WTF Four

Well, WTF 3 was a complete disaster. It was a clark airfoil and it looks as if I set the wing incidence too high. This resulted in its complete destruction on maiden!

Introducing the WTF 4 – This one I’ve gone back to the sipkil airfoil, mid mounted, at 40″ span. Slight changes to the rudder and elevator to help overall balance.

This one had to be designed while it was being built, as a motor from the Durafly Tundra is powering this one. I chose this motor as its base design is to use a 12×6 prop. It is much heavier than other 28 series motors I have tried, but accounting for this during the build/design stage ensured CG @ 1/4 was easily achievable. As typical for this design, a 3s 2200 lipo powers the plane.

The wing is hotwired from expanded foam, body is built from the 6mm grey depron (much less ridged than the white depron!) and tail section from 9mm depron.

May it fly as well as the WTF 2.

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WTF Three

This time I took approximate measurements from a “worldmodels” EP40 balsa plane.

Wing is 40″ with a sipkill airfoil on the balsa model, but I wanted to try a foam cut clark Y airfoil, so cut two 20″ units out of blue foam. These were joined flat, with no dihedral, and are approximately 8″ chord with a 3″ aileron.

From there, I used the same fuse length, 36″, but placed the wing at the lower, rather than central position. Rudder and elevator just eye balled, and set at approx. center of motor thrust.

The motor is a sunnysky 3508, fed by a 30amp esc from a 3s2200 lipo. Design of the fuse was just starting with a square depron tube, then cutting a way parts that did not look like an airplane!

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I’m not really certain what this WTF is modelled after. I started with a slostick measurement, reset size based on a twist, then a mojo40, and then eyeballed a NACA 6412 airfoil for best strength/size combo based on a 2826 1100kv motor I had.

I think it will fly, but have ordered larger motors, in the 36 range. As it sits today, the 1100kv mtr is set up with an 11×8 Prop, balanced to accept a 3s2200 battery with a 40a ESC. Full throttle seems to pull enough that I think it will lift off, but unlikely to be fast.

The airfoil is almost 2″ think at the widest, so the intent is to use it as a slowflyer.  Wingspan is 40″ and cord is 10″.
Time will tell…

And for you nuts that want to know how heavy, without a battery, 502g.

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Checkerboard Pattern for Wings

I was asked if I have anything to create a Checkerboard Pattern to be placed on rc aircraft wings. I immediately thought it would be easy using the Zing, and I was half right…

Thinking about it, my first thought was to cut opposing squares on two different sheets of vinyl.  However, when I really thought about this, I would have to offset one layer color over another during the cut, or create opposing cad diagrams with the squares perfectly offset. While neither is an issue to do, it would be tedious to join the opposing colors… And I have ZERO Patience!

So, an easier way would be for the wing to have the primary color as the base – this could be the natural color of the foam, or a square area could be first painted. This would allow for a simple template to be applied to the foam, then spray painted with only a single color.

Once the template is removed, a natural checkerboard pattern is achieved.

This sounded simple enough, but I quickly discovered there needs to be an Offset between each square on the template, otherwise the squares will not remove cleanly from the overall template piece. A minor offset of a few mm is enough to create the “areas” to hold each square together.

As usual, since I have no patience, I quickly printed out two templates using inexpensive sticky backed repositionable paper that I had kicking around, stuck them to the ends of the wing, and blasted them with black paint. Actually not a bad look and more than good enough for a foamy!

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