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Help with my own creation

Old 03-24-2010, 01:35 PM
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Default Help with my own creation

Greetings guys.

As a complete newcomer here, I hope I am posting in the correct forum.
Below is a creation of mine I would like to turn into reality. It is modelled in Blender 3d and hopefully sometime in the near future also in balsa/foam etc. Before I hear comments regarding the practicallity of it all, let me assure you that I am well aware of the problems regarding counter rotating props, flying planks etc. Who was it that said we do things 'not because they are easy, but because they are hard' ...

Needless to say I have created a few problems for myself. If it is unclear on the picture let me explain a bit. The propellers are counter rotating, sort of in the middle of the fuselage, this obviously creates a problem as the fuselage in front of and behind the propellers are stationary. How can I connect the twofuselage parts, with the spinning bits in the middle?
Has anybody got an idea of a good wing airfoil for a flying plan?

I would like to go electric initially, because I think it would be the easiest and cheapest approach. Once the hickups are ironed out, I would realy like to build a gas/nitro version. What would be a good approach to match electric motor to model size?

Thanking everybody in advance
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Old 03-24-2010, 06:48 PM
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Default RE: Help with my own creation

looks very interesting
but if you are a newscomer to the hobbie( if I understood right) it will be very dificult to start from a plane this complex.
Only way to keep the 2 fuse halfs stationary is to connect them with a shaft in the center of the prop hub but I cant think of an easy way to do this. maybe a shaft with bearings and gear driven outher race..........
I wish you good luck and keep us posted, this will be the most interesting project if you get it to work
Old 03-24-2010, 07:25 PM
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Default RE: Help with my own creation

Other than aesthetics, what would be your reasoning behind having counter rotating props in the middle of the fuselage? To go even further, why counter rotating props?
You will have a very nose heavy issue here to contend with and certainly electric is the way to go. Unless you are a machinist and can do a ton of work/rework to your engines, glow gas will be almost out of the question with any stock engines available.
Also, you have omitted the stabaliser. Again I would have to ask why? Are you trying to work backward from a certain "look" and then trying to make it work, or do you have a performance objective in mind?
It certainly looks interesting and good luck. You have many hurdles here. Have you ever heard the story of the "Bugatti" pylon racer? I think you would very much like this unique design. Do a google search for this dual propped machine.
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Old 03-24-2010, 08:15 PM
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Default RE: Help with my own creation

Why not use a ducted fan, side discharge.
Old 03-24-2010, 09:45 PM
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Default RE: Help with my own creation

Well, for the fun of it I drew this up just to see where my mind would go. Got to thinking about how to eliminate a traditional prop hub so some fuselage structure could be passed thru a rotating prop. Looks unpractical and expensive but definitely possible.
Cheers.
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Old 03-24-2010, 10:09 PM
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Default RE: Help with my own creation

The ducted fan is a good solution.
Old 03-24-2010, 10:20 PM
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Default RE: Help with my own creation

The main problem I see is the structure connecting the two-part fuselage.
That structure must be internal, then your propellers must be mounted on two floating rings, actuated by belts of gears to the motor/motors.
These rings must have face or thrust bearings in order to transfer the thrust force to the fuselage.
In a normal propeller mounted on a shaft, this thrust force is transferred to the fuse via shaft-bearings-crankcase-firewall.

Being a tailess, your airfoild should be reflexed, for pitch stability.
It is basically a fying wing with a stretched fuselage-tail.

Good challenge!!!
Old 03-25-2010, 12:08 AM
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Default RE: Help with my own creation

You're going to want to shorten the fuselage a bit. Plank style flying wings do not have a lot of pitch control leverage, for lack of a better term. Because of this long fuselages such as you're showing leads to the design wanting to over rotate during pitching maneuvers and to set up a fugoid oscillation in pitch at some flying speeds.

Now there's two ways to make it a little better. One would be to shorten the fuselage. The other would be to widen the wing chord a bit. But as it sits now a "real" one would be too heavy in the nose and tail to fly well. You may make it work with a model but only by making the nose and tail extremities far lighter than a possible full sized version would be.

And from a nit picking point of view I'm guessing that the hole in the nose is for radiator air intake. But I don't seen any air outlets. What goes in has to come out. Even if it's just for cooling the engine or motor that you'll be using to drive this thing.

The others make a good point about the need for a good stiff connection between the "engine" in the nose and the rear portion. It'll need to be joined with a tube of some sort to be both light enough but strong and rigid enough. I said "strong and rigid" because the two are not the same thing. Strong implies that it needs to withstand the loads that will be experienced by the weight of the "engine" in the nose during high G's. Rigid implies that it will not flex enough from that same G force to cause the drive system to bind up. Your sketch looks good but your fuselage "rail" should be a lot larger in diameter to properly support the loads and not flex to a detrimental degree.

Other than these sadly real world observations your design made me smile a lot. It's extremly Crimson Skies influenced or very worthy of inclusion in that game if you didn't know of it before.
Old 03-25-2010, 02:04 AM
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Default RE: Help with my own creation



Hi guys and thanks for the the comments.

I am not completely new to the hobby, just to scratch building and power flying bit. I have flown gliders in the past and a friends Zagi and have joined a club recently to do a bit of power flying. Then the bug bit. What can I say, power flying got under my skin ...
Thats where my imagination ran away (Crimson skies certainly helped). After the Zagi I was intrigued by flying wings. It 'bothered' my eye a bit that they had no or only very short fuselages, so i wanted to do something about it. I never thought about pitching behaviour during maneuvres. Thanks for pointing that out. Maybe I should just add a canard or horizontal stabiliser.

The propeller in the middle of the fuselage idea came from the two attached images. So did the counter rotating propellers. I know of the problems with them, heavy noisy etc. Still I just like the look of them. Look at the TU-95 'Bear' or the Avro Shackleton. Truly amazing aeroplanes! Or the Bugatti 100 racer, stunning aircraft keeping in mind it is a 1937 design! Planes are not built like that today anymore ...

I will keep at it and keep posting updates ... I need to go and buy a thinking cap.

Cheers</p>
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Old 03-26-2010, 05:42 AM
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Default RE: Help with my own creation

I sure would not want to be the pilot trying to bail out of that Daimler Benz aircraft if the explosive bolts on the prop blades or rear fuselage section didn't work....... (shudder)

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