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Old Jun 30, 2010, 07:45 AM
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Cool the contest, hope they will post pictures too!

Also nice to see the pictures of Bruno's Wigs on the Yahoo group, I am most interested in the Wing profiles. He uses the Bixel shape, but I believe he is using odd shaped fully symmetrical profiles, instead of flat plate wings. What would this do with the pitching moments

I looked up some aerodynamic measurements from thicker symmetrical profiles, they don't seem to give the same CP shift as Bixel described on his flat plate wings. Also, even the large oneman sized bixel, has this box shaped wing, with a blunt trailing edge, instead of using a more aerodynamical symmetrical profile, so there must be a difference otherwise he wouldn't have done this.. I guess!

BTW, I didn't manage to find the video of the Cushion crow, I'll give it a try at my parents computer in the weekend, maybe I have it in some of my older folders. On the video you could see the model accelerate and unstick from the water, at a fairly high angle of attack.

Marijn
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Old Jul 01, 2010, 07:35 AM
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Today I made an experiment with GM2, and I crashed it...

I removed the horizontal stabilizer. First I made this experiment on the glider. I found the new CG position, then I made the modifications on GM2. First it was a little nose heavy, but then everything went good. Except one thing. Its turning was hectic. I guess it caused by the new CG position, which was placed further back. Once I made a sharp turn, it's left side lifted up (higher then normal), and wind lifted up the whole craft, almost rolled it over. Landing was hard. It's fuselage partly ripped of, but it seems to me the motor, and the electronics are fine. I only broke the propeller, because it hit the battery (the battery get loose during the crash).

It can be repaired, but I think I will build an other ekranoplan. It won't be a Bixel type again. There is many other configuration I have to build

Gabriel
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Old Jul 01, 2010, 11:50 PM
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wow i'm thinking that a depron cushioncrow is in order! that thing looks awesome
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Old Jul 02, 2010, 05:00 AM
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Quote:
Originally Posted by derk View Post
wow i'm thinking that a depron cushioncrow is in order! that thing looks awesome
Cushioncrow? Maybe
But I also considering a Jörg-type tandem...
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Old Jul 02, 2010, 11:47 AM
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Haha that looks great haha, don't know how you should call it. If you build it, don't forget the stabiliser, this profile isn't autostable and the cushion crow had quite a stabiliser too

Tomorrow, if everything goes right, I'll fly my commercial pilkot license(yes, I did the instrument rating first), then I'll finally have time to test and film the Lippisch!

Marijn
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Old Jul 02, 2010, 05:09 PM
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Thanks! I built its glider version. I didn't tested it yet, perhaps tomorrow.
I added the stabilizer as you advised.

I won't have a net connection until Monday or Tuesday till then good luck and good speed!






Gabriel
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Old Jul 05, 2010, 01:27 AM
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Looks cool, really wonder what your results are going to be, and if the thick wing offers an actual advantage. I didn't find the cusshioncrow video, I did however find a picture of this craft:

If you look closer at it, it actually isn't far off from the cusshion crow design.
In this configuration, it looks a lot more realistic

Marijn
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Old Jul 06, 2010, 02:15 PM
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Hi

This thick airfoil/lifting body design could work, but not for me :P My guppy-like glider always do pitch up movements. It managed to do some high alpha gliding, but it's very unstable, and very ineffective.

I built an other glider, which combines the best working elements of my flat airfoil ekranoplans.

It has large, very low aspect ratio main wing, a smaller, but also low aspect ratio outer wing. Their CPs are in different positions. So it's something like a tandem wing. It's not that stable, but wings don't disturb each other. Both wing has its own side-plates. It makes the model more resistant to surface unevenness. It also has a large T-tail which makes the craft absolute stable. It has at least three times larger ground clearance than my bixel glider at the same speed. Smaller side wings have flaps for trimming. In head wind it was able to float for a sec at the and of gliding. Its glide distance is also bigger than my other gliders, and sometimes its able to get back to ground effect without touching the ground after a bad toss or wind lift. I could see how its bouncing on its air cushion.






Gabriel

ps: How was your weekend? Did everything go OK?
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Old Jul 07, 2010, 03:58 PM
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Hey Gabriel,

I passed my Commercial Pilot License exam, I have never had so bumpy weather, but the Cross wind landings were great

Your model looks interesting, a sort of reverse Bixel? I had two pictures of these WIG designs, have you seen them?



Funny that the stability seems to be just as good as the Bixel craft.

I haven't found time to test the Lippisch again, I hope to fly it before the weekend though.

Marijn
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Old Jul 07, 2010, 09:32 PM
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ok here is my micro rc lippisch style WIG:

8.25 inch span
10.5 inch length
7mm pager motor with 45mm prop
receiver from a kyosho cessna
100mah single cell lipo
weight is 17.4 grams with balance weight added

i got this one going freeflight first, then added the radio gear. its pretty quick, maybe 15mph tops. it flies about 3 inches stable with a pull to the left, it has a very slow wide turn radius, maybe 30 feet while in ground effect.
with a better thrust line it should go straighter, and with a lower thrust line it should improve the ground clearance.
no video yet but i will try.

also this is NOT intended for water use
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Old Jul 08, 2010, 01:39 AM
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@hoverman

I have seen these WIGs before, but I didn't realized that they have the same configuration as my glider. I started to build it without plans :P It's hard to find a really new configuration

@Derk

It's a nice little WIG! I think it's the smallest rc WIG I have every seen I always wanted to build a micro size rc WIG like yours. Unfortunately in Hungary it's hard to get the electronics, or they just to expensive :/



My next experiments will be about circular wing WIG like CLST's ES-1. On the photo version 03 didn't have stabilizers and prop. I guest it's towed or it's a ground effect boat or it's just a displacement test with the unfinished craft. On The WIG Page says :"The craft is also referred to as E-120 by some sources, but this is believed to be incorrect." E-120 and "CLST" can be seen on the wing. Font type is also the same. So there was at least two version of this craft.
Version 02 had manned and unmanned flights on Moskva river. It had a two stroke motorcycle engine.

Gabriel
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Old Jul 09, 2010, 06:37 AM
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So, finally some time to test the Lippisch model! The results were..as positive as they were bad There are two design flaws, the first is that the forward hull is too small, and too shallow. I partly compensated for this by adding the two foam blocks, but a whole new hull is needed to really solve the problem. Currently, It needs full up elevator and full power, to keep the nose up enough. During acceleration you can lower the elevator, but for Take off it is always needed.

Second of all is that the stabiliser is located exactly behind the propeller
this gives you excellent pitch controll, but as long as your applying power, the Stabiliser is giving muuuch more lift, than what it was trimmed to do for. So as long as your applying power you'll need full up elevator to keep the nose level, otherwise it will nosedive. If you cut the power during flight, still giving up elevator, it will fly out of ground effect..blabla

Anyway, it is a pain to fly

But, my brother made a few nice pictures, here are some of them:

Take off, the wing is allready lifting and you can clearly see the airgap between the trailing edge and the water:


A rather crude Take off:


and a high flying flyby, you can clearly see how it looses roll stability as it ascends in the ground effect:


This is what happens if you don't apply more up elevator when increasing throttle:


And this is what happens if you don't decrease the up elevator when decreasing throttle


And finally after several rather lucky crashes:

And the rescue boat:


So...Time for a new model, a longer wider front hull, a slightly higher angle of attack for the main wing, and a much higher located stabiliser(outside of the prop wash!)

Cheers,

Marijn
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Old Jul 09, 2010, 07:25 AM
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cool
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Old Jul 09, 2010, 02:13 PM
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So, I build a new hull, I scrapped the wings of the old model, why build new ones?

It looks even more ugly than I had thought, but a well, if it works... suits me





so..now painting the new parts.

Btw, cool Lippisch model Derk, small but effective!

Marijn
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Old Jul 09, 2010, 03:37 PM
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Ugly? IMHO Lippisch WIGs are always beautiful

Did your electronics survived the crash(es)?

Better luck next time!

Gabriel
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