Good idea! I'll add that to my list of videos that I want to produce. I am also working on a video to diagnose why a ship might be listing to one side.

My apologies. I have seen many simplified bulbous bows based on capped pipes, where the pipe length was not calibrated to produce the correct interference pattern. I'm especially impressed if your company has created effective bulbous bows with such a simplified construction. Nice job. And I'm glad to see you verified it with model test data. That is a true professional. For anyone interested, you find videos of model tests conducted by this firm here: kzfaq.info/get/bejne/rNR6YNR4ubXPf2w.html

This should not be as funny as it is, but it is :D He also got the minimum amount of required CFD calculations, when used during the design phase, wrong... Though I guess his video series is aimed at non professionals so... Edit for it not showing Nicholas' answer. Props for that!

Patrick Bray thats good news now rry usung that bulb for a 30 foot sailing catamaran wide hulls rhat still sail fast and are blue water capable would make a good livaboard.cruising yacht.

A hundred thousand for cfd calculations? Are you serious? We charge a fraction of that. And yes. Bulbs work great for one trim, one draft and one speed... So great for ferries.

Hahaha, what are the odds that this dude is watching KZfaq and sees a picture of himself under ‘bad design’ !

Hi bro

Jets are the future propellers will soon be obsolete

@@joshlower1 Nope.

@@freefall0483 yup

@@joshlower1 Although there are some advantages to water jets, fuel efficiency is definitely not one of them.

@@christianeriksson4733 like anything else they will eventually be made more efficient

Outside of the strict linguistics of the physical sciences, meaning everywhere else the language is used, the meaning is much closer to hypothesis. The word was not formed for the express use of scientific literature.

Hi Tom, great comment, w h at you stated males a lot of sense in regards to the laminar flow at the bow of the vessel.

Gibbs & Cox was the Nav Arch / Marine Engineer for the Burke Class.

Good point about debris dispersion, for example semi-submerged containers floating aimlessly. Also the small boat captain may not necessarily survive the accident after being flipped out of his boat , ca use he then has to face the prop. next on the stern of the ship....

@@kenlee-97 Going thru Singapore I saw an old lady oaring a sampan, successfully cross the path of a container ship. It was something to see.

@@kenlee-97 I know how to build REAL sailing boats.

In theory - yes. And perhaps in practice it is possible to design such variable flow profile or "speed" bulb design. There were some studies done. But it is not practical for few reasons. As it was pointed out in this video, bulbs are added to increase efficiency of slow moving large ships, and benefits are felt over a longer period of time (i.e. imagine oil tanker on 1,000 miles route, even a 0.5% increase in efficiency will be practical). For those ships it make sense to design a bulb for cruising speed and slap the steel and leave it be. Where one may think variable bulb may make difference is ships with dynamic "performance" - think of faster moving ships (military vessels), yachts and so on. Their overall performance is largely improved and affected by special hull shape, propulsion systems and so on. They are not economical ships for the most part and having the "fast hull" or multi-hull or different propulsion (variable) will have far greater effect than any BB added. Let's say, a BB will increase efficiency 2% efficiency over 5% of time (low velocity/speed scenario i.e. in ports). That is not much - given that the design will be very complex, added weight and require maintenance. So, it would be a cool feature - but with minimal economics (in fact, mostly negative). Fast moving vessels, or vessels that are maneuvering a lot at various speeds - require either smaller wetted surface to reduce drag (friction) or hull shape of low "box coefficient"...

strelnikoff7 it’s about harmonics, as I understand it. I read that motorcycle companies toyed with telescoping exhaust manifolds to adjust back pressure at different RPMs.

I was thinking about that too. I guess it would be quite a hard to get it working and be reliable for years under water. Rubber that is inflated with water is one thought but it would lack rigidity and change form on it's own.

What if you reinforced it with leaf springs and a pistion,creating a wisk shap that can change sizes and shap Via compressing the leaf spings with the piston?

@@skunkjobb What about using one of those expandable rhombicosidodecahedrons, or whatever they're called?

Of course, why did nobody think of putting our magical expandy-thing on ships that accomodates the waves, yet is strong enough to be placed on the most stressed part of any ship? Also, it cannot have moving parts, but its magical, so thats fine, isnt it?

Looking at simplified bulb construction, length, diameter, and vertical position are major parameters. Length could be varied with a telescoping bulb. Diameter strikes me as the most difficult major parameter to change in operation.

never show your extendable bulb in public

Also - this is an idea I have been thinking about for a while now - would a retractable bulbus bow be a decant concept? Let's say your ship's engines can operate at a maximum speed of 25 knots; but your ship usually operates at 18 knots. Why not make a bulb that can move forewords and backwards to match the speed of the ship and operate at maximum efficiency at all times. BTW: I'm still only a kid so I think it's an accomplishment on my part to even know about complex subjects like the operation of ships.

@@woxof46 brilliant son!!!

Only if your RC boat is a bearing sea icebreaking RC boat.😁

if you want an rc container ship, then get a bulbous bow

The bow rake (vertical angle of the stem) is more concerned with seakeeping capability. I will release a video next month that discusses this in more detail. But the short version for now: The original forward raked bow mostly evolved from tradition. Ships always had pointy bows, period. But with modern design techniques like CFD, we are able to look at the flow patterns of the bow in more detail and explore alternatives. Those vertical bows and reverse raked bows are designed around new flow patterns that benefit the ship. Vertical bows typically try to maximize the waterline length. That allows you to stretch out the bow and make a sharper bow angle. Reverse raked bows usually happen for seakeeping reasons. Reversing the bow often reduces the violent pitch motions that many complain about.

The more raked a bow is the less efficient the bow will be due to increased surface area of material in the water.

SHIP BONER

You want my other video where I compare different bow types. That includes wave piercing bows: kzfaq.info/get/bejne/a8uVo9iQ1N2qeH0.html

Theoretically, yes. Fins would work. But adjustable fins is a different story. To cancel the waves would require some property to adjust the length of the cancelling wave. I don't know of any fins theories that could achieve this. (But I also admit that I can't keep up with every paper on ship science.)

Interesting thought. Possible, but I'm not sure the benefits would be worth the extra hassle. Generally, any situation where the ship frequently changes speed will be when the crew are maneuvering the ship in a busy area. In those cases, I doubt they would take the extra time to adjust the bulb. But I could be wrong. I'm sure there is a niche application where this could work. There are other examples of tackling the problem of multiple speeds. I believe MARIN offers a service to optimize the bulbous bow to work at two or three different speed (but not the whole range between them). I'm a little skeptical about those. But there are other examples of adjusting for speed. Propellers face the same problem that they are design to be most efficient at one ship speed. So we created controllable pitch propellers where the crew can actively change the angle of the blades to get best efficiency at their current speed.

Right just rub as needed lol

My thoughts exactly you beat me to the comment

@@DatawaveMarineSolutions It is all automatic. A variable geometry bulbous bow would also be.

The first priority is a sonar cover. But as the design evolves, the shape of that sonar cover can also provide some wave cancelation. I can't say if the Arleigh Burke class specifically meant their sonar cover to also provide wave cancelation. I would need to analyze their hull form for any definitive conclusion.

Not really. Any waves that the ship generates get dispersed away from the ship. This is what we call the Kelvin Wake (www.wikiwaves.org/Ship_Kelvin_Wake). So by the time the wave from the bulbous bow reaches the stern of the ship, it has already dispersed too much to be effective. However, I have seen some limited studies into creating bulbous sterns. (www.sname.org/pubs/viewtechnicalpaper?DocumentKey=a50b80a4-463e-426f-bfb8-fe9a9432951d) Same idea as a bulbous bow, but with the flow direction reversed. The problem with bulbous sterns is that any bulb also reduces the efficiency of the propeller, which still hurts you. The other part of your question: application to small ships. In theory, a bulbous bow might work for the stern on a very small ship. Unfortunately, with a ship that small, your Froude numbers (en.wikipedia.org/wiki/Froude_number) get high enough that bulbs of any type are no longer recommended. With a small ship, your best bet is to make the hull as skinny and streamlined as possible. All that being said, you are definitely thinking along the right track. Bulbous bows are not the only trick we do to improve efficiency. There are other things like guide vanes for the propeller, designing for pressure recovery on the stern, optimized propeller inlets. I have even seen a stern lifting foil on some yachts. I think there are still plenty of opportunities for creative innovations.

I don't remember anything in ABS rules for ice class that specifically excludes a bulbous bow (but I also don't memorize class society rules). However, ice class rules size the bow plating based on the angle between the hull plate and the ice. The more your bow looks like a knife edge, the less plate you need. A bulbous bow would generate so much pressure for ice breaking that it would require extremely heavy plate. So I suspect this is more an issue of economics for ice class, rather than anything preventing it in the rules.

That one is in the works right now. I plan to release it next month.

Cool and thanks in advance!

Most of the studies I came across focused on new shapes of bulbous bows that deliver improvements across all speeds. The idea is to sacrifice perfect performance at one speed to get generally better performance over a larger range. But still a single bulb length.

Not necessarily. With ships at this scale, we don't just build the hull to achieve the fastest speed possible. The speed is a target selected at the beginning of the design stage. The SS United States may have just been designed to go faster. If you want to compare the two, you need to examine the resistance curve for the two vessels. That shows power required at each speed. The lower curve is the more efficient vessel.

It would just make more sense for the designer of the United States to give it a bulbous bow then, to achieve his goal of fastest ever liner. Wonder why he didn’t.

Some designers are working towards that effect. But instead of a shape changing bow, they are trying to adjust the shape so the bulb still works at a range of speeds. Sacrifice performance boost at one speed to improve overall performance across a range of speeds.

Seems like it would be relatively easy to find an "overall performance" shape as you say, but then put the bulb on a ram that adjusts its projection from the bow as needed. I would think fuel savings would pay for development costs.

Surface area is only part of the problem. Ship resistance comes from two major sources: friction and waves. On a good hull, the friction is only about 20-35% of the total resistance. Wave making is normally the dominant part. Hence why we often go for bulbous bows.

Yes, but her use in service should be the 1st consideration. From what I understand, the bulbous hull was 1st used on the Japanese Battleship Yamamoto due to her wide hull. Ships in the early 20th century reduced surface area with sharp straight bows, narrow hulls and rounded transoms, but this is very limiting on overall design and comfort. The sea is a world of compromises. I like planing hulls for the speed :-) Thanks for your reply and I enjoy your channel.

hydrodynamics is more of a or just as much a challenge than aerodynamics

I have that one coming out within the next few months. Looking forward to it!

Yes. That is the ideal scenario for a bulbous bow. They work best when we have a single predefined speed to optimize for.

@@DatawaveMarineSolutions Can you accurately simulate water flow around a ship bow to determine how to minimize water eddies? Eddies cause drag.

@@richrepublican3493 Yes. But it isn't automatic. CFD tells you where the eddies happened and can even measure the impact of each eddy. But it can't use that to back calculate a fix to the hull shape. That is why a CFD engineer must be a fluid expert first. They use their knowledge and experience to manually try refinements to the hull shape. CFD let's them quickly test those refinements and tells them exactly where to apply the changes.

You are correct, that is the basic idea behind a bulbous bow. But they don't achieve that canceling effect at every speed. And they are not a perfect asynchronous wave. Due to that, I tend to think of bulbous bows as specialist devices, only useful to specific operating profiles.

XtremeBudgetMusician I imagine with how random sea waves are and how much shear power it would take to move hunk of steel submerged and flowing through a relatively dense fluid, the ratio of energy expended to energy preserved would not be favorable.

Ryan Nelson I would imagine that the forces involved would be similar to the use of control surfaces of aircraft at very high mach values.

Submarine design is so specialized that I have not worked on any projects designing a sub. But I do know the underlying principles. As for more organic shape, it could be beneficial. But think carefully about directional control. A streamlined sub can also act as a giant wing on a turn, pulling you in the wrong direction. Worst case scenario:. The sub goes for a turn and gets pulled down below crush depth. ☹️

@@DatawaveMarineSolutions yeah i thaught about that. My sub has two forms of propulsion. A swimmer mode and a new hydroget design. We have three sizes of sub we are working on. A one seater a two seater and a twelve person sub. I designed them to follow the forms of dolfins sharks and whales. Strearing controls are designed along the lines of fins. I am using an anamorphos fin design that allows me to reshape the fin depending on speed. Programing the controls was complex but we got it to work. I was curious as to if anything like this has been considered in ship design and if you think the actual phisics of organic design would be benificial to other areas of ship building. What about the bulb designs on super freighters. What if it was designed to change its shape through out the speed curve of acceleration would such a design actually help those ships perform better.

I love this question! Great thoughts of looking to other examples and applications. And this shows one of the key elements of surface ships: the water surface. That water surface drastically alters the flow patterns around a surface ship. But designers optimize the submarine for travel far beneath the surface, and we don't get the same benefits any more than 5-10 meters deep. So the subs are still best as their current shape, unless someone designs something better.

I was thinking of gluing a sub on the bottom of the ship rather, to make the ship go faster. My original (barely educated) view was that the protuberance moved the bow wave forward, so the ship didn’t have to climb up it, and it made the ocean think the ship was longer and had a more narrow length to width ratio. But what do they do with aircraft carriers? The one on the JAG intro had a waterfall in front and no wake, just a ship-wide line of white water back to the horizon it seemed. BTW, the best bow wave I ever saw was on the Tugboat Annie TV show, during one of her races with Capt. Bullwinkle the water must have gone down over 20 feet and a bit under the hull. This comes from the early-ish B&W days of TV so my recollection may be cloudy.

Probably. But you never know. I have been surprised before by some of those seemingly simple bulbous bows.

Hi. Fashion is definitely a part. But in this case, the biggest factor was better science. I don't have the exact dates, but from around 1960 to 2010, the prevailing science said that a properly designed bulbous bow would always reduce resistance. (Provided that the ship operator used that bulb at the correct speed.) But that science all assumed perfectly calm water, with no ocean waves. Around 2010 - 2014, some new research came out that added waves back into the mix. That showed that in many cases, the bulb increased average resistance, because of the wave interactions. So that is the current state: bulbous bows can still help some vessels. But it takes more effort to make sure they are beneficial. Now, we need to look at calm water performance and wave interactions. Given all that, many owners decide to avoid the hassle of a bulbous bow.

@@DatawaveMarineSolutions Thanks. It was just she sheer variations of size and proportions that has fascinated and puzzled me. But that's a greta expiration,T hanks for taking the time f to explain to a layman. :-)