It all began when I purchased an Evolution 20cc gas engine.It had been in use, and the seller had told me it was in an ideal shape. There are few 20cc engines, and there are not many planes tailored for it either. I had found some planes, but they seemed expensive and would not satisfy me as prototypes. I wanted a nice-looking RC piece. I really like Edge 540 Version 3. Needless to say, I decided to build it myself. From the ground up! It was winter time, so I had plenty of time.All advanced RC hobbyists (or, at least, many of them) use Solid. Before that, I had only worked in Compass and only in 2D. Now I had to go further and boost my skills and knowledge. I installed Solid Version 14 and began to study it. Although it took me at least a month, I did grasp the basics of designing. YouTube helped me a lot as well.Let’s figure out the dimensions first.There were tons of drawing and redrawing to be done. I decided to start with the fuselage – the most challenging part of it. Material: architectural plywood (3 mm). I also used balsa sheets of different thicknesses and 6 mm beechwood plank for a motor former. This is what the whole thing looked like thirty days later: I came across a cool visualization program – Key Shot (this is not an ad!), so I imported my model in it:My drawing ended in DXF files, and now I had to cut out parts. I saved the files on a flash drive and went out to town for a cutter. No way! Nobody wanted to sign up for that, because parts were too small by advertisers’ standards! That was quite a mishap! I did not want to use a hand fretsaw, because the cut would have an excessive length. Epic fail? But I had to build the plane! Well, what about cutting? I’d use an electric fretsaw! However, it would be pretty hard to cut out complicated parts with a hand tool, because I’d have only one free hand. There was only one alternative: building a cutting machine featuring an electric fretsaw. It consisted of a body with a desktop and the fretsaw underneath bolted to the machine with the saw sticking out over the desktop. I fixed pieces of bike tire to the bottom to damp vibration and prevent the machine from slipping off from the table. I connected a good-sized light switch to the machine, so I could use it as a foot switch in case of emergency. Then I started using the wonder machine! When I gained the dexterity of hand, I began to craft not-quite-so-bad quality pieces. I would cut out a few ones in the garage and then finish them at home. That was much easier than hand-sawing it! I was really happy when I realized that my first parts fitted perfectly!Then I had to go through the routine of cutting out pieces in the garage and finishing them at home. I used white Moment Stolyar glue.I built the keel I covered it with 1 mm balsa.This is what it looked like at this stage: Then I cut out cover parts and glued them together:

The cover is fixed in a time-tested and reliable way – insert pins at the front and spring latch in the back. No screws, and it takes a second to remove/fix it! In the next picture there is a bamboo piece instead of a spring – a temporary measure just for the assembly period.Now it is time for the tail wheel. Here is a virtual model:Now the real one. A 3 mm thick duralumin strut and a wheel from a foam plane. I fixed it and used big grease seal springs as transmission:The rudder is fixed on four 5.5 mm pins. I also fixed an engine mount:All horns are made of 1.5 mm laminated fabric and riveted to plywood ribs. Quick and strong!Then I mounted the engine, ignition, and made a canopy out of a plastic bottle:The fuel tank is made of a plastic 220 ml juice bottle:Here is the stabilizer with a diving rudder. The halves are removable: they are perched on a 10 mm pipe and fixed to the fuselage with M3bolts. The wiring duct, stabilizer and diving rudder are covered with 1 mm balsa.The rudder rod is a separate matter. To reduce tail weight, I decided to use one servo. To connect the halves of the diving rudder and provide due solidity, I made a coupling link to divide the load and distribute equal amount of it to each half. Here is the digital version of the coupling link:Here is the real duralumin link, which I ordered from a turner and then filed it down myself! The plane features a mount for the coupling link:The central 7 mm rod links the servo with the medium rocker. The halves of the diving rudder are connected to the lateral rockers with 5-4 mm rods, which are made of fishing rods. This is how it works:I covered the area under the cowl with thinned-out epoxy to protect it against the engine’s waste products. The main strut is bolted to the body with two m4 screws. I decided not to use more screws because if I did, a rough landing could result in severe damage to the landing gear olate and the rest of the plane.Both the landing gear plate and the motor former are made of 6 mm beech plank, which is very strong!Now I’m through with the fuselage woodwork. Now it’s time for my ‘favorite’ fiberglass cowl. Here is my initial cowl design:Later, I decided to hide the engine cylinder beneath a nose cone. Here is the result:Here is my PENOPLEX cowl dummy made up of plywood sections:Processing it:Put on a separation layer of wax shoe polish and place the whole thing in plaster.Once the plaster mold dried (in my case 24 hours in a warm place proved enough), I cast the second half. Then I cast two halves of the cowl in eggshells, did some measurement and fitting.The halves are glued with SA, and it holds very well. Then I glued in a resin-soaked strip of fabric on the inside.Then I primed, ground-coated, and painted it using a $3 spray paint.Now a bit of artwork on the fuselage:The empennage:Bottom view:The fuselage:Well, finally I could take a sigh of relief, as the fuselage is ready. Now, the wings. I hate building wings, because it is all so classic and dull. But I had to. Everything must be even. Ideally, I should have used a holding frame. It does not hurt to dream. I have two friends of mine who are now busy building NC milling machines, but I think there is still far from finishing them. It was then that I met another old friend of mine who was running a small engraving business. I asked him if he could laser-cut it. He said that would be no problem, just get the stuff over here, it would take but a couple of days for the chicks to cut it. What was supposed to be two days smoothly turned out to be two weeks. Then they phoned me and said to come over and take it. The laser disappointed me pretty much. The balsa was all right, but the edges of the wooden parts were burnt too much causing the overall size to shrink pretty bad. And the grooves got too wide. To top that off, the loop plate was lame (the work piece had slipped, they said). They promised to make another one ASAP. Happily, I had some plywood leftover. Eventually, I had to make the wings out of laser-cut parts.I fixed 9.5kg servos ($13 each). Those were made in China, but I had bought them at a servo-only online store.This is the little classic structure of a wing:The second one:Now the little wings are complete, let’s cover them:A top view:A bottom view:In daylight:The takeoff weight totaled 4,260 g with a wingspan of 1,680 mm. That was too much, because I was trying to fit in 4 kg. However, the architectural plywood that it was made of, was pretty heavy, and I had no choice.The cowl turned out to be heavy too. Yes, I have all but zero experience, but I’ll continue to practice. The test-flight was smooth, no surprises.The plane flew very well as a piloted aircraft, and maneuverability was great. However, the thrust is a little low for a 3D.I test-flew it on a 16*8 prop. I should try 16*6. I ran the engine in the garage, and there it outran the former by 1000 rpm, although the beam scale showed an increase by only 100 g.One of my buddies filmed the test-flight. The quality is no good, but still better than the landing.Please, don’t kick me too hard.At that time I ran into trouble: as I was flying my favorite 30cc Sbatch, vibration caused a wire to come off from the BEC. The systems were cut off electricity, and the plane tumbled 30 meters down in a forest. It is not beyond repair, maybe I’ll do it in winter. However, that was a good lesson. All switches and the BEC are going tastefully into the wastebasket, and all systems will be powered directly from Ferrum. Therefore, all flights of my “Hedgehog” are now suspended until the battery arrives.This is a link to the templates and pictures. This is the end of my little story about the little Hedgehog. I hope you have liked it. If you have a specific questions, please, contact me.Yours faithfully,Alexey.Kostanai City, Kazakhstan.