Hi Guys,
here is a quick and dirty mock of my ducted wing design. The idea is to create the wing from rapid prototyped poly carbonate with a carbon fibre spar bonded to it. The duct is built into the design and feeds air over the wing from a ducted fan. The RP machine builds wall sections to 1-0.5mm and can create a structure with complicated ribs and internal structures in one go.

what do you think of the concept?

Any idea of where I can find a good aerofoil shape suitable for a low speed UAV?

regards


Oliver

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Nice wing design, but (putting moderator hat on), there's absolutely no need to share a single picture in an attached Word file. Please just embed it as a picture in your post, like this:

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Can you please explain the purpose behind this design? Is it for propulsion, or more lift?
Hi there,

the idea is to run air from a ducted fan to increase lift on take off and landing to create a STOL effect. The main propulsion would be from seperate ducted fan(s). I am hoping to start making some wing sections in the next week or so, initially I am going to try and make a traditional wing shape to prove that I can make it light enough, If the rapid prototype wing concept is too heavy, there is always the option of making a rapid prototype honeycomb wing centre to lay CF or even balsa wood......The original idea was to make a modular rapid prototype UAV airframe that users can just print off when they break some thing or when a new design is released.

The first wing sections will have internal ribs and a wide box section centre spar 0.7mm thick. I will post some pics and weights when they are done.

Obviously all this is just idle speculation and daydreaming that will need to be confirmed by testing and comparison etc.


Oliver
I have a friend with a full size (4'x8' bed) CNC router. He said he'll make me parts for free if I supply the material and mill bits. If you need any help just ask.
i would be glad to run some numbers through xfoil and javafoil for you just give me your specs ei wing cord,span, plane form, desiered stall ,cruise,top speeds airplane weight and any other perameters you already have nailed down .i can calculate stall speed ,lift, drag(not "highly" accurate) and produce poler coordant files from any known airfoil or most you can draw . this looks like a fun challenge. from the face of it it should produce some lift but basicly the top of the airfoil aft of the exaust of the duct will be operating at a much higher reynols number the the rest if the wing section .any way i digress., send me some specs and also i have a cad system so if you want to send me a drawing you can.
Hi there,


thanks for the kind offer, what I know about aerofoils would just about fill the back of a stamp!!

I am still trying to make sense of all the parameters to be considered. I think I might come up with a basic concept for the airframe. If I do this I will know the mass of the plane plus I can then estimate the weight of the propulsion (edf) and battery pack and RC controls. I can then feed all this information back into the wing design.

I am trying to make a slow flying plane to use as a cam platform with good lift that can run for about 1hour. The ducted wing design may be a bit of a red herring, and as I need to prove the RP method of wing production first I think I will produce a standard aerofoil in small sections so that I can extrapolate the weight and stiffness of a couple of different designs.

Do you have a generic aerofoil section I can use just to get the proportions right? I imagine I can scale it up or down to suit? I am using solidworks CAD so i can take in dxf,iges etc.



Oliver
From my experaince i think you will cause break away of the air flow and possiably stall the wing if the forward speed is low.
If i remember rightly one of the migs had air blown from the main engine to the leading edge to improve landing speed and low speed handling.
Also to get an equal balance of pressure though all the ducts will be a mission.
Ducted systems cause great losses so a lot of hp will be required to achieve air flow resulting in more weight reducing STOL.

But as a said in the other blog an idea allways produces other ideas so keep it up.
sure here are a few . ok . E197 ,E201 ,and E205
these a glider airfoils. if you can clue me in a little about what "slow" means in mph and some idea about weight i can send you other foils .For slow usually the best foils to use have huge amounts of camber but they can make higher speeds way too draggy . I don't need exact numbers just an idea . as far as slow flight I've seen a design that uses a "squirrel" type fan along the wing to make it virtually stall proof
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Blown flaps have been used on several aeroplanes to reduce landing speed, most notably the Blackburn Buccaneer and TSR2. This increases lift by increasing the effective velocity over the wing and delays separation, the later increases the stall angle of attack above 16 degrees (for a symetric thin 2D aerofoil if you're being pedantic), and therefore the stall speed. Unfortunately blown flaps and ducted wings (effectively blown slots) require large volumes of medium velocity air, in gas-turbine aircraft this is usually taken from bleed air (leading to high compressor loads, so high throttle settings and to the large air-brakes used to soak up the excess thrust), but in this case you will have to have a large fan - 20% or so of the main propulsion power, maybe more at this scale, it depends how slow you want to go. Remember the slower you go the larger your control surfaces will have to be to maintain adequate stability and control.

Aircraft on this scale benefit aerodynamically from a fairly thin aerofoil, but to fit the ducting in you may wish to opt for a thicker aerofoil, sacrificing some cruise efficiency. A NACA 0010 (symmetric 10%) would be suitable or maybe a slight camber if you want better landing attitude. Flaps are often a better method for solving you landing attitude problems. You can find the NACA aerofoil reports on the internet, they give aerodynamic (lift and l/d) info and construction co-ords, bear in mind that they are 2D airfoils. Helpfully they give reynolds number as the aerodynamic 'velocity' parameter, so can be used on any size design (and any speed, flying in any fluid... theoretically).

Hope that helps, and wasn't too complex.

Alec
Did you look at the idea of slats? they kind of work the way you need and you can make them retractable.
You appear to have got quite a few people going with this one and all though I like the ambitious design, I have to agree with Ian, ducted fans are greedy on power and getting the flow equal for the length of the wing will almost certainly involve varying the size of the individual apertures all along the wing to the tip, which will be quite a challenge! Air, like water and electricity will always take the easiest route. Thin symmetrical sections, are generally used for speed rather than lift and the TSR2 was a supersonic aircraft, so I doubt a copy of that profile would suite your purpose. Try looking to a more conventional airfoil design for your AP platform, leading edge slats and trailing edge flaps are both good for slow flight ( take a look at the Fieseler Storch ). I have 30-40 or so wings, all of different profile, chord, root thickness, span etc for various different weather conditions, lifting capability and terrain and probably 15 of these are made up of the Clark Y section. This airfoil has a thickness of 11.7 percent and is flat on the lower surface from 30 percent of the cord back, it has excellent lifting capabilities, very forgiving stall characteristics and will happily fly backwards if the wind is blowing strong enough.
If the purpose of this design is to drastically decrease a take-off distance you may want to re think your design. Ducted fan thrust is proportional to the velocity of the air at the inlet, so you probably will not see significant effects at take off speeds. Not to mention that the design as is will produce turbulent airflow (Going of the picture posted by Chris).

If you really care about a short take-off distance, design a plane with a low stall speed (~10 mph), try thrust vectoring, even flaps would work. The problem with flaps if that it will increase the drag significantly so you will need a large propulsion system.

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