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Sep 25, 2021, 05:04 PM
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Build Log

Two new scatch build


Last week the weather was not cooperative at all, especially the windy storm over the weekend. So got stuck at home and build.

Our previous flying wing got some cracks so I decided to build another one. Last time it seemed to me the hardest part was to get the CG right. I had to put the battery all the way to the nose and taped two quarters to the nose to balance the weight. I tried to move the motor around and it seemed to help but totally not enough. So I did some simple math and realized that contradicting to my instinct, the most weight at the rear end of the flying wing needed to be balanced by battery is not the motor/prop. The weight actually came from the foam itself, for the lightweight build I am building.

So I wrote some simple Python code and enumerates all sorts combination of wing span, sweep, root cord and tip cord, taking into consideration of motor/prop location, as well as where to open the slot for prop, finally decided a wing shape that would make me most easily to balance the CG with the stuff I have, as well as having a low wing loading.

The wing span is 30', AUW 185gram.
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And because I was not able to try to fly it immediately, I decided to build another one.
This one is a FT Flyer like plane. The wing/stabilizer were all cut by following the FT Flyer plan. However, to make things simple and light, I decided to skip the fuselage (or the power pod as the plan called), and just stick the two parts together with hot glue.
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My original plan was to not have the landing gear, but this time, the batter I am using was not to balance the weight again, so I put the landing gear on.
Wing span 26' as the FT Flyer plan, AUW 138gram including the 20gram landing gear.

This week, got some chance to fly those two. And both flied very well.
The FT Flyer can fly so slow and being floaty, it gave my son and I a very good chance to improve our skills with rudder.
This video was an almost perfect flight by my son, except the ending. With such a big field, the plane had to find the pole of the soccer goal.
FT Flyer 20210924 183323 (0 min 25 sec)


The flying wing also flies pretty good. But I had to admit that people were right, RET plane is a lot easier than elevon to handle for beginners like me. But even crashing with the elevon is still fun.
Flying wings 20210925 140913 (0 min 21 sec)

Flying wings 20210925 140603 (0 min 8 sec)


To my surprise, both planes ended up with exactly the same Wing Cubic Loading, per some calculator online. But the FT Flyer can definitely fly much slower and much more floaty. That makes me think maybe the big stabilizer of the FT Flyer is also providing lift and should be counted in for Wing Loading?
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Sep 26, 2021, 08:55 PM
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Nice. The wing still seems tail heavy. I love wings, especially planks.
Sep 28, 2021, 06:02 PM
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Quote:
Originally Posted by FeiJi
Nice. The wing still seems tail heavy. I love wings, especially planks.
Thanks!

Could you give more details about how you feel the wing is tail heavy? I know it was flying with some AOA. But I also knew I was rocking the right stick to get the elevator up a lot. I am not sure how exactly to tell it is tail heavy here.

Thanks!


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