ! Thanks mate, very good video and narration !
I’m kind of curious why many new cruise ships like the Celebrity Edge, Scarlet Lady, and Norwegian Prima are going for the straight bow design now rather than the flared one, if the flared bow is suppose to reduce pitch?
yeah I believe it is much more comfortable for passengers with the reduced rise in fall of a bow that slopes backwards. it's also a bit of a fashion thing too.
Do ships get taxed/classified differently by their total length? Maybe there's also some port restrictions caused by a flared bow?
It's less drag so less fuel consumption. Pitching isn't a good thing. The only real disadvantage of a straight bow is it is wetter
@@deerfootnz thanks. And by wetter what do you mean? And how is it a disadvantage?
@@sergel02 wetter : more water on deck. The flare tends to distribute the bow wave out and down. A straight bow cuts through the wave. In yachts, especially multihulls the bows with reverse are often called "wave piercing bows"
An excellent illustration of how the design parameters change the outcome.
I once used the simple door as an illustration of this. Why are there so many different types of doors? Because of the parameters influencing its design, like strength, each of access, difficulty of breaching, maintenance, cost, aesthetics, privacy provided, etc.
Thank you so much i learn to make Lines plan this year and this explanation help me a lot
OMG There's so much good info comming so fast at you in this video! Love it! I am gonna rewatch this thing, there's too much good info that you can't possibly get it all the first time. I love the fast pace, but that may only be me. One of your best videos if you ask me.
Thank you, another great video, always interesting, easy to follow, and great production too.
Glad you enjoyed it
Great and informative video as always! I actually went on a car ferry last month in northern Germany and near the staircase there was a technical graphic of its engine and propellers. This new ship (called Norderaue) had a Voith-Schneider Proppeller and even though a crewmember tried to explain it to me, I simply could not understand how this type of propulsion works. So this may be a interesting video topic since I find it very intriguing that this is not even a new technology.
@Retired Bore great explanation, thank you!
I love that you use the Queen Mary 2 in your vids, I used to work on it! Keep up the good work!
2:40
I like the little happy face on the left side.
Even by this channel's standards this is awesome work. Well-written, well-delivered narration and lively, insightful animations. It's crazy how good you've gotten at this, and your vids were already pretty great.
I thought the same about airliners then I learnt that pointy isn't always best.
I just took a minesweeper across the north Atlantic and I can tell you that rounded bows and flat bottoms don't mix well in anything over sea state 2. A stem like that cuts waves about as well as a snow plow, and the flat bottom causes you to ride on top of them - creating that good ol' fashioned corkscrew effect when the sea's on your bows and quarters.
Fascinating video and information. My father was a commercial fisherman and would go out for a month at a time. Thank you again.
Tumblehome ships are perfect rammers. Zumwalt’s last resort.
I wish he would have discussed the Nelson Class battleships. Forward sloping bow with practically no flare but an extremely long length to maximum beam supposedly for maximized speed.
Inevitably, interesting information in Wikipedia, although not too relevant to the bow-shape topic. Design parameters were restricted by the 1922 Washington Naval Treaty, so amusing to read that the two ships were often referred to as the "Cherry Tree" class, because they had been "cut down by Washington" :D
I would really love to see a video from you about the origin of the beaufort scale. How sailors came up with this kind of scale is such a cool tale to tell and I believe a lot of people don't know about it and think it is just about windspeeds or something.
Nicely explained and the animations sure helps to understand it better.
Well done! 👍
Commercial X-bow design also accounts for less wind drag, hence the bow continues all the way up upto the birdge.
Ulstein frigging rocks!
one thing with flared bows is that they are rather pointy at the waterline to cut through the water. but near the deck. they are more round. the shape means that when they come down after riding a wave the water when it crashes down goes up the bow and broken apart. when you see videos of ships in choppy seas. you can see the water splashing outwards. this helps reduce damage to the ship as it brakes it up and helps protect the superstructure as it will mainly encounter swash and not a big wave.
ships include well nearly all of them.
fishing vessels, passenger ships, cargk ships and warships.
Another thing is, when they come down, that because of the flared shape a fair amount of water is pushed forwards.
This greatly reduces the forward speed of the ship, a problem the axe-bow or a tumblehome don't have.
Wow, I never knew or even thought about this. Excellent.
Wow, I’ve actually been searching around for a good place to learn more about boats and boat design for a story I’m working on and I gotta say, you’re doing a great job of neatly and quickly going over the basics, complete with visual aids. This is actually really really helpful, I’ll be having my characters talking like old salts yet lol, subscribed!
Yar!
«It has to be pointy»
- a wise man
Bow to the superior bow design
Again, very well done.
More information I did not know I did not know.
I don’t know anything about boat designs and yet this was super fun and interesting.. great video!
Nice way to wake up. Thanks
Good morning!
But why would you want to ride the wave? Sounds like cutting though the waves gives more comfort for cruise ships
That's obvious now, but it was something that had to be relearnt twenty years ago resulting in xbow and axebow development.
My understanding is that it was about riding the wave _better_ (than no flaring at all), as well as keeping the deck dry. Unless I misunderstood
I suppose it's to keep most of the water out of the deck. After all, they're essentially floating hotels with lots of windows, balconies, openings, furniture and the like.
Your videos are so nice that, even though i am a naval architect that knows this by heart, i still enjoy watching them.
The animations are phenomenal and really helps explain things very well
My dream is a large custom built sailing catamaran. I am leaning toward the axebow concept; essentially a vertical or slightly backward raked bow, but with a deeper keel to reduce the slamming when a wave tries to lift the bow out of the water. I would probably still have it flare out at the top to keep usable space on the deck.
One problem with catamarans is that with two hulls the bow buoyancy is halved so the danger is submerging the lee hull by running into a wave and pitchpoling.. The current answer seems to be a backward raked bow with tumblehome to cut through the wave rather than trying to ride over it.
A problem with cruising cats is that while they have enormously high initial stability, if they run into a situation where they DO heel (say, during a gust of wind that puts the windward hull out of the water), the stability drops VERY rapidly. In contrast, as a monohull keel boat heels and the keel opposes the heel, the stability increases as the righting moment increases. Because of that, even though I love multihulls, I wouldn't have one for cruising open water.
Feel like you should have mentioned the Iowa Class Battleship (and to a lesser extent preceding Battleship classes) that has a unique (iconic) extremely long, narrow bow. As I understand it the ship was designed this way primarily to increase the length to beam ratio and increase the ship's top speed but it does make for an interesting shape.
So much of bow design owes itself to the 1898 paper "The Wave Resistance of a Ship" written by mathematician, John Henry Michell. His brother, A.G.M. (George) Michell invented the Michell Tilting Pad Thrust Bearing. This bearing enabled ships to grow the size of the Titanic, which was as big as the technology of the day would allow, to more than five times that size today.
Waited so long for this video. Great content as always, love the animation
May I add that in the case of submarines, they also need to fit a giant sonar.
Back in the old days, the sonar was not actually that giant, and many subs still have bow mounted torpedo tubes where you'd expect the sonar to be if you've only looked at modern nuclear subs with midships torpedo tubes.
I would be interested in hearing about catamaran hull design, what kind of advantage/disadvantage does a "double hull" offer (probably not the technical term, but you see what I mean), and why is it so rarely used for large ships ?
The main reason cat's are rarely used for large vessels is they cannot support the weight a mono hull can.
There are several reasons.
The advantages of a cat hull are.
Increased area above the waterline.
Decreased drag, and weight.
No need for ballast. The twin hulls are ultimate form stability.
Once you go significantly above 100ft you are now in freighter or passenger territory.
These ships are large enough that form stability is no longer relevant.
You plan on having a lot of cargo weight in the hull anyway so ballast weight is also not relevant.
The twin hulls, and superstructure cannot carry cargo, and add unused expense.
Speed is still limited by hull length so an 80ft mono hull can go faster than a 40ft twin hull.
A twin hull tanker will not fit in any port, canal, or shipyard in the world.
It's hard enough to fit a twin hull small luxury cat.
@@capnbilll2913 "Speed is still limited by hull length so an 80ft mono hull can go faster than a 40ft twin hull." - only partially correct. In the 1988 America's Cup match, a 60 ft catamaran destroyed a 90 ft monohull. The reason is that the hull shapes (and therefore the form factor multiplied by waterline length) were very different, with much higher length/beam ratios for the cat hulls than the monohull. Also, multihulls are much lighter than monohull keel boats for a given size, and therefore can accelerate much faster than monohulls.
When I was in my late teens/early 20s, I had a Hobie 14 (catamaran) (bought it after it got hit by a car, and fixed it up, which is another story entirely). I used to go out into Long Island Sound and look for monohull yachts. I would sail literal rings around any monohull under 40 ft. Kind of a dick move, but I was young. ;-)
Another issue that adds to your reasons why there are NOT multihull freighters is that the wetted surface for a multihull vessel will always be greater than a monohull of the same weight. That will be important at the relatively low speeds and low power of cargo vessels.
@@gregmead2967 The reason a small cat, (or small mono like Opti or Lazer), can go faster than a cruising mono is weight.
Lighter hulls can achieve planing speed allowing them to exceed hull speed which is a mathematical function of water viscosity, and is proportional to hull length at waterline.
A catamaran used as a freighter would be subject to this laws of physics speed limit.
This is why all modern freighters have a large bulb at the bow, it gives them another knot of maximum speed.
Congratulations . An informative light hearted docolette . Not too stern . Take a bow .
your content really helps me in my college course. thanks a lot!!! keep it up sir
The terminology "Tumblehome" and "Flare" refer to the cross-sectional profile, not the fore/aft bow profile. The correct terms are "ram" or "Inverted" bow and straight bow or clipper bow.
Should have added in some Kriegsmarine Bows. Designed for speed, but also to redirect as much water as possible down or out, rather than over the decks, while maintaining shallow draughts for the Baltics and Coasts of the North Sea.
S- boot only?
@@jinksomiabodyart3189 No. Deutschland, Scharnhorst, Gneisenau, Bismarck, Tirpitz, and plenty of other cruisers and unbuilt designs were designed with a very shallow draught for shallow waters, and Fjords. But the freeboard around and behind the bow had to be flared to prevent water washing over the deck.
Scharnhorst, Gneisenau, and the Hipper's still had huge issues with water washing over their bows. Despite redesigns and rebuilding most of them.
I've been working on a 3D model of a sci fi railgun battleship for a novel. I designed the hull with an inverted bow similar to the Zummwalts' just because it has that exotic and speedy look to it. Now with this video I'm tinking a flared traditional bow would help to keep the guns and their eletronic equipment dry. I'll model a new hull and see how it looks.
2:06 The evil wave is pleased to see a liner sink.
Why did those sailing ships have such a rounded keel then? Surely it would've been possible to build a different keel shape from wood as well.
probably to maximize capacity, while being able to sail in more shallow areas
i guess it is also a measure to increase the structural strenght of the ships
@@MrJakson112 Exactly. There wouldnt be all the infrastructure that there is nowadays and they had to get as close to land as possible. Minimising depth was important
Pointy is scary
5:06
This ship brought me back to when I was around 6 because I had a model of this ship that I used to play with
Ngl, I clicked on the video only seeing the title, and thought it was why bows( as in bow and arrow 🏹) were that shape. Immediately realized it was about ship bows, and was not disappointed. Thanks for the awesome content and great video!!!
I spent so much of this video wondering when he'd bring up the giant poison gas cloud in the background, and it wasn't until near the end when I realised it was supposed to be grassy land 😅
My art skills do need a little improving still, haha
2:05
"And no wonder! For Sea Satan disguises himself as a smiley face in the waves. That demon sits there in pleasure, laughing over the stern of the Empress as she settles down deeper and deeper in the water. He watches with a terrible grin on his face as not a single soul survives the rapidly sinking ship. Something as seemingly innocent as a smile in the waves can harbor such inherent, and pure, evil."
- 2nd Corinthians 69:420.
Probably the most important design consideration is that the front doesn’t fall off.
Yeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeees!
Plowing vs cutting also has an effect on efficiency, but I guess when you talked about drag that was maybe implied.
Streamlining.
this was very useful, thanks for sharing!
Hehehe, "Dumpy"
Sir, you have the BEST mix of both professionalism, and humor
the funny thing is though the Zumwalt class US Ships failed scale model testing for sea trials, which is done in a controlled wave pool. The same pool that ALL naval vessels get scal model testing done. It is the only vessel to fail since the pool started tests.
Excellent explanation, thank you!
No ads, straightforward and comprehensive. This is what UA-cam videos should be like.
I on a sailboat love a clipper bow it seems to me to be a perfect blend. The best boats I have had or crewed on had that bow design
Great vid. One comment - on leasure yachts I think it is generally assumed that plumb bows pitch *more* than a long forefoot. The fine foretoot / long flare *progressively* increases boyancy as it hits a wave, so more gently lifts the bow. A plum bow raises boyancy rather more suddenly. The advantage of the plum bow - and reaso it is now popular is that it lengthenes the waterline so makes the boat faster. As a general rule, plum bows are popular with racers and cruiser racers - but a more traditional long forefoot is still highly prized by long distance cruisers who expect weeks of heavy weather and put a bit more emphasis on a kindly motion than absolute speed.
It would be cool to see a video on offshore sailboat racing bows like those on the new generation IMOCA 60s. There is incredible variance in bow shape for boats designed for the exact same purpose
I wish you would have also covered: 1) bulbous bow (reducing drag) 2) bow design in cruise ships (less pointy) vs Atlantic sailing ships (very pointy)
Excellent article. Many thanks.
This is your best video to date. Well done!
Tumblehome bows were mentioned regarding underwater hull damage, but not bulbous bows! Most large vessels have bulbous bows and it's the relationship in terms of length between bulbous bow and the (above water) bow, and the height of flared bow versus the deck edge height that dictates how much damage will be done to the other vessel. Big flared bows are good for impacts with high-sided vessels, but dont help against those with low freeboards. Vessels with short bows will inevitably impact other vessels below the waterline with their bulbous bows.
Great comparison and explanation.
Excellent video and per usual! Really interesting 👍
I remember fishing in Alaska commercial, and getting “on step” on the way to the fishing grounds.