I had been wanting to fiddle with the famous Multiplex Fox for a while and I had been going though all the build logs I could find on the internet, from gentle 3Ch slope gliders to beastly speed demons, they all exist. Unfortunately, while I was at that, the Fox at the local hobby store was quietly sold out and honestly, I didn’t have much patience to wait for one from outside the country.
In all my despair, the corner of my eye caught the FMS G600 at another local store and I definitely wasn’t letting this one go. The G600 is an EPO hand launch glider with a wingspan of about 500mm, a wee bit bigger than the Fox. The most distinctive difference between the both is the T-tail on the G600 versus the conventional empennage on the Fox. I knew T-tails had a sort of smooth and damped tail moments but I had never flown one before and that was something I was looking forward to. Another observation I could make is the slightly under-cambered aerofoil on the G600 and referring to the pictures on the internet, looks like the Fox has a flat-bottom aerofoil.
The RC conversion of these hand launch gliders isn’t as straight forward as assembling other EPO kits because the placements of components is critical to achieving proper CG at the end, but also it isn’t as painstaking as building a beginner’s balsa kit. One obvious constrain comes from the small size of the model, I would suggest to keep the wing loading to a minimum which means using lightweight micro electronics. Although, you can always thrown in an immensely powerful motor and overpower your way out of high wing loading, I personally don’t prefer the rocket pig approach for one specific reason that the model’s structure and aerodynamics are more favorable for a lightweight, slow speed setup. Talking about slow speed, I was expecting it to be a nice indoor slow flier but the stall speed is deceptively high, with higher wing loading, stall speed increases further making it impossible for gentle landings. Nothing to complain about, I still happily fly it outdoors even in mild breeze.
- Hextronic 10g 2000KV brushless outrunner
- ZTW Mantis 12A ESC
- Hextronic HXT500 5g servos
- KS-Servo 4Ch receiver [FrSky compatible]
- ThunderPower 2S 325mAh 70C LiPo
- 5x5E composite prop
The model flies nice in calm and no-wind conditions and my power setup allows for 8 to 10 mins of flight time depending on how aggressively I fly. I’m not sure about other conversions, but my plane has a less-than-impressive glide slope even though it’s lightly loaded, partly because it has an unpredictable pitching tendency. The plane noticeably tends to pitch up with increase in throttle or in headwind and nose-dive on throttle cut or tailwind. Adjusting thrust angles or adequately trimming the control surfaces will help to a certain extent but does not totally eliminate it simply because the pitching tendency varies through the entire throttle range. The reason I mentioned this is because I spent quite a bit of time playing with different thrust angles and trim settings only to find out it’s the inherent flight characteristics of under-cambered wings. It’s not a big deal though, I got used to it after a couple of flights.
My conversion isn’t nearly perfect, I have identified and mentioned a few flaws and possible corrections based on my assessment of the issue, please do carefully take note of all the mentions if you’re following my build procedure. Suggestions and questions have my attention. Please do share your builds, I’d love to see them!
Mark and trim a small angle out to allow for elevator deflection
Carbon rod to reinforce wing, really helps
mark and carve out the cockpit area for electronics
Nose mounter motor
add a small piece of ply to give the servo mounting screws something to hold on to
Adding 1mm carbon rods to support the elevator add more rigidity.
- Maintain a wall thickness of at least 5mm around the cockpit cavity and the canopy space, anything more flimsy can start to deform overtime since it’s a belly lander.
- I’ve used HXT 500 servos, although they fall into the 5g size category they weigh about 7-9g and are pretty over-sized for this plane , I probably would use something that is actually around 5g overall and a smaller physical profile.
- Do not make any cavities or mount servos on the tail boom section, it tends to weaken the section by allowing for stress raisers when you land on the tail. The tail section my plane ripped apart around the rudder servo mount in a hard landing.
- It’s a must to add supports to the horizontal stabilizer, a couple of carbons rods on either sides will be adequate.
- The rudder authority seems very laggy and not really interactive. I would not cut the rudder and save the unnecessary weight of an additional servo.
I short my Arduino boards quite often, as unlikely as it seems. Mostly because my desk is littered with solder blobs and steel rulers and other desperate conductors of electricity. Although, the shorts haven’t caused anything more than harmless reboots, I figured I should get a case before my boards are fried. So I get on my usual online marketplaces seeking nifty cases for my Arduino Mega ADK and Uno. In the meanwhile, my boards are seeking shelter in a “tiffin box”. Given my very choosy nature, all the cases I came across on the internet were either utterly bland with no consideration to aesthetics of my liking or simply out of my budget. What do I do? I do what I always do, make my own. Having scrolled through pages of different products offered by a variety of sellers over a range of prices, I set some fundamental design rules based on my observations.
1) Most products use the mounting holes on the Arduino board to secure it to the case using screws and if you ever took a close look at the holes, you can see they are uncomfortably close to exposed solder pads and other active components. Another potential issue I found with screw-mounting the board is that if you ever drop the case accidentally, chances are, the screws might transfer the impact stresses to the board which does not sound very good. In my design, I constrain the board by slotting the protruding female headers through the top plate of the case, nothing “holds” the board, rather it simply “floats” in a tight tolerance space on foam padding. When you do drop the case, the impact stress are likely to travel through the case’s outer structure and not the board itself.
2014 is about ending now, begin tomorrow, its only a memory. It would be an understatement to call it an amazing year.
I learned lots of new things, went to new places, most time spent away from family, met a lot of new people, good or bad, a few are here to stay and some taught me valuable lessons and walked away. A few things set my ’14 apart making it a little sweeter, I can’t seem to find words that describe my year to the fullest.
No matter how delicious the cake is, that cherry atop the icing is the sweetest and I’ve got a few cherries on my ’14 that are memories forever.
My friends and family who helped me grow, that stranger who returned my lost wallet, my roomie for all that Maggie and unlimited fun, all the makers and hackers who fixed my ugly code with a lot of patience and put a smile on me, that girl with cute hair, aeroplanes that we thought were spaceships, I scored distinctions and failed exams, cars and boats and love and emotions, put a price on it and the world wouldn’t be able to afford it, because some things just don’t come by the second time.
I’ve got one life, and it’s about time I start living it, my resolutions for ’15 don’t spill anything enlightening, I just want to be happy, make a small bucket list, eat a lot of ice cream, tell her I’ve got crush on her, read a good book, write until I run our of words, party like a bitch and work like a dog.
I owe it to a lot of people for all the good things that happened around me this year, all the good memories and priceless experiences, I’m glad we met, thank you!
I don’t want to start this story like, ”Once up on a time there was a boy and a girl, they were best friends and he fell in love with her hair and whatnot”. I’ll save the drama for another time. This is not about her hair, nor so much about her for that matter. It’s about me. I got to bed hours after midnight and this happens everyday. Occasionally, I wake up broken into pieces, mind out-of-place and everything feels bland as air. I see no shine in the sunlight, no harmony in music, no reasonable thoughts in my mind; a lot of questions, but very few answers. Its one of those days I just want to fast forward in my record of life, a day that portrays your pleasant past to just be a mere hollow dream you deceived yourself with. A past that feels too good to be true, maybe it was one of my gloomy day fantasies. I do not know, I cannot figure it out.
I’m a firm believer in the supremacy of time and how little changes in actions at the smallest instant would have changed your life by a lot in retrospect. The chain of events in life look so complex in order and seem so precise that it almost feels like a perfectly prepped and executed plan, how I met her. I’m not a very attentive person when it comes to catching random details, it takes a bit of authenticity in something if I have to take note of it. But she, she had, incomparably, the most beautiful hair that day when I first saw her. So right in form, running down her pretty face that is so genuinely beautiful, I just had to keep looking at her to feel alive.
I can’t tell what it really is, I can only tell what it feels like. That one time in your life, you meet that one other person whom you awaited tirelessly, sketching an unconscious personality and sinking all the beautiful feelings into that character. It almost feels like you’re daydreaming when you meet that real life personification of your brain speck. How I subtly stalked her, never missed the smallest glimpse I could catch of her, the incredibly good feeling of wanting to run my fingers through her beautiful lock of hair. Those dreams, that feel so good, that leave you lost and scrambling for love, you don’t want to be alone anymore, you just don’t know what to do. She’s like that intriguing star in the sky that you want to touch, I want her.
Last year this time, a five-man team including me were working on a mini tricopter for a competition which later got replaced by the mini quadcopter for unexpected reasons. In the span of less than two months (Dec 2013-Jan 2014), a bunch of guys who had never before been around a multirotor and watched months of partial failure with the tricopter which barely lifted a foot off the ground and turned into a three bladed weapon of mass destruction, actually pulled off a working quadcopter that complied with the competition rules.
Honestly, trying to build a mini FPV multirotor with a flight time of 15 minutes is quite a challenge for any beginner. To build a mini quad that weighs in close to a kilogram to do 15 minute flights is out of question. But, we did manage to build a 330mm FPV quad that flew 10 minutes+ on a 3S 1Ah LiPo which is not really bad.
How we did it is not complicated as it is, but it took a lot of prototyping and design optimizations before we saw any real exciting number like 400g AUW and 10 minute flight times. I’m sure there are better contraptions than what we managed, but I’m going to share one crucial thing about our quadcopter, its frame, just in case someone out there is trying to build something quick & dirty similar.
The quadcopter’s frame was the centerpiece of this puzzle, it needed to be very light and very strong — classic engineering paradox — and the final product was a light 28g and about 50 crashes strong fiberglass frame. We improvised on most parts of the glassing process, but you don’t necessarily have to.
Back in October 2013, I made an Arduino based adapter that allows unidirectional aeroplane ESCs to work with surface/pistol radios for RC cars and boats. I used a ATmega8 microcontroller in that adapter and honestly, that by itself was the size of an average ESC, I couldn’t really put it anywhere conveniently on my car due to space constraints and weight concerns (If I can cut down on 5g, believe me, I will).
Even back then, I was trying to make the code work on an ATtiny45 and I wasn’t sure what was going wrong until, Justblair pointed out in the comments that the Tiny45 doesn’t have 16-bit timers, only 8-bit ones and my code was based on the Arduino servo library which utilized 16-bit timers. He also suggested a solution to get my code working on a Tiny45 and that fix is the Servo8Bit library.
Its about 6 years now since I fell in love with contraptions rolling on three wheeled under the influence of instantaneous torque from an electric motor working its magnetic magic inside a metal can held against sintered magnets.