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Piper Cub J-3 Build Log

MarioGdV

Active member
#61
Do you have a heat gun? You'll find some spots where an iron doesn't shrink the film but the iron pressure stretches it instead. I find a heat gun works better. It spreads the heat over a wider area without pushing on the film. You have to be careful with a heat gun. Set it to medium-low heat. A bit too close or a bit too long in one spot and the film melts. It took some practice but I find a heat gun a better tool than an iron on some difficult to cover areas.
I don't have a heat gun, but I used the iron for the entire covering and it worked fine. The problem is that the horizontal and vertical stabilizers look good while the elevator and the rudder don't. Maybe I just forgot to shrink those pieces. I'm going to shrink the film, I guess it will be fine after that.
 

TooJung2Die

Well-known member
#62
I don't have a heat gun, but I used the iron for the entire covering and it worked fine.
Covering film will relax over time.

I am not suggesting a heat gun can replace a sealing iron. An iron is a required tool and works for the majority of covering applications. Many people get by with nothing more than an iron for covering. My weakest building skill is applying covering film. I'm never 100% satisfied. I use the iron most of the time but discovered having a heat gun got out wrinkles I couldn't remove with the iron. I can't get compound curves covered with an iron. The first time I used a heat gun it was an epiphany.

The best tool to use is whatever works best for you.
 

MarioGdV

Active member
#63
Hello guys! I've studying and doing very important exams these days, and I couldn't spend time with the plane. But, tomorrow I have my last exam, so I'll finish the build after it. However, yesterday I finally had the piece that I wanted 3D-Printed, and I installed it with the motor in the plane:
(Sorry, the images are blurry because the plane was attached to the ceiling)
IMG_20190624_212710.jpg IMG_20190624_212650.jpg
The motor can't separate from it since the screws are long enough to get trough the firewall (is that how it is called?) of the plane.

Since I measured the distance I needed to separate the motor from the firewall, I can install the propeller in the axis of the plane correctly without having problems with the size of the cowl:
(Sorry again for the blurry pictures)
IMG_20190624_212521.jpg IMG_20190624_212613.jpg

I don't know what to do here. The instructions say that the cowl has to be screwed into the plane. But if I do that, I will have to remove the screws (and the propeller) every time I had to connect the battery. Maybe I have to screw it and cut the part that blocks the battery hatch?

Another thing I need to do (I think it's the last one) is to put the black decals. I'm just going to make the classic "black rays" in the fuselage, and I've drawn them in AutoCAD with the correct scale, and I've printed them. The problem is that the line gets really narrow in the end of it and it's hard to cut. I'll try to do that tomorrow. If it doesn't work, do you think it's a good idea to make the line thicker and removing the pointy end?
 

mayan

Well-known member
#64
Looks really good. I don't have much ideas about your questions, but have a few of my own. What is the cowl made of? Is it something that can easily be cut through?
 

MarioGdV

Active member
#66
Looks really good. I don't have much ideas about your questions, but have a few of my own. What is the cowl made of? Is it something that can easily be cut through?
Sorry if you can't understand somethings, I'm Spanish and sometimes I can't explain what I want to say correctly :S.

Also, the cowl is made out of plastic, like the windshield. I painted it with spray and cut 2 squares to stick the black pieces (so it looks like a real engine) on it.
 

MarioGdV

Active member
#68
Nice motor mount. Can you engineer a cowl mount that holds the cowl on with magnets and keeps it aligned with dowels?
I was thinking about using screws, and replace them for magnets later (when screws stop working properly). I think it could work, but I don't know if gluing magnets in a plastic cowl is effective/easy.
 

MarioGdV

Active member
#69
Today I managed to put the decals. There just 2 lines, but it took me a few hours. They are really thin and it was hard to cut them without breaking them. I think they look good:

IMG_20190627_182812.jpg

Also, I installed the 4 metal bars that keep the wings together, and they are kind of heavy. The wings are supposed to be detachable, but I'm not going to disassemble the plane, so maybe I'll glue the wings to the fuselage and remove the metal parts in the future (or maybe not, we'll see how the plane flies with that weight). This is how it looks now:

IMG_20190627_182830.jpg

Now I just have to install the screws/magnets of the cowl and solve the landing gear problem. The kit should include 3 of these:

15616536459059123560325185935750.jpg

But there's only one for the tail wheel. Tomorrow I'll go to buy 2 for the other wheels. I tried to use hot glue, like in the FliteTest landing gears, but it didn't work.

I'm so excited, in a few days this plane is finally going to fly!
 

MarioGdV

Active member
#71
I've solved the wheels problem. The batteries are charged and tomorrow morning I'll go fly it. The windspeed is low (~8kmh (less than 5mph)), so I don't think there are gonna be problems with that. I'm a bit afraid of crashing the plane, after all this time building it. Wish me luck!
 
#72
I've solved the wheels problem. The batteries are charged and tomorrow morning I'll go fly it. The windspeed is low (~8kmh (less than 5mph)), so I don't think there are gonna be problems with that. I'm a bit afraid of crashing the plane, after all this time building it. Wish me luck!
The plane looks awesome!

Good luck tomorrow morning!
 

MarioGdV

Active member
#75
Good luck @MarioGdV. Just remember if something does feel right don’t push it go home figure it out and go back to the field a different day.
I checked everything before I went to the field, but I forgot to bring the transmitter :S. My house is far away from where I was going to fly it, so I'm going to fly it this afternoon. I hope I don't forget anything this time.
 

MarioGdV

Active member
#77
I did it! It flew fantastic, yet there was a lot of wind, even though I went to the field in the morning (yesterday I decided not to fly it the afternoon because of the wind, but there was also wind today). I made videos of the takeoff and the landing:


(Sorry for the bad quality)

I stalled just before the landing, I guess it happened because I was flying it slowly, or maybe because of the wind. Next time I'll try to land faster. The good news is that the plane is okay and it doesn't have any damage.

Thank you all for your advices and for helping me building my first balsa kit. It was a bit complicated sometimes and I would never have finished it without the people of this forum. Thanks!
 
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TooJung2Die

Well-known member
#78
Woo hoo! She flies great! Half my landings look worse than that. I'd be fine if I never had to land. Congratulations on building and flying your first balsa airplane. May there be many more in your future.
 

MarioGdV

Active member
#79
Woo hoo! She flies great! Half my landings look worse than that. I'd be fine if I never had to land. Congratulations on building and flying your first balsa airplane. May there be many more in your future.
Thank you! Building a balsa plane for the first time (and flying it) was awesome. I think everyone should try this at least once. I can't wait to build another one, but the price is a bit expensive. Anyways, I'm happy with this plane, I don't really need another one (but I'll probably end buying more).