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2nd Scratchbuild, First Success - 1740mm Flying Wing.

#1
First post - I'll just chuck this in here - Loving the Flitetest videos and website. It's a great, friendly and informative presentation. You guys deffo need to keep up the good work. I also like the move toward the site being an informative and supportive information base and moving away from just being about reviews. The project work has been hilarious to follow and massively inspirational.

So - Project Flying Wing MK2 (Jokingly referred to as STH2, STH being my initials).

This was my second flying wing attempt here, the first wing was a learning experience and it was built out of a Hobbyking delivery box because it was faster using the box than waiting for Hobbyking to send a back ordered wing out. The first wing was a complete failure and a really good example of not doing enough research and going at the project like a bull in a china shop. Still having the failure and understanding why it was a failure allowed me to drastically improve my approach.

The wing is built out of 5mm foam board. The wingspan was dictated by the maximum allowable space on a single sheet to create both a top and bottom surface of the wing using a technique close to, but not as elegant as, the Armin Wing from ExperimentalAirlines. 1740mm wingspan, 400mm root chord, 150mm tip chord and 350mm sweep.

In terms of electronics I'm using 2.4GHz radio gear, 2 unknown servos ripped from a cheap plane that didn't live up to it's potential (I assure you that lack of flight experience had nothing to do with it being written off... honest...), a 30amp ESC coupled with an 800kv motor and a 2200mah batt. The power output was not even remotely close to what it really needed and I have a 1200kv motor waiting for next weekend (or the weekend after) to remedy the issue.

The entire build including batteries, ballast and motor comes in at around 1.2kgs (2.6 - 2.7lbs) which is not brilliant but again it's been a learning experience and I think my next one will have a shorter wingspan, broader wingtip chord and more power :D It needed around 250g (0.55lbs) in weight to get the COG right as calculated by a flying wing COG calculator which worked out well because this is a potential payload for chucking a camera in.

All in all I think it was pretty successful and as a model it has quite a bit of life left in it. I removed some of the balast and stuck my Contour HD camera in the nose of the plane and have flown it with that in it, I'll post the video of that as well.

First version of the wing had too much tape on the elevons and the end result was a terrible COG and servos that could barely shift them.


Second edit - Tape removed and replaced sparingly, engine installed and COG shifted a good 60mm forward which I hoped would make it less of a handfull.


Maiden Video - Excuse me giggling like a child but I was immensely chuffed with it's flight characteristics and genuinely surprised at how flyable it was even in its underpowered state. The motor had been flown into the ground 5-6 times which is why it sounds so rough. I was also having to fly it at 100% throttle all of the time. Please excuse the terrible landing.

This was about the 4th flight and the second with a camera in it. The first had the camera pointed too far up and it was mostly a video of sky. This attempt was significantly more successful and the landing markedly better.

Then I stuck a camera in the nose.

Hope you enjoy. I have and I get the pride in building your own plane and having it fly well :D
 
#3
Thank you :D I derived an immense amount of joy out of the success - I get the distinct feeling that this could be the start of a long and enjoyable addiction :D
 
#6
Cheers guys - was out of two sheets of 5mm foam board but it's not $1 like it is over there. In Aus they're about $10 a sheet. Build time was 3-4 hrs all up and there's a bunch of thing's I'll do differently with my next attempt, not the least being changing the way I formed the airfoil. I set a pile of blocks along where I thought I wanted the top of the airfoil to be and the foamboard sagged where I didn't have them so next time I'm either going to use ribs or a long strip on its edge the length of the wing. The other thing I will do is increase the depth of the tip chord and shorten the overall wingspan as 1700mm is a pain to fit in the car :D
 

SteveOBHave

Senior Member
#7
She's dead Jim!

Well, that's it, I killed her.

I had bought a larger motor which added an extra 30-40% power with pretty good results but following on from my FPV addition I had weakened the top of the wing too much and the result was an oscillating flutter that was ultimately fatal.

My apologies for the quality of the video, it was a really grim morning but it wasn't going to stop me going out and having fun. White on grey is not the best for tracking a plane but you get to see the really exciting bit :D Ignore my suppositions as to what was causing the problem, I had just set the dual rates to 50% and I though that it might be messing with the servos (they're really budget ones). Having an aircraft engineer for a father soon corrected that assumption.

Basically what happens is that the wing flex over emphasises your aileron inputs and then the spring of the wing returning produces the same effect the other way eventually oscillating so much that the wing fails. So lesson learned? Don't compromise the load bearing wing structure otherwise the wing with wave goodbye... literally...


RIP big wing - you can rest in some comfort that one of your wings made a pretty decent nutball!