1/3rd Scale Mita Type 3 Production Notes
The final part of a twelve part series.
You may want to read the previous parts of this series before proceeding to this article. Also if you prefer, you can read this article in its original Japanese.
Fabrication Part 55: Carrying Jigs
I immediately disassembled the fuselage and made jigs to transport it on my car.
Fuselage Carrying Jig
The fuselage is about 2,420mm long without the tail wings, so it cannot fit in the luggage compartment of my car (Subaru Forester). The fuselage tail section, which is relatively thin, is placed in front, and the rear fuselage sticks out from between the driver’s seat and the passenger seat. I made a jig to mount the single-wheeled aircraft in such a way that it would not move. This is the finished jig.
The underside of the jig is made of two kinked plates. This is because when the rear seats are folded down, the floor of the luggage compartment and the back of the rear seats are not completely flat, but have a slight angle to them. This is the result of adapting the jig to the car. The bottom surface of the jig is in line with the floor of the car side, so it can take the weight on all sides.
Outer Wings Carrying Jig
The outer wings are about 1,670 mm long. At first, I thought I could load it by folding the rear seats, but it turned out that the hatchback door was unexpectedly thick and slightly hit the wing. If I remove the wing tips, I can pack it without any problem, but if I stack it flat, it will take up a large area and I won’t be able to load anything else. So I decided to carry it standing on both sides of the fuselage with the leading edge down. Photo 283 shows the jig I made for this purpose. Stand up the outer wings and sandwich the fuselage with them.
Center Wing Carrying Jig
The center wing is about 1,000mm long when disassembled. The wing chord length is also 400mm, so it needs to be carried upright. The jig made for this purpose is shown in Photo 284.
Checking the Entire Machine on the Car
Now that the in-vehicle jigs for the major components have been completed, they are loaded into the car for checking.
The horizontal tail is placed between the center wings. Vertical tail can also be placed behind the center wing. The left side is left empty because there is still a big dolly. I need to fit the dolly, tools, transmitter, etc. into this space. It looks like the dolly should have to be assembly type to fit this space. As for the area around the driver’s seat, the rear body sticks out at the shoulder level, but I was able to confirm that it is not that much of a hindrance. With this, the on-board transportation jig was somehow completed.
Fabrication Part 56: Dolly
Following the fabrication of the transport jig, the ground-launching dolly was fabricated.
Drawing of the Dolly
There are two types of dollies, depending on how they support the fuselage. One is to support the lower part of the fuselage, and the other is to support the main wing. The former is relatively compact because it is a dolly that supports the thin fuselage from below, but it lacks stability due to its narrow tread in the left-right direction. My 1/5 Mita model uses this type of dolly. In this method, a pin sticking out of the dolly is inserted into a hole in the bottom of the fuselage to tow the dolly.
The latter method supports the left and right main wings from below. Since the dolly supports the main wings across the fuselage, the tread is wider and the stability is increased, but it is inevitably larger. The leading edge of the main wings is held by a dolly to tow the dolly. This method was adopted for the 1/3 Mita model because the lower part of the fuselage is covered with cloth as in the actual model, and holes cannot be made. Drawing 66 is the drawing.
The Dolly I Made
Photo 286 shows a dolly made mainly of 5.5mm plywood cut out according to the drawing.
The boards that connect the left and right sides are made in the same way as the front and rear. The notches are to avoid contact with the lower part of the fuselage, and by unscrewing the six screws that hold the front and rear boards together, the dolly becomes four boards, making it easier to transport. But still it is very large.
Trial Installation of the Fuselage
I immediately installed the fuselage. In this state, I held the propeller shaft and pulled it to the front. Although there was a lot of grass on the ground, I was able to confirm that the wheels rolled without applying too much force. It seems to be able to glide well.
Ground Test
Finally, it was time for the final ground test before the first flight. The aircraft was transported to the club’s airfield for assembly and disassembly, and various ground tests were conducted to confirm that there were no major problems.
Transport to the Site and Assembly at the Site
Using the transport jig, I put the glider on my car and transported it to the club’s airfield, which is located about 30 minutes from my house. I was able to confirm that I could carry it smoothly by car without any problems.
I immediately assembled the dolly and aircraft at the site. This is a picture of the assembly in progress with the help of my friends.
Since it was the first time for me to assemble on site, I made a few mistakes in the procedure, forgot to insert washers, forgot to connect the elevator linkage, misaligned the center wing mounting bolts, and lost the nut for the rudder linkage. So it took about an hour to complete the whole assembly. I think I will be able to assemble it in less time next time. I put the assembled aircraft on the dolly and took a commemorative photo.
Ground Test
The first thing I did was to check the radio check.I set the output level of the transmitter to Low, and rotated the plane 360 degrees while steering it from a distance of several dozen meters, and confirmed that there were no abnormalities. I was a little worried about the reception performance because of the carbon tubes truss structure, which does not allow radio waves to penetrate, but this is a relief.
The next step is to test the propeller. After connecting the LiPo for power, I asked my friend to hold the plane and raise the throttle to full. There was no abnormal propeller shake or vibration, and the thrust was OK.
Next was a test run on the dolly. When the throttle was gradually increased, the dolly started to move even though the grass on the ground had grown considerably. When the throttle was increased, the dolly increased speed.
I was able to confirm that the plane was generally going straight without flowing to one side. I was a little worried since the wheels of the dolly might be a little too small for the size of the plane that it might be difficult to increase speed, but it seems to be fine. However, the attitude angle of the aircraft is slightly nose-down. Therefore, the tip of the propeller hits the growing grass leaves. At the time of designing the dolly, I took into consideration that it would be about 2 degrees raising head, but in reality it is head down. Therefore, you can see in the photo that the elevator is pulled up.
I found out that the thick sponge on the wing support of the dolly was causing the problem. I made the wing support curved so that it touches the underside of the main wing, and put a 20 mm thick sponge on it to protect the wing. If uniform pressure is applied to the lower surface of the main wing, the sponge will be compressed evenly and the fuselage attitude angle will be as designed, but due to the location of the center of gravity, the sponge on the leading edge shrinks more, resulting in this result. I will correct this by putting a spacer under the sponge on the leading edge side.
I handed the transmitter to Mr. Sato, a veteran pilot of the club, and asked him to check the feeling of the ground run. It was so straightforward that it looked like it was about to take off. I was tempted to take off as it was, but the wind direction was opposite that day, so I decided to wait until a later date for the first flight and finished the ground test.
I also found that disassembling the dolly and fuselage and carrying them into my car would take about 30 minutes.
First Flight, a Success!
I dared my first flight on September 19, 2019, and it was almost a success.
Conditions of the First Flight
The weather was changing rapidly in the changeable autumn sky, but it was sunny and the wind was calm, so I decided to make the first flight. I asked Mr. Sato, a fellow club member and veteran pilot, to fly the plane, and Mr. Shiratori, a colleague from my working days, to take pictures. Also, an editor from “RC Technology” magazine came to cover the event.
Ready for Takeoff
Photo 293 shows the aircraft assembled, controls checked, and ready for launch.
Take Off
The transmitter (FUTABA 10J) is currently set to airplane mode, not glider mode. This allows the pilot to adjust the throttle and fine tune the thrust. Mr. Sato gradually increased the throttle and the dolly started to run. After a few meters run, the aircraft floated away from the dolly.
In fact, at this moment, we had a close call, which I will explain later. Mr. Sato, a veteran pilot, managed to take off with a quick recovery operation.
Climbing
With the propeller at full speed, the aircraft climbed powerfully into the autumn sky.
Cruising
The aircraft folded its propellers and moved into cruising mode.
It looks as if it is flying very slowly. I still can’t determine if it looks like that because the plane is big or if the speed is actually slow because the wing loading is small. However, Mr. Sato, the pilot, said that it might be better to make it a little heavier and with a more forward center of gravity to get speed. I will have to wait until we have flown it a bit more before I can make a decision. Here is a picture of it playing with the clouds (Photo 297). This is what a glider is all about.
Also, he pointed out that it has a slight right roll. This is to be expected since the right main wing is 30g heavier than the left main wing. I will put a weight in the left wing to balance it out before the next flight.
Landing
After flying for about 10 minutes to get a feel for the flight characteristics, Mr. Sato moved on to landing. Before landing, he turned on the spoiler to see how it worked. Normally, the transmitter would be set to glider mode, and assign the spoiler control to the throttle stick so that he could continuously change its output. However, since it was set airplane mode, the spoiler is assigned to the toggle switch and can only be adjusted in two steps. When the spoiler is released, the plane drops altitude rapidly at a descent angle of about 45 degrees, and I was able to confirm that it works well enough to adjust the descent angle.
With the spoiler out, the glider descended close to the ground.
This is the shot just before ground contact.
As the glider entered the final flare, it turned out that the spoilers were not protruding enough to have much of a deceleration effect. However, Mr. Sato was able to land the plane safely with a nice landing. The power consumption of the LiPo (8-cell 5,100mmAh) was only about 30% so far. It is clear that it has enough power supply.
With the above, we were able to complete its first flight. There is no problem at all with the flight characteristics. There was no sign of wing tip stall even in steep turns. The only regret is the lack of deceleration effect of the spoiler. This is very frustrating, but it cannot be corrected unless the center wing is rebuilt.
A Close Call That Occurred Just after the Take Off
Just after the takeoff, at the moment when the aircraft was leaving the dolly, the horizontal tail caught the dolly and the dolly fell over. The aircraft also lost its attitude. This moment is reproduced from the frame feed of the movie in image 300.
As the aircraft was pitched up for takeoff, the right horizontal tail hit the dolly. As a result, the aircraft bowed heavily and was on the verge of hitting the ground. Just before the propeller struck the ground, the pilot, Mr. Sato, made a quick maneuver to recover and started to climb rapidly. The heavy dolly was flipped over backwards. The tail skid appears to touch the ground. The aircraft did not stall during the steep ascent, and it was able to escape the disaster of the first flight catastrophe with a close call. I got the benefit from the installation of a larger motor in case of unforeseen circumstances, as described in “Reconsideration of the power system”.
When I was making the dolly, Mr. Shiratori, who took the video this time, pointed out the danger of this problem. I had judged that there was little possibility of contact because the pitch attitude change of the aircraft would not be so fast for such a large aircraft, and the attitude change in the short time before the aircraft floated and left the dolly would be negligible. However, it was my mistake in judgment because the aircraft actually hit the dolly.
Making a Small Dolly
To avoid the above problem, I decided to switch to a small dolly that would not be in contact with the horizontal tail wing.
The Small Dolly I Built
The new dolly is a type that supports the fuselage from below. The shape of the dolly is quite simple, with the wheels used in the previous dolly attached to a rectangular frame.
On top of this, the jig for transporting the aircraft to the airfield in my car is placed, and the dolly is complete. Place the fuselage on the dolly as shown in photo 302.
The fuselage transport jig has a stop plate in front of the main wheel.
The main wheel hit this plate to tow the dolly. I have tried to take off with this small dolly many times since the end of September 2019, and confirmed that it can take off without any problems.
Flight Video
Cygnus Tori (Mr. Shiratori), a fellow club member, took an aerial video of this aircraft flying gracefully with his drone. This is the 2nd flight which used the completed small dolly for the first time.
This completes all the work on the 1/3 scale Mita Type 3 rev.1 that I started researching at the end of 2017 and started building in March 2018. I have been enjoying it for about 1 year and 10 months.
What I Felt through the Design and Fabrication
Followings are what I felt during the building of the first large scale aircraft with a wingspan of over 5.3m and a weight of about 10kg.
- It is possible to build an aircraft with a hand drill and an OLFA cutter, even if you don’t have a drilling machine or an electric fret saw. I confirmed that there can’t be any excuse for not making a model because of not having the tools.
- Drawing is the most important part of making a model. I felt 80 to 90 percent of the work was drafting. Thinking about what materials to use and how to put the parts together in my head, and then expressing it in detailed drawings is the majority of the effort I have to put in. Once the detailed drawings are drawn, all that is left is to cut out the parts and assemble them following the drawings. If you can’t draw a detailed drawing, it means you can’t imagine how to make it in your head, and you can’t make it no matter how many materials you have in front of you.
- I was reminded that the key to successful fabrication is to spare no effort in using jigs. Jigs are very effective in making each part precisely and assembling it precisely. If the parts are made accurately, assembly is easy and there is no need for rework. Most of the parts that required rework in this project were the parts that omitted the jigs.
The above is a very long description of the design and production process, as I exposed all the problems and failures I encountered, along with the things I thought about and considered during the production process. I hope this will be of some help to those who are planning to try their hand at homebrewing. I’m sure there are many people who are refraining from going out because of the COVID-19 disaster. I hope you get your beloved machine while trying to refresh yourself by building your own during this occasion.
©2022 Norimichi Kawakami
Resources
- Full Size Drawings — The full-scale drawings of the 1/3 scale Mita Type 3 rev.1 that I made in this project are available at this site. If you are interested, please take a look. You are free to copy them.
This is the tenth part in this series. Read the next article in this issue, return to the previous article in this issue or go to the table of contents. A PDF version of this article, or the entire issue, is available upon request.
