Excellent content. Spent years at sea in the Navy, and a lot of the principles are readily observeable, but its great to now have more answers to why. I had never considered the fundamental differenced in the physics of planing vs non planing hulls.
Great video on planning hulls. If you have not already done a video on semi-displacement hulls please add that to your list. I operated an 82' USCG Patrol Boat that was fast for it's size in heavy seas. A very stable boat, but rocked side to side even in clam seas. I use to have fun surfing her on the swells in a following sea. In a 6' swell you could find the sweet spot and ride the swell. She even broached on a 40" wave but recovered. I was standing on the bridge's bulkhead "waiting" for her to come back. And it did, just in time for the next wave. Fun times.
Outlaw Eagle has an interesting solution to the problems and weight distribution conundrums and risky situations caused by waves and rough waters on high speed planing hulls designed for white water river jet boat racing. They have attached small canard wings near the prow. Each wing is about a meter long and 250 mm wide. They use the speed through air to make lift and let ther front of the boat glide over waves and avoid porpoising and augering in or slamming into most of the roiling water they race through
great video! thanks for pointing me here. I was curious, what disadvantage does the axe bow have on large ships? I'm thinking about damens 105m SeaXplorer concept yacht with an axe bow. Is that just a terrible design to have an axe bow on such a large yacht? thank you!
these videos are awesome! thanks for your time, could you do a video or quick breakdown of monohull center consoles vs catamaran center consoles? Cats seem to be the big thing now even tho they have been around for a while, have they perfected the design or is it just marketing hype? what are the pros and cons of Cats in a center console silhouette is it wide enough for the benfits of a true Cat to show?
@@DatawaveMarineSolutions Please do! I'm trying to learn more about hydrofoiling because it seems they would be the most energy efficient way to go fast. They simply don't waste energy on making any sort of wave. Power required seems to scale linearly with speed. What more could you ask for? I'd be very curious why there aren't more of them e.g. a motor powered cruising yacht. Seems like it would make it possible to use solar power to travel relatively fast.
Yes and no. Hydrofoils and planing boats both use dynamic lift. Meaning when the boat stops moving, it sinks back into the water. Same way that planes need speed for their wings to generate lift. But you hit on a good point. A hydrofoil is generally much more efficient at generating lift than a planing hull. So we can get more lift, allowing hydrofoils to still work on larger ships. That being said, I tend to think of them as two different categories. Because the physics and design challenges are very different for the two.
First, thank you for your channel and the way you explain. I don't understand: the maximum planing hull size is 20-24m, but the wally 118 (36m) is a planning hull. Do you mean that past 24 meters , the amount of energy required to put the hull at speed will cost too much for most of the shipowners?
Good question. I don't mean that the 20-24 m size is a hard limit. There are no physics that suddenly turn off planing forces above 24 m. That's just the general limit that I picked based on most of the planing hulls I have worked with. You can absolutely go larger. But as you go larger, the margin to support the boat weight in planing becomes narrower. Shipbuilders need to really minimize the vessel weight. And the designers need to perform detailed analysis to get maximum planing force from the hull. Mostly, I just want people to avoid the fallacy of thinking they can scale up without limit. I saw boat builders that took a hull shape designed for a 9 m hull and scale that shape up to 24 m. They were surprised to find out planing hulls don't work that way. So just avoid that mistake.
Yes, planing hulls are different from hydrofoils. Hydrofoils use miniature wings under the hull to lift the boat completely out of the water. In a planing hull, the boat still has a small section in the water. But to make matter confusing, the hull of hydrofoil ships is often a planing hull. This helps the hydrofoil vessel get moving fast enough for the hydrofoils to take over. Just like an airplane needs to reach a minimum speed before it can takeoff from the runway, hydrofoils also need to reach a minimum speed before the hull can clear the water.
These two articles were my main sources for a 5 minute introduction to the Ghost. www.militaryfactory.com/ships/detail.asp?ship_id=Juliet-Marine-Ghost-Stealth-Boat www.businessinsider.com/juliet-marine-systems-ghost-boat-2016-11 That vessel has a LOT of unique physics combined. But from what I read, I would not call it a planing hull. It's closer to a SWATH. I have a video to explain the SWATH idea. th-cam.com/video/jJAHyDl6KS8/w-d-xo.html Those individual hulls may generate some lift at higher speeds, but I don't think that is the main intended effect. The supercavitating drive is a little misnamed. It's actually a combination of two ideas: air lubricated hull and supercavitating propeller. The idea of an air lubricated hull is to inject large amounts of pressurized air along a hull. Then the hull avoids direct contact with the water and this lowers the skin friction on the hull, usually around 4-6%. Normally, we get the pressurized air from an air compressor. But in this case, they seem to use a supercavitating propeller. In most propellers, we try to avoid cavitation. (See this video for a quick explanation of cavitation: th-cam.com/video/MyZzhwYMytc/w-d-xo.html) But at high enough speeds, you can't avoid it. So we design a supercavitating propeller that intentionally takes advantage of that. But you get a large stream of bubbles coming from the propeller. On the Ghost, they had the idea to mount the propeller at the front and use that stream of bubble for lubricating the hull. Interesting idea, not sure how well it works. Those cavitation bubbles normally don't last long. They typically collapse under the water pressure. For long term care of ships, we like to avoid putting any hull structure in the path of those collapsing bubbles. But you never know, maybe Juliet Marine found a new trick.
I will ask you your opinion, if possible please. Much sailing cruising boats or day sailors are below 25 foot of length, they run most of the time well below displacement speed, are expensive for the sails new technology, ballast, winches, etc. and generally have an auxiliary engine to avoid a lee shore, or to maneuver, or going upwind. And most of planing hulls in the same size are a deep V bottom with huge outboards or sterndrives, very wide and heavy. My question is if there is not an unexplored niche for flat bottom recreational planing hulls intended to run in the low tens knots. They will need a very small engine, will be quite economic to run and safe, and can be built in a budget and low time. Because for cruising or camper cruising a boat of this kind makes more sense than a trailler sailor, except if people likes sails for sport. And almost all commercial recreational planing boats in this size can't run below the low twenties. A small planing hull with a flat bottom can cruise for several hundreds of miles, will need less water and food for the crew and at low speed more forgiving but at a pace double of the sailboat or more. Thanks and sorry if is a very silly question.
Not a silly question. There may be a niche opportunity there. To oversimplify the problem, your planing speed is roughly tied to ship length. To get a ship up on plane at lower speeds, we need a very short planing surface. (There are ways around this problem, but we'll keep it simple for now.) To start planing at 10 knots, you are looking at a ship length around 9 ft. Still achievable though. This would probably be a stripped down, basic boat. Mostly intended for pure transportation. A 1 or 2 seat capacity with a motor, fuel, and not much more. Imagine the motorcycle equivalent of the boat world.
Nicholas i always have so many hypothetical questions but ill keep it quick, could you tell me what the price ranges of hiring an Architect are and what are some things to consider when choosing an Architect?
The price ranges vary, depending on the country and region. But in general, naval architect prices vary from $100/hr to $200/hr (USD), based on the experience of the naval architect. But the billing rate is only the starting point. The total price depends a lot on the project and what work they need to perform. As a general guide, most projects cost at least $2000 or more. (This is all for the commercial side, where every ship gets customized.) For how to hire one, I actually did a whole video series on how to hire a naval architect: th-cam.com/play/PLhupav37c1P8ThgTixOc6cj5mFDr8gw-3.html Best advice I can give: The more clearly you explain your project with the consultants, the better price you can get. Allow 2-3 weeks for the consultant to prepare a quote for you. This gives them time to discuss the project, ask questions back and forth, and then prepare a really well detailed quote.
My little boat i need a couple hundred pounds of ballast in the front for it to get on plain and ride well im too fat for it sitting in the back where you steer
So planing catamarans that use the air pressure between the hulls to reduce slamming are much more sea-kindly. And the two narrow hulls reduce resistance at low speeds. What's your verdict?
I agree with the initial idea. But unfortunately, the scale of the different effects makes this unlikely. The two narrow hulls would reduce resistance at low speeds, true. But it also reduces their effectiveness at planing speeds. Imagine you have a monohull planing hull and cut it in half. Turn the two halves into a catamaran. Problem is, you don't get the same effective planing force on those two halves. Planing works because we force the water to turn downwards to avoid the hull. But in this half monohull, the water finds it much easier to just go to the inside of the planing hull. With a catamaran, your hull design could easily become dominated by the planing requirements. The pressure between the hulls is a good idea for reducing slamming. But the magnitude of the air pressure normally doesn't make any difference. The air can easily escape the big cavity between the hulls without increasing in pressure. So it doesn't really affect the slamming operation. I have seen some concepts that change the hull design and try to trap the air before it can escape. That has some effect. But when we trap the air, we compress it. That compression is how we damp out the slamming. Now things get really interesting. Air heats up when you compress it. And since water is 1000 times more dense than air, we need to compress A LOT. Assuming we compress the air to only half of water density, that would increase your normal air temperature up to around 240 deg C (assuming we start at 20 deg C). Twice the boiling temperature of water. So now we need to worry about heat burning the hull, and generating steam in the water. What can I say, the physics makes things complicated quickly.
My experience is different, take for instance the deep vee hull, in that situation the vector of the planing force is directed outward rather than downward reducing slamming. In the case of cats I have driven, the reduction of planing surface has no effect on it ability to plane, at least in the age of 650 HP outboard motors and the reduction of slamming because of air pressure under the center of the hull is quite noticeable and results in a forward "sneezing" of spray from between the hulls. In other words, you can feel it happen. Personally, I could give a rip about large steel ships as I will never own one, how ever in my shopping for a offshore fishing boat, I have yet to see a monohull that can compare to a cat.
Interesting! I admit that sometimes the theory doesn't predict things accurately. Those are the really fun points. I'm a little surprised about the "sneezing" spray from the forward hulls. I would expect it to spray aft, out the transom. Do you see spray on the aft end too? I wonder if the damping experience has anything to do with the shape of your cross deck. Is it just a flat cross on the catamarans you drove?
Basically the bottom of the deck between the hulls is high in the bow and just above the resting waterline aft. The outboards are mounted on the center-line of the hulls and the weight seems to be quite aft. The result is as the bow is forced up by a wave, the stern stays planted and when the bow comes down, air is forced out forward resulting in the sneezing I described. Worldcat, the boat I have decided on explains the idea on their web site. worldcat.com/ and here is a You Tube video of one in a seaway. th-cam.com/video/VtBiHnP6oSI/w-d-xo.html
Ah. You found an exception to the general rules that I said in the video. Flying boats still work as planing hulls because of several reasons. 1. As an airplane, they generally employ lighter materials than boats. The cube-square law still applies. But the airplane operates on an entirely different scale than your conventional boat. 2. Many of these planes actually use stepped hulls to achieve stable planing. It has the effect of acting like one planing hull behind another. This isn't really for planing force, but more to ensure pitch stability as you reduce to just the tip of the transom in the water. 3. The airplane wings help during planing. They take part of the weight during takeoff and landing. So the planing hull doesn't need to do all the work. Fun fact: Some of the original experimental work on high speed planing hulls was conducted specifically for flying boats.
Okay, that makes sense. Thanks. I believe you did mention that experimental work on flying boats during the video, which is what made me think of these giant flying boats.
Hi Nick I saw this odd looking twin mast sailing catamaran called "mastfoils", I couldn't find any videos explaining pros and cons about it, can you enlighten me and any other interested subscribers please? thanks!
Do you mean this: www.chriswhitedesigns.com/mastfoil-discussion ? The Chris White website offers their explanation on the advantages of a Mastfoil. But to provide some background on it, all sails are lifting foils. They work on the same principles as airplane wings, only we turn them sideways to push the boat forward instead of carry an airplane up. Problem is that soft fabrics do not make the best shapes for lifting foils. Instead, several designers tried to actually create a rigid lifting foil in place of a sail. That is the basic idea behind the Mastfoil. That rigid wing replaces the mainsail. I would need to research it more to give justice to the pros and cons. But here are some simple observations: Pros: - Rigid foil lasts longer than sails - Rigid foils perform better than sails. So you can fit more power into the same area Cons: - We always worry how to "turn off" the sail. A rigid foil can't be furled. The Mastfoil design by Chris White gets around this problem by giving the foil an option to freely rotate and always feather into the wind. - Rotating mast sections mean that you can only put stays at the top and bottom of the mast. Everything else is unstayed. This requires stronger, heavier, masts to avoid buckling.
Thank you very much. You do raise a question or two. Since we don't get to see the bottom of aircraft carriers other then the flat bottom model types sold in kits, and you can't be sure of the exact shape is represented in the kit. Now the secret is that the aircraft carriers are suppose to only goes about 35 knots but in actuality if it needs to be displaced in a hurry they can go over 85+ knots with everyone hunkered down below. My first question is under your numbers can they go 35 knots? And the second are you aware of the UFO type technology that will enable it to go the above mention unbelievable speed the sailors have been subject to. Lots of love
It's possible. They absolutely can go 35 knots. But not using planing technology. That ship will never use planing technology. Just too heavy. The aircraft carrier is exploiting a wonderful trick of displacement hulls. To oversimplify: the longer the hull, the easier it is go faster. Normally don't see large hulls moving fast because most commercial ships are designed for efficiency. But the aircraft carrier needs speed, and has the power to match it. At over 1000 ft long, they are only at a Froude number of 0.31 when doing 35 knots. That is fairly easy for any hull to do. At 85 knots, they are near a Froude number of 0.77: fast, but still within the realm of displacement hulls. You don't see solid planing until you are near a Froude number of 1.0. So yes, 85 knots is potentially possible if they have enough power. What could stop them from running 85 knots? - Power. Even nuclear reactors have their limits - Propellers. They may not be able to push that much power through the propellers - Slamming. Any waves will have a HUGE impact on the bow at those speeds. You might dent or break hull plating. - Hull bending. If a wave tries to pitch the carrier up at those speeds, nothing good will happen. Yes, it's possible. No UFO technology needed. Just lots of power, and a VERY calm day to avoid any waves.
At that point, your main limit isn't power. It's the structure. If you tried to push the carrier at 85+ knots, the entire ship will vibrate violently. And when we include waves, the story changes completely. A typical seastate on a nice day would be seastate 4, with a significant wave height around 1.88 m (6.2 ft). (Significant wave height is one of the measurements we use to define a seastate. It has a mathematical definition. But practically, it is the height you would guess when making a visual estimate.) But at 85+ knots, every wave would be like a bullet slamming through a brick wall. We don't build ships to withstand life as a bullet. And the story gets worse if we talk storm conditions. Now imagine significant wave heights of 5-8 m (16-28 ft). Now the ship is pitching and bending flexing in the waves. I can't say with certainty what the carriers can handle. I would need to know the details of their structure for any reliable estimate. And I doubt the Navy will give away those crucial details. But to take an educated guess: I wouldn't push anymore than 40-45 knots in good weather. In rough weather, that speed would be down to 10-20 knots. Anyone have experience working the carriers? Want to chime in with a sea yarn?
Of course that makes sense about the force of water at these speeds would be earth shattering and would create waves of gigantic proportions. I have come to understand that there is some other technology in the making. Just like UFO craft that make 90 degree turn on a dime at speeds double the jet following it. Couldn't this type of tech. be a factor? I realize that your concern is mater of state as earth as developed in the last century and understand but we need to move on to the next level. Lots of love Sorry just wanted to push the envelop in the thinking of peoples mind to a new upcoming reality.
Hey Nick, I really enjoy your explanations. Could you comment on Beneteau's hull design (th-cam.com/video/v8NmQM_s8_E/w-d-xo.html) and Shannon's hull design (th-cam.com/video/HVPEAU_gK0o/w-d-xo.html)? To me both designs are similar, they just go about getting the air under the stern in different ways. What say you? -johnny
![[LIVE] : ONE ลุมพินี 88 | คู่เอก "ป้อมเพชร vs อัสลามจอน"](http://i.ytimg.com/vi/1ZqTVVbMgbo/mqdefault.jpg)
How have I missed this channel all this time?!?!
Excellent content. Spent years at sea in the Navy, and a lot of the principles are readily observeable, but its great to now have more answers to why.
I had never considered the fundamental differenced in the physics of planing vs non planing hulls.
Great video on planning hulls. If you have not already done a video on semi-displacement hulls please add that to your list. I operated an 82' USCG Patrol Boat that was fast for it's size in heavy seas. A very stable boat, but rocked side to side even in clam seas. I use to have fun surfing her on the swells in a following sea. In a 6' swell you could find the sweet spot and ride the swell. She even broached on a 40" wave but recovered. I was standing on the bridge's bulkhead "waiting" for her to come back. And it did, just in time for the next wave. Fun times.
That's a great topic. It will nicely round out the different hull categories I've already looked at.
I just sank my planing hull due to slamming... never a take thin skinned glass lake boat to the ocean... sigh
Outlaw Eagle has an interesting solution to the problems and weight distribution conundrums and risky situations caused by waves and rough waters on high speed planing hulls designed for white water river jet boat racing. They have attached small canard wings near the prow. Each wing is about a meter long and 250 mm wide. They use the speed through air to make lift and let ther front of the boat glide over waves and avoid porpoising and augering in or slamming into most of the roiling water they race through
great video! thanks for pointing me here. I was curious, what disadvantage does the axe bow have on large ships? I'm thinking about damens 105m SeaXplorer concept yacht with an axe bow. Is that just a terrible design to have an axe bow on such a large yacht? thank you!
Hi Nick, great video, would love to see a video on Rigid Inflatable Boats!
I'll add them to the list.
I would be interested to hear how the hull on a ship like the USS Freedom works if you get a chance to do a video on that hull type.
these videos are awesome! thanks for your time, could you do a video or quick breakdown of monohull center consoles vs catamaran center consoles? Cats seem to be the big thing now even tho they have been around for a while, have they perfected the design or is it just marketing hype? what are the pros and cons of Cats in a center console silhouette is it wide enough for the benfits of a true Cat to show?
Where have you been my whole life
I can agree with the fatigue part. On patrol in a RHIB you can get pounded until you're tenderized like a good steak.
can you make a video explaining planning stability problems ? bow down steering and porpoising?
Excellent idea. I'll add it to the list.
Datawave Marine Solutions yeah thanks a lot. Cheers from Argentina .
ss turbinia planed at 34 knots she also has about 10 screws
Can you cover planing hulls for sailing craft?
That's a good idea. I will add it to the list.
are you going to cover hydrofoils?
Eventually, yes. They are on the list of videos that I want to make. (It's a very long list.)
@@DatawaveMarineSolutions Please do! I'm trying to learn more about hydrofoiling because it seems they would be the most energy efficient way to go fast. They simply don't waste energy on making any sort of wave. Power required seems to scale linearly with speed. What more could you ask for?
I'd be very curious why there aren't more of them e.g. a motor powered cruising yacht.
Seems like it would make it possible to use solar power to travel relatively fast.
@@dejayrezme8617 why? the prop has to stay deep enough in the water even the boat flys above the water..
Are hydrofoil boats in the category of planning ones? There are much bigger hedrofoil boats than 24 m. USS Plainview is 67 m long.
Yes and no. Hydrofoils and planing boats both use dynamic lift. Meaning when the boat stops moving, it sinks back into the water. Same way that planes need speed for their wings to generate lift. But you hit on a good point. A hydrofoil is generally much more efficient at generating lift than a planing hull. So we can get more lift, allowing hydrofoils to still work on larger ships.
That being said, I tend to think of them as two different categories. Because the physics and design challenges are very different for the two.
First, thank you for your channel and the way you explain. I don't understand: the maximum planing hull size is 20-24m, but the wally 118 (36m) is a planning hull. Do you mean that past 24 meters , the amount of energy required to put the hull at speed will cost too much for most of the shipowners?
Good question. I don't mean that the 20-24 m size is a hard limit. There are no physics that suddenly turn off planing forces above 24 m. That's just the general limit that I picked based on most of the planing hulls I have worked with. You can absolutely go larger. But as you go larger, the margin to support the boat weight in planing becomes narrower. Shipbuilders need to really minimize the vessel weight. And the designers need to perform detailed analysis to get maximum planing force from the hull.
Mostly, I just want people to avoid the fallacy of thinking they can scale up without limit. I saw boat builders that took a hull shape designed for a 9 m hull and scale that shape up to 24 m. They were surprised to find out planing hulls don't work that way. So just avoid that mistake.
So are plaining hulls different from hydrofoils? Or is Planing hull the more technically correct term?
Yes, planing hulls are different from hydrofoils. Hydrofoils use miniature wings under the hull to lift the boat completely out of the water. In a planing hull, the boat still has a small section in the water. But to make matter confusing, the hull of hydrofoil ships is often a planing hull. This helps the hydrofoil vessel get moving fast enough for the hydrofoils to take over. Just like an airplane needs to reach a minimum speed before it can takeoff from the runway, hydrofoils also need to reach a minimum speed before the hull can clear the water.
Could you do a video on the X type bows?
That one is coming out next month.
Nicholas Naval Architect Sounds good, spent several months on a mini X-bow type vessel in the north sea. Look forward to the video.
Should have dicussed the maths like you did for hull speed video.
Nick, have you looked at the USN's Ghost? Is it a Cat, planing hull or a combination? How dose the cavitation drive work?
These two articles were my main sources for a 5 minute introduction to the Ghost.
www.militaryfactory.com/ships/detail.asp?ship_id=Juliet-Marine-Ghost-Stealth-Boat
www.businessinsider.com/juliet-marine-systems-ghost-boat-2016-11
That vessel has a LOT of unique physics combined. But from what I read, I would not call it a planing hull. It's closer to a SWATH. I have a video to explain the SWATH idea. th-cam.com/video/jJAHyDl6KS8/w-d-xo.html
Those individual hulls may generate some lift at higher speeds, but I don't think that is the main intended effect.
The supercavitating drive is a little misnamed. It's actually a combination of two ideas: air lubricated hull and supercavitating propeller. The idea of an air lubricated hull is to inject large amounts of pressurized air along a hull. Then the hull avoids direct contact with the water and this lowers the skin friction on the hull, usually around 4-6%. Normally, we get the pressurized air from an air compressor. But in this case, they seem to use a supercavitating propeller.
In most propellers, we try to avoid cavitation. (See this video for a quick explanation of cavitation: th-cam.com/video/MyZzhwYMytc/w-d-xo.html) But at high enough speeds, you can't avoid it. So we design a supercavitating propeller that intentionally takes advantage of that. But you get a large stream of bubbles coming from the propeller. On the Ghost, they had the idea to mount the propeller at the front and use that stream of bubble for lubricating the hull.
Interesting idea, not sure how well it works. Those cavitation bubbles normally don't last long. They typically collapse under the water pressure. For long term care of ships, we like to avoid putting any hull structure in the path of those collapsing bubbles. But you never know, maybe Juliet Marine found a new trick.
I will ask you your opinion, if possible please. Much sailing cruising boats or day sailors are below 25 foot of length, they run most of the time well below displacement speed, are expensive for the sails new technology, ballast, winches, etc. and generally have an auxiliary engine to avoid a lee shore, or to maneuver, or going upwind. And most of planing hulls in the same size are a deep V bottom with huge outboards or sterndrives, very wide and heavy. My question is if there is not an unexplored niche for flat bottom recreational planing hulls intended to run in the low tens knots. They will need a very small engine, will be quite economic to run and safe, and can be built in a budget and low time. Because for cruising or camper cruising a boat of this kind makes more sense than a trailler sailor, except if people likes sails for sport. And almost all commercial recreational planing boats in this size can't run below the low twenties. A small planing hull with a flat bottom can cruise for several hundreds of miles, will need less water and food for the crew and at low speed more forgiving but at a pace double of the sailboat or more. Thanks and sorry if is a very silly question.
Not a silly question. There may be a niche opportunity there. To oversimplify the problem, your planing speed is roughly tied to ship length. To get a ship up on plane at lower speeds, we need a very short planing surface. (There are ways around this problem, but we'll keep it simple for now.) To start planing at 10 knots, you are looking at a ship length around 9 ft. Still achievable though. This would probably be a stripped down, basic boat. Mostly intended for pure transportation. A 1 or 2 seat capacity with a motor, fuel, and not much more. Imagine the motorcycle equivalent of the boat world.
Thank you
heard you say the mass doubles,
were relative irritated,
read weight,
were releaved.
Nicholas i always have so many hypothetical questions but ill keep it quick, could you tell me what the price ranges of hiring an Architect are and what are some things to consider when choosing an Architect?
The price ranges vary, depending on the country and region. But in general, naval architect prices vary from $100/hr to $200/hr (USD), based on the experience of the naval architect. But the billing rate is only the starting point. The total price depends a lot on the project and what work they need to perform. As a general guide, most projects cost at least $2000 or more. (This is all for the commercial side, where every ship gets customized.) For how to hire one, I actually did a whole video series on how to hire a naval architect:
th-cam.com/play/PLhupav37c1P8ThgTixOc6cj5mFDr8gw-3.html
Best advice I can give: The more clearly you explain your project with the consultants, the better price you can get. Allow 2-3 weeks for the consultant to prepare a quote for you. This gives them time to discuss the project, ask questions back and forth, and then prepare a really well detailed quote.
My little boat i need a couple hundred pounds of ballast in the front for it to get on plain and ride well im too fat for it sitting in the back where you steer
So planing catamarans that use the air pressure between the hulls to reduce slamming are much more sea-kindly. And the two narrow hulls reduce resistance at low speeds. What's your verdict?
I agree with the initial idea. But unfortunately, the scale of the different effects makes this unlikely.
The two narrow hulls would reduce resistance at low speeds, true. But it also reduces their effectiveness at planing speeds. Imagine you have a monohull planing hull and cut it in half. Turn the two halves into a catamaran. Problem is, you don't get the same effective planing force on those two halves. Planing works because we force the water to turn downwards to avoid the hull. But in this half monohull, the water finds it much easier to just go to the inside of the planing hull. With a catamaran, your hull design could easily become dominated by the planing requirements.
The pressure between the hulls is a good idea for reducing slamming. But the magnitude of the air pressure normally doesn't make any difference. The air can easily escape the big cavity between the hulls without increasing in pressure. So it doesn't really affect the slamming operation. I have seen some concepts that change the hull design and try to trap the air before it can escape. That has some effect. But when we trap the air, we compress it. That compression is how we damp out the slamming. Now things get really interesting. Air heats up when you compress it. And since water is 1000 times more dense than air, we need to compress A LOT. Assuming we compress the air to only half of water density, that would increase your normal air temperature up to around 240 deg C (assuming we start at 20 deg C). Twice the boiling temperature of water. So now we need to worry about heat burning the hull, and generating steam in the water. What can I say, the physics makes things complicated quickly.
My experience is different, take for instance the deep vee hull, in that situation the vector of the planing force is directed outward rather than downward reducing slamming. In the case of cats I have driven, the reduction of planing surface has no effect on it ability to plane, at least in the age of 650 HP outboard motors and the reduction of slamming because of air pressure under the center of the hull is quite noticeable and results in a forward "sneezing" of spray from between the hulls. In other words, you can feel it happen. Personally, I could give a rip about large steel ships as I will never own one, how ever in my shopping for a offshore fishing boat, I have yet to see a monohull that can compare to a cat.
Interesting! I admit that sometimes the theory doesn't predict things accurately. Those are the really fun points. I'm a little surprised about the "sneezing" spray from the forward hulls. I would expect it to spray aft, out the transom. Do you see spray on the aft end too? I wonder if the damping experience has anything to do with the shape of your cross deck. Is it just a flat cross on the catamarans you drove?
Basically the bottom of the deck between the hulls is high in the bow and just above the resting waterline aft. The outboards are mounted on the center-line of the hulls and the weight seems to be quite aft. The result is as the bow is forced up by a wave, the stern stays planted and when the bow comes down, air is forced out forward resulting in the sneezing I described. Worldcat, the boat I have decided on explains the idea on their web site. worldcat.com/ and here is a You Tube video of one in a seaway. th-cam.com/video/VtBiHnP6oSI/w-d-xo.html
I'm impressed. I can see how that design would work. I gave too little credit to the air damping effect. Kudos to World Cast.
What about flying boats? Some of them get well above 24m, and they certainly plane.
Do you mean something like the boat shown in this article:
www.hoteliermaldives.com/flying-fish-with-heart-of-car/
More like this:en.wikipedia.org/wiki/Martin_JRM_Mars
Or this:en.wikipedia.org/wiki/Hughes_H-4_Hercules
Ah. You found an exception to the general rules that I said in the video. Flying boats still work as planing hulls because of several reasons.
1. As an airplane, they generally employ lighter materials than boats. The cube-square law still applies. But the airplane operates on an entirely different scale than your conventional boat.
2. Many of these planes actually use stepped hulls to achieve stable planing. It has the effect of acting like one planing hull behind another. This isn't really for planing force, but more to ensure pitch stability as you reduce to just the tip of the transom in the water.
3. The airplane wings help during planing. They take part of the weight during takeoff and landing. So the planing hull doesn't need to do all the work.
Fun fact: Some of the original experimental work on high speed planing hulls was conducted specifically for flying boats.
Okay, that makes sense. Thanks. I believe you did mention that experimental work on flying boats during the video, which is what made me think of these giant flying boats.
Hi Nick I saw this odd looking twin mast sailing catamaran called "mastfoils", I couldn't find any videos explaining pros and cons about it, can you enlighten me and any other interested subscribers please? thanks!
Do you mean this: www.chriswhitedesigns.com/mastfoil-discussion ?
The Chris White website offers their explanation on the advantages of a Mastfoil. But to provide some background on it, all sails are lifting foils. They work on the same principles as airplane wings, only we turn them sideways to push the boat forward instead of carry an airplane up. Problem is that soft fabrics do not make the best shapes for lifting foils. Instead, several designers tried to actually create a rigid lifting foil in place of a sail. That is the basic idea behind the Mastfoil. That rigid wing replaces the mainsail.
I would need to research it more to give justice to the pros and cons. But here are some simple observations:
Pros:
- Rigid foil lasts longer than sails
- Rigid foils perform better than sails. So you can fit more power into the same area
Cons:
- We always worry how to "turn off" the sail. A rigid foil can't be furled. The Mastfoil design by Chris White gets around this problem by giving the foil an option to freely rotate and always feather into the wind.
- Rotating mast sections mean that you can only put stays at the top and bottom of the mast. Everything else is unstayed. This requires stronger, heavier, masts to avoid buckling.
Thank you very much. You do raise a question or two. Since we don't get to see the bottom of aircraft carriers other then the flat bottom model types sold in kits, and you can't be sure of the exact shape is represented in the kit. Now the secret is that the aircraft carriers are suppose to only goes about 35 knots but in actuality if it needs to be displaced in a hurry they can go over 85+ knots with everyone hunkered down below. My first question is under your numbers can they go 35 knots? And the second are you aware of the UFO type technology that will enable it to go the above mention unbelievable speed the sailors have been subject to. Lots of love
It's possible. They absolutely can go 35 knots. But not using planing technology. That ship will never use planing technology. Just too heavy. The aircraft carrier is exploiting a wonderful trick of displacement hulls. To oversimplify: the longer the hull, the easier it is go faster. Normally don't see large hulls moving fast because most commercial ships are designed for efficiency. But the aircraft carrier needs speed, and has the power to match it. At over 1000 ft long, they are only at a Froude number of 0.31 when doing 35 knots. That is fairly easy for any hull to do. At 85 knots, they are near a Froude number of 0.77: fast, but still within the realm of displacement hulls. You don't see solid planing until you are near a Froude number of 1.0. So yes, 85 knots is potentially possible if they have enough power.
What could stop them from running 85 knots?
- Power. Even nuclear reactors have their limits
- Propellers. They may not be able to push that much power through the propellers
- Slamming. Any waves will have a HUGE impact on the bow at those speeds. You might dent or break hull plating.
- Hull bending. If a wave tries to pitch the carrier up at those speeds, nothing good will happen.
Yes, it's possible. No UFO technology needed. Just lots of power, and a VERY calm day to avoid any waves.
At that point, your main limit isn't power. It's the structure. If you tried to push the carrier at 85+ knots, the entire ship will vibrate violently. And when we include waves, the story changes completely. A typical seastate on a nice day would be seastate 4, with a significant wave height around 1.88 m (6.2 ft). (Significant wave height is one of the measurements we use to define a seastate. It has a mathematical definition. But practically, it is the height you would guess when making a visual estimate.) But at 85+ knots, every wave would be like a bullet slamming through a brick wall. We don't build ships to withstand life as a bullet. And the story gets worse if we talk storm conditions. Now imagine significant wave heights of 5-8 m (16-28 ft). Now the ship is pitching and bending flexing in the waves.
I can't say with certainty what the carriers can handle. I would need to know the details of their structure for any reliable estimate. And I doubt the Navy will give away those crucial details. But to take an educated guess: I wouldn't push anymore than 40-45 knots in good weather. In rough weather, that speed would be down to 10-20 knots. Anyone have experience working the carriers? Want to chime in with a sea yarn?
Of course that makes sense about the force of water at these speeds would be earth shattering and would create waves of gigantic proportions. I have come to understand that there is some other technology in the making. Just like UFO craft that make 90 degree turn on a dime at speeds double the jet following it. Couldn't this type of tech. be a factor? I realize that your concern is mater of state as earth as developed in the last century and understand but we need to move on to the next level. Lots of love Sorry just wanted to push the envelop in the thinking of peoples mind to a new upcoming reality.
Hey Nick, I really enjoy your explanations. Could you comment on Beneteau's hull design (th-cam.com/video/v8NmQM_s8_E/w-d-xo.html) and Shannon's hull design (th-cam.com/video/HVPEAU_gK0o/w-d-xo.html)? To me both designs are similar, they just go about getting the air under the stern in different ways. What say you?
-johnny
Police
I don't like fast boats...
what kind of no good landlubber thinks that smaller can be better? any real sea dog worth his salt knows that bigga is always betta!