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Old Jul 14, 2010, 03:58 PM
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I think the bottom of the wing has to be straight / flat because all the models I've tried flat wings have flown better than those who had curbed.ex1

Wing also in the back has to be completely horizontal so that when you leave the water to drain completely and not only part and the other miss aire.ex2

Also, in some models of very low rate lipisch flight along the trailing edge of the wing to an upward curve for air and then unzip the wing hit the ground as it occurs along the wing maintains all on the ground although some models can not be achieved. ex3

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Old Jul 15, 2010, 01:28 PM
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Hey,

I know that flat undersides work a bit better, however till now I have found that the shape of the underside doesn't change the performance a lot.

But, the idea of using a symmetrical profile, was to test if the pitching problems, encountered on WIGs, can be solved by using these profiles.

And, as we have found in the other thread, flat profiles and maybe even the thicker symmetrical ones, do improve the handling a lot(just not the performance)

So, the curved symmetrical profile without a flat bottom actually had its reason, but as RDsG, Derk and me have found in the General Ekranoplan Topic, it is possible to build stable WIG models with curved profiles as well, and you're right, they do perform better

Marijn
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Old Sep 11, 2010, 05:36 PM
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So...it has been a long while since I last touched this model, but I had promised it will fly again. Anyway, as can be found in the General Ekranoplan Topic, I made quite some progress on other WIG models since I built this one, and I must say that I learned quite a lot about CP movements, but also on directional aquaplaning stability.

So..Either, I would someday build a totally new ekranoplan, or I would adjust this one.

One thing was certain, the whole bottom of the model had to be replaced, as it was generally wrong. It had two hullsteps, one lying far behind the CG, the other one lying alltheway under the nose. As the model rises on step, it won't just ride on the rear step(because of it's location), but also on the front one, allthough that one wasn't meant to do that. The result is that it becomes directionally unstable.

The new bottom had to future 1 large step, located infront of the CG(but not too far), to give the model a slightly nose up attitude. Buy using a keel behing the CG, it will still be directionally stable.

Blabla, hard to describe, I will show a quick drawing: (look at the bottom)


The other change is, it will feature 3 engines this time, allthree located in such positions and angles, that alltogether they cancell out the moments, thus not interferring with pitch stability. They are placed in such a fashion that the front two motors will permanently provide PAR.

Anyway, I don't have the slightest idea when I will have time to finish this, as I allready have only 2 days for the next weeks, and I also have to test the Heliferry model. But still, here are some photo's of today:

This really hurt:






Then I started on the flaps:





Next step: sanding the bottom!

Marijn
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Old Sep 13, 2010, 02:16 PM
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hello, sorry for the delay, I had a very bad problem with internet.

The model is interesting but maybe two servos to control the flaps are better than leaving the flaps fixed.
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Old Sep 15, 2010, 01:58 AM
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Well, the point is that I Messed up the position and angle of the main wing when building this model, so I would either cut off the wings and build new ones, or try this. Flat wings provide better Longitudinal stability, but with the large stabiliser on this model, I figured it should be possible to make this thing stable, even with very strongly curved wings.

So, I added flaps, to curve the wings and correct for the positioning error, and at the same time, create a better cavity for the PAR. As I am not going to make the engines rotatable, I am just going to mount them fixed in an upward position, the model is always in "Take off Mode".

Alltogether, I decided to fix the flaps in this position, because I can't figure out what the real advantage would be if I could move them, except for the model going a bit faster. It's just proof of concept

Marijn
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Old Sep 19, 2010, 02:02 AM
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Anyway, there was way too much wind to test the heliferry, plus I had to finish painting the pushboat, so I had some time to continue on the Spasatel. I finished the bottom by sanding it into shape, then using acryl base paint(and sanding in between) I smoothened it out, and then covered it with cray acryllic laquer.



I also added some windows, and the two front PAR engines. The one on the tail will follow soon!






Marijn
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Old Sep 19, 2010, 07:45 AM
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So..the progress of today, the 3d engine has been fitted, pointing slightly upwards, wchich allowed me to set the front engines more upward too.

Then the soldering began..about 2 hours Never had so many cables in one model! Anyway, everything is finished now. The controll layout:

Throttle = all 3 engines
Yaw = rudder
pitch = Elevons up&down
roll = Elevons differential







Looking good
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Old Sep 19, 2010, 01:20 PM
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Well guys, be prepared to be overwhelmed with a bunch of photo's, I just can't post enough of them to show my enthousiasm!

From this you can conclude that the testing was a succes

I tested it twice today, Once you power up, to nose of the model rises steeply, because the bottom side of the hull below the tail really gets sucked into the water. Anyway, this was an easy fix, I added a small foam block behind the second step, to create a sort of third step.

On the second test, it shows that if you power up quickly, the nose still rises steeply, but then comes down again, afterwhich the model immediately planes on step, and Takes off after just a few meters.

What about flying? Well, all the controlls work, Rudder, roll and elevator, but I found that playing around with the elevator too much often results in "crash" landings. If you apply only a bit UP elevator, and keep your finger steady, it can really fly up to about 20-30 cm's, and you can make real banked turns, whitch the sponson skimming the surface!

Enough talking, just watch!


Overenthousiastic Take Off


Than flying:


Than real flying:




Banked turns, No problem!






& Landing:


How cool is that

Haha sorry, I am just too glad that it works!

Marijn
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Old Sep 19, 2010, 01:44 PM
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woooooooooooooooooooooooooooooooooooooooowwwwwwwww www

this is legendary   

is realy beautiful    

congratulations     


im waiting the eliferri
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Old Sep 20, 2010, 04:07 AM
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Haha cool isn't it!

Never thought it would work so well, straight away, without any big changes. I didn't even have to change the CG

About the heliferry, the current model has been put on hold, I am first going to build a more conventional model without surface piercing hulls, to test some features, before I am sending the Helicopter to it's death

But first I'm going to enjoy this model a bit more

Marijn
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Old Sep 20, 2010, 10:36 AM
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Congratulations Marijn!

It looks really cool!

Gabriel
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Old Sep 20, 2010, 11:57 PM
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awesome, glad to see it worked so well

so are you going to try for a larger one with MORE motors?
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Old Sep 21, 2010, 02:51 AM
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Thanks Gabrial, I couldn't be more happy about the results

Quote:
Originally Posted by derk View Post
awesome, glad to see it worked so well

so are you going to try for a larger one with MORE motors?
Haha now that would be cool wouldn't it I had thought about it, allready with this motor setup this model is vastly overpowered. I can easily Take off using 60% throttle But allready, it is quite large, this one is 1.5 meters long, with the wings stuck to it in one piece, so I can hardly fit it up the stairs.

But building a 2,5 meter long model of "The" Caspian Sea monster, the KM..hmm

Maybe after the heliferry

Marijn
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Old Sep 23, 2010, 02:34 PM
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Nice job Marijn!
Aymeric.
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Old Sep 24, 2010, 05:37 PM
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Thanks, nice to see you here too! Looking forward to the model you guys built actually skimming the wavetops

Marijn
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