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May 17, 2019, 06:53 AM
3pa
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Flight pictures,


More flight testing, now with prototype Version 2
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May 17, 2019, 07:05 AM
wov
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Great stuff! I am hoping for the same result in a few hours
May 17, 2019, 07:20 AM
3pa
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Sure you will do it! So far all the testers have been able to successfully fly the airplane.
I recommend you to set the CG between the 2 marking, where the two wing sections meets.
Then start to move the CG rearward (step by step) until you feel confortable.
May 17, 2019, 09:13 AM
wov
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The maiden flight was succesfull. I flew the Blackwing for a few minutes, landed it and it still looks like new. I hand launched it at first without turning on the motor. It glided pretty well, but it was clear that you have to throw it. A gentle toss is not enough. On the second launch I threw it quite hard, still with no motor as I didn't like to see a spinning 10" prop only a few centimeters behind my fingers. Due to the hard throw and a gust of wind the wing immediately rolled to the right and I was only just fast enough with full left aileron and full throttle a second before the right wingtip touched the ground. I fly Mode1 and threw the plane with my right hand, which meant that it took a second for the aileron and throttle input.

The first flight was OK, but I am not sure I am happy with the CG. I set the CG, as you wrote, right on the line between the two markings. The battery I used is a 3s 4.000mAh (325 grams) plus 65 grams of lead on top of the battery. Both were placed furthest forward, right behind the hole for the camera lens. There was no other equipment on board, except two 9g servos, a very light receiver and a 60g 2212 1200kv motor spinning an APC 10x3,8" Slowfly prop. I think the combination of this motor and prop on 3s is really good. The climb angle is more then 60°, but I had to hold down elevator on full throttle.

A roll was no problem at all and I did not experience adverse yaw on aileron inputs. It actually looked like a small amount of proverse yaw, but I could be wrong. I also tried to fly as slow as possible and had a few situations with a banking angle to one side and the nose pointing to the other. But even then I still had full control and the Blackwing sorted itself out with a little bit of throttle input. So far, this looks very promising. I will try flying it with an Autopilot, but for now I am going to have fun flying the Blackwing as it is.

I had the Gopro started, but the recording stopped right before I hand launched it the first time. Bummer. It's charging right now and I will do more flights.

Pros:
I am one of the lucky guys who received the STL files for the Version 2 for testing, but this is a plane I would definately buy. The overall design is very good, everything fits nicely. It prints fast, looks good on the ground and in the air and it also flies very well.

Cons:
- I wish there would be more space in the vertical direction inside the compartment. I had to search for the heaviest and slimmest battery, but it was not heavy enough. That's why I am flying with 65 g of lead in the nose. I could add a camera, FPV equipment, an Autopilot etc, but all this stuff is pretty light (compared to a lipo battery) and adding a camera means you would have to move the heavy stuff further back, which could be a problem. If I had the choice, I would ask for a smooth bubble shaped buldge in the center to increase vertical space maybe by 50%.

- hand launching the Blackwing with the tiny keel part at the bottom is possible but not easy. It's a bit windy today and I had problems holding the wing with one hand, actually you can only place two fingers on the keel. If the wind catches one wing you have to grab it with the other hand if you don't want to drop it. A slightly larger keel could help. But the good thing is, the keel is not glued to the wing. You could simply screw a bigger version to the wing if you want to.

Neutral:
- no vertical stabilizer. I am sure it could fly even better and it would be easier to see with a vertical stabilizer. Does it need one? No, and the whole point is having a wing like Horten or Prandtl without a vertical stabilizer. If there would be an option for a vertical stab, I would not use it.
Last edited by wov; May 17, 2019 at 09:19 AM.
May 17, 2019, 10:20 AM
3pa
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Thanks for the info and congratulations!

-To properly balance the plane we will propose using two batteries at both sides of the wing, 3s 3000 mah each. this way you will have space to place the camera at the center.

-We will probably increase the size of the keel needed.

-We don't want to use vertical stabilizer because this will reduce the proverse yaw and will create more drag. Totally agree , visibility would be better to fly it 3 person.
May 17, 2019, 01:12 PM
wov
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I totally agree, two batteries lengthwise makes a lot of sense. Up to which max. weight did you fly the Blackwing so far? Mine is at 1.110 g with the 3s 4.000 mAh battery and 65 g of lead. On your homepage you mention a max. payload of 800 g. Does that mean 1.3 kg max. total weight?

In the meantime I managed to fly roughly 10 more times, all flights (almost) without incident. Almost because, finally, after trying really hard, I managed to see a tipstall, which really was not easy. I flew tighter and tighter circles with increasing up elevator, which eventually means that the inner elevon was at >45° up and that was too much. The wing flipped upside down and straight down. With half throttle it recovered after loosing about 10 meters of height and everything was back to normal. I was surprised it took so much abuse at the sticks to tip stall it.

This time the Gopro was running and I managed to film two short flights. I am already getting used to throwing the wing into the wind and if I get it right I have quite a lot of time to start the motor. The wind is helping though.

Eclipson EBW-160 Blackwing (5 min 14 sec)
May 18, 2019, 05:57 AM
DDC Rules!
Wow @3pa!! that is a real cool wing!! been in love with the Horten type wings for decades!!
Any estimate on when will it be available?? if not, I'll have to ask to become a tester ;-)

On the other hand, after reading all the stuff around the ailerons and servos, have you thought of using an all-internal system for the servos and ailerons? like this one: http://augiemckibben.tripod.com/g2_instructions.html

keep it up and comming!!!!

Congrats!
May 18, 2019, 06:00 AM
DDC Rules!
Or even a direct servo to aileron approach, should there be enough room to host the servo at the root of the aileron....

In any case that's a great design!!! Can't wait to start printing!!
Last edited by DaniSaez; May 18, 2019 at 04:50 PM.
May 20, 2019, 04:22 AM
3pa
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Wow, the aerodynamic analysis was done exactly with 1,1 kg of weight, theoretically with this weight the airplane will be trimmed ( Elevons at neutral position and CG at the rear marking ) at 50 kmh (airspeed under international standard atmosphere condition)

1,3 kg is the maximum recommended weight, no problem if you exceed a bit, you will add more stresses on the structure but as far you don´t perform very extreme maneuvers will be fine. From the aerodynamic point of view the more weight you add the faster the stall speed and also the trimmed speed. Curiously the max lift to drag ratio increases a bit due to the higher Reynolds number achieved for the optimal angle of attack, but in general the extra weight has more disadvantages than advantages on a powered airplane.

DaniSaez thanks for your proposals there is not enough space for direct servo, the idea of this servo is nice, very clean solution, to be honest I didn´t know those types of servos. unfortunately is too late to make this modification for the blackwing, but we will analyze that option for futures designs.

Hopefully the wing will be ready to sell by the end of june.
May 20, 2019, 01:11 PM
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Don't you need another tester? I bet you need this one!! ;-)
May 22, 2019, 08:18 AM
3pa
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Danisaez thanks for your interest but it is too late, there is not enough time to build, test and redesign anything.
May 22, 2019, 04:01 PM
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Quote:
Originally Posted by 3pa
Danisaez thanks for your interest but it is too late, there is not enough time to build, test and redesign anything.
Had to try ;-)

thx!
May 22, 2019, 11:53 PM
wov
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Quote:
Originally Posted by DaniSaez
Had to try ;-)

thx!
@Dani, wait for the released files. They will be worth it.

PS: where are you flying around BCN?
May 23, 2019, 03:22 PM
DDC Rules!
We got a couple of spots near BCN, but we like it best going to the mountains, it's just an hour an a half away to some great places ;-)

If you come by, get in touch, we can go for a flight and/or a beer ;-)
Last edited by DaniSaez; May 23, 2019 at 03:50 PM.
May 23, 2019, 03:51 PM
You know nothing....
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Quote:
Originally Posted by DaniSaez
We got a couple of spots near BCN, but we like it best going to the mountains, it's just an hour an a half away to some great places ;-)
You should try slope soaring without the motor pod.I bet it would move really well


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