Bonus Entries
Entry 5, Custom Swept Wing Plane
Pics
Plans
Reasons for Choosing This Plane
I figured it was time to start working with simple air foils, so I watched a vid about KF airfoils and explained about pitch problems with flat plate wings at high speeds(which I've experienced with a few of my planes when they got up to high speeds). I decided that was all the more reason to start learning how to make some simple air foils that would be durable and more stable at high speeds. I opted for a simplified version of the KFM that's basically just glue and no fold, at least until I practice and get better. This is kind of how they do it on the FT delta anyway as far as I know.
At first I though about doing a familiar style of wing like a delta or straight wing, but decided to try something new. The only reason I hadn't done a basic swept wing before was because it needed an air foil or spar to be strong enough and all I was making for the longest time were flat plate wings. I figured this would be a good style of wing to try while experimenting with the KF style air foil. The design is extremely basic, but a completely new experience to me.
I chose the salvaged stick and elevons from my stick tandem air frame because the stick was the perfect lightweight fuselage to test my new design concept, and because I didn't want to waste the nicely linked servos and elevons that could still be used. To be completely transparent, the stick tandem(including the linkages and controls I re-used) was built before February started, but I built it for the stick tandem with no plans or knowledge that I'd end up using it for any of the FTFC20 entries. I also did have to cut down and rework the old rear wing into the new tail plane, and remove the old front wing from the stick.
Build Log
1.)Total Approximate Hours: 3(Including 4ch upgrade and elevon extensions)
I built this plane as a 3ch plane first over one day with a total build time of two hours, one hour at a time with a break in between. I started by stripping the front wing off of my old stick tandem in the boneyard, and converting the old rear wing into a swept tail plane, retaining the 3ch elevons. I drew up a basic swept wing with about a 28" span. The main challenge would be to design and draw up by hand any sort of real KFM fold, which would be no problem for a straight wing, but swept wings and deltas are a bit trickier.
As far as I know, the FT delta just folds it over on one side and glues it, leaving foam core leading edges, unlike a lot of KFM versions I see with full foldovers and smooth or even curved leading edges. If this works on the delta, than just gluing the top layer on from a separate piece should be just as functional, so that's what I ended up doing for simplicity's sake, until I practice fancier techniques. Other than this consideration, designing and building this plane was a no-brainer.
2.) After flying the plane successfully as 3ch, I decided to take
@L Edge's advice and convert it to 4ch. I added a spare 3.7g servo I found, a rudder, and I also extended the elevons by 50% chord after making some clearance cuts for the rudder. I went from using a 650mAh 3s or 850mAh 2s to using a 3s 850 or compact 1100 to get the CG back in line and provide more flight time. These additional upgrades added about an hour to total build time, and ended up improving the plane's maneuverability and wind resistance considerably.
Build Rating
1/5, as basic as it gets
Fly Rating
1.5/5, as easy as it gets without being a first plane/dedicated trainer
Maiden Video
Maiden, 3ch
4ch Flight w/Rudder and Elevon extensions
Closing/Reflection
I consider this one a big success, because I ended up with a great flying plane that didn't require a lot of time and effort to build, but broke new ground by being my first swept wing design(and first swept wing plane I've ever built and/or flown before) and gave me my first real success with KF style air foils(or air foils in general on my custom planes). I'm glad I decided to convert this one to 4ch, it went from good to great with that little adjustment, and I'm really enjoying flying it

.
I look forward to working more with both KFM air foils and swept wing planes in the future, and I'm already planning to make a bit larger swept wing plane with a three step air foil, longer and more highly swept wings, full ailerons, and a full box fuselage. This one will definitely have a bigger motor than the 1806 A pack motor.
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Entry 6, Custom Forward Swept Wing Plane
Pics
Plans
Reasons for Choosing This Plane
I wanted to try another simplified KFM air foil on a wing type I hadn't tried before, and I've wanted to try a FSW plane for a long time. The V tail elevons/ruddervators were built and linked as part of my old four wing plane long before the start of this challenge and saved me a good little chunk of build time, but they were not made with plans or foreknowledge of using them for one of my entries now.
Build Log
Approximate Total Build Time: Between two and three hours
I built this plane over one night in a couple of sittings. First, I cleaned up and lightened the old V tail piece and attached it to a spare wooden stick spar. I then drew up and cut out the wing pieces and couple other body pieces, assembled the wing, and painted it. In retrospect, I should have not painted the thin part of the wing because it did warp a bit, although the warp is even, adding slight dihedral and a slight up curve from leading to trailing edge, which I reasoned should not be detrimental to performance with a tiny bit of trim. after that, assembly was a no-brainer.
Build Rating
1/5, as simple as it gets
Fly Rating
2-2.5/5, straight forward, but not a trainer or beginner plane, and is finicky with CG and not completely stall proof. Stable and maneuverable, but a little challenging with launch and landing.
Maiden Video
Closing/Reflection
I was about to possibly scrap this one because it was still flying a bit tail heavy on a 1300 mAh battery, but giving it another chance with a 1600, a bit of trim, and a different prop was well worth it. This plane isn't perfect, is a tiny bit quirky, and it finicky with trim and CG, but it's been pretty fun to fly, provides a use for my 1600 mAh battery, and would actually make a decent camera/FPV platform with its stability and flight duration if the design were developed a bit more.
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Entry 7, Custom Three-Step Swept Wing Plane
Pics
Plans
Reasons For Choosing This Plane
After testing out the mini swept wing plane I made for this challenge, I immediately wanted to try a larger, more ambitious and highly swept plane with a profile similar to the English Electric Lightning, and try a three step KF style air foil. There's a plane called the "Blitz" on Outerzone I've always liked, which is basically like what I built, based on the Lightning, but has a much smaller tail plane and the ailerons are elevons. The major difference is my three step air foil and use of a small T tail horizontal stabilizer. I wanted to make this one a four channel plane to begin with no retrofitting later. I also wanted a plane that was fairly straight forward, but would push my build skills to the best of what I can currently do.
Build Log
Approximate Total Original(pre-maiden) Build Time: 7 hours and 30 minutes
Approximate Extra Post-Maiden Build Time (servo adjustments, nose rebuild) 1 hour 30 minutes
I knocked this plane out over one day working a lot of the day straight through with minimal breaks. I started with the wing before even drawing anything else, assembling it from the few big pieces of foam I had left. If I were doing any proper folding this would be a more challenging wing to make, but with more expedient methods still took me about two hours just for the wing. After that, I drew up everything else at once and cut it out, assembling the fuselage, mounting the V.S./rudder, motor, and doing servos and linkages. Next, I taped down my electronics, hooked all the cables up(without mounting the wing yet), and set up/dialed in the plane on my TX before mounting the wing to the fuselage.
I kept the design simple and parts count as minimal as possible, but this one still took some real effort. I kept the wiring pretty clean, using through-wiring and keeping most of it in the fuselage.
Build Rating
2/5 straightfoward
Fly Rating
1.5/5 gentle
Maiden Video
Closing/Reflecting
This one was a bit rough to get off the ground, but a lot of that was small build flaws and errors. Once I got this plane flying properly, I was blown away by the stability, smoothness of handling, and the almost scale-looking manner of flying(moves a lot like a real jet). I learned a bit about positioning the control horns and clearance concerns as far as using a KFM air foil, and I learned how to work around it no problem. I also realized the way I'd been haphazardly mounting landing gear(the built in gear motor mount) was causing a lot of shock stress and damage to the nose and motor mount area every time the plane landed. It was already noticeable using it on the tandem, but this plane's weight made it even worse.
The only thing I'd change about this design is maybe a bigger motor. The F pack radial seems to go through batteries fast keeping this plane flying with a draggy three-step air foil and 14.5-15oz of all-up weight.