Seeking Ground Effect Craft Info

Hang gliders is a development of the "Rogallo" wing and is stable because of the low center of gravity with the person flying underneath.

64 lbs/ft2 is much higher than your design goal of 7 lb/ft2 (post number 4).

 

Leo,

Sorry, I should clarify. I found a lot on google also, but the reason I posted on Boatdesign.net was in the hopes of finding some more obscure projects and knowledge that might not be found on google. I'm hoping some of the people here might know of backyard projects, homebuilt designs, or maybe projects in the 70's, 80's, or 90's that never got posted to the internet yet. I was also hoping to get in contact with someone who has actually designed or built a WIG craft, especially something small. I really want to know what challenges came up during construction and testing.

 

Here is another ground effect machine on water.
http://www.gizmag.com/go/6864/

http://images.gizmag.com/hero/6864_21020763011.jpg

 

rxcomposite,

I'm well aware of the history of hang glider development, and why they are stable. There are clearly huge differences between them and my design.

Please help me understand what you are trying to tell me about the wing loading. I agree that 64 lbs/ft2 is much higher than 7 lbs/ft2. That means each square foot of wing needs to develop that much lift for the craft to fly. How does it accomplish that? It seems to me that it either needs to fly faster, have a higher lift foil shape, use an extra force such as ground effect, or a combination of these factors. It seems to me that a lower wing loading, such as 7 lbs/ft2 would require much lower airspeed and allow a more forgiving and stall friendly wing. I may be misunderstanding something (actually very likely!) so if you have the patience, please explain what you are trying to tell me about the wing loading. I'm open to learning!

 

rxcomposite,

Thanks! That skimmer link is exactly the sort of thing I'm looking for!

 

Wasn't that a proposal rather a fully-tested production vehicle? It looks like
another idea where wishful thinking has preceded maths and engineering.

 

Leo,

Yes, it was a proposal, but I hadn't heard of it before. I want to know which projects didn't work as well. But, you are right, I am still looking for completed and flying projects that I haven't heard of yet.

 

(That means it needs to generate about seven pounds of lift per square foot,) 64 lbs of lift/ft2, we are talking of the same thing, not wing loading. The article appeared in Popular Mechanics several years ago.

If I were you, I will build a styrofoam model and tow it with a small boat. You willl be able to find at what height the towline should be. As the WIG becomes airborne, the towline angle quickly changes. Maybe you need a bridle line. You will also be able to see how to coax the WIG to detach from the water. Airflow above the wing surface would not be enough to create lift with the the lower surface in contact with water.

 

Yes it is! "Verhagen is now seeking partners in his project. “For the next step in the development from concept to product,"

 

rxcomposite,

A foam model simply would not fly with any control. This design needs a rider to make fast and constant adjustments, much like a bicycle. If you tried to build a model bicycle it would roll a few feet and fall over without a rider balancing on it.

A bridle attached to the wing is extremely dangerous. There is a history of flying inflatable towables that have hurt many people because the towable is attached to the tow boat. Being able to let go is part of the safety of the design, especially as speed increases. When the wing reaches 25 - 30mph there should be too much drag and pressure for the rider to hang on. That way, it can't reach speeds that would allow it to fly out of ground effect. The wing can't go "kiting" around out of control behind the boat (especially with a rider on it!) this way.

As for the height of the towline required, please refer again to my foilboards. They require the ski handle to be raised and lowered by the rider, and in fact this is the primary means of altitude control, even more than shifting the riders weight. It takes a little bit of practice but is easily learned. I believe something similar will happen with my wake wing design. The rider will be required to raise and lower the handle to augment altitude control.

Also, detaching from the water surface will require the wing to be at a very high angle of attack. This will be accomplished by putting most of the riders weight on the back foot. This will rock the wingtips back, closer to that water, increasing ground effect for take off. As soon as the wing is airborne, the ground effect will immediately decrease as angle of attack decreases, keeping the board close to the water.

I still don't understand what your point is about the 64 lbs of lift. Should I be trying to achieve higher lift/ft2? Less? I really don't understand. Please don't think I'm stupid, I'm just trying to learn.

 

If you don't mind some kind of rod(s) attached to the base and sticking into the water with control surfaces at the rod's end, that might be a way to steer/add stability/control height by the operator. Also an interlocking deadman switch design with adjustable slow release (elastic?) might help the safety issue, perhaps more reliable than relying on letting go of a tow handle in a freeze/panic/fast response situation... Also letting go of the handle might mean tumbling with the craft and possible injury from contact with hard parts or flying pieces. Would there be injuries from just water impact at 20mph, even if the vehicle is pulled clear away from you?
Sorry, just trying to think out of the box, FWIW.

PC

 

portacruise,

Thanks for the comments and thoughts. I agree that something trailing in the water might help stability significantly. That is why the tails are designed to trail in the water except when the wing is near it's maximum altitude.

The elastic idea is good, but the wing is already designed to have so much drag the you can't hang on past 25-30mph. You won't have to remember to let go, you won't be able to hold on if the speed limits are exceed.

As for hitting the board or the water, I ride surfboards and foilboards behind boats all the time, and sometimes I do hit them. It is a risk in any board sport. A helmet and impact vest are advisable for all these sports. Also, I hit the water at 20-30mph dozens of times every time I ride. It is usually fun and not a problem.

I really appreciate the comments and thoughts outside the box! Unless all the problems are addressed I will never be able to make it fly safely!

 

In the spirit of discussion, and to be a constructive part of your education - may I say , you seem to have no concept of the difference between the two mediums.

If you think you have to be fast when riding on 'solid' water, air is a like riding smoke.

"Water has a density of 1000 kg/m^3. If you had a meter cubed of water it would weight about 1000 kg. Air that is near sea level has a density that averages 1.275 kg/m^3. If you have a balloon containing a meter cubed of sea level air, the air itself would weight only 1.275 kg. ... volume of air at sea level has 0.1275% of the density of the same volume of water"

Pictures are the last thing you need right now, what you need is to pay someone to do the calculations you obviously cant do yourself.

If you cant calculate the pressures/lifts of the board at the different angles of attack using math, all the 'illustrations' in the world wont be of any use.

 

What happens to the vehicle when the handle is released or the rider knocked off? Do the wings catch the water surface and stop suddenly or can a coast down mode be employed?

PC

 

rwatson,

Just because I haven't shown all the math on my site doesn't mean that it hasn't been done. I have studied the characteristics of many different airfoils, and by choosing an existing shape many of the calculations of pressure and lift at different angles of attack have already been done. I have also done the calculations myself on many different shapes that I thought might work better four years ago when I first started designing this.

Thanks for the lesson in the difference between the two mediums. As someone who flys, hang glides, windsurfs, kitesurfs, wakeboards, foilboards, scuba dives, and designs and builds hydrofoil sailboats, powerboats, and watersports equipment, I feel reasonably solid in my understanding of the two. However, I'm not closed minded and am very interested in learning new and useful information.

Maybe in order for me to understand your criticism better, can you explain to me exactly what you think will happen to the board when some one tries to ride it? Will it flip? Oscillate in pitch? Yaw uncontrollably?