Pleasantly surprised to see the boat that I worked on in the late '80s. I was one of the handful of Naval Architects who worked on the design of this boat at McDermott Shipyard in Amelia, Louisiana. This is one of the 4 T-AGOS (19,20, 21,22) vessels we built for the MSC. I had the opportunity to do stability, scantlings, vibration isolation, structural foundations, Surtass winch foundation, steering gear, module lifts, coatings etc on this project. We launched these vessels using our 5000 Ton shear leg crane since Navy rejected our dry dock facility. That lift design was unique with 8 lift points and I designed it. I can email you a photo of the lift if you promise to add it as part of this presentation. These days I am designing Trimarans powered by water jets at Austal.
Awesome! I bet you can add all sorts of useful tips on SWATH design. My email is n.barczak@dmsonline.us . I will definitely use that picture the next time I do this presentation. (Sadly, TH-cam won't let me edit the video after I post it. But I can add it to the matching article: dmsonline.us/smooth-sailing-pros-and-cons-of-a-swath-vessel/)
The US Navy was doing research on this type of vessel back in the 50's, it was known as an SSP. They also considered it for use as an Aircraft Carrier.
Thank you, for the explanation of the forward canards now I understand there purpose,. I have just recently completed a four month voyage onboard the USNS Able, this video has been insightful.
My 1-time experience on a swath: like gliding on waves, near zero pitching. But sea conditions were favourable: not a storm, and not 10 metre waves. If speed is like a cat or tri, a swath could enable storm avoidance during journeys. I see many potential advantages to a swath for say a 74ft yacht.
I have to imagine that these ships aren't necessarily limited on weight - the submerged hulls could be made any size - but are very sensitive to weight changes, as there is very little change in displacement for a large change in draft. To keep it at the right height, I'd imagine ballast water must be used. Not a huge problem, but adds some more complexity to design and operation. The biggest drawback from what I can see is, along with cost, a deep draft of the vessel.
Unless you oversize the floats and use the water tanks to submerge them. Of course, ballast tanks can then also be used to trim the ship out both left-right and back-forward. A fun idea I had though not sure about the benefits is a SWATH container ship that uses ballast tanks to keep its waterline during loading and unloading.
We used fuel as service life on T-AGOS ships, at least that was the design intention, how MSC operated them in service I cannot say. Minimum wet deck height is the real concern to avoid slamming.
can't stress that weight sensitivity enough, you also need to make damn sure your ballast system works flawlessly, even at excessive pitch and roll angles. ref, Ocean Ranger. the ballast control room was in a vulnerable position and a portal wasn't as good as it could have been. to compound things, once the ballast control was sorted out, the tilt caused by the shorted controls had tilted the platform in a way that moved the water in the tanks away from the pipes that pull the water out of the tanks. so the tanks could be filled but not drained. That in combination with other issues with escape systems in 1982 caused a significant loss of life. Just be damn sure ye know the systems will work.
As a yacht, the swath seams to be the ideal hull configuration. Offering an excellent deck volume and the very best in sea keeping stability. A long range vessel would likely forgo high powered engines in favor of fuel efficiency, mitigating the engine room requirements on deck space. A diesel electric drive is likewise advantageous considering all the hotel systems that need electrical power.
Don't forget about the structural weight fraction differential between SWATHs and monohulls and the added structural complexity that comes with the complex structural load paths. There is always a tradeoff between ease of production and weight, which is complicated on a SWATH. Also, you didn't mention the resistance and powering differences for achieving the same payload. If the design is done properly, like the Navy did for the T-AGOS ships, the hump in the speed power curve will be designed to be at the endurance speed to maximize range due to diverging wave cancellation. But the increased frictional resistance of a SWATH is a primary price you pay for the small waterplane as is slam pressure loads. As noted, the arrangements are also a challenge, so most SWATHs I have seen are electric drive. This can be a challenge as well, but more recent advancements with A/C motors can reduce the space and weight necessary for the electrical equipment, like giant thyristors and power conditioners. Use of complicated Z-drives with 90 degree shafting never made the cut in our designs. Thanks for the post.
Nice - I didn't know you were leading up to this - hence my comments on another thread. Now all I've got to do is shrink that to a 5m by 2m SWATH dingy and use water ballast to overcome variable load… :) Oh, and a joystick to control minimal active fins at the 4 corners. I suspect that a rectangular rather than a circular cross section will be better at water flow around the hulls
Now that's really interesting! Who knew? Why would some idiot give it a thumbs down? It is designed for specific water functionality uses. So if it doesn't address one's needs but the type that will. Duh....
Sadly my dream SWATH vessel was sold before i could nab it up with my theoretical lottery win. Rip Rogue. She's a perfect SHTF boat for the more advanced prepper
Really like the videos, keep em coming. I have been tinkering with different boat designs for a solar powered cruiser, and I was big on swath for a while, but I think a better idea might be having a suspension on a cat to achieve good sea keeping without the higher drag of the bigger hulls. And while I'm posting, let me ask you a not-really-related question, of how much additional drag is created if you have two pontoons inline that are shorter vs one longer pontoon? One could 'fold up' the pontoons in shallow water, if you can interlace them as offset pontoons, they can be very deep or wide or very shallow.
Anywhere between 25-45% more resistance to have two pontoons inline. That is a guess from some similar work I did in the past. That second bow adds a lot to the resistance. I did some similar research about 9 years ago looking at running boats all in a line so one could "draft" off the other in front. Unfortunately, we found that any effective drafting required you to be so close that it should just be one hull.
I'd be interested in any research papers available. Let me ask this question a different way, let's say I have two catamaran hulls, would it be any less resistance to put them inline vs in parallel? I can't understand how it could be more resistance, same two hulls.
Small Waterplane Area Single Hull, I've also seen it referred to as a Mono-SWATH. Examples include the Abeking and Rasmussen built inshore tender, and the Windersver series from Fjellstrand.
Somewhat, but not recommended. The problem with sails is they generate a heeling moment. All that wind is great for pushing the boat, but the hull also needs to react to the heel moment and stop you from capsizing. That reaction comes from the hull shape. And SWATHs are intentionally designed to NOT react as they heel. So to have anything effective, you would need a HUGE SWATH with small sails. The sails would not move the ship very fast.
@@DatawaveMarineSolutions this is a fantastic video! Do you know if SWATHs have used lifting bodies in the submerged hull tubes? It would also seem like high volume bubbling (like cavitation) would be helpful. Thoughts?
SWATH always has bigger wetted area of the hull for same displacement, which means more resistance. And SWATH usually needs more displacement to have the same cargo carrying capacity because of its complicated hull construction. In theory sometimes you could minimize wave resistance by using SWATH, but in reality you always need more power on a SWATH vessel for the same speed and deadweight.
Thanks Nick, I am very much delighted to watch videos on your channel. Can both the engine and fuel tanks be located in underwater hull(in a swash model)? please guide me
Sure. No rule against that. The only catch is practical considerations for the engine. An engine needs empty space around it to for crew to maintain the engine. Most engine installation drawings even specify the extra overhead space required if you were to remove a piston. That extra space becomes problematic if you have a very narrow hull.
@@DatawaveMarineSolutions You are so kind Nick, another question which is very disturbing for me is, if I am planning to build a 13m submerged hull with 1.5m diameter, what is it ok to use 6mm steel? What should be framing type? If I use scantlings, what should be specs?
I've seen these on the hard, and now I finally know what they are. Thanks :-) I imagine these require the chief to be on the ball with the ballast system... Couldn't sufficient carrying capacity be achieved by using large enough ballast tanks? Of course this would incur a performance / cost penalty, but these will never be your passenger mile per liter fuel winners anyway...
Yes indeed. You got it in one. One of the hardest things for operating a SWATH is weight discipline. Most chief's want to have plenty of spares onboard, which is generally a good idea. Example: I once saw a vessel that had 4 spare pumps, totaling about 1 long ton. That's fine on a monohull. But with a SWATH, the weight of all those spares take away from your mission weight.
Our Purchase Orders to vendors indicated a $ x.xx per pound penalty for every extra pound on the equipment delivered, above its previously quoted weight !!
Very interesting & informative. I wonder if the vertical planes (?) connecting the upper deck of the vessel to the submerged flotation amas could be minimized to where they have just the minimum amount of wetted area. Essentially supporting the upper deck at only its corners, leaving the deck to appear floating in air? Side wave action effect would be further minimized. Hope I'm making myself reasonably clear. Thanks from a land architect!
Many SWATHS have tried that approach and go down to just four struts supporting the cross deck. Unfortunately, other practical concerns take over the design. Normally, the struts still need to be large enough for a single person to go down them. That is necessary for maintenance of machinery in the hulls and responding to any emergencies like fire or flooding in the hull. But you also have the problem of vessel weight control. Vessels change weight all the time. Everything from people stepping on, to offloading hundreds of tons of cargo. The ship balances out that weight change by changing its draft and displacement. This is actually a parameter we calculate: TPM: Tonnes per meter immersion (the acronym changes depending on your units.) On a normal ship, you may have a TPM of 800 - 5000 tonnes / meter. But in a SWATH with super small struts, that number gets very low. Maybe 50 - 100 tonnes / meter. At some point, we acknowledge that ship still has to carry cargo without sinking straight to the bottom. Then those cargo weights and mission parameters drive the SWATH strut design.
Does a SWATH hull escape the limitations of a displacement hull and behave more like a submarine hull combined with axe bow? Does it need less power to be driven relative to displacement?
I think the US Navy did. The main limitation is probably that carriers want to be long not wide (the jets need enough distance for takeoff and landing) and there is a need for lots of internal space below the top deck (for the hangar), neither of which exactly fit the standard SWATH concept. A SWATH carrier would be rather long and skinny for a catamaran and would have a deep, boxy cross-deck to contain that hangar, presumably putting the flight deck a very long way above the water.
Yeah, as with catamarans, this doesn't seem like a great match. Even if you put the runway along the diagonal, you want the runway to be as long as possible, and that means you want a rectangular ship over a square one; The closer to a square the ship is, the less efficiently it'd function as an aircraft carrier...
If anything would make a good argument for an unconventional cruise ship design, surely a SWATH hull would be it. The cruise ship is all about those passenger amenities. And nothing beats a SWATH for that basic comfort factor...
There are such boats. It is called a nauti-craft. They have some great videos on TH-cam. The reason we don't use that for larger ships:. The hydraulics would be huge and require lots of power. For bigger ships, there are more efficient methods to reduce or eliminate seasickness.
Would you like to comment on structures for seasteading? www.reddit.com/r/seasteading/ www.seasteadtalk.org About the concept of seasteading: en.wikipedia.org/wiki/Seasteading www.seasteading.org
So for a sailing vessel in the 40 - 50 foot range, the draft on a monohull is generally 5 - 7 feet, and on a catamaran about 3 - 4 feet. I've never seen a SWATH sailing vessel in that size range so I'm assuming the draft requirement is too deep to be reasonable? Or is it just not worthwhile building a small sailboat SWATH because of other reasons (drag, amas too close to the surface, heel, etc)?
@ kobin. A SWATH is not suited for a sailing boat. On such a boat you have very variable loads on the hulls coming of the sails, besides the sea. In few words, the resulting center of power from the engine (sails and masts) is several meters above the deck, and worst not aligned with the hull(s). A mono reaches a new equilibrium heeling, a multi immersing the ama thus creating an opposite force up (I wildly simplify). And a SWATH how will it do? no possible safe heeling, no variable immersed volume of the ama as the volumes are underwater and fixed...To solve that, you enter in very complex systems; foils, ballasts, active systems , hydraulics, sensors, computers and so on. Gosh.... A well designed cruising trimaran is far simpler and is very effective for getting sweet sea motions..
Would SWATHs be recommended for small, diesel-electric, pleasure craft/yachts (40 to 80 ft) or superyachts? If so, what sort of reasonable payloads and missions can we expect from them?
Yes, SWATHs can be ideal for yachts, depending on your budget. The motion control systems will drive the price higher than a conventional yacht without motion control. But you pay for comfort. That is the whole point of a SWATH ship. As to capacity, it depends on the ship size and desired speed. The good news, on the scale of ship weights, a few people weigh next to nothing. Reasonable missions? Normal coastal cruising, offshore cruising. Even relaxed cruising in slightly bad weather (mild thunderstorm). I would not take a SWATH yacht to high latitudes or polar regions. But almost everything else is reasonable.
@@DatawaveMarineSolutions Why would you not take a swatch to polar regions? Because of the extended motion control fins? What about retractable fins? I realize that stability would be compromised, but would a swath without the motion control fins still be superior to a monohaul of the same lenght?
@@mojojojo_BB I imagine it would have something to do with the reliability of the control systems in the cold rather than just knocking into a bit of ice. But let's see.
@@mojojojo_BB Nothing to do with the control fins. It has to do with survivability and responses in extreme waves. Higher latitudes and polar regions have worse weather. Larger waves. You need more reserve buoyancy to survive that type of weather, something that we normally design a SWATH to minimize. Now there are exceptions to this idea. The US Navy created the T-AGOS vessels, which were SWATHS designed for heavy weather. But a Navy vessel has far different standards than a yacht, including crew comfort. en.wikipedia.org/wiki/USNS_Victorious_(T-AGOS-19)
Datawave Marine Solutions You mean if the ship encounters waves that exceeds its sea state rating, a monohull has a greater probability of surviving it than a swath.
The fins don't control yaw. I think you may have meant pitch and roll. It depends on the SWATH. Most will go for active control of pitch and roll. Some use passive control, with static fins that don't move. I would always recommend active control. And the underwater hulls definitely include ballast tanks. They need the ballast tanks to counteract changes in loading and still maintain close to the same draft.
Thank you. Yes I did mean pitch and roll. Is it correct that ballast tanks are used for pitch and roll trim and the fins are for active control of these parameters?
@@JDI4DAVID yes. The tanks are normally used to trim and level the vessel at the start of a voyage, depending on the Master's preference, and the fins mantain active control against waves.
@@DatawaveMarineSolutions Thank you so much for explaining this. I guess the passive or active fins are essential for pitch and roll stability. Can the hulls' ballast tanks can be flooded and the ship operate as a catamaran if they fail?
@@JDI4DAVID Most SWATHS can operate as a catamaran with the ballast tanks pumped out and the ship light loaded. As to fail safe design of the ballast tanks, that is a little risky to make a general comment on. It depends on the individual system. But in general, we can create systems that are fail safe, if needed.
I would guess that's highly variable. For one thing the hulls are very much built like submarines. It seems unlikely you'd get an immediate total loss of buoyancy. The rest would depend on whether any of the upper structure of the ship floats, and to what extent, and then what the buoyancy of the other hull is. If one hull sinks, then it depends on the superstructure as to what happens next... I rather doubt you could get one to capsize completely, given it's nature. It'd just sink outright before it would be able to flip over completely...
They are very stable designs in both intact and damaged stability. Due to the very large beam, you have a high transverse metacenter. In a damaged case, not only do you have the subdivision bulkhead spacing limiting the extent of damage cases to pass (which you also have on monohulls, et al) but if the WL were to be high enough to wet the haunches, you start to pick up a massive restoring moment. So the wet deck is as low as you can practically go and weight is the big design concern, to keep from slamming and damaging structure, but damaged stability survival and the height of the transverse center of gravity is never an issue. LGC is more the issue.
Short answer: theoretically yes. Slightly longer version, an aircraft carrier would require extensive calculations for stability that go far beyond the selection of the hull shape. At least on USA aircraft carriers, I believe they heavily armor the flight deck, which adds a LOT of weight up high. That creates a major challenge for stability in general. So aircraft carriers may need to design in reverse. Instead of creating the hull shape first, you start with calculating the stability requirements. Then create a hull shape that can meet those requirements.
@@DatawaveMarineSolutions as I understand in case of an aircraft carrier the beam (ranging from ¾ of the front bow section through midship & all the way to the rear stern section) of a tumble home hull design has to be significantly more (65% - 70%) than usual in order to offset the weight topside & in turn that would mean an increase in length & draft of the aircraft carrier as well!!! and ofcourse overall height!!!
I just want a Catamaran that has propulsion or I can use the sails and travel for free. But I want a computer system to deploy the sails as needed to the set course.
Quadmarans were tried. I was involves in several different research projects that tried variations on this idea. So far, none of them work out. The fourth bow generates too much additional resistance to be worth it. If you see any examples of quadmarans in action, generally, they were not built for reasons of reducing resistance.
Many people asked me about this one. I'm not sure how well the SWATH design would work for sail configuration. I agree that the SWATH would allow smooth rides. But the problem comes with balancing the sail. That sail produces a heeling moment, and to counter that moment, we need to submerge more of the hull. As the ship heels, one side submerges, increasing the buoyancy on that side. That extra buoyancy produces a righting moment and balances the sail's heeling moment. Problem is that SWATH are designed with small struts at the waterline to specifically minimize that increase in buoyancy. I'm not saying it would be impossible. But it would be an interesting challenge to balance the seakeeping capabilities with the buoyancy that you need for a sail.
@@DatawaveMarineSolutions could this be countered by making it wider, thus increasing the leverage of the force, also passive fins perhaps? This concept has beenbouncing around in my head, but i'm no engineer...
It's a tradeoff of weight capacity vs comfort. An X-bow is still a traditional monohull. As a monohull, it can carry a large amount of weight. But the X-bow will handle steep waves better. A conventional bow shape has a tendency to bounce over a wave crest. The X-bow does better at following the wave up and down, without bouncing. Compare that to a SWATH. A SWATH has very little weight capacity. It starts with one weight when first built, and it needs to maintain a similar weight throughout its life. So SWATH's are very bad as a cargo ship. But they do offer comfort. In a SWATH, you don't bounce over the waves. You don't even follow the wave surface up and down. The wave just passes by under the SWATH, with very little disturbance to the ship. (Within limits. For a large enough wave, even a SWATH encounters problems.)
I would think that a Diesel/electric hybrid would be the best power configuration. This along with computerized controls would make it even more stable. That leaves the question of whether the hull configuration is more efficient to operate over the life of the boat?
Yes, electric drive was always the answer, and that is synergistic with missions requiring large electrical deck and mission loads (which are not used then the motors are using a lot of power). Although I did tour the MBRI SWATH back in the late 1990's and as I recall it had small tandem diesel engines in each lower hull (I dont recall how the reduction gear was arranged, but this was more of a boat than a ship). That was the only SWATH I have seen with that sort of machinery arrangement, and it was not that great a design, as bolsters were being added to it at the time!
Why not use SWATHs for pleasure craft (ocean-crossing privately-owned yachts)? These part-timers would like a smooth ride & their cargo carriage is pretty fixed. Almost all of these private yachts (even the 60 footers) also have stabilizer systems, so the extra cost of the SWATH's motion control system... may not be that much extra...
I have seen some interest for building a SWATH yacht. And yes, it could be very useful for a larger yacht. I think part of the challenge is that SWATHs require a little more engineering than your average yacht. That creates a higher startup investment for a production boat builder.
I worked for MSC for years. Ive been on one of those T-AGOS ships in Sasebo Japan to trade food and supplies. I have some friends who worked on them. And all of their opinions are the same. It fucking sucks being on those ships. Loud loud loud. Waves slamming and slapping the hull makes life miserable. Yeah they're fast and cut the waves pretty good but even on fairly calm days the waves slap the vertical hull loudly. Cool looking though.
Same purpose of the inverted bow, more smooth rides by reducing pitching but not rolling! -the pattern Norwegian Ulstein X-BOW😊 th-cam.com/video/MZ934OKFnHY/w-d-xo.html
Naval architects????? Absolutely and unequivocally WRONG! The SWATH design was invented by Frederick G. Creed in 1938 and patented in 1946. He died before the first vessel was launched in 1968. When he drafted the first concept drawing, he was laughed off as a lunatic - only to be heralded as a hero when someone finally proved his design works.
![ILLSLICK - KILLSHOT REMIX [FULL VERSION]](http://i.ytimg.com/vi/RIK8RrqIAzE/mqdefault.jpg)
My Dad was Kurt Schmidt .I am totally excited to see his ideas in play .Thank you.I miss him.Annette
Pleasantly surprised to see the boat that I worked on in the late '80s. I was one of the handful of Naval Architects who worked on the design of this boat at McDermott Shipyard in Amelia, Louisiana. This is one of the 4 T-AGOS (19,20, 21,22) vessels we built for the MSC. I had the opportunity to do stability, scantlings, vibration isolation, structural foundations, Surtass winch foundation, steering gear, module lifts, coatings etc on this project. We launched these vessels using our 5000 Ton shear leg crane since Navy rejected our dry dock facility. That lift design was unique with 8 lift points and I designed it. I can email you a photo of the lift if you promise to add it as part of this presentation. These days I am designing Trimarans powered by water jets at Austal.
Awesome! I bet you can add all sorts of useful tips on SWATH design. My email is n.barczak@dmsonline.us . I will definitely use that picture the next time I do this presentation. (Sadly, TH-cam won't let me edit the video after I post it. But I can add it to the matching article: dmsonline.us/smooth-sailing-pros-and-cons-of-a-swath-vessel/)
Many asked me for a video on SWATH vessels. It's finally here!
Great video
Nicholas Naval Architect thanks Nick
Nicholas Naval Architect today I learned about swath ships, thanks
I really enjoy the channel, i was curious if you know how efficient (in general) Swath hulls are to competition.
Thank you for this video
Nicholas- So glad I found your channel! I'm fascinated with Naval Architecture and am grateful you take the time to put these videos together. Thanks!
You look like you're going to sell me a bible "for only $49.99!!!!"
Love your channel, zo much awesome!! Thanks
Nigga gives disclaimers tho
The US Navy was doing research on this type of vessel back in the 50's, it was known as an SSP. They also considered it for use as an Aircraft Carrier.
Thank you, for the explanation of the forward canards now I understand there purpose,. I have just recently completed a four month voyage onboard the USNS Able, this video has been insightful.
My 1-time experience on a swath: like gliding on waves, near zero pitching. But sea conditions were favourable: not a storm, and not 10 metre waves. If speed is like a cat or tri, a swath could enable storm avoidance during journeys. I see many potential advantages to a swath for say a 74ft yacht.
Can an engineer be pedagogic and funny at the same time? Yes. This channel is the proof.
You neglected to credit the designer of the SWATH concept, Frederick G. Creed.
I have to imagine that these ships aren't necessarily limited on weight - the submerged hulls could be made any size - but are very sensitive to weight changes, as there is very little change in displacement for a large change in draft. To keep it at the right height, I'd imagine ballast water must be used. Not a huge problem, but adds some more complexity to design and operation. The biggest drawback from what I can see is, along with cost, a deep draft of the vessel.
Unless you oversize the floats and use the water tanks to submerge them. Of course, ballast tanks can then also be used to trim the ship out both left-right and back-forward. A fun idea I had though not sure about the benefits is a SWATH container ship that uses ballast tanks to keep its waterline during loading and unloading.
We used fuel as service life on T-AGOS ships, at least that was the design intention, how MSC operated them in service I cannot say. Minimum wet deck height is the real concern to avoid slamming.
can't stress that weight sensitivity enough, you also need to make damn sure your ballast system works flawlessly, even at excessive pitch and roll angles. ref, Ocean Ranger.
the ballast control room was in a vulnerable position and a portal wasn't as good as it could have been. to compound things, once the ballast control was sorted out, the tilt caused by the shorted controls had tilted the platform in a way that moved the water in the tanks away from the pipes that pull the water out of the tanks. so the tanks could be filled but not drained. That in combination with other issues with escape systems in 1982 caused a significant loss of life. Just be damn sure ye know the systems will work.
As a yacht, the swath seams to be the ideal hull configuration. Offering an excellent deck volume and the very best in sea keeping stability.
A long range vessel would likely forgo high powered engines in favor of fuel efficiency, mitigating the engine room requirements on deck space.
A diesel electric drive is likewise advantageous considering all the hotel systems that need electrical power.
The application has been used on a yacht
Don't forget about the structural weight fraction differential between SWATHs and monohulls and the added structural complexity that comes with the complex structural load paths. There is always a tradeoff between ease of production and weight, which is complicated on a SWATH. Also, you didn't mention the resistance and powering differences for achieving the same payload. If the design is done properly, like the Navy did for the T-AGOS ships, the hump in the speed power curve will be designed to be at the endurance speed to maximize range due to diverging wave cancellation. But the increased frictional resistance of a SWATH is a primary price you pay for the small waterplane as is slam pressure loads. As noted, the arrangements are also a challenge, so most SWATHs I have seen are electric drive. This can be a challenge as well, but more recent advancements with A/C motors can reduce the space and weight necessary for the electrical equipment, like giant thyristors and power conditioners. Use of complicated Z-drives with 90 degree shafting never made the cut in our designs. Thanks for the post.
Why not make the submarine hulls bigger/longer to increase weight capacity?
I've worked on that TAGOS swath. It was awesome.
Nice - I didn't know you were leading up to this - hence my comments on another thread.
Now all I've got to do is shrink that to a 5m by 2m SWATH dingy and use water ballast to overcome variable load… :) Oh, and a joystick to control minimal active fins at the 4 corners. I suspect that a rectangular rather than a circular cross section will be better at water flow around the hulls
Now that's really interesting! Who knew?
Why would some idiot give it a thumbs down? It is designed for specific water functionality uses. So if it doesn't address one's needs but the type that will. Duh....
Sadly my dream SWATH vessel was sold before i could nab it up with my theoretical lottery win. Rip Rogue. She's a perfect SHTF boat for the more advanced prepper
I'M ON A BOAT!!!!
Or am I?
LoL The green customs ship in the comparison video is from my Hometown.
Didn´t think it would ever get famous.
Really like the videos, keep em coming. I have been tinkering with different boat designs for a solar powered cruiser,
and I was big on swath for a while, but I think a better idea might be having a suspension on a cat to achieve good sea keeping without the higher drag of the bigger hulls. And while I'm posting, let me ask you a not-really-related question,
of how much additional drag is created if you have two pontoons inline that are shorter vs one longer pontoon?
One could 'fold up' the pontoons in shallow water, if you can interlace them as offset pontoons, they can be very deep or wide or very shallow.
Anywhere between 25-45% more resistance to have two pontoons inline. That is a guess from some similar work I did in the past. That second bow adds a lot to the resistance. I did some similar research about 9 years ago looking at running boats all in a line so one could "draft" off the other in front. Unfortunately, we found that any effective drafting required you to be so close that it should just be one hull.
I'd be interested in any research papers available. Let me ask this question a different way, let's say I have two catamaran hulls, would it be any less resistance to put them inline vs in parallel? I can't understand how it could be more resistance, same two hulls.
You forgot another downside of a SWATH is that it cannot traverse in shallow seabed.
Could you do a video comparing SWATH and SWASH platforms?
SWASH. I'm not sure I've encountered that acronym. Small Waterplane Area Submerged Hull?
Small Waterplane Area Single Hull, I've also seen it referred to as a Mono-SWATH. Examples include the Abeking and Rasmussen built inshore tender, and the Windersver series from Fjellstrand.
@@cyberfemme319 That does look interesting. I'll add it to the list of videos to make.
Could you make a video about the suspension boats from Servo Yachts?
please make a video of the new seakeeper® system
Just found your channel so please forgive the late question... can this concept be used with sails? Subbed.. :-)
Somewhat, but not recommended. The problem with sails is they generate a heeling moment. All that wind is great for pushing the boat, but the hull also needs to react to the heel moment and stop you from capsizing. That reaction comes from the hull shape. And SWATHs are intentionally designed to NOT react as they heel. So to have anything effective, you would need a HUGE SWATH with small sails. The sails would not move the ship very fast.
@@DatawaveMarineSolutions this is a fantastic video! Do you know if SWATHs have used lifting bodies in the submerged hull tubes? It would also seem like high volume bubbling (like cavitation) would be helpful. Thoughts?
Thanks, Great work, you remind me of William Christopher / Father John Mulcahy !
Great video!
Really interesting. How does the power required to drive them compare to a monohull or catamaran with similar carrying capacity?
SWATH always has bigger wetted area of the hull for same displacement, which means more resistance. And SWATH usually needs more displacement to have the same cargo carrying capacity because of its complicated hull construction. In theory sometimes you could minimize wave resistance by using SWATH, but in reality you always need more power on a SWATH vessel for the same speed and deadweight.
Thanks, that makes sense.
@@bozidarsaric3348 thank you
Thanks Nick, I am very much delighted to watch videos on your channel. Can both the engine and fuel tanks be located in underwater hull(in a swash model)? please guide me
Sure. No rule against that. The only catch is practical considerations for the engine. An engine needs empty space around it to for crew to maintain the engine. Most engine installation drawings even specify the extra overhead space required if you were to remove a piston. That extra space becomes problematic if you have a very narrow hull.
@@DatawaveMarineSolutions You are so kind Nick, another question which is very disturbing for me is, if I am planning to build a 13m submerged hull with 1.5m diameter, what is it ok to use 6mm steel? What should be framing type? If I use scantlings, what should be specs?
@@muzammalnazir0134 Sorry, any specific details like that require an engineering analysis.
I was just thinking do you travel further having to ride up and down the waves, along with across them?
I've seen these on the hard, and now I finally know what they are. Thanks :-) I imagine these require the chief to be on the ball with the ballast system... Couldn't sufficient carrying capacity be achieved by using large enough ballast tanks? Of course this would incur a performance / cost penalty, but these will never be your passenger mile per liter fuel winners anyway...
Yes indeed. You got it in one. One of the hardest things for operating a SWATH is weight discipline. Most chief's want to have plenty of spares onboard, which is generally a good idea. Example: I once saw a vessel that had 4 spare pumps, totaling about 1 long ton. That's fine on a monohull. But with a SWATH, the weight of all those spares take away from your mission weight.
Our Purchase Orders to vendors indicated a $ x.xx per pound penalty for every extra pound on the equipment delivered, above its previously quoted weight !!
Very interesting & informative. I wonder if the vertical planes (?) connecting the upper deck of the vessel to the submerged flotation amas could be minimized to where they have just the minimum amount of wetted area. Essentially supporting the upper deck at only its corners, leaving the deck to appear floating in air? Side wave action effect would be further minimized. Hope I'm making myself reasonably clear. Thanks from a land architect!
Many SWATHS have tried that approach and go down to just four struts supporting the cross deck. Unfortunately, other practical concerns take over the design. Normally, the struts still need to be large enough for a single person to go down them. That is necessary for maintenance of machinery in the hulls and responding to any emergencies like fire or flooding in the hull.
But you also have the problem of vessel weight control. Vessels change weight all the time. Everything from people stepping on, to offloading hundreds of tons of cargo. The ship balances out that weight change by changing its draft and displacement. This is actually a parameter we calculate: TPM: Tonnes per meter immersion (the acronym changes depending on your units.) On a normal ship, you may have a TPM of 800 - 5000 tonnes / meter. But in a SWATH with super small struts, that number gets very low. Maybe 50 - 100 tonnes / meter. At some point, we acknowledge that ship still has to carry cargo without sinking straight to the bottom. Then those cargo weights and mission parameters drive the SWATH strut design.
Wondering about a sailing version...
Not having to slam into each wave and expend energy to overcome the wave energy, wouldn't the SWATH also be more efficient?
Does a SWATH hull escape the limitations of a displacement hull and behave more like a submarine hull combined with axe bow? Does it need less power to be driven relative to displacement?
How are 24m leisure boat length regulations applied to SWATH vessels?
I wonder if anybody's ever explored the idea of a swath Hull aircraft carrier?
I think the US Navy did. The main limitation is probably that carriers want to be long not wide (the jets need enough distance for takeoff and landing) and there is a need for lots of internal space below the top deck (for the hangar), neither of which exactly fit the standard SWATH concept. A SWATH carrier would be rather long and skinny for a catamaran and would have a deep, boxy cross-deck to contain that hangar, presumably putting the flight deck a very long way above the water.
Yeah, as with catamarans, this doesn't seem like a great match.
Even if you put the runway along the diagonal, you want the runway to be as long as possible, and that means you want a rectangular ship over a square one;
The closer to a square the ship is, the less efficiently it'd function as an aircraft carrier...
If anything would make a good argument for an unconventional cruise ship design, surely a SWATH hull would be it.
The cruise ship is all about those passenger amenities.
And nothing beats a SWATH for that basic comfort factor...
Wow! I didn't know about that. Thank you!
Why aren't there any SWATH boats with hydraulic struts to compensate for motion? It could probably solve the large problem of seasickness.
There are such boats. It is called a nauti-craft. They have some great videos on TH-cam. The reason we don't use that for larger ships:. The hydraulics would be huge and require lots of power. For bigger ships, there are more efficient methods to reduce or eliminate seasickness.
Did I miss the part which said that these hulls, like cats, have two stable states?
Hi Nick, New to your channel and I love boats! Nick can you talk about the comparison of fiberglass and aluminum hulls? Thanks
I'm working on a video right now that touches on the subject.
Would you like to comment on structures for seasteading?
www.reddit.com/r/seasteading/
www.seasteadtalk.org
About the concept of seasteading:
en.wikipedia.org/wiki/Seasteading
www.seasteading.org
Great video. How does the draft on a SWATH compare to a catamaran and monohull?
Draft on SWATH vessels always has to be much larger for the same displacement, for SWAHT-s to be effective and sail smoothly :D
So for a sailing vessel in the 40 - 50 foot range, the draft on a monohull is generally 5 - 7 feet, and on a catamaran about 3 - 4 feet. I've never seen a SWATH sailing vessel in that size range so I'm assuming the draft requirement is too deep to be reasonable? Or is it just not worthwhile building a small sailboat SWATH because of other reasons (drag, amas too close to the surface, heel, etc)?
@ kobin. A SWATH is not suited for a sailing boat. On such a boat you have very variable loads on the hulls coming of the sails, besides the sea. In few words, the resulting center of power from the engine (sails and masts) is several meters above the deck, and worst not aligned with the hull(s). A mono reaches a new equilibrium heeling, a multi immersing the ama thus creating an opposite force up (I wildly simplify).
And a SWATH how will it do? no possible safe heeling, no variable immersed volume of the ama as the volumes are underwater and fixed...To solve that, you enter in very complex systems; foils, ballasts, active systems , hydraulics, sensors, computers and so on. Gosh....
A well designed cruising trimaran is far simpler and is very effective for getting sweet sea motions..
Wouldn't they also be pretty fast due to the 'submarine hulls' being a very non-resistant shape in water?
_"They come with a cost?"_
If *SEASICKNESS* becomes a thing of the past, I will GLADLY PAY IT...👌
I wonder the performance of a swath with a sea keeper in it would be
SWATH boats make good pilot ferry vessels as can be seen in that video.
what about swaths for container shipping?
Awesome!❤❤❤
Would SWATHs be recommended for small, diesel-electric, pleasure craft/yachts (40 to 80 ft) or superyachts? If so, what sort of reasonable payloads and missions can we expect from them?
Yes, SWATHs can be ideal for yachts, depending on your budget. The motion control systems will drive the price higher than a conventional yacht without motion control. But you pay for comfort. That is the whole point of a SWATH ship.
As to capacity, it depends on the ship size and desired speed. The good news, on the scale of ship weights, a few people weigh next to nothing.
Reasonable missions? Normal coastal cruising, offshore cruising. Even relaxed cruising in slightly bad weather (mild thunderstorm). I would not take a SWATH yacht to high latitudes or polar regions. But almost everything else is reasonable.
@@DatawaveMarineSolutions Why would you not take a swatch to polar regions? Because of the extended motion control fins? What about retractable fins? I realize that stability would be compromised, but would a swath without the motion control fins still be superior to a monohaul of the same lenght?
@@mojojojo_BB I imagine it would have something to do with the reliability of the control systems in the cold rather than just knocking into a bit of ice. But let's see.
@@mojojojo_BB Nothing to do with the control fins. It has to do with survivability and responses in extreme waves. Higher latitudes and polar regions have worse weather. Larger waves. You need more reserve buoyancy to survive that type of weather, something that we normally design a SWATH to minimize.
Now there are exceptions to this idea. The US Navy created the T-AGOS vessels, which were SWATHS designed for heavy weather.
But a Navy vessel has far different standards than a yacht, including crew comfort.
en.wikipedia.org/wiki/USNS_Victorious_(T-AGOS-19)
Datawave Marine Solutions You mean if the ship encounters waves that exceeds its sea state rating, a monohull has a greater probability of surviving it than a swath.
Are the fins actively controlling pitch and yaw? Are they critical to balance the ship in SWATH mode? Do the underwater hulls feature ballast tanks?
The fins don't control yaw. I think you may have meant pitch and roll. It depends on the SWATH. Most will go for active control of pitch and roll. Some use passive control, with static fins that don't move. I would always recommend active control. And the underwater hulls definitely include ballast tanks. They need the ballast tanks to counteract changes in loading and still maintain close to the same draft.
Thank you. Yes I did mean pitch and roll. Is it correct that ballast tanks are used for pitch and roll trim and the fins are for active control of these parameters?
@@JDI4DAVID yes. The tanks are normally used to trim and level the vessel at the start of a voyage, depending on the Master's preference, and the fins mantain active control against waves.
@@DatawaveMarineSolutions Thank you so much for explaining this. I guess the passive or active fins are essential for pitch and roll stability. Can the hulls' ballast tanks can be flooded and the ship operate as a catamaran if they fail?
@@JDI4DAVID Most SWATHS can operate as a catamaran with the ballast tanks pumped out and the ship light loaded. As to fail safe design of the ballast tanks, that is a little risky to make a general comment on. It depends on the individual system. But in general, we can create systems that are fail safe, if needed.
Has a SWATH ever turned turtle? (turned over.) If the buoyancy in one hull fails, what happens?
I would guess that's highly variable.
For one thing the hulls are very much built like submarines. It seems unlikely you'd get an immediate total loss of buoyancy.
The rest would depend on whether any of the upper structure of the ship floats, and to what extent, and then what the buoyancy of the other hull is.
If one hull sinks, then it depends on the superstructure as to what happens next...
I rather doubt you could get one to capsize completely, given it's nature.
It'd just sink outright before it would be able to flip over completely...
They are very stable designs in both intact and damaged stability. Due to the very large beam, you have a high transverse metacenter. In a damaged case, not only do you have the subdivision bulkhead spacing limiting the extent of damage cases to pass (which you also have on monohulls, et al) but if the WL were to be high enough to wet the haunches, you start to pick up a massive restoring moment. So the wet deck is as low as you can practically go and weight is the big design concern, to keep from slamming and damaging structure, but damaged stability survival and the height of the transverse center of gravity is never an issue. LGC is more the issue.
can a 50,000 ton aircraft carrier be based on a tumble home hull design??? please advise!!!
Short answer: theoretically yes. Slightly longer version, an aircraft carrier would require extensive calculations for stability that go far beyond the selection of the hull shape. At least on USA aircraft carriers, I believe they heavily armor the flight deck, which adds a LOT of weight up high. That creates a major challenge for stability in general. So aircraft carriers may need to design in reverse. Instead of creating the hull shape first, you start with calculating the stability requirements. Then create a hull shape that can meet those requirements.
@@DatawaveMarineSolutions as I understand in case of an aircraft carrier the beam (ranging from ¾ of the front bow section through midship & all the way to the rear stern section) of a tumble home hull design has to be significantly more (65% - 70%) than usual in order to offset the weight topside & in turn that would mean an increase in length & draft of the aircraft carrier as well!!! and ofcourse overall height!!!
I just want a Catamaran that has propulsion or I can use the sails and travel for free. But I want a computer system to deploy the sails as needed to the set course.
is this a good hull for an aircraft carrier?
What about a quadmaran is there such a thing so you have a small gap between the two smaller centre hulls.
Quadmarans were tried. I was involves in several different research projects that tried variations on this idea. So far, none of them work out. The fourth bow generates too much additional resistance to be worth it. If you see any examples of quadmarans in action, generally, they were not built for reasons of reducing resistance.
Yes, I saw a US Coast Guard vessel like that on youtube.
So..is a sailing swath feasible?
Many people asked me about this one. I'm not sure how well the SWATH design would work for sail configuration. I agree that the SWATH would allow smooth rides. But the problem comes with balancing the sail. That sail produces a heeling moment, and to counter that moment, we need to submerge more of the hull. As the ship heels, one side submerges, increasing the buoyancy on that side. That extra buoyancy produces a righting moment and balances the sail's heeling moment.
Problem is that SWATH are designed with small struts at the waterline to specifically minimize that increase in buoyancy. I'm not saying it would be impossible. But it would be an interesting challenge to balance the seakeeping capabilities with the buoyancy that you need for a sail.
@@DatawaveMarineSolutions could this be countered by making it wider, thus increasing the leverage of the force, also passive fins perhaps? This concept has beenbouncing around in my head, but i'm no engineer...
Thanks !
How does a SWATH compare with a x-bow?
It's a tradeoff of weight capacity vs comfort. An X-bow is still a traditional monohull. As a monohull, it can carry a large amount of weight. But the X-bow will handle steep waves better. A conventional bow shape has a tendency to bounce over a wave crest. The X-bow does better at following the wave up and down, without bouncing.
Compare that to a SWATH. A SWATH has very little weight capacity. It starts with one weight when first built, and it needs to maintain a similar weight throughout its life. So SWATH's are very bad as a cargo ship. But they do offer comfort. In a SWATH, you don't bounce over the waves. You don't even follow the wave surface up and down. The wave just passes by under the SWATH, with very little disturbance to the ship. (Within limits. For a large enough wave, even a SWATH encounters problems.)
@@DatawaveMarineSolutions Thanks for this answer. Can you make a detail video on this please. Including other bow types which increase comfort.
I would think that a Diesel/electric hybrid would be the best power configuration. This along with computerized controls would make it even more stable. That leaves the question of whether the hull configuration is more efficient to operate over the life of the boat?
Yes, electric drive was always the answer, and that is synergistic with missions requiring large electrical deck and mission loads (which are not used then the motors are using a lot of power). Although I did tour the MBRI SWATH back in the late 1990's and as I recall it had small tandem diesel engines in each lower hull (I dont recall how the reduction gear was arranged, but this was more of a boat than a ship). That was the only SWATH I have seen with that sort of machinery arrangement, and it was not that great a design, as bolsters were being added to it at the time!
@@Fgway Most electric drives are liquid cooled. Shouldn’t be a problem for a ship. You just need a heat exchanger.
I attained enlightenment based on the first twenty-three seconds of this. Good-bye.
Why not use SWATHs for pleasure craft (ocean-crossing privately-owned yachts)? These part-timers would like a smooth ride & their cargo carriage is pretty fixed. Almost all of these private yachts (even the 60 footers) also have stabilizer systems, so the extra cost of the SWATH's motion control system... may not be that much extra...
I have seen some interest for building a SWATH yacht. And yes, it could be very useful for a larger yacht. I think part of the challenge is that SWATHs require a little more engineering than your average yacht. That creates a higher startup investment for a production boat builder.
I worked for MSC for years. Ive been on one of those T-AGOS ships in Sasebo Japan to trade food and supplies. I have some friends who worked on them. And all of their opinions are the same. It fucking sucks being on those ships. Loud loud loud. Waves slamming and slapping the hull makes life miserable. Yeah they're fast and cut the waves pretty good but even on fairly calm days the waves slap the vertical hull loudly. Cool looking though.
I love it! SWATH = offshore oil rig w/ diesel electric propulsion 😁now I just need to win a (poor man tax) lottery 🙄
Sadly we can't gomthere
👌
We need swath aircraft carriers
Same purpose of the inverted bow, more smooth rides by reducing pitching but not rolling! -the pattern Norwegian Ulstein X-BOW😊 th-cam.com/video/MZ934OKFnHY/w-d-xo.html
electric motors would fit in the submarine downriggers it would be ignorant to put a diesel power plant on these
SWATH FOR PRIVATE LUXURY
Its an over glorified Pontoon boat hahaha the legs are just shock absorbers using the water
🌟🌟👍👍👌👉✌👈👏👏👏
Naval architects????? Absolutely and unequivocally WRONG! The SWATH design was invented by Frederick G. Creed in 1938 and patented in 1946. He died before the first vessel was launched in 1968. When he drafted the first concept drawing, he was laughed off as a lunatic - only to be heralded as a hero when someone finally proved his design works.
👬👈✊✊✊💪💪💪