Splitting Waves and Hairs: Comparing X-bow, Axe Bow, and More
ฝัง
- เผยแพร่เมื่อ 2 มิ.ย. 2024
- We currently enjoy an explosion of variety in bow shapes, each suited to a different task. Nearly the same bow shape, used on a different hull, may work for entirely different reasons. This time we distinguish between four prevalent bow shapes: conventional hull, X-Bow, Axe Bow, and wave piercing.
REFERENCES
[1] Wikipedia Authors, "Large Waves Create Sea Spray over the Bow of the Amphibious Assault Ship USS Peleliu," Wikimedia Commons, 23 Oct. 2009. [Online]. Available: commons.wikimedia.org/wiki/Fi.... [Accessed 18 May 2018].
[2] TH-cam Contributors, "Warship Takes Huge Wave Over Bow," TH-cam, 8 Jun. 2016. [Online]. Available: • Warship Takes Huge Wav... . [Accessed 18 May 2018].
[3] Wikipedia Authors, "Container Ship Stefan Sibum VorStapellauf," Wikimedia Commons, 17 Oct. 2008. [Online]. Available: commons.wikimedia.org/wiki/Fi.... [Accessed 19 May 2018].
[4] Ulstein, "X-bow," Ulstein, 2005. [Online]. Available: ulstein.com/innovations/x-bow. [Accessed 19 May 2018].
[5] U. Kvamsvag, "The Foreship Arrangement for a Vessel of the Displacement Type," PCT, vol. No. 000073, 2006.
[6] D. E. Nordas, "Optimization of Bow Shape of Large, Slow Ships," in Master Thesis in Marine Technology, Trondheim, Norway, NTNU- Trondheim: Norwegian University of Science and Technology, June 2012.
[7] M. A. Mosaad, M. M. Gafaary, W. Yehia and H. M. Hassan, "On the Design of X-bow for Ship Energy Efficiency," in Influence of EEDI on Ship Design & Operation, London, U.K., 22 September 2017.
[8] Ulstein, "CFD Simulations - Comparison of Different Bow Designs," TH-cam, 20 Sep. 2016. [Online]. Available: • CFD Simulations - comp... . [Accessed 19 May 2018].
[9] Damen Shipyards, "Sea Axe design," Damen Shipyards, [Online]. Available: www.damen.com/en/innovation/s.... [Accessed 19 May 2018].
[10] J. Gelling, "The Axe Bow: The Shape of Ships to Come," in 19th International HISWA Symposium on Yacht Design and Yacht Construction, Amsterdam, The Netherlands, 13 and 14 November 2006.
[11] M. Waters, "A Look At Wave Piercing Bows on Multihulls," Sail Magazine, 21 May 2015. [Online]. Available: www.sailmagazine.com/multihul.... [Accessed 19 May 2018].
[12] TH-cam Contributors, "Animation - EARTHRACE 2 in 100 foot waves," TH-cam, 10 August 2016. [Online]. Available: • Animation - EARTHRACE-... . [Accessed 19 May 2018].
[13] Tekay Corporation, "ALT Striker: Bollard Pull Testing," TH-cam, 14 Dec. 2016. [Online]. Available: • ALP Striker | Bollard ... . [Accessed 20 May 2018].
[14] TH-cam Contributors, "Seven Sisters - Fast Stable 40' Hybrid Wavepiercer Yacht," TH-cam, 28 Sep. 2013. [Online]. Available: • Seven Sisters - Fast S... . [Accessed 20 May 2018].
[15] Flow Science, Inc., "Hydro-dynamic Response of a Planing Hull," TH-cam, 4 Nov 2013. [Online]. Available: • Hydro-dynamic Response... . [Accessed 25 May 2018].
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I can’t believe this held my limited attention span for 20 min. Really neat. I actually learned something watching TH-cam.
I’ve been curious about why we see different bow types for a while. Thanks for the awesome and in-depth discussion
Very interesting video with lots of information - I had been wondering how an X-Bow design would work and handle at sea. Thank you for sharing a designers insight, I loved it!
That was a great great video thank you for going through this information in a very simple way in English!!! Keep up the great videos!!!
Thank you for the detailed information & the effort in making the video!
this channel is great. your explanation is technical enough but not too difficult to understand. perfect for a naval architecture student like me. good job nick!
Thanks Nick. Another excellent video, I learned a lot. As usual you deliver the right amount of infomation for a layman like myself to understand without being too technical or too simplistic.
well said
Super cool video! Thank you very much. Subscribed and cant wait to see more.
It got me to thinking about the affects of these bows when you have a following sea.
I truly enjoy your video lectures. Most interesting.
Great and very informative video.
Thank you for taking the time to make it and for the free lesson on hull shapes.
hey just to make clear when you find yourself in a storm no matter what type of ship you have its not easy trust me
Think for every thing you want from amazon or ebay someone need to shipp it across the world
thik about people stuck on shipps because of Covid
I like your energy and how you explain things in a way a layman can grasp. Keep it up!
Thanks for the excellent presentation
I'm not even really into boats and I find this channel fascinating! I'm already mentally designing a hypothetical tri-hull swath, but with a aft-biased centre of gravity and with a wider structural section rising from the forward part of the submerged swath pods to improve seakeeping, with wave piercing tips to the three hulls, resulting in a W-shaped planform.... lol, I've only the barest idea of what I'm talking about, but what I do know is thanks to the channel, and it's fun to think about!
“I’m not even really into boats”…🤣
Thanks for the information and your teaching it! Appreciated!
Great explanation.
Excellent video about mechanics of bow design. I just discovered the wave splitting hull catamaran and wondered how well they do as the size of the wave increases. Lots of green water. Thank you!
wow amazing channel.... citations omg this is great
u really don't waste any of people's time in this presentation, tight and to the point, it feels great when you find a channel you know you're learn something from
Very well explained Nick.
Nick, this is the best video I have seen on the subject. As they say "a picture is worth a thousand words" this video is worth 10X the thousands of blog posts I have seen bouncing this topic around and never achieving any resolution. I think your insights on attributes are all true, but you stop short of putting numbers and dimensions on these concepts. Wave height capacity and frequency response would make deciding on a bow design clear and simple. I know that as a professional you can't give away all your secrets, but I have seen so many NAs insisting that this is a mystical process I think you could clean up as the guy who makes this a clear and simple optimization. All these bows have a wave height capacity with varying negative consequences from exceeding that capacity. Wave height from the ships perspective is wave height apparent, which is a function of incident frequency which is a function of ship speed, wave incidence, and ship heave natural frequency. You don't even have to be a genius to know what the expensive CFD studies are going to find.
Thanks for the education. Learned something new today. Love that!
Thanks for your presentation.
I Truly enjoy your video.Thanks Nick🏔🏞⛰🏕🏖🇦🇱🇦🇩
Thank you for providing clear reasoned explanations as opposed to the marketing waffle I’ve seen on other videos.
Was about to go boat shopping. Good thing I ran into your video.
Great breakdown and comparison
What a great man! As a yacht designer I found out a tonn of usefull information here!!! Grand thanks!
so, i saw the video of the thunderchild II and damn, thats an interesting entry in this whole bow form theme, i like it.
Kudos, oddly fascinating material and unexplainably engaging style. I’m in a land locked state, may never own a boat, but still fascinated.
Great! Super informative. Thanks
Super interesting!
Thanks for sharing. Good explanations
17:16 Could you put an image of every bow ship with every bow type? Thanks!
I would be intrigued to know about the often backward racked bow of a dreadnought class battleship and zumwalt class destroyer.
Fascinating. I've just been trying to explain to someone the difference between a plumb bow, a straight-stem bow, an axe bow and an X-bow - this will be very useful in clarifying it.
The axe bow reminds me of what was called "Destroyer Bow" as used on military destroyers of old.
Or the Titanic’s bow. lol
I think the Iowa-Class Fast Battleships also had the Axe Bow as well.
Whale wars has like 80 of those Damon shipyard axe bow vessels
@@Orvz475 NO, the Iowa has a classic bow. One could even say a clipper bow.
Yes, I served on a wwII era destroyer. Man that was not much fun in really heavy weather. And we saw plenty. We killed 3 men and injured several more and put several over the side while going out an inlet in Taiwan. The force of the waves severely bent the steel ladders going up the sides of the superstructure. The ladders were SIDEWAYS to the water flow. Really bad call to have men on the bow in these conditions. He lost his ticket on that one.
Thanks for sharing this!
slight broaching?? the one i worked on would broach just thinking about a following sea!!
From my small experience at sea - deck hand to master over 37 years, sadly I find that Marine Architects and the ships crew are at different ends of the spectrum - rarely do the two meet (a bit like shore side architects and builders) on the one side the architect designs grandiose shapes on the other side both crews and builders put themselves at risk to either operate or build these designs. despite that I would like to congratulate the presenter for at least looking at both sides of the coin. Very well done sir, we are finally getting somewhere, let us hope others will move that way too (I do of course include ships crews who often complain as a matter of course despite the efforts of the architect)
To be fair, a naval architect who goes to sea exposes him or herself to danger, wet, cold, heat and seasickness. Horrors!
@@OgamiItto70 Just a minute - the idea of being a so called Naval Architect is to design things that go to sea! This means that the naval architect should have some idea of what he's doing, this can only be got at sea! If you were such a being I certainly wouldn't buy any of your designs nor go anywhere on one of them!
@@mikewalrus4763 Yeah, but heating, air conditioning, supermarkets, bars, restaurants, bookstores, coffee shops, movie theaters, bowling alleys, female women of the opposite sex...all in much greater, more reliable supply ashore than at sea!
@@OgamiItto70 What has that got to do with designing sea going vessels other than the fact that some or all of it may be required at sea? Or at least facitities for and to use such items
@@mikewalrus4763 Cost/benefit analysis for college boys or girls.
This is so cool. Thanks man.
learned a lot here! Great vid!
Great video footage from HMNZS Otago
I remember the launch of the first x-bow vessel, the Bourbon Ocra. I was allowed onboard for a look around. I found it incredibly wired looking. And to be honest, I still do.
I don't work at sea myself, but what I hear is that the x-bow is stable with sea straight on, but is uncomfortable with waves hitting from a 45 degree angle.
This was really good!
I have seen videos on youtube that show an x-bow next to a conventional bow of oilfield service ships in the north sea and notices that the x-bow had less pitching. This seems to me to cause the thrust from the props to remain more horizontal. This will make the thrust more efficient, improving effective thrust, improving fuel economy, or reducing thrust requirement to maintain a given speed.
Thanks Nick 👍!!!
Thanks Nicholas!
Thanks Nick.
Plumb bows similar to the axe bow are very common on a lot of modern sailboats. They are often very wet and they pound in heavy seas. Often made because of ease of manufacture, length of waterline, and increased interior volume at the cost of excess windage and comfort at sea. Many older sailing designs would use a deeper profile fore and aft to allow the hull to rise and fall in waves more smoothly, and tend to stay more dry.
Love your work! suggestion for a topic - parametric rolling
Hey Nicholas, just discovered your awesome channel. So far i've neglected the outboard swap in my driveway for 4hrs and counting....all because of curiousity and hunger for knowledge on anything nautical, but particularly design theory and concepts that can (or have been) measured in real-world application. 4hrs and counting....
Anyway, regarding bow designs, I'm interested to see your take on some more unconventional builds, in particular:
A) the Seaski boats,
B) how hydrofoils in general are seemingly being embraced in the sailing world, but dismissed as "tried that, too hard" in power boats. The exception being the 'wake/wave' damping foils more recently fitted to to some large ships with apparent success.
cheers
I read Seaski's explanation behind their vessel: www.seaski.com.au/portfolio_page/about/ . It apparently uses a combination of two planing hulls on the sides and compressed air under the hull for lift. I have seen this concept before. I'm not sure how well the air under the hull works. That is an area that I need to personally research further. But the side planing hulls should work just fine. The only downside to the whole hull is that I would not trust that with any large waves of 1.5 - 2 m wave height. The same hull design that compresses air will also create huge pitch motions on a hull.
I need to make a whole video on hydrofoils. But for the short explanation: It's important to remember that hydrofoils in the sailing world are only going on high performance racing vessels. The people that use those boats are highly experienced sailors, who want a bigger challenge. And hydrofoils are a challenge. On a normal boat, you only need to worry about your direction of travel (yaw motion control). The ship's hull handles motion control in all your other degrees of freedom (surge, sway, heave, roll, and pitch). But a hydrofoil needs motion control for all six degrees of freedom. Either very attentive crew, or an autopilot more suited to an airplane. That is the main challenge of hydrofoils: you need to worry about controlling all six degrees of freedom.
Very interesting and perfectly explained! I would love to learn more about the specifics of seakeeping and behavior of recreational boats with a planing hull in the size of 35 to 45 feet. This seems to me the main criteria when buying a boat like this, but there is not much substantial information out there. If you want to go out at 5 bft with your family on a planing boat, what hull specs should you consider? How important is deadrise for a smooth ride with minimized slamming? How big are the differences eg. between a northern hull like those of a Windy or Marex and one like Atlantis or Sea Ray? I would be so thankful for some answers!
I remember as a kid looking at the old photographs of the dreadnoughts with inverted bows. Now they are back for some new warships.
Speak of the devil. I was just searching your channel for any vid on X-Bows yesterday.
Consider this another well earned sub.
Very good presentation. I think the X bow is the future trend, way better than others.
Excellent Vid.. Thank you.
I think the long bow is simply moving the personnel spaces toward the center of pitch rotation. That is, the tip of the bow experiences the same high accelerations, because it is moving up and down a significant distance... but the crew spaces are at or near the center of that rotation and simply move a shorter distance in the same period.
Thanks for sharing.
Thank you for this information
I'm very curious about the M-Hull as seen on the M80 Stiletto and the water taxis for Venice. How effective would that be for commercial cruiser boat, as opposed to a catamaran or trimaran? From a total novice perspective (and that's more credit than my knowledge deserves) it seems like it would provide advantages in weight, seakeeping, available area etc?
great explanations...
The AXE bow dates back more than a century
Wouldn’t the reduced pitch motions and smoother ride both be beneficial when towing. As this is a major use for X-bow ships, if so, that would a benefit.
Thanks Nick, love the simulator thru waves. Have you come across the 1910 Hickman Sea Sled, and opined on its wave handling claims? Cheers
Fascinating. Thanks
Very interesting, had no idea!
HMNZS Otago in rough sea in the southern ocean... ahhh the memories..
èxcellant video Mr Nick
In the late 1800s and early 1900s vertical bows and deep draft was dominant and to me resemble axe bow. And they made the boats that way because of experience. The fishermen in fishing smacks noticed that vertical bows pierce waves better and result in smoother ride. I guess what goes around comes around.
Outstanding!
Very interesting video, thanks! Now, I can't avoid thinking of the bows in canadian canoes which I guess are suitable for rivers and lakes (small and short waves). I would love to hear some comments on that.
hmm I think that may be largely the result of the traditional construction technique making the boat out of a sheet of tree bark. That's the bow shape that's easy to make.
Hi Nick, thanks for teaching me today! I am into a project you may find interesting; I am refitting a 100' wooden tug (keel laid in '25 for Wrigley by Muller in San Jose) into a mini cruise ship. She has a plumb prow, beamy midships, deep draft, big wheel and fan tail. My name is Dj, I am on her in the Salsh Sea.
Love your channel. Live long and proper 🖖
propeller?
Veldtian1 prosper
Good stuff. Now I understand why the Zumwalt class destroyers are having some minor structural issues in front of the super structure and why the advanced gun system is having reliability issues.
Came across what seems like a wave piercing trimaran cruiser a while back called the Alibi 116. Have you seen that? What do you think about it? Looks interesting!
Definitely interesting. I'm curious about the structural and hydrodynamic design. With trimarans, the big game to reduce your resistance is finding the right balance for wave resistance and viscous resistance (hull friction + some other stuff). They have very thin hulls. Good points there. But the side amas are all full length, and they have a lot of appendages in the water. Lots of surface area for skin friction. Not sure if that was the best approach.
I'm also curious about their forward daggerboards on the amas. Those boards are curved, which means they partially act as a hydrofoil as well. That might help reduce their resistance.
I can't say if it is a good or bad design. That requires far more intimate knowledge than I can get from a five minute review. But it certainly has some interesting ideas.
There is a video of an X bow going through the waves, alongside a normal bow ship,the video shows the X bow cruising through the waves with ease,while the normal.bow would rise up and slam down.
Hands down your best video yet. Especially your analysis of the X-bow was very informative. I find the balancing act of contradictory requirements in ship design extremely interesting, and wrestle with the idea of "the ideal hull" for my application, long range cruising. The interplay between transportation economy (speed x cargo mass / fuel usage) versus constructive cost and how the life cycle economy works out in different usage cases is complex enough, but it gets really interesting when you throw sea keeping requirements into the mix. Perhaps a subject for a future video? BTW, I was under the impression that the X-bow was more efficient when running at speed in heavy weather, which I find very thermodynamically intuitive since the sheets of green water represent a lower state of entropy than the foamy spray kicked up by a conventional bow.
It gets even more fun when we add in all the mechanical elements. For example, vibrations are a big concern on the ship for passenger and crew comfort. One of the main sources of vibration comes from interactions between the propeller and hull. So we often decide on separations between propeller and hull based on vibration concerns, rather than propeller efficiency.
Don't I know it. My current boat is roughly 13.5m LOA / 25 T displacement, and came with a 36" / 90 cm CPP in a poorly designed Kort nozzle. That configuration was bad enough to break windows under full power, but things improved immeasurably when I cut the nozzle off and re-ground the blade tips. With a 15 cm blade-to-hull clearance, I expect things to get almost nice once I re-locate all the ballast to the wedge keel that carries the shaft.
Could you do a review of the Rafnar hull? I would be extremely interested to hear you opinion. Mahalo
Loved the video. I never considered 1/4 wave behavior or wind-loading. Makes a ton of sense! Thanks for the explanations. Afterthought #1: Is SWATH the last remaining hope for overall stability in the widest variety of conditions?
For ultimate smooth motions, yes a SWATH is probably your best bet. But that also has its own array of challenges. You can learn about them in this video on SWATH boats: th-cam.com/video/jJAHyDl6KS8/w-d-xo.html
excellent vid
the backwards angled bow has become very trendy on high performance racing multihull, and also luxury cruising multihull. I'm a little bit wary of it to be honest. For a racer, if you don't win, well you might as well sink, so they care more about going fast than keeping dry, but a crusing cat speed is cool, but not really as important as comfort. Although, if the boat is only sailed in moderate conditions, then comfort is much easier. But if the boat is sailed in extreme conditions (something that may not be the plan, but ends up happening). A sailing multihull is also light, so it doesn't have the inertia that you recommended. So, is a wave splitting hull more likely to pitchpole? it's definitely more likely to dive into the wave, but would have less resistance to come out, but would that be enough to make it safe? or would a flared bow that's less likely to enter the wave be safer? I guess this depends on the drag of the submerged shape and is a question for a naval architect!
thanks for share!
I have nothing to do with ships, boats, yachts, hulls or anything, but I still found this interesting.
That video embedded in this video is a New Zealand navy ship in the sub antarctic ocean. Big waves, growlers and bergy bits!
I wonder what happens all these various bow types when waves come from directions other than straight ahead?
What would you classify the USN DDG1000 class bow (besides fugly)? Wave piercing cross section with the large slab sided tumblehome, but then there's this giant sonar dome of a bulbous bow down there!
What about the Zumwalt bow??
As they all look more or less the same, Will you recommend a different bow for an inflatable bot such is the Zodiac ones?
Fantastic video, I was on the vessel in the greenwater example. HMNZS WELLINGTON, OPV in the Ross Sea
Awesome! Did you see any big waves like shown in the video?
@@DatawaveMarineSolutions Absolutely, i was standing next to the guy taking the video, while this was occurring a mayday was received from a single mast yacht which due to the conditions we could not attend to. Unfortunately we never found the yacht or the crew
Good job explaining the differences. Thanks
-johnny
What about clipper bows or straight-stem bows? Also, do the old ram bows of pre-dreadnoughts qualify as wave piercing bows?
Speaking generally, clipper bows still behave much the same way as a traditional ship bow (without any bulbous bow). They have much lower resistance and better seakeeping due to their fine entry. But you get that same behavior with any bow if you make it thinner.
Straight stem bows are halfway between traditional bows and the X-bow. But the stem matters less than the shape as the bow gets wider. Most straight stem bows are still shaped like traditional bows when you move aft.
And the old ram bows: I would not qualify them as wave piercing. They may have had some of the same side effects. But with a wave piercer, you really need an intentional design effort to make that work correctly.
All this is absolutely true. That is assuming that draft is of no concern which I would like to see a video of.. I’m new to the channel. Do you have a video about draft???
How about deep V with sharp entry bow?
Thanks for the information contained in this video
It's the same as a conventional bow however you're giving up moment arm to reduce the rate of deceleration on the crew and vessel.
Hi
Very good videos
May you give me mor information about axe bow ?and axe bow in sailboat?
Nice video
Can you make a vid on hull effects on design ?
At 4:30 into your description, you said "...initial shock of entry", not 'shock of initial entry', which I mistakenly thought I heard and then I formed a new concept of that "point of lift" at the point of entry to "cushion" against the shock of entry you described as ride quality. A video of this is from waverider boats in Australia, and would love to hear your views on that design he used on a trihull hydrofoil. Though my thought is to make the bow of a "V" hull affecting greater lift at the point of entry and causing an improvement in ride quality and handling, especially during a following sea.
Good video, there are some things that were shaken up, but I like them.
Look into my eyes, look into my eyes
Not around out the eyes, don't look around the eyes
Look into my eyes
You're under
👍👍👍 Thank you Schlomo!!! You saved hours for me trying to find out what that guy reminded me off! Brilliant! 👍👍👍
(Drools aimlessly, half hypn ....)
I loved it, it was better than Cats, I will see it again and again.....
Can ask what program you are using to simulate the water flow between the conventional bow and the X bow?
Does the program work with designs? Like if you designed your own bow, would simulate water flow around it?
I appreciate the info and I truly enjoyed your video. I liked and subscribed. Thank you again stay safe.
Great series! Can you do a video on electric propelled cruising catamaran hull design for getting the best range on electric engines and batteries? Thx
I have that one in the works now. It should get released sometime next year. (I plan the videos out several months in advance)