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B-25 bomber scratch Build

#1
Hi, so I have designed a few planes in the past and decided to step it up some so I decided to design a dual engine plane. I started my build in the winter and completed the first version but realized some flaws in my design that would make it hard to fly so I never attempted to fly it and went back to the drawing board. The second version I designed fixed some of the problems I saw in the first design. Here is the time lapse of the designing process and the build.

Now lets go over some specs.
wing span: 60in or 152.4cm
weight: 2 pounds exact (with out battery)
motors/esc: power pack c twin
batterys x2: lumineer 2250mah 3s (makes this thing a rocket ship)
rx: spectrum 6ch
servos x3: 9g

finally I got some good weather and went to do the maiden

I wanted to see how it flew with only differential thrust no rudder. The differential thrust didn't seem to do much but I am going to do some more testing before I put rudders on it. Overall it flew okay I think it was a little tail heavy and once I get it balanced out it should fly fine. I will say the elevator is really sensitive so it is going to need some expo. I did notice that the was some adverse yaw going on in the turns and I want to fix this in version 3. I didn't try to design this to be scale I just based my design off the b-25 If you want to see some scale b-25 builds there is a bunch of amazing builds on the forums. I may try to make It look more scale looking in the future but I want to get it flying perfect first. In the next version I plan on doing a couple things first adding a bomb drop because its not a true bomber if it doesn't have a bomb drop. second I noticed when I was doing some run ups the elevator was moving just slightly.
The elevator is only one sheet of foam thick


IMG_0074.JPG IMG_0083.JPG IMG_0084.JPG
so in the next version I think I am going to make it 2 sheets thick like this
IMG_0085.JPG

I also plan on designing some stronger landing gear
If you guys have any suggestions or questions let me know, thanks!:cool:
 
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#2
After the second flight I decided it needs rudders. Also the ailerons are to far out on the wing. The roll rate is really slow and it is hard to get out of a turn especially with out rudder. I think if I make the ailerons bigger or move them closer to the fuselage it will help the roll rate. I am going to start by making them wider.

This is the current size of the ailerons
image.jpg

I also changed the elevator. I made it smaller and double the up the foam board image.jpg

That's it for now I will let you know how it flys with larger ailerons, rudder , and the new elevator. Thanks
 
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#3
image.jpg well ummm. So it is extreamly hot here where I live. When I went to fly it was 92 at 8:00pm. I changed basically all control surfaces for this flight. Ailerons were made larger elevator was smaller and I designed a rudder.
When I took off it was extremely tail heavy I barely got it safely on the ground. I put weight in the nose. The glue that was holding the nose landing gear on fell off so I had to hand lanch it. It took off and flew great the rudder was working it had a better roll rate than last time. then the wings started to let lose but that's not what caused the crash no the wing tip with the ailerons were bent 60 degrees up and I still had control. When I was on final in to the wind my left motor came off the motor mount and the right motor kicked the plane all the way to the left and crashed. But I am not done it flew great for the little time it was up so I am building version 3.
Version 3 is going to have bigger ailerons doubled up elevator, rudder, smaller wing span and more. I will post pictures of the build but I am not going to film it.
 

Hai-Lee

Old and Bold RC PILOT
#4
Sad end for the plane but great fortune for the project.

Having so many issues identified at the same time will definitely help the project.

Watching with interest!

Have fun!
 

rockyboy

Skill Collector
Mentor
#5
That sounds like an epic maiden flight/crash! Congrats! :applause:

One thing I'm finding a whole lot of value in for these projects is the glide testing to confirm CG before powered flight. Especially in an area of high grass where I can get a soft landing. I'm thinking on my next design I'm going to do initial glide testing with just the bare foam airframe before loading in all the electronics and batteries to really confim where the CG needs to be while it's still lighter in weight and doesn't need as much airspeed to glide well. Sort of like a poor mans wind tunnel testing :)
 
#6
That sounds like an epic maiden flight/crash! Congrats! :applause:

One thing I'm finding a whole lot of value in for these projects is the glide testing to confirm CG before powered flight. Especially in an area of high grass where I can get a soft landing. I'm thinking on my next design I'm going to do initial glide testing with just the bare foam airframe before loading in all the electronics and batteries to really confim where the CG needs to be while it's still lighter in weight and doesn't need as much airspeed to glide well. Sort of like a poor mans wind tunnel testing :)
Thanks :). Yes I agree. it was balanced for the first flight then when I added a thicker elevator and rudder servo and I didn't rebalance it luckley I was able to land it.
 
#7
Here is an "quick" update. I completely redesigned the wing twice. The fist version couldn't support the weight of the motors on the wing. The second version is super strong. here are some pictures of the wing build
IMG_0100.JPG IMG_0106.JPG IMG_0107.JPG IMG_0108.JPG

Also I put less under camber on the ends of the wings because they folded in flight last time.
I also built a different nose because the last one didn't survive the last flight. IMG_0118.JPG

Finally here is it put all back together. IMG_0119.JPG

The fuselage and tail section was intact so I reused it. I hope to maiden it before I go back to school.
 
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