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Old Aug 10, 2010, 02:29 PM
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Hi Marijn!

I read through the site, and I think this heliferry is a great idea. Obviously more complicated then a simple wig, but it could eliminate several disadvantage that WIGs have.

I have no experiences with helis and autogyros at all, so I don't how complicated could it be, but I think if someone could build it, it would be you

BTW nice drawings.

Gabriel

Ps: Why did you choose Bixel configuration?
ps 2: My only useful observation about bixel is that the rudder should be as far from the CG as possible. So I think the design with the tail should works better.
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Old Aug 10, 2010, 08:53 PM
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so, is it an autogyro or a helicopter? as a heli type, the thrust would blow all over the top of the wings and eliminate most lift from it....
i guess if it were like an autogyro, it would have a shorter takeoff speed as do normal gyro's. its interesting thats for sure
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Old Aug 11, 2010, 02:46 AM
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Quote:
Originally Posted by derk View Post
so, is it an autogyro or a helicopter? as a heli type, the thrust would blow all over the top of the wings and eliminate most lift from it....
i guess if it were like an autogyro, it would have a shorter takeoff speed as do normal gyro's. its interesting thats for sure
As I know it is an autogyro which able to provide enough lift to take off during the pre-rotation process.

I don't know how this "rotor above the wings" configuration could works. However there are helis which has wings under there rotors. For example the mil mi-6. Its short wings give 20% of the lift during forward flight.

Gabriel

PS: This type of autogyro is called gyrodyne or heliplane.
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Old Aug 11, 2010, 03:40 AM
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Quote:
Originally Posted by RdsG View Post
Ps: Why did you choose Bixel configuration?
ps 2: My only useful observation about bixel is that the rudder should be as far from the CG as possible. So I think the design with the tail should works better.
You're right, and we haven't established the final configuration yet. I am more of a fan for the long tail with pusherprop all the way on the rear, but this isn't going to be the final configuration for the actual heliferry, so we don't want to change the design too much.

Why the Bixel? Well, initially it was Lippisch, but Luc stated that there are certain oscillaitions in cruise flight which don't seem to dissapear on a reversed delta wing, thus he wanted another configuration. At first he suggested using the Tandem wing, which I strongly rejected because..well if you are going to use a rotor for Take off, you know that during the Take off run the altitude will probably vary quite a lot. And as we have seen, Tandems hate one thing the most, that is flying just a bit higher than what they are designed for

Thus, the Bixel shape, as it simply provides incredible stability, in&out of GE.

So...Autogyro or Heli?

Well, actually it is a Ground effect flying Cartercopter.

If you want to read about this concept for some hours:P:
http://www.cartercopters.com/faq-general.html

It comes down to beeing an Autogyro with wings. Before Take off, ti pre rotates it's rotor, than applies forward thrust and at the same time positive pitch to the rotor, to make a sort of Jump take off. It then continues to fly as an autogyro, but as it speeds up more and more, the rotor is lowered in pitch more & more, and is then slowed down. It keeps turning so the Centrifugal forces keep the blades straight, but further it's just a very flat disc, producing little drag. It is then flying like an airplane.

Now this is quite a mouthfull, and building a model of this concept..phew! And then on top of it, imagine combining it with a Wig..

So, we went down to the basics of what we really wanted to test, that is more like..can you do a Take off with a WIG, which can't TO on it's own power, but can using a rotor, and can then fly in GE, without using this rotor?

This sounds the same, but it's easier. You can now take a normal Collective pitch helicopter, and mount it ontop of a WIG. You take all the controlls from the swashplate on the transmitter, as normal, so Cyclic pitch&roll, Collective pitch, and yaw. On the throttle channel, will be the engine for the rotor, the engine for the thrust, and the collective pitch. It will be mixed like this:

@ 0% throttle: no engine running, no collective pitch

@ 50% throttle: both engines running 100%, no collective pitch

@ 100% throttle: both engines running, positive collective pitch

So, during Take off, the throttle is pushed forward, the rotor and thrust propeller spin up, the model starts to speed up a bit, the throttle is then pushed even more forward and collective pitch is introduced. The now lifting rotor lifts the model out of the water, afterwhich it rapidly accelerates, and the Bixel wing starts to lift. Then the throttle is reduced again, till the collective pitch is 0 again.

Nothing like an autogyro, but the concept is proven like this

So.. colelctive pitch heli, bixel wing.. owyeah, the surface piercing hulls.

Take a look at this thing:
http://www.centaurseaplane.com/

That's why

Marijn
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Old Aug 11, 2010, 08:42 AM
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Just pictures and some info (that you perhaps didn't see):

http://obimapua2004.multiply.com/journal > 4th place, a corroplast ekranoplan model.

And models of the Russian concept with two different wing panels ("reversed bixel"):

http://77rus.smugmug.com/Military/IS...39_xfDc7-O.jpg
http://77rus.smugmug.com/Military/IS...04_QdU5u-O.jpg

Gabriel
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Old Aug 11, 2010, 11:27 AM
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Nice model, looks sort of like an underpowered hydrofoam. Pitty they don't have a video of it

Nice High Res pictures btw, just another company trying to commercialize WIG's. Are you planning to build a new model soon?

Marijn
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Old Aug 11, 2010, 05:01 PM
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Marjin, the idea is good, is a new concept and could work but I have a hunch that not fly so well as you expect.

I bring you a link to the University of singapore, where a ekranoplano desarroyan lipisch model, have 2 videos and pictures of what I think is the program called autowing and some other things.

http://dynlab.mpe.nus.edu.sg/mpelsb/...gid/index.html
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Old Aug 12, 2010, 05:47 AM
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Quote:
Originally Posted by hoverman View Post
Nice model, looks sort of like an underpowered hydrofoam. Pitty they don't have a video of it

Nice High Res pictures btw, just another company trying to commercialize WIG's. Are you planning to build a new model soon?

Marijn
Yes, as I mentioned I want to build a small rubber band WIG. I have the "motor", now I just can't decide which configuration and how should I build. And in the mean time I am looking for better better rubber bands. It will be my first rubber band model so I don't have too much experience with it.

Gabriel
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Old Aug 12, 2010, 11:50 AM
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Hi

My first rubber band WIG. Simple Lippisch design with PAR. It could fly 10-13 meter. It's able take off without help from block paving. Unfortunately it's rubber band stretched so It could be better with a new rubber band.



next to a 30 cm ruler:



Gabriel
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Old Aug 12, 2010, 03:18 PM
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Simple, but effective! does it realy improve of it's PAR?

BTW Gabriel, as the Heliferry is going to use a Bixel wing, were was the CG on your model? I want the rotor to be approximately on the right place, and the Bixel documents don't show it accurately. Could you measure it up? (distance CG compared to the chord) I trashed my Bixel model a while ago

Marijn
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Old Aug 12, 2010, 04:07 PM
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Hi

Bixel's CG... Honestly I don't know. My model's CG: it was 790 mm long, the CG was at 367-370 mm. The problem is that the stabilizer had zero incidence, but in flight the rear of the craft lifted more than the front, so the stabilizer should have a negative incidence :/ So I removed the stab, because I thought it is useless, more over it just pushed down the craft. As I remember I should moved the CG back to 400 mm. But I think wasn't enough. But it is remained a mystery since I crashed it. I think the crash was due to that cg was to close to the rudder.
My model was built according to this drawing: http://www.twitt.org/WIG_Dbl_Wing.gif (middle one) If I am right, it shows the CG at ~337 mm if the model is 790 mm.

Gabriel
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Old Aug 12, 2010, 04:38 PM
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Video of the rubber band model:

PAR really helps at take off. It need just a little push and it is on cushion...

Rubber band ground effect model (0 min 27 sec)
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Old Aug 12, 2010, 05:57 PM
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seems to work well, I do not like the ruberband is that the principle is stronger than during the flight, but in case of ekranoplanos this extra force is useful at first to get off the ground u.U.

ps: your dog is beautiful, that sure is the envy of the neighborhood
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Old Aug 12, 2010, 06:15 PM
BEOWULF
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it works great

love the dog
Quote:
Originally Posted by RdsG View Post
Video of the rubber band model:

PAR really helps at take off. It need just a little push and it is on cushion...

Rubber band ground effect model (0 min 27 sec)
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Old Aug 13, 2010, 03:20 AM
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Haha nice dog! And the model seems to work great! Very stable, and it also flies in a straight line Next an RC version?

About the CG, thx, I remember that I tried a whole range of CG's on my model, with different stabiliser settings, and it seemed to work on all setups, really a great concept! Anyway, I think I am going to detirmine the correct CG with a small non powered model first. I want the rotor to be exactly above the CG.

Marijn
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