Curved wings too loose

I did some flight tests, but it pitches down too much. I moved the battery to the middle of the tail, but it rolls over. You can see from the gliding video that the wings are too loose. This happened with the previous model when the wings were too loose.
I will find a way of tightening the wings. Maybe some struts from the fuselage to about 10% point of spar.

Servo Ornithoper June 2018

I made a Wing module for my HeeksCAM software, to allow me to specify a wing with leading edge shape, trailing edge shape\, root profile, tip profile, angle graph and vaious parameters.

I wrote a function which allows me to print out the sections of the wing, flattened out with a 2mm border.

I traced these through pieces of ripstop nylon, cut them out and sewed them together with a sewing machine. I sewed on pockets for battens, which I originally thought would be 1mm carbon fiber rod.
The carbon fiber rod wouldn't bend to the tight front part of the wing section shape, so I 3D printed some 1mm thick, 2mm across, PLA battens.

I still need to do a little sewing by hand to hold the battens in, and to tie the front of the middle of the wing to the fuselage. Then I shall be waiting for dry weather for flight tests.

Servo Ornithoper April 2018

I watched these videos of an ornithopter by y. takemura

I was amazed that he was controlling the thrust steering and pitch control with just two servos.

I had a go at making my own version, based on takemura's.
2.0mm carbon fiber spars.
servo x 2
  KST MS320 HV Contactless Servo - 6.2kg.cm 0.07s 21g 12mm
flight computer ( arduino nano )    6g
battery 17g
receiver.  Micro Flysky Compatible Receiver FS82 AFHDS 2A IBUS PPM For Flysky.  1g
fabric 238T

The fuselage is made from some low quality cardboard. I planned to make it from carbon fiber or similar, but haven't yet.

I wrote custom software for my arduino nano.

My first version had cheap lightweight servos. It didn't have enough thrust to stay up.
It didn't even have enough torque to overcome the lift from the wings most of the time.
video

I spent the £36 x 2 on the real servos. It almost stayed up. :) but was maybe flying too slow?

Still not quite staying up.

I tried seriously loosening the wings. It didn't work.

I put the inner cross bracing back, but 1mm instead of 1.5mm and some 1mm cross bracing across the fingers. I had my first climbing flight.

With a better tail, I could actually steer. No sign of climbing with the wings on the right way up, though.

More staying up. It could stay up indefinitely.

It seems to climb when in ridge lift, which looks impressive, but a good glider could possibly do as well.

Conclusion:  It's not as good as takemura's.
I believe that the wing section is not good enough.
So, for the next post you will see my work on a different, hopefully improved wing section.

Flywings Raven

I got one of these.

I taped my phone to it and took a video
http://youtu.be/3HXBxR8xfWU

geared prop test 2.5:1

6 inch 105g 2.53A                            41.5g/A
8 inch 180g 3.84A                            46.9g/A
10 inch 200g 3.25A 307g 5.21A         61.5g/A 58.9g/A
12 inch 200g 3.42A 420g 7.40A         58.5g/A 56.7g/A

geared prop test 3:1

motor cf2812 from giantshark.co.uk with and without homemade 3:1 gearbox

about 11.5V in battery

propeller size    current    thrust    geared down ratio    thrust to amps ratio
6 inch 3 blade     2.05        46g       3                       22.4
8 inch 2 blade     2.95       127g       3                       43.0
10 inch 2 blade    3.69       230g       3                       62.3
12 inch 2 blade    5.70       384g       3                       67.3

6 inch 3 blade      8.07      238g       1                       29.5
8 inch 2 blade     10.00      283g       1                       28.3
10 inch 2 blade    10.00      369g       1                       36.9
12 inch 2 blade    10.00      313g       1                       31.3

no prop            no throttle 0.09   half throttle approx 0.77  full throttle 1.2

Model Hexadecacopter Flying

I got my hexadecacopter flying. These motors aren't up to the job. They are only rated for 2 cells and I am using 3 cells.  If I use a 2 cell battery, it doesn't really have enough power. So time to try some other motors.
Also, after a few crashes, the frame is getting a bit flexible. I'll try super-glueing the pieces together.