techwing gets winglets and slots

Hey everyone,

 I wanted to post an update on the work I have been doing on the techwing design.


The new design is scaled up some to a 40 inch WS. It also includes real Grantz type winglets, a longer tip cord and fixed LE slots.

Flat plate:


 With winglets:


By reducing the vortex, you can expect less drag, greater lift, and better stall characteristics.

The next thing I did was add fixed LE slots to the outboard panel. LE slots allow the wing to fly at much higher angle of attack .

This is the techwing at a 13 degree AoA. Dark blue is the most negative pressures.


Here you can see the slotted airfoil at a 13 deg AoA. It achieves a 1.19 CL  normally this airfoil would have a Cl max of ~0.75.


The slots also help to increase aileron effectiveness. I just finished the first mold for the prototype. this is the bottom of the fuselage.


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  • 40" is a interesting size.

    Puts it pretty much in the Funjet category, which is actually a pretty excellent UAV platform too.

    I wonder if the plane could be improved further by perhaps using a blow moulded plastic fuselage.

    Or perhaps increased efficiency with plastic or wood trailing edges and control surfaces. Foam trailing edges are very inefficient.

    Foam is a great material for durability. But it does not age well and has some pretty bad disadvantages.

    The squishability is not really that important in a UAV context. Because you would no want to land a UAV hard anyway. Fibreglass is too brittle for rough terrain. But plastic could be the answer.

    (I loved the fuselage of my Phoenix 2000 Glider. It was strong, light weight and not a bit brittle.)

  • Wayne, Thanks for that.  I take it from the pic that the chord is approximately 8in across the span?  I'm looking for a decent sized chord and this could just do the trick.

    I look forward to seeing your how-to on openfoam.



  • 100KM

    hear are some general specs.


    I plan on doing a detailed how to on openFoam as soon as I get the time. No I have not done any comparisons although it is appealing as it can do multiple surfaces like javafoil can. 

  • Wayne, this is great work. I have a couple of questions if you don't mind...

    1. What is the chord of the wing from root to mid span?

    2. More importantly - can you go in to your openfoam work flow?  I've tried it before and had very little success with the provided tutorials so to see someone using it and getting meaningful results for meaningful shapes is very interesting.

    3. Have you compared a 2D openfoam run of your airfoil against the javafoil result?

    Many thanks,


  • 100KM


     Things have changed alot since three years ago, when I was designing the techpod. For one I have a 3-D printer which allows me to instantly make any plastic part I want. I am thinking the fuselage should open like a pizza box, for the best access to the payload area. I have an idea for a mod for the TP to make the entire nose removable just forward of the wing LE. Thanks for the input.

  • 100KM
    Very interesting. For aerial mapping, I agree to keep it as compact as possible while able to carry a 250 gram camera and fly for one hour. May be we can take advantage of the new low C, super light weight lipo to pack more capacity to achieve the require endurance. 1 hour is good cos camera like Canon S100 with CHDK will operate about 75 minutes.
    I hope this time around the new design will pay more attention to usable and easy access able payload area. Techpod is a pain to load battery and camera, together with other not so user friendly feature, this is the main reason we do not continue using it as our mapping airframe.
    Removable wing is a must for easy transportation. Keep up the great work and I am looking forward to test your prototype. Cheer.....
  • Ok, in that case the graphs seem more reasonable.

    Slots are an interesting design choice. Haven't seen (m)any model airplanes using those.

  • 100KM

    Yes it was an inviscid result. this is the polar before the slot. For this foil. th Cl max is quite low. I was being generous when i said 0.75


  • A Cl max of 0.75 is a bit too low estimate for a reflexed airfoil, it should be around 1.

    Also, the flow field at alpha=13 doesn't seem quite right. The boundary layer should be a lot thicker in the aft region of the airfoil. Are these inviscid results or am I just underestimating the effect of the slot?

  • 100KM

    Thanks Guy,

     I agree with you about the size, for that application. The "pro" market wants small and inexpensive while the hobbyist wants more room and weight handling with the better low speed handling the larger aircraft will have.

    Yes actually NASA stall safe droop LEs was my first choice. 


    Not nearly as good a the slot for increasing Cl max. I will use a tool-less type system like on the recent techpod upgrade.

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