|Apr 02, 2007, 12:13 PM|
WIG - Wing in Ground-Effect
I don't know if here is the best place for this vehicle, but is flies and ROW...
Some weeks ago I was watching old videos from my HD and remembered a russian ekranoplan.
As we had a schedulled trip to our favorite flying site, a farm with two lakes, I decided to built something to try the wing in grond-effect concepts.
AUW is 500g, and equipment is:
2 400-sized motors with 4x3 props;
1 2-channel airplane (non-proportional) radio set;
1 Kan 950mAh 9.6V NiMh battery pack
The correct measures are not know iet, since I make it "by instinct", but it was very funny.
I just turn motors on and the surfaces were waterplaning, a few seconds more of acceleration and it was flying low, literally.
The video is very funny, around 20s per turn on a 100m closed circuit... Not bad for a toy made from spare parts.
|Apr 03, 2007, 05:06 AM|
No ailerons, no rudder, no elevator, no servo.
Just two motors and an old 2-channel toy model radio, those kind that turns off one motor to steer. I used the cheapest set I had, because I did't know what could happen.
At this first flight the horizontal stab had a incidence of 1.5degrees, so when get off water it was too nose-up.
After that I just bended it down a little to reduce the incidence. On next flights it get off water gently (I think my friend caught it on camera), so I could keep it on grond-effect a few inches over the water by turnin on-off the motors (the radio was not proportional) to keep speed (when speed increases it tends to takeoff higher, but there are no control surfaces to keep it flying).
I made a drawing for my friends, it is on portuguese but easy to understand:
Motors are 2 400-sized (PM101TR, from a local factory), with 4.1" x 3" props (GWS EP5030 cut to this size)
Battery: NiMh Kan 950mAh 9.6V
Motors are aligned 5 degrees up and 5 degrees out, so it blows part of airflow under wing. The 5 degrees out are for better turning with differential thrust.
A very cheap and funny toy, I think it is the cheapest way to get something between 25mph and 30mph on water. A single water propeller on a local hobby store costs more then I spent to make it.
|Apr 03, 2007, 05:23 AM|
CG is at leading edge of main wing.
The winglets are both side (I drawn one of then apart to show the correct dimensions) and are mounted at 45 degrees, but I am not sure if they are really needed, will try without then next time.
Wing and canard are made from 5mm depron sheet. Hull is made from cheap white insulation foam (EPS), but any foam works.
AUW is 500g with this battery pack. I tried a 1500mAh 11.1V Lipo also. With more thrust and a CG a little forward it was even faster.
|Apr 03, 2007, 03:02 PM|
We're planning a WIG run here, we named it "Formula Eka" (in portuguese eka is a sound like bleargh!! )
We will place two buoys on the lake and run several WIGs around it. With a lap time around 20 seconds it must be a funny race. With standard motors each racer must find a good balance between acceleration, speed and turning capacity.
|Apr 06, 2007, 11:12 AM|
Yesterday after some tests and talk with friends I started to make the next one. It is currently a draw and a draft 1/4 scale free-flight model to check CG.
Will use a Clark-Y airfoil on main wing and a thinner flat-bottom airfoil (probably Clark-Y reduced to 8% thickness) on stabilizer.
Incidence will be the same both on wing and stabilizer, with CG around 50% wing-chord, like an old-timer or a CLG (advice from a friend when I asked he how to make an airplane to get a good speed without looping).
In the smaller model, it worked. At low altitude the main wing gets in ground-effect and is more effective, making a lot of lift. The stabilizer generates lift too, making the CG just a little forward from CP, resulting on stable flight.
At higher altitudes, wing will have less lift, but stabilizer will have the same lift, so CG will be far forward from CP and will make it dive. I expect it will be able to increase the altitude as speed increases, but not enough to get off ground-effect.
This is the theory, on small model it worked, I will check on practice soon.
I will reduce the canard to be only a hydrofoil (or a step on hull) to help getting off water for fast takeoff.
The flat-bottom airfoil is because it is easier to start waterplanning on water with a flat hull like an airboat. The step on hull on the trailing edge is to avoild the tail from touching water.
I will try to finish it on a couple of days, so I can test on swimming pool this weekend and make a better test on an indoor flying site nearby.
As me and my friends started a little competition, there will be several designs flying soon. Most of then are most brave then me and will use powerfull brushless motors instead of cheap brushed, so I expect the speed of these toys will get over 50mph.
|Jun 17, 2008, 07:11 PM|
did you ever finish it? I've made a couple models myself, mostly the delta types. If you did finish, could you post pics? this is cool stuff!!!
|Jun 18, 2008, 10:48 PM|
Seems to me Lippisch was playing with this stuff, full-size in the 30s. Eventually, the thing flew, anhedral and all; latest incarnation was done by the Russians as a troop carrier.
I was well on my way to getting one going with a long-shaft outboard for power, reason being that I did NOT want the thing to fly. By using the outboard, once the thing got too far off the water, the prop on the outboard would come free, and it would drop back down again. Personal catastrophe put paid to that idea, but I was convinced that it would work...
|Jun 19, 2008, 07:23 AM|
I didn't finished the last one, because I'm out of hobby since that because of too many work...
But it will be my next try.
I didn't tried deltas because I was afraid of instability in case of takeoff. In my design the main design has neutral stability and the winglets provide a little dihedral effect, making it stable on air.
Did you tried it?
I liked the idea of keeping prop on water, but I am aircraft guy, I can choose good propellers for air, but I don't know anything about props on water, long shafts, and so on, and it is more difficult to get it from our local hobby stores. But I started some research on water propellers to understand it better.
|Jun 19, 2008, 10:52 AM|
Ah, sorry to mislead you, alexmag, I didn't make it clear that this was to be full-size with about 25-30hp, carrying 2 people! At the time, my work on a remote weather buoy allowed some research at a Federal Oceanography Library; talk about a kid in a candy store...
As far as keeping a prop in the water, all the necessary research has been done by the model boat boys: their vessels literally fly on the bottom half of the prop, with the occasional contact by the sponsons. Disaster is never more than a heartbeat away.
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