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I've never heard that ekranoplans are supposed to be incapable of flight out of ground effect, except on youtube channels and their comments. All of the original research I've seen says full scale ones were expected to gain altitude and fly at hundreds or thousands of feet to avoid boats or obstructions like bridges. Flying in ground effect is meant to save fuel by lowering induced drag, and to make it possible to have a shorter wingspan on a heavy vehicle by increasing wing loading while keeping the induced drag low. They all have enough engine to fly because of starting water drag.
Exactly, the whole point is it has more efficient flight profiles, usually for very heavy loads, if its capable of 'real' flight or not isn't and never was the point, most if not all of them will be able to fly at least a little above the WIG effect. That is all arbitrary 'rules' as to what this type of vehicle should be and how it should be used, it doesn't mean it can't do something out of its preferred operational envelope...
As for getting off the water, perhaps use a retractable boat foiling, thus using water-lift instead of air-lift to push rather than pull the vehicle out.
There seems to be a false dichotomy here. To be a "ground-effect vehicle," it needs to be designed to take advantage of the ground effect. It doesn't need to be incapable of flight above the ground effect. Using the ground effect for increased efficiency above and beyond that obtainable through normal flight is certainly a legitimate endeavor, even in a craft capable of normal flight.
Yeah, the difference between a ground effect vehicle and a plane is what they are optimized for. Many planes can also roll around on the ground. And still we don't say "well, then it's only a car with wings glued to it".
@@toml1446 That is not true. First, most aircraft are outside of the ground effect really fast and thus they don't use it for anything. Actually, the only thing a regular pilot is trained to do with ground effect, is to be careful, transitioning in and out of GE doesn't upset their flight path/landing. Most Ground Effect Vehicles are able to fly outside of GE, same as many planes are able to fly within GE. But GEV are optimized to generate as much GE as possible (due to their wing shape) and are built to make use of it. Flying a regular plane in GE is incredibly difficult. In the end, if you add enough thrust, any vehicle that is able to take off from the ground will be capable of free flight. And since any serious aircraft is always designed with a decent power margin for emergencies, there is no such thing as a GEV according to your definition. Also, your definition would mean, that a fully loaded GEV suddenly becomes a plane if you unload all the cargo and it becomes capable of free flight. Did you even put a minute of thought into that argument?
@@dak1st " That is not true. First, most aircraft are outside of the ground effect really fast and thus they don't use it for anything. Actually, the only thing a regular pilot is trained to do with ground effect, is to be careful, transitioning in and out of GE doesn't upset their flight path/landing." Tell me you have never flown an airplane without saying you have never flown an airplane Also flying an airplane in ground effect is easy as fuck, the only thing the airplane does is generate more lift. thats it. Every pilot has done it when they practice touch and goes, the training we have had on "how to fly in ground effect" is if you land and your airplane bounces on the runway dont force it back down or you will crash. Thats about it. Adding enough thrust.... no shit but we are not talking about that. "And since any serious aircraft is always designed with a decent power margin for emergencies, there is no such thing as a GEV according to your definition." This is also untrue. most aircraft do not have a greater than 1:1 power to weight ratio and in an emergency if they are not positioned well they crash, or if they his a down draft thats severe enough they also crash. I dont think you understand what a loaded and unloaded aircraft mean in the context of how they are used. Because again, if a GAV can fly out of ground effect it is simply just an airplane. That is the TECHNICAL and LEGAL distinction of them.
@@toml1446 Nope. Legally, there are three classes of GEV. Only GEV class A cannot exit GE. GEV class B can temporarily fly up to 150m, class C can exceed 150m even for longer durations. All three of are classes of GEV. Your argument is like saying, a plane is only a plane when it can only fly, but not roll. Almost all planes can taxi, so by that definition, they obviousily aren't planes.
I always thought of a ground effect vehicle as being a plane with insane efficiency in ground effect regardless off real flight ability. A plane that cant get out of ground effect could just be a bad plane. It would be cood to see you try to optimize ft/watt hour.
I had a mini quadcopter with a partially fried ESC. It could generate enough lift to stay within ground effect, but could not get out of it. I guess, I made an RC ground effect vehicle incapable of real flight^^
IMHO Having them be puller props is a mistake; you are taking some of the propulsion thrust and converting it to lift as it goes over the airfoils. An excess of lift, especially outside of ground effect is what you don’t want, and what the propulsion system you have causes. Also having them be aggressive airfoils I believe is also a mistake. Keep them flat ramps like the full scale unit. You just want to trap a pocket of air under the vehicle, like a ram air hover craft. The airfoils you have not only do that, but function as a lifting surface outside of ground effect
This touches on my initial thought when I saw the design. It's okay to increase angle of attack by lengthening the top surface and have the air leave the trailing edge at a steeper angle, but the "hollow" underside of such an overly curled airfoil (imho) destroys the ground effect (and it pushes the nose down). So I was going to suggest to test it out, simply by foaming up the underside of the wing to a planar surface. It will have the slightest of angles which will be enough to capture the air. With the hollow, the pressure in the middle of the wing is definitely less than at the leading edge, which in turn is less than the pressure at the trailing edge. Fill that gap and there should be a more stable pressure under the wing helping the lift (and that pressure would disappear with height, which is exactly what you're looking for) (disclaimer: not sure if "pressure" is the correct word that I'm using here. I'm translating in my head as I go, so pardon me if I'm off-jargon here)
It needs a very "inefficient" airfoil to work correctly. Noice how all of the commercial wings have long cords, very thick camber, and a flat bottom profile. I believe this is to minimize the lift from airspeed, and maximize the lift from ground effect. Also the thrust vectoring was accompanied with massive flaps. This allowed them to fine tune the amount of air trapped under the wing withouth releying solely on engine thrust.
It looked to me like the air off the props was going over the front wing and under the rear wing causing it to lift the rear and the nose to skip. The air could not get under the front wing. You hit the nail on the head for ground effect without realising it when you said the pilot throttled back the engines when airborne. Ok so at full throttle it could fly higher but in ground effect it only needed much less power and probably at that smaller power it couldn’t fly higher. Good video 👍🏼
Front upper motor position kills differential pressure. You are getting high pressure under wing, and above. Front lower, or rear upper. (Notice position in original vehicle)
Definitely consider putting the prop in the back. It's stabilizing whereas a prop in front of the CG is destabilizing. I know that sounds backwards, but that's just because it's easy to imagine it as the prop pulling versus pushing, and in that case pulling it would stabilize it. But, the prop isn't pushing or pulling, it's moving a column of air. So now imagine a few degrees of yaw and the air is entering the prop disc at an angle and that air is then being accelerated in a direction parallel to the prop shaft. If you break that into force vectors it will make sense that having the prop behind the CG adds a stabilizing component.
I love your experiments and videos. It is clear that your shorter WIG wings are at too high a pitch angle and the upper surface blowing is preventing any stall on the canard - hence the instability.
for clarification there were 2 soviet ekranoplans (the one with and without missiles), the one without was much larger and destroyed many years ago, the newer smaller missile one is the one found on a beach!
Perhaps try putting the motors on or the tail just like the one that inspired this design? It would remove any backwash from the propellers creating lift, meaning that lift is only created from the air passing over the wing when it is moving.
The definition of ground effect has always been incorrect. The caspian balances on it's upper end of ground buffering. It can't fly over 50 feet, so ? When landing my piper, you can definitely feel buffeting starting at about 30 feet having a wingspan of 35 feet, um?. . . If it can't go up to open air, then it's a ground buffer
This reminds me of the comments section of food recipe web sites: some people change half the ingredients in the recipe then complain about how bad the result is.
When I was working on mine, I started to realize that it was very much just an aircraft trim problem to get the most efficiency out of ground effect. I’m thinking of revisiting my version of the ground effect controller and adding 2 integration terms that try to minimize throttle required: one on pitch attitude setpoint, and one on altitude setpoint. Both would be constrained to reasonable values, but it would quickly be able to find the minimum of the pitch-altitude-throttle plot…hopefully But hey, I’m a controls guy-very excited to see you pursuing the problem from an aero design / dynamics perspective! Wish I had your level of patience to iterate as much as you do
I think you're right. The ground effect is an efficiency mechanism. In order to take off from the water, the vehicle needs a lot of power because water has a lot of drag. It's likely so much power that it would have enough to fly outright. But they don't, because doing so is inefficient. I'm also unsure if the simple mathematic definitions of ground effect and assumptions about proportions scale down to this operating size. Gas laws and physical behavior don't have linear terms, they have exponential terms which are roughly linear when operating in a small region, but which can quickly become non-linear. I wouldn't be surprised if the ground effect window for a wingspan in this scale was much smaller than the window for a large vehicle like the famous Soviet ekranoplan. Likewise, given the real-world performance of the Caspain sea monster, I wouldn't be surprised if the "correct" or optimal ground effect height was also higher. For example, the ground effect may be present between a certain height relative to wingspan or wing area, but using the "middle" may be pointless. It is precisely the interface between ground effect and regular flight which is proposed to be the efficient flight mode, where the vehicle rides on a cushion of ground effect air. Definitionally that seems like riding on the boundary.
@@haphazard1342 First and foremost the assumptions of power and flight are incorrect. Caspien Sea Monster weighed the same as the A380, with 75% of the wing area, 75% of the power, and lower lift off speed, despite having simple flaps over complex multi-slotted flaps. Second, ground effect should scale similarly to inertial "dynamic" scaling of RC aircraft. Ekranoplan work with high wing loading and higher pressures (compared to aircraft). It is very likely the window for proper ground effect is smaller (altitude), and the required wing loading relatively high to make an RC ground effect truly work. Unless of course you have a permanently augmented thrust vector to help pressurize the bottom surface of your wing.
Its amazing how simple the idea feels like it should be to implement... but it is anything but that! Good work man! You are doing a lot of valid testing. Can't imagine what could be wrong.
This was a fantastic video. Love the background sources and videos before showing your work. Thanks for the shout out for WCRC, much appreciated! Looking forward to part 2 and 3.
Great video 5:54 - In addition to getting very lightweight and precise parts is that it's also fairly simple to manufacture and replace an identical spare part or a copy of the whole thing if it gets damaged.
Everything you do is amazing and the steps you take to get there, Soo good. Love coming along for the ride. Sooo interesting. Can't wait for more. Thanks for the awesome content! 🙂
So stoked to see this "true ground effect" video series! I've been curious about ground effect and the physics / mechanics of it ever since I first learned about it, probably from the ekranoplan. But there is so little out there about functioning machines that implement it. Looking forward to the rest of the series. Great work!
First time I heard of ground effect was when I was reading up on helicopters and found out that if the engine failed it was still possible to land using autorotation and the ground effect. And for anyone who haven't heard about this autorotation is what you get if disengaging the drive shaft to the prop on a helicopter in the air. If you are high enough and reacts quickly enough you can angle the blades negatively so that the air going up through the prop will accelerate it. The helicopter will fall pretty quickly, but by adjusting the blade angle you can keep the blades spinning and somewhat moderate the descent speed. The important thing is you keep the prop spinning at a decently high RPM. Then when you get close to the ground you pull back on the collector, using the rotational speed of the prop to push air down instead which further slows your descent. If you do this correctly the ground effect will help slow your descent even more making it possible to set the helicopter down instead of crashing. The ground effect is however as said in the video strongest in a very narrow height span, and it's measured from the plane of the prop not from the skids or wheels. Now I certainly haven't tested this as I'm not a helicopter pilot. But I have talked to some pilots who has confirmed that it is a thing. They have also confirmed that the ground effect is a noticeable phenomena that they can feel when doing an ordinary landing. I'm adding this last bit as I've seen comments from people who claim that GF doesn't really exist.
FWIW I was a 747 captain, retired now, but one thing I remember on landing was that we'd start to feel ground effect at about 200', which is the same as the wingspan. You'd have to add a little nose down elevator to push down through the ground effect or the big plane would start to shallow the descent.
Great video! Not every experiment has to be perfect. I agree having your props that high up is pushing air under the rear "wing" causing lift in the rear and over the front wing pushing the front down.
At this rate, pretty soon you'll be joining bald and bankrupt to visit the OG Ekranoplan, fixing it up on the beach, and driving it back home! I really appreciate your drive to keep pursuing this concept - so much work! Woah!
If you're in RC planes, you know that basically you can make anyithing fly, if you have a motor, and the basic control surfaces. All because the power to weight ratio is much-much higher than a life size aircraft. You basically don't even need profiled wings, as tilting the plane gives the lift, and the motor just takes over the forces that you don't get from wing lift.
The flarecraft vehicles had a 70hp outboard to help it get up to speed while on the water. They could leave ground effect, but not sustain flight out of ground effect.
Using the water itself as reaction mass is an interesting way to gain velocity during takeoff that I haven't seen much beyond this example. I would imagine a future vehicle using an impeller driven by the jet turbines' excess power (if that's even possible) to accelerate itself out of the water.
I like the shaping you do all the smooth rounded. I was cuttin my foam with a band saw. I had homemade hotwires but it was always a hassle. I can cut half my lines takin my time a better cut than the hotwire.
I think the most important factor for a feedback loop that keeps the vehicle in ground effect is that the lift in the front is more sensitive to the ground effect than the back lift. That way, if you are lifting out of ground effect, the lift in the front will decrease more than the lift in the back, and it will pitch down. And obviously when you pitch down you get back into stronger ground effect, stronger ground effect means the nose gets lifted up more than the tail, and nose getting lifted up more means rising out of ground effect. I'd almost say that the rear lift surface could even be a normal wing (i.e. fully out of ground effect). It currently looks like your front lift is more sensitive to speed than the rear one, so that you get a nose-down attitude at speeds that are too low to lift off, as seen at 11:56. And at higher speeds the nose just lifts up uncontrollably, as seen at 10:45 , 11:19 , 11:35. I would have guessed that it has something to do with the high pressure air from the bottom of the front wing getting pushed under the rear wing - except that that would cause the opposite effect...
A wig-V has always been a boat. They are constructed like boats not lightweight planes to pound on waves. The flyers are not wigs but designed intermediaries. No one really wants to not be able to jump an obstacle like shipping container. Single wings are generally fliers and the body lifts. You are correct that this model is a wig-V and the others are planes.
I know I am overstating the obvious but the flair boat uses a pusher arrangement angled so the motor thrust line passes just forward of mid ships of the craft. This forces the craft flat as it moves forward. I am planning to build some of these vehicles shortly. The flair boat is a great starting point as it stays low rather wanting to fly high like other ekranoplans shown in the video. Thanks for the video it is very encouraging for me. all the best Allen
I'm subscribed because I can't wait to find out what you did to correct your plane for ground effect. And hopefully, if I keep watching, I will understand why ground effect is important. ☺️
"Gunter spent decades designing a fully functioning full-size ground effect aircraft that works... but I'm going to change the design completely" wtf bro
I like that you are answering the objections with flight test. I think you are correct, the negative pitching moment of the airfoil is a problem. The big problem I see in these kinds of attempts is they are all very low wing loading park-flyer type of projects. An Ekranoplan was like a heavy but powerful muscle car. You need big wing loadings and high speeds at those loadings to get into the zone. Machine it out of something more dense like oak.
I've been wondering exactly what ground effect is 🤔 Thanks so much for going over this and physically showing examples etc with the RC. I definitely understand much more now. 👍 Can't wait to see the next vid 🔥👍✌️
The caspian sea monster from my understanding actually turned of all of the eight frontal engines when it had gotten into ground effect and flew only with the two rear engines on the fin.
When I was at university one of our projects was to produce a ground effect R/C vehicle. Of the 20 or 25 vehicles only 2 or 3 couldn't fly but none of them flew well due to the configurations. But we had the advantage of taking off from land so the power required to get airborne was only very slightly more than the power needed for ground effect flight.
it looks like both of your wing’s angle of attack is too steep. i’m a huge fan of what you are doing and have been following for so many years!!! you are a big motivation and inspiration for all of us!
Around 1990 I saw that open-cabin full sized one on a tech show on TV, and thought of making a model. I got some foam wings from a crashed RC plane ..... and did nothing! I am enjoying your experiments.
You put flaps on the forward airfoil, maybe you could make the rear wing have a little up elevator or less concave on the bottom? I love your work; I really like watching ideas get developed into prototypes.
One idea for reducing the energy required to generate enough speed in the water to transition to ground effect is utilizing your experience with active hydrofoils. Enjoy watching you troubleshoot on the fly, thank you for documenting your struggles along the way.
Thanks! I know hydrofoils and GEVs intuitively seem like a great match but turns out they are pretty much completely incompatible. I've experimented with this myself and know others that have done so as well. Even though hydrofoils have a lot of hype about having very low drag, they actually have quite a lot of drag at high speeds compared to a hydroplaning surface. They are also very picky about their speed range making it almost impossible to match an aircraft's ground speed which can vary greatly.
For the sea monster wouldn't you need to also kick into account the wing area of the front planes and tail when calculating maximum ground effect height? That tail is almost the same size as the wings are.
This is fascinating to watch! I feel like I'm part of your experiments, learning what you learn. Thank you. Aerodynamics is not completely intuitive, there are dynamic effects that need to be understood. You may need a supercomputer to calculate all of the variables at play to design the best wing/s to sustain "in ground effect". But trying different wings is more fun. I think it's called "chord", the length of the wing front to back. Shortening (or lengthen) the chord of one or the other wings, or both could help the in ground sustainability. That might also reduce the pay load though, so...6 of this, a half dozen of that. Truly, you inspire all to think, and that's a good thing
I would start with a symmetrical airfoil and just a shallow aoa to avoid excessive pitchingmoments. Maybe a sililar pusherarrangement like on the jörg-craft with downward facing line of thrust will help to cancel pitchingmoments out aswell. Great project, 👍
So as far as aviation in planes, when flying they tell you you only start to experience ground effect when you are within one wingspan above the ground. Cool videos though as always.
12:06 reminded me of the issue with some flat bottom race cars. They depend on a steep rake angle (among other things) to make a lot of downforce - but if a little bit of air gets underneath them then they flip.
You know a video is good when you go to press the like button not 2, but 3! times throughout the video only to realize you've already pressed it. Keep 'em coming!
Symmetrical airfoils at an incidence of about 6 degrees on fore wing and 4 degrees on aft wing and a pusher prop with some downward tilt to compensate for the high thrust line may work.
The whole point of the ekranoplan was to transport as many troops, gear, vehicles and armour as possible, as fast as possible without being detected by radar during the invasion of mainland USA. It really is that simple. R/C ekranoplans carry no cargo, are built using R/C aircraft techniques and have an exponentially higher power to weight ratio than any full size WIG. Try a 3 motor model, add ballast so you need all 3 motors at full power to get off the water then cutting 2 for cruising.
I had a fast RC boat that took off when the engine was put to full power. It usually pulled air into the propellor (ventilation not cavitation) but when it did bite the boat flipped. Designed right, it could have lifted the whole boat, though I didn't have the knowledge to make it happen reliably.
You need 4 motors to create and keep the pressure under each wing. The wings should form a pocket trap for air but without losing airspeed below those wings. Reduce the aileron length and inclination a bit, the problem is once they approach the surface of water or ground the air loses speed and hence the pressure. Watching these videos helps to identify the problems.
I really enjoy your series. I’ve followed your experiments for years. I’ve been thinking about this question: How does air density figure into all this. When we’re dealing with ground effect, to what degree would the performance be different between a small, very light model and the full-sized craft traveling over the same water? thanks again for all your work.
It seems to me that a lot, if not most, of the problems you had with this design were caused by the motors being placed in the front of the vehicle instead of the back. Very excited to see the continuation of these experiments!
Remember that the caspian sea monster has multiple engines of which only 2 run while in ground effect, if they just blasted all the engines the thing forsure could fly
Looks like most of your thrust is going under the rear wing. Pusher propeller or moving the props forwards could help. Also looks like the AoA of the cambered airfoils is too high for the Cl you want to run at cruising speed. Maybe some way to trim the wing angles on the beach would help. You’re probably right about a flatter airfoil helping. My gut feeling is that more slowly compressing the air along the chord will ride smoother. Might be worth trying raising just the back wing? Could be possible that there’s too much back pressure between the wings and the plane is relieving that by raising the tail. Too much back pressure could kill some airspeed over the top of the front wing further decreasing front lift. Love the thrust vectoring to get going, looks sweet. Excited for the next episodes!
All of the training I’ve received in fixed wing aircraft and rotary wing aircraft has been that ground effect happened one wing length from the surface. Helicopter hover heights are extremely dependent on ground effect especially in high density altitude.
I think when you're playing with a new design, setting up one of the pots on your controller for the tilt servo might help with finding specific angles.
I think using a boat design as a starting point, rather than an airplane, may have worked better. Sounds like you already figured it out though. I look forward to the next video. I've always been fascinated with ground effect vehicles.
Love watching these!! My thoughts are- 1. Extended the nose and motor postion to only PAR thrust the front foils, and reduse wing span, that will help lift the nose at speed but reduce the overall lift that makes it want to fly above GE. 2. It appears to me you are trying to fly a plane capable good altitude but keep it in GE. Just like hovering any rc craft an inch the ground its very hard. Maybe change the design philosopgy to building a device that is incapable of flying at any good altitude, but can slip along the water surface very quickly, I think GE is relative to air speed, not so much thrust wash or wing span. Also as you see on the big scale versions the tail fin and stabiliser are massive, like a weather vane, they help keep the machine planted and comb out the steep up down pitching effect.
I think the design point you missed from the craft you mimicked was, that it used a pusher prop. That would eliminate the tendency for the prop to lift the front of the craft. For what its worth, my concept would be to have two fans, one mounted on the rear of each float, and steer with those ie. no rudder. If you look at swamp craft, they also use pusher fans, so there's a clear design precedent. .
This is actually pretty important work. I do large model aircraft design for competitions and one of the struggles is that aerodynamics doesn't always scale down. Almost all literature is about full sized aircraft and the best of the rest is hidden in military drone design offices. Ground effect is even less well studied and there was/is the distinct possibility that it doesn't exist for R/C aircraft in any meaningful way.
