|Jun 03, 2012, 06:39 PM|
68" Foam Board wing - the rise and fall...and rise... and fall...
Sorry this is a cross post from the Scratch Build section but I think it really belongs in here - especially now that it has an end to the story... well at least this one...
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 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.
|Jun 03, 2012, 06:47 PM|
Let this be a lesson to you kids...
Now all was well - mostly because the plane was quite underpowered and the flight with the Camera in it was not really compromised because the camera became part of the upper wing structure. I had ordered a larger motor and that arrived last week. In my haste to get it back up in the air, I'd forgotten that I'd cut out a good chunk of the leading edge and the only strength in the wing was from the bottom and a single 4mm square hollow carbon spar... ooops...
Chucked her into the air and she climbed beautifully having around 30-40% extra power. My ignorance in the wing structure coupled with my bull in a china shop approach essentially ended in tears and my wing waving goodbye... literally...
Wing flutter... it'll get you in the end... especially if you tempt fate. You'll have to excuse my ignorance in supposition with regards to the cause of the flutter - I though it might be due to my cheap servos and dialling in 50% dual-rates. Having an aircraft engineer for a father means that you ultimately get the real reason but he's been good enough to allow me to learn from my mistakes.
I think the weather was fairly appropriate for the death of a plane... a little hard to see it though
|Jun 03, 2012, 06:48 PM|
RIP big wing - you can rest in some comfort that one of your wings made a pretty decent nutball!
I have some more interesting stuff in the pipeline having just got my hands on a pretty large hotwire rig and a stack of blue foam. We're going to sit down and really have a go at designing something from the ground up with purpose and application of proper construction technique.
Having said that, foam core is a hell of a laugh to build with but really difficult to form a clean airfoil (i.e. not KFm) and retain a good light weight and all the Ritewing Zypher chaps make me insanely jealous
|Jun 13, 2012, 01:53 AM|
Southern Darling Downs Qld, Australia
Joined Sep 2010
Hi, can anyone tell where i can buy foamboard ...... the cheap insulation type ($1.00 per sheet) they mention in the American scratch build forums and videos? Some of the ones i see mentioned in the USA is Readi-board from Dollartree and Dow but searching in Australia i seem to come up blank. Thanks Ken
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