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Old Dec 18, 2011, 07:43 PM
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Interesting, you are quite right, making the tail and stab bigger makes it way more stable.
This one has a slower GE speed, and is rather sensitive to going to fast.
A lot better than the previous ones though, as it can travel over carpet with the same performance as over vinyl. Seems to me that it flies/hovers higher

I added instructions for how to make the first paper model (which is rather long and thin)
Have a look at them here

I have also adjusted the template to fit the new design. Print at the same size.
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Old Dec 19, 2011, 12:30 AM
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Sorry to post so much in so shorter space of time, but here is a clip of my RC vehicle:
Radio Controlled Ground Effect Vehicle #1 (0 min 34 sec)
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Old Dec 19, 2011, 02:09 AM
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Quote:
Originally Posted by sdfgeoff View Post
Interesting, you are quite right, making the tail and stab bigger makes it way more stable.
This one has a slower GE speed, and is rather sensitive to going to fast.
A lot better than the previous ones though, as it can travel over carpet with the same performance as over vinyl. Seems to me that it flies/hovers higher

I added instructions for how to make the first paper model (which is rather long and thin)
Have a look at them here

I have also adjusted the template to fit the new design. Print at the same size.
This one is a real WIG. Actually I made a few glider with the same design.http://www.rcgroups.com/forums/showp...&postcount=728
My latest RC is also developed from this design.

On the other hand I still think that, your first design is not using ground effect since it has 0 angel of attack, that means it's not producing lift at all.

Gabriel
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Old Dec 19, 2011, 03:07 AM
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Actually when I added the sidewalls I gave it about 3 or so. After several runs it was down to only 1 or 2 degrees...
I'll be starting another WIG tomorrow (based on that paper template), and will let you know what happens.
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Old Dec 19, 2011, 04:08 AM
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On the other hand I still think that, your first design is not using ground effect since it has 0 angel of attack, that means it's not producing lift at all.

Gabriel[/QUOTE]

if i may, ground effect affects all airfoils in that it modifies the airflow around that airfoil by reducing the downwash behind the airfoil and reducing the vortex induced downwash(induced drag) by throwing the vortex outward and farther away from the wingtip.

'ram effect' increases the ground effect of the airfoil when the when the wing is designed with endplates, anhedral, etc, to trap more air under the wing and thus increase press differential which in turn alters the circulation even more further reducing induced drag.

i think i'm right, please correct me...."the more we know, the more we know how little we know"
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Old Dec 19, 2011, 06:10 AM
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@ sdfgeoff: At least 5 degree AoA needed to experience visible ground effect (ram air). If the trailing edge is rising up during flight, that means the cg and the amount of lift generated by the stabilizer is not correct.

@ captarmour:

As I know:
There are two kind of ground effect. Chord and span dominated GE.
Span dominated GE is when the wing tips are close enough to the surface to reduce wingtip vortices. So this kind of GE reduce drag coefficient.

Wing chord dominated GE means when air pressure is buids up under the wind (ram air), so more lift is generated. This kind of GE increases lift coefficient. WIG crafts are specialized to use this kind of GE.

This all means that L/D ratio is increasing.

Gabriel
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Last edited by RdsG; Dec 19, 2011 at 07:03 AM. Reason: span dominated -> wing chord dominated, sorry
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Old Dec 19, 2011, 12:08 PM
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Thanks Gabriel
I think both types r always present, maybe the AR determining which dominates. The reason low AR wings r probably better is that they create more down wash to support the same load as the are pushin a smaller tube of air downwards They have to fling less air downwards harder in other words...but high AR is pushing down a lot more air so maybe it's 6 of 1, half dozen of the other...
Theoretically a big square wing with end plates would have the greatest efficiency IGE, except u need a great big draggy tail to balance it. How about trying one with a close coupled canard(tandem). If it is trimmed for a slight descent OGE the up wash IGE may keep it balanced, however you wil need a forward CG...anyhow enough rambling!
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Old Dec 19, 2011, 12:37 PM
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Actually best performing wings are always the high AR ones. And it doesn't matter if the wing in or out of GE. I mean high AR wings in ground effect would be even more efficient but GEVs have to meet requirements that do not allow the use of high aspect ratio wings.
With big spans you can't turn in GE, on the other hand shorter chord length means lower flying height in GE. So that is why GEVs have relatively low aspect ratio wings.
Composite wings (low aspect ratio+high AR wing in right combination) are the best solution to reach max. efficiency.
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Last edited by RdsG; Dec 19, 2011 at 12:50 PM.
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Old Dec 19, 2011, 05:32 PM
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Makes sense, i saw a low AR GE vehicle with high AR OHS, I'll look to c if I can find it. Thanks for that info, I like it!
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Old Dec 19, 2011, 07:38 PM
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And another prototype, the paper-template one now made in balsa and paper.
Size: 19x12cm
Weight: 5grams (not sure the scales weigh accurately down that low though)

Performance:
Floats quite clearly in GE, good 0.5-1cm, possibly a bit more.
Good range of speeds without flipping or touching the ground.
Seems stable enough when going.

I tried under RC (without rudder 'cause it broke), but the weight seemed too much for it. It was an extra 9 grams. This takes it's wing loading from roughly 2g/dm2 to over 12g/dm2. (No idea exactly how much noseweight I had to stick on it. I had the prop mounted on the rear stab, which wasn't a good idea)
Red Line is CG (actually it's slightly further back)

So when I get my hands on some foam, and a hotwire I'll start on a proper RC GE vehicle.
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Old Dec 20, 2011, 05:02 PM
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It's the smallest GE glider I have seen

My experience is that bigger/heavier models works better even with much higher wing loading.
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Old Dec 20, 2011, 09:00 PM
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That's what I figure, so if it work s ok at this size then it should be great at a larger scale. I made a hot wire and will hunt down some foam tomorrow.
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Old Dec 21, 2011, 12:04 AM
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hotwire + packing foam = the best tools ive used since the exacto blade
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Old Dec 23, 2011, 09:54 AM
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Quote:
Originally Posted by RdsG View Post
Actually best performing wings are always the high AR ones. And it doesn't matter if the wing in or out of GE. I mean high AR wings in ground effect would be even more efficient but GEVs have to meet requirements that do not allow the use of high aspect ratio wings.
With big spans you can't turn in GE, on the other hand shorter chord length means lower flying height in GE. So that is why GEVs have relatively low aspect ratio wings.
Composite wings (low aspect ratio+high AR wing in right combination) are the best solution to reach max. efficiency.
gabriel

just an idea for a high/low AR design where wingspan is 1.5 times wider than mainwing chord. outerwings with dihedral but sweepback will cause TE to be at same level as main wing, ie is from wingtip to wingtip TE will be one straight line.
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Old Dec 23, 2011, 10:10 AM
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Would it have OGE stabilizer?
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