Wig Hovercraft

[metroidrc]

Is anyone going to attempt a Wing in Ground Effect craft similar to the ones on hovercraft.com? that would be really amazing..

http://www.hovercraft.com/content/images/kits/18spw_yellow_600.jpg

[bloberts]

im not sounds an intresting prodject though

[boredom.is.me]

I like wig vehicles. I was wondering what the first rc version would be.

http://www.aerospaceweb.org/question/aerodynamics/ground-effect/flarecraft-l325.jpg
http://www.aerospaceweb.org/question/aerodynamics/ground-effect/km01.jpg

[metroidrc]

its gonna be interesting to see how ground effect works on such a small vehicle.

[HybriGuy]

Hi,

http://www.walter-group.com/WG-DRC-YJ1-HighHover2-27Jul07_sm.jpg

MetroidRC - We not only attempt them, we've successfully built and flown/driven several dozen. So far, the smallest is under 8 inches (~20 cm) across, and the largest is about 8 feet (~2.4 m) - that one wasn't RC, though. :D The Yellow Jacket shown above, measures about 3 feet (.9 m) across the middle, and a little longer front-to-rear. As shown, it weighed a little less than 18 pounds (~8 kg).

We're having our latest creation painted today! This one is remotely controlled, gas powered, and just over 5 feet (~1.5 m) across. Weather permitting, we hope to have images posted by year's end, and new operational video to the Internet soon thereafter. You're right: it is really amazing!

Bloberts - Interesting project? That's an understatement. Is your name Ken?

Boredom.Is.Me - I don't know that we were the first, but we started operating HybriCraft remotes in the 1970s. Here is the late Bill Walter (HybriCraft inventor, bio (http://www.walter-group.com/management_team.htm#William_C._Walter), history (http://www.walter-group.com/company.htm#History)) working with a little electric one.

http://www.walter-group.com/william_walter_air_cuishion_flight_hedgehopper_76B .jpg

MetroidRC (10Aug post) - Ground Effect works just about the way you'd expect it to work, even at such a small scale. Probably because of the size, controls are very sensitive, but manageable. When I fly them, HybriCraft feel ready to get airborne (OGE) at any moment - provided weight, balance, and trim are all dialed-in. Because HybriCraft perform as air-cushion assisted WIGs, you can't mistake the evident benefits of operating in ground effect and on a cushion.

They are stable - yet nimble and responsive; operating well off the ground, they forgive all but the worst payload abuses. Add to that the ability to takeoff and land vertically (VTOL), no tail rotor, and no real wings to speak of, what you have is something like a Land Speeder from Star Wars.

See and learn more here (http://www.HybriCraft.com).

Matthew

[metroidrc]

Matthew that looks cool, I want to see a video!

[metroidrc]

after looking at the website and seeing more pictures, I didn't realize theres a big prop at the top like a helicopter. how does the design differ from a helicopter? you had me fooled there! I thought it was some new type of hovercraft that can levitate inches above the ground! its more like a VTOL than anything else. very cool pictures though... nice job!

[metroidrc]

I want to work on some kind of wig when I get time... its gonna have to look cool though!

[HybriGuy]

Hey MetroidRC,

HybriCraft are a special type of hovercraft; skirtless hovercraft. They are also aerodynamically suited to operate as WIGs do, where the cushion does not always account for all of the vehicle's lift. If you could go where hovercraft go, and you could lose your skirt, then you could go many more places also!

Great question about the helicopter similarity; the difference is not apparent at first glance. Actually, there are many differences, so I'll break them into categories, and address them that way. Let's look at Construction, Operation, and Application first, then I'm sure you'll have some more questions. We also have a review of this subject here (http://www.walter-group.com/hybricraft.htm).

Construction: As you pointed out, we have a fan on top of the Yellow Jacket (and many other evaluation vehicles), and most helicopters have an articulated rotor - also overhead. I say most, because some designs have two, like the CH-47 Chinook and some Sikorsky test vehicles.

So, one huge difference is that our shaft mounts rigidly to a hub, with blades mounted rigidly onto it. There is no swinging, swiveling, or tilting going on at the fan hub, and the flange is the same as you might find on a hovercraft thrust fan/prop.

Now, compare that mental image with the busy gizmo atop the helicopter mast, to which they connect all their rotor blades.

http://www.tpub.com/content/aviationgenmaint/TM-1-1500-204-23-5/img/TM-1-1500-204-23-5_62_1.jpg

I figure the difference is clearer with a closer look at the details above. Also, most helicopters have tail rotors, tail booms (that bar that sticks out the back), and lift themselves with the rotor blades. HybriCraft manage the tail rotor/boom thing differently, so we don't have those appendages. Our fan is too small to create lift, and we just use it to pump air to other places - just as a hovercraft does. Likewise, a lot of our lift comes from the cushion underneath; very different from a helicopter.

Operation: In essence, the FAA says that Ground Effect Machines (GEMs), such as WIGs, hovercraft, Flarecraft, and similar surface effect vehicles fall outside their jurisdiction for regulation (certification, licensing, etc.), unless the builder creates them with capability to operate continuously in free air. What all that boils down to is that if you must operate in ground effect, or if you cannot sustain operation in free air, you're operating a GEM, and the FAA couldn't care less.

That is another huge difference between helicopters and HybriCraft. While HybriCraft can operate out of ground effect briefly, we haven't designed one yet that can sustain free-air operation indefinitely. This is not to say that an end-user couldn't make a few modifications - just as Universal Hovercraft did with their UH19-XRW and UH18-SPW HoverWing. As long as we build them the way we do, a standard driver's license and maybe a DMV recreational vehicle (or off-road vehicle) registration may be all you need to stay within the law. Helicopter pilot certification is a very different (and fairly expensive) achievement, by comparison.

Application: Simply put, application or mission differences between HybriCraft and helicopters come down to:
Where do you need to go?
How soon do you need to be there?
How much are you willing to pay to make this happen?

If you need to overcome impossible terrain (a straight line across the Rocky Mountains, land on the top of a skyscraper, or enter a football stadium from above, for example), a helicopter probably will serve you best. If you have to get from Corpus Christi, TX, to an oil rig 450 miles out in the Gulf in three hours, jump in a jet-powered helicopter, and hang on! In real life, these needs arise, and helicopters will continue serving these missions best for many years.

But what if you want to do what people do on a jet ski, only you want to do it in the Utah desert? What if you just need to travel the same unimproved, relatively mountain-less terrain up-and-down 700 miles of Arizona's US Border fence-line (or Minnesota powerline, or North Carolina coastline)? Does your company hope to afford a couple helicopters to provide security along 1850 km of Canadian oil pipeline - crossing arctic tundra or similar frozen wilderness that never really goes up or down much of a hill?

At first, someone might think, "yeah, but I can do all of those things on my quad...". Well, what happens when the bushes get three feet high - or the soft, powdery snow becomes four feet deep? What about crossing the 6-foot deep creek? What if you want to go across the lake, instead of around it, and you can't change vehicles?

In some roles, helicopters are the best choice. Sometimes though, helicopters are overkill - in initial cost, maintenance downtime, horsepower, and minimum skill level required. In these cases, I think HybriCraft provide a much smarter, more efficient solution, and they don't cost millions of dollars.

Working to get some good video out,

Matthew

[metroidrc]

Mathew that looks very complicated. Thanks for the answer. I like the simplicity of hovercrafts though... two or one fan and a rudder.... and for wig craft just small wings on the side.

[Kmot]

Heli or autogyro with a cushion. Looks nothing like a WIG.

I'm not saying it isn't interesting. It is. And it is a flying machine. But a Wing In Ground Effect machine I do not think it is.

[metroidrc]

well I want to attempt one, probably just do a mod of my razorback and put some wings and a tail on it.

[micro_builder]

here's a thread with some good links and info. the pic below is a little WIG i built from this thread also http://www.rcgroups.com/forums/showthread.php?t=324417

nick

nice work getting this forum going, Josh :)

[metroidrc]

thanks i'm glad it went up too, looks like alot of people enjoying it here. that micro wig looks great! I can't wait to build one. I guess it would be rudder only. I'm an edf guy so I guess it needs to have an edf in the back...

[micro_builder]

hmmmm, did someone say EDFs? :D

the little AA jetscream has two of these 32mm 2 bladed EDFs. the impeller isnt just a normal 2 blade prop, its been designed for the EDF, even has a nice little rounded hub. around 10 grams of thrust per fan seems to be the norm. they would work great in a normal hovercraft too.

nick

[metroidrc]

yep i messed with those a bit on my micro f100. i have better luck with the brushless fans... too bad they don't make a little 7mm brushless for that one!

[Sky-walker]

Hi Mathew nice to have you here, i know of your craft hybrid since long ago.. but never though understood it.. what it does is that it lifts with an aircushion without skirts but how? .. how do your craft blow air at the perimeter and the same time blowing strait down? it is very intersting craft and a landspeeder would be nice too

did you test it in zerospeed hover? how stable was it?

Kalle

[derk]

hmm, i bet you could buld a tiny one with 2 foam plates glued together and trimmed. use 2 props from an aa so they counter rotate and maybe even use its stock radio :)
im going to try this tonight and see what i can come up with.

[metroidrc]

derk... can't wait to see something! i'd like to come up with something that does not require elevator control, just rudder, but gets up in the air a few inches.

[derk]

well, I believe that the aa radio will work for this. I glued 2 motors end to end and reversed one so the props still counter rotate. I also slightly increased the pitch of the lower prop so they have equal torque. it should turn just like the small 3 channel helis do. I will be adding a twin rudder and elevator on top for trim and directional stability. I want to balance it to slowly go forwards.
off to hack out a foam body :)

[HybriGuy]

Hi Kmot,

You added a curious and brief entry in this thread, and I want to look a little more closely at it.

Heli or autogyro with a cushion. Looks nothing like a WIG.

I'm not saying it isn't interesting. It is. And it is a flying machine. But a Wing In Ground Effect machine I do not think it is.
"Heli or autogyro with a cushion."

If that was a statement, it appears incorrect as worded. If that was a question, no, it is neither of those. The two vehicles you indicated generate their lift from their rotors. As I explained, we use a fan to pump air, not for thrust.

"Looks nothing like a WIG."

Aye, it does not. The Wright Flier, a modern glider, the Concorde, and the F-35B look nothing alike either, and these are all airplanes. A Robinson R22 and a CH-47D Chinook look nothing alike either, yet those are both helicopters. I hope it does not have to look a certain way to be considered a WIG. I have never come across such a requirement.

I think a qualifying WIG vehicle needs to do two things to earn the designation:
1. The vehicle should operate in Ground Effect, and
2. It should have wings - or be entirely a wing.

HybriCraft that operate as WIGs all have a wing-body, an approach similar to the YB-49, Northrop's Flying Wing. Admittedly, our wing isn't in the conventional wing shape - any more than the wings on a Flarecraft WIG are. What about throwing a Frisbee 40 meters along the beach - just barely above the sand? Isn't that a wing in ground effect?

"But a Wing In Ground Effect machine I do not think it is."

Why don't you think that yellow HybriCraft model is a WIG?

Curiously,

Matthew

[nbrophy]

I think good candidate is to use the "RAM wing" paper glider plans (http://triton.naoe.t.u-tokyo.ac.jp/akimoto/WISES_old/WISE/ramodel.html) as the basis of WIG/WISE RC model like Nick did. Scale it up the template for a depron-constructed model. It could be power by a single EDF40. At least this was the route I was looking at going.

There was some discussion of this paper glider model on the Yahoo WIG discussion list (http://autos.groups.yahoo.com/group/wig/).

[metroidrc]

Mathew,
Because your Hybricraft has a propeller at the top, people are gonna confuse it for a helicopter.
-Josh

[derk]

it also "operates" as a heli that is in ground effect but the body is being used to recapture some of the vortex energy generated at that height. so it doesn't need a really big rotor or as much power to stay in ground effect. that's right isn't it?
I fly helis every day so I could see how this works pretty good.

Matthew, did your models need to be stood up off the ground (landing skids) to avoid adhering to the ground and start the vortex underneath?

[Kmot]

Mathew, show me a cross-section of your HybriCraft wing.

[HybriGuy]

what it does is that it lifts with an aircushion without skirts but how? HybriCraft have skirts, ours are just high velocity air (jet sheets, 1 or 2 cm thick - called curtains), so we benefit twice from this. First, all the weight from the peripheral skirt and attachments goes away. Second, we don't suffer frictional losses from the skirt dragging over obstacles or an uneven surface beneath. Inside the curtain, pressure from the cushion lifts the vehicle - until you get going too fast, then the WIG parts start adding lift separately.
how do your craft blow air at the perimeter and the same time blowing strait down? The fan you saw on the yellow model can also be more than one fan. We can put fans in many places, but having just one makes it simple (easy to get to, change, work on, etc.). The fan charges a chamber, called a plenum. The plenum converts some of the high velocity air to pressure, and the excess air sort of spills out around the outside. We use the pressure in the plenum to feed nozzles around the body.

Some of these nozzles point straight down. When the air (accellerated through the nozzles) exits, it grabs most of the excess air we let spill over the sides. Called entrainment, this air also gets accellerated. Together, they form a jet sheet - around the periphery, headed toward the ground, initially at very high speed. This sheet is now the curtain, and like skirts on a hovercraft, it serves to contain the cushion inside it, beneath the vehicle's belly.

Here is a simplified diagram (http://www.walter-group.com/hybricraft.htm) on our website.
did you test it in zerospeed hover? how stable was it? When I was learning to fly the first one, it had a handle on it, so I could feel its behavior. The first remote control HybriCraft I tried was that yellow one, and stationary hover was where I had to start. I was afraid to crash it, so I probably spent two or three hours just learning to hover - steadily going higher, then higher, then...okay, sometimes I put in too much control, and I had to chop the throttle in a panic! :D

What we call "deep in the cushion" is where the Yellow Jacket sits most stably. Add throttle, go higher, and it becomes incredibly responsive and nimble. Stability is a funny term, because if you have too much, your performance ends up being sluggish. Fighter jets, for example, are intentionally unstable, and that makes them very maneuverable.

I would say it is very stable to about 1/6 of its diameter (roughly 6 inches for the Yellow Jacket). Then, as you go higher, it becomes more and more difficult to hold on station. Basically, as you add throttle, you really ought to plan on going somewhere with it - because they really want to go!

Thanks for the great questions,

Matthew

[HybriGuy]

Hey guys,

Thanks for the thoughtful questions.

Josh, you're exactly right! Before taking a closer look, a lot of people wonder what kind of helicopter this is.

Kmot, here (http://www.walter-group.com/hybricraft.htm) is a simplified span-wise cross-section of the primary wing (the body, basically). In practice, just as with other wings, the leading edge is a bit "thicker" than the trailing edge. The chordwise cross-section resembles a Frisbee more than a traditional airfoil - for a couple of reasons. First, the body has to do many jobs, not solely provide aerodynamic lift. Second, there are several lift contributors, not just a wing.

Derk, before answering your question, I'm going to talk with our R&D guy and make sure that the way I want to explain things is okay with him. We have some secrets we like to keep - well - secret. I want to respond thoroughly however, so I'm going to bounce it off him, then come back to you.

In the meantime, think about this. Helicopter X has a 30-foot rotor diameter, even though it sits on two 6-foot long skids 5 feet apart. From a 30' rotor diameter, the rotor disk covers an area of (pi X r^2 or about 700 square feet). Now, let's say the heli's body (roughly the same area stradled by the skids) "blocks" about (6' X 5' =) 30 square feet of the downwash.

The "unblocked" air hitting the ground has a footprint roughly (700 square feet minus 30 square feet) 670 square feet. The rotor wash flows down to the ground, then out across this footprint. This air mass flow produces some force felt by the helicopter - an equal and opposite force. Add enough collective, move enough air, and the heli lifts off of the ground in ground effect.

Imagine what a fan would have to do if it were only 5.5 feet across - not thirty - and mounted to the same helicopter! The fan's tip speed must remain subsonic, but it has to push a whole lot more air than the rotors did - because all of that air is "blocked". HybriCraft don't really work the way helicopters do.

More great questions,

Matthew

[derk]

well, after reading more on the website, I see why my little model didn't work. I had missed the part about the upper surface airflow containing the fans high pressure like a "skirt" does on a hovercraft.
if you could, give me an idea what sort of power to a given size that a hybricraft needs, that would be a big help.
I'm not out to steal any secrets but just would like to build a model of such a fine concept :)

[Sky-walker]

thanx alot Mathew, I am intersted in this really and waitng to see full products hopefully, Ill be teh first to buy I assure you:D!

so do you have to have " holes or slits in the donut ring" or can you also have just a normal torus ring and put a prop over it? what do you think? the air will both circulate around the outer edge and make a curtain and at the same time go strait down and propell the craft upwards?

Kalle
regards

[HybriGuy]

Hello again, Derk!
it also "operates" as a heli that is in ground effect but the body is being used to recapture some of the vortex energy generated at that height. so it doesn't need a really big rotor or as much power to stay in ground effect. that's right isn't it?
I fly helis every day so I could see how this works pretty good.
Let me start with the "vortex energy" part. We take air from the fan before an organized swirl forms. When people talk about vortices, they often focus on the rotational part of the flow. In our system, we want as little rotational flow as possible, because that could add some yaw or torque. Remember that HybriCraft up on the cushion provide almost no resistance to forces - gravity being the obvious exception.

If you've ever kept a helium balloon around for a couple of days, you've seen it go through the stage where it doesn't stick on the ceiling - but it doesn't stay on the floor either. This equillibrium state leaves it wandering around the house at the whim of tiny air currents, sometimes able to ride thermals as a hang glider or hawk does. Just as with a HybriCraft on the cushion, it doesn't take much applied force to get it moving (in any lateral direction).

Next, "so it doesn't need a really big rotor or as much power to stay in ground effect. that's right isn't it?" Yes, exactly right! Now as you probably figured, this benefit goes away when you decide you want to get into free air. At that point, I think the heli starts to take back the efficiency lead. HybriCraft like to chill on the cushion.
Matthew, did your models need to be stood up off the ground (landing skids) to avoid adhering to the ground and start the vortex underneath? They don't need to be on skids, but I recommend skids strongly to anyone new to VTOL craft. I can't tell you how many times I could easily have totaled the Yellow Jacket if my hard landings (usually because I was scared about crashing) weren't absorbed (at least a little) by the skids' flexing.

No, ultimately we removed the skids (your basic cheap-o RC Heli-type, nylon and aluminum tubing), and stuck 8 little foam hemispheres on around the belly. This reduced the idle height (sitting on the ground, engine idling) to about half an inch (and shed some weight also). As before, any liftoff vortex we generate is transient, momentary, and otherwise undesired. Similar in this regard to a helicopter, we want clean flow into the fan(s), and no recirculation. The latter can be quite a design challenge.
if you could, give me an idea what sort of power to a given size that a hybricraft needs, that would be a big help.You may not like this, but the Yellow Jacket has a 1990s 2-stroke weed-whacker engine (crank-case conversion kit by A&M Aircraft), originally rated (as new, by some factory physicist) around 3-4 HP, but probably delivering 2 or 2.5 HP today. That model is also over 15 years old, so it's tough to make a state-of-the-art comparison with it.

The Yellow Jacket is just under 20 pounds, and I personally think it is overweight, over powered, and the CG is twice as high as it needs to be - but that's just my perfectionist criticism. We're building another one right now, so watch the website for details. Even though I didn't say anything, you heard it here first! :confused:

Back to sanding primer,

Matthew

[derk]

Matthew, when i was referring to the "vortex" it was a rin gshaped one not a "tornado" style one. like a doughnut rotating in on itself. so yeah i think i get it now :)

[Sky-walker]

Mathew, all, i have had an idea about an air cushion vehicle with special "design" but first I want to ask if anybody know who Leonard G cramp. he is a true sadly unknown pioneer into hovercraft and he build the hovercraft long long before sir corell did

[HoverTim]

never heard of him sir Christor cockrell and Dr bertlson but never this guy allthough cockrell is conciderd the inventor

[metroidrc]

well I've been experimenting with some small wings on my hovercraft. While I can get it to fly like an airplane, I'd much rather have it stay close to the ground in "ground effect" does anyone know how this can be achieved?

[hoverman]

I have built a lot of Ground effect craft, at the moment I am building an rc version of an a-90 Orlyon Ekranoplan, in GFK. On your hovercraft you'll need small stubby wings with a high cord(very low aspect ratio), also they need to be placed at a fairly high angle of attack, think of something of 10 degrees.

Ofcourse you also need the stabiliser, which works better when it is a bit larger. Make sure it has a POSITIVE angle of attack, not a negative angle, as on an airplane. This means ofcourse, that the stabiliser is making positive lift, just as the main wings. If you place the centre of cravity somewhere between the stabiliser and the main wing you will get a very good stabilising result which will litteraly stick your model in ground effect. How?

Its quite simple, the CG of the craft is placed between the ground effect wings and the stabiliser, so the craft is carried by both wing pairs. If the model increases its cruising altitude, it tends to pitch up and flip back, but in this case, it also means that the lift of the main wing(the front wing pair) reduces. The stabiliser however, which doesn't use the ground effect at all, still gives the same amount of lift --> bingo, your craft is now nose-heavy and wants to pitch down. If you make sure this effect is strong enough it will overrule the pitchup tendency of a ground effect craft.

This system actually can ensure that the model always stays in ground effet, nomatter what the speed of the model is.

Good luck ;)

http://i218.photobucket.com/albums/cc320/Helipilot/ek6.jpg

Marijn

[metroidrc]

very helpful thanks! :D I'll try to work on that this week if I have time...

[derk]

so what then if you wanted to leave ground effect? and fly like a seaplane? just change the incidence of the main wing and tailplane? but then as an aircraft, it is not balanced properly... i think that will be how i setup my next WIG, with the ability to operate in ground effect or lift out of it by altering the angles in-flight. would be fun to play around with.

Derrik

[hoverman]

sure, indeed it isn't balanced as an airplane. the point is that if you build a wig which really uses very extreme ground effect, ram air under the wings, so the air sort of stagnates under the wings, than the wings will have a shifting neutral point, not as on the wings of an airplane. Sure, the aerodynamic centre shifts on an airplane wing, but the neutral point is stationary, as long as you don't use the ram air effect.

For this effect the clearance between the trailing edge and the water needs to be very small, so most WIG's don't use it. Pitty ofcourse, because the really huge increase in lift is achieved by this effect, but on the other sides it causes major stability issues, as can also be seen on hydroplanes (flipping backwards ;))

It is not entirelly true, one can also use a gyro unit ofcourse ;), which gives new possibilities. But ah whell, here i am telling like i know everything, there are still loads'a things which i haven't tried yet!

Marijn

[metroidrc]

I just built a little wig, but i need to add the power system and rudder

[hoverman]

Great, love to see some pictures!

Here is a picture of the progress on my orlyonok model. Its is full GFK but it still is far away from beeing finished...

http://i218.photobucket.com/albums/cc320/Helipilot/DSC_0736.jpg

Marijn

[metroidrc]

wow impressive!!!!!!!!!! mine is just made out of a $3 foam glider toy!

[hoverman]

a whell, as long as it works ;)

Marijn

[metroidrc]

should be able to finish it up tomorrow... with any luck. I might need to change the motor. not sure if it has enough poop to get it up a little...

[metroidrc]

Marijn,
going to post any pics or video of that new one?
-Josh

[metroidrc]

hoverman has left the building...

[Airboatflyingshp]

You might find these of interest see the three views and look for the Hovercraft UC transport plane, experimentals, this includes the Ekranoplans and supersonic hydros http://translate.google.com/translate?hl=en&u=http://www.airwar.ru/xplane.html
Also look up Skycat and Sky Kitten airships on google.

There is a wig /hovercraft out there that uses simple fabric wings that form an aerofoil wing from a tubular spar LE and that does fly out of GE but they have it registerd as a wig and keep it lower to avoid CAA licencing/approval.

[metroidrc]

I'm not going any further with this project - I built a wig (not a hoverwig)
and it was good...

[hoverman]

damn i completely forgot about this thread, allthough it was nice to see you're wig flying metroid, on the video you send me by email.

I haven't made much progress on the orlyonok lately, considering building an entirely new one because this model is very heavy for its size, but it was my first glass fibre model.

Marijn

[y.takahashi]

damn i completely forgot about this thread, allthough it was nice to see you're wig flying metroid, on the video you send me by email.

I haven't made much progress on the orlyonok lately, considering building an entirely new one because this model is very heavy for its size, but it was my first glass fibre model.

Marijn

Hi!. hoverman san. :)
It is interested in my orlyonok :cool: .
There is a desktop model of orlyonok of the miniature in my neighborhood.
I want to have made orlyonok some time. However,
I : to a red dragonfly, SRA-1, and lCS-2 for a while because I am busy now though cannot hang in production:p. I think that it is preceded by someone :o .
Please hold out.
This concludes my report.