RC Aircraft
Nano Gremlin FPV
After building the Pico Goblin, I wanted to try a larger model that could stay in the air longer. Of course, this design is based off the Strix Nano Goblin. However, I can't justify spending 80 plus dollars on a piece of foam and a few other common parts. I don't understand how people keep buying these for such crazy prices. It's the same foam planes you can get at Walmart or wherever in the toy section for kids, just in a slightly different form, so it's obvious there's no reason for them to be that expensive - other than pure greed.
Looking for a cheaper alternaive I found the Nano Gremlin. After watching the videos I was sold. I downloaded the plans for the amazingly low price of one dollar. I had just bought a new 3D printer to replace my old one, as I wanted one that could print LW-PLA, which my previous one couldn't. The first plane I printed, the Mini Delta, printed out fine (after a bit of figuring out the right settings for LW-PLA that is), but this one did not. It was extremely thin in some areas, had a lot of gaps, and was just just not going to work. I tried to open the STL file in Blender to possibly fix it myself, however, it was just a nightmare, it was created from planes instead of one solid shape, so was going to be impossible to change or fix in any way. I saw in the comments that others also had trouble printing the plane, so I figured it was just not going to work, and oh well, it only cost a dollar, and maybe that's why it was so cheap, because it wasn't that great.
Fast-forward to about a year later, and I decided to look at it again, I don't know why exactly, maybe because others did have success in printing it, and maybe I had missed something. Or maybe it's that stubborn part of my brain that refused to let something beat me. So I started digging through the almost 300 pages of the forum post for an answer, and found what might have possibly been the issue. Apparently, when this design was made, it was made when most slicing software was using something called the Arachne engine. Since this was over three years ago, slicing software has adapted a newer engine, which is supposed to be better (hence why it was adopted by most slicers). However, it seems this newer engine has problems with some models, so the answer may be to use a slicer with the Arachne or "classic" engine instead. For my Creality printer, I used Creality Print v5, which allows you to change the engine under Quality -> Wall Generator. I made the change, tried to print out the fuselage piece again, and to my surprise it worked.
From there I just printed out the rest of the parts and put it together according to the build video. I decided to use two 18650 cells for the battery, and instead of making a 2s battery from them, I just bought some two-battery holders. I then glued velcro to the bottom and to the cockpit so I could move it around to balance the plane.
Maiden Flight(s)
As always, the maiden is a bit nerve-wracking, especially in the case where you paint the model first like I did. I hate the idea of making something that looks to nice that has a good chance of being destroyed in a couple of seconds.
I chose a favorite area close by that has some very tall grass, which I figured would help mitigate some damage if it crashed.
Maiden #1
I launched the plane near full throttle, and it dove to the left (away from the taller grass of course) and crashed.
- Assessment: not enough power; probably tail heavy; possible torque roll causing it to roll left.
- Remedy: throw the plane harder on launch; make sure not to roll it left on launch, possibly giving it some slight roll to the right; add nose weight.
- Damage: Front fuselage broken off, motor detatched, esc wire detatched.
- Fixes: Glued fuselage back, mounted motor internally instead of externally as it needed more nose weight.
Maiden #2 and #3
Launched the plane near full throttle, putting more power into the throw, making sure to keep it level and somewhat to the right. I also positioned right over some all brush to help minimize any impacts. Crashed both times, and was wondering how this was ever able to use THREE 18650 batteries, I was having a tough time getting airborne with just two. Not only that, I was using active foaming LW-PLA, not pre-foamed like the author was using, so my model should have been even lighter.
- Assessment: Not enough power.
- Remedy: Add a larger propeller.
- Damage: Slight cracks to fuselage.
- Fixes: Glued small cracks; added a larger propeller.
Maiden #4
Found that I was actually using a 2680kv motor instead of a 4200kv as was stated in the build. This would explain the lack of power, so to compensate, and since it was a lower kv, I used a bigger 5 inch prop with a more aggressive angle (Gemfan Hurricane 51499). Launched the plane near full throttle, putting a bit of power into the throw, making sure to keep it level and somewhat to the right. To my surprise, the nut and propeller came off immediately. This was actually a somewhat good thing, seeing as it happened immediately, and not mid-flight. I was also confused, seeing that I was using a lock-nut, and I tightened it quite well. You do the same with quads, so you don't have to worry about CW/CCW nuts, so I'm not sure why there would be a difference here. It may have had something to do with the canopy coming off immediately and hitting the propeller.
- Assessment: Not enough power.
- Remedy: Add a larger propeller.
- Damage: Lost prop and nut. Reprinted canopy cover.
- Fixes: Reversed the motor and propeller so that it turned the opposite direction of tightening of the nut (motor and propeller CCW, nut CW).
Maiden #5
Apparently the lower kv motor was indeed the issue, and the larger propeller was the cure. I was in a really small area so didn't want to chance hitting any of the many nearby trees, so landed it early. Was able to land in tall grass with no damage.
FPV Flights
Coming soon.