• This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn more.

Lockheed U2- Master Series 70mm BDF

#1
This is a plane I've wanted to build since I got into RC last fall. It was on my original short list of future builds, and was pretty high up there too. To date it is the only plane on that list I've attempted to build. Plans change, what can I say? I need to learn to fly before I start building big scale warplanes.

external-content.duckduckgo.com.jpg


The U2 is by far one of my favorite aircraft. As far as jets go the F-86 is my all-time favorite but the Lockheed Spy Plane is pretty high up there. I'd love to fly something like it someday but I don't think I can take a UH-1 to 80,000 ft MSL and that's probably what I'll be flying.

For this build I decided on a 60" wingspan powered by a 70mm BDF. At this scale I can maximize wing area and keep AUW light to get better wing loading. I want this to fly slow and scale and be easy to handle.

I finished the nose yesterday, the rest of the fuselage is only two pieces so it shouldn't take too long.

IMG_20200420_183618.jpg


So far so good. The duct for the BDF arrived today so I can go about installing that. I just barely fits in the tail, I need to do a bit of clever engineering to fit all the sections together. I'm using a Dynam EDF duct with an Emax 2207 motor, this is a pretty easy way to make BDFs if you don't have a 3d printer. I bought my duct on MotionRC for less than $5.

I probably won't be making plans for this one, a lot of what I did and am doing isn't exactly repeatable in an FT-style kit.
 
#7
I'm going to the mountains to work for my grandfather for a few days so I won't be able to work on this until the weekend. As I said the fuselage isn't complicated so depending on how motivated I am I may have it nearly done by the end of next week. The rest of the parts should arrive by the time I get back so I won't have to wait on anything.
 
#9
Dang, I was hoping for plans. I loved seeing these fly when I was deployed.
It shouldn't be too hard to replicate my design, it's just I'm building with removable wings and other accommodations to make it fit in my car. I'd have to make changes to the design to make plans without those features and it just seems like more trouble than it's worth. The design itself is reasonably simple, maybe I could just make plans for a "bare" airframe and just leave the internals for the builder to figure out.
 
#10
It shouldn't be too hard to replicate my design, it's just I'm building with removable wings and other accommodations to make it fit in my car. I'd have to make changes to the design to make plans without those features and it just seems like more trouble than it's worth. The design itself is reasonably simple, maybe I could just make plans for a "bare" airframe and just leave the internals for the builder to figure out.
That will work!
 
#11
Props and ESC arrived while I was gone so I got the BDF set up. I had to run the wires through the duct to make it fit, it's very tight. If I make plans I'd suggest using a 64mm at most.

IMG_20200425_125414.jpg


I'm not too sure about this ESC, it starts up at about 1/4 throttle and seems to pulse a bit at full throttle. It's designed for quads so I probably just have to mess around with the programming.
 

CustomRCMods

Well-known member
#13
Looks good! I wish you best of luck! one thing I learned on my concorde build is the importance of having enough thrust, obviously airflow is a big part of that, as you know I love my cheater holes :). Also be sure to optimize your thrust tube length and diameter, and I would reccomend staying on the shorter side to maximize static thrust. Also it could benefit you to coat the inside of the thrust tube with something smooth, posterboard is common. The concorde just had airflow directly into the foam which may have absorbed/redirected some of the air...

Looks great! What battery are you going to run?

Also keep in mind EDFs/BDFs eat up current like crazy, I am running a 40a ESC in my 70mm setup and that thing gets burning hot to the touch after every flight...
 
#14
Looks good! I wish you best of luck! one thing I learned on my concorde build is the importance of having enough thrust, obviously airflow is a big part of that, as you know I love my cheater holes :). Also be sure to optimize your thrust tube length and diameter, and I would reccomend staying on the shorter side to maximize static thrust. Also it could benefit you to coat the inside of the thrust tube with something smooth, posterboard is common. The concorde just had airflow directly into the foam which may have absorbed/redirected some of the air...

Looks great! What battery are you going to run?

Also keep in mind EDFs/BDFs eat up current like crazy, I am running a 40a ESC in my 70mm setup and that thing gets burning hot to the touch after every flight...
I've got a 2300 mAh 4s on a 35a ESC. For cooling I'm putting the ESC directly in the airflow to the fan. I agree with what you said about thrust, I don't think the inlets on this will be enough so I've planned to put cheater holes under the wing roots.
 
#17
I think I'm going to start working on the tail feathers today. In this picture you can see hat this might not be as straightforward as one would think. The elevator is in kind of a weird spot but I think I've figured out a way to do it. The issue is that the elevator sits right up against the top of the fuselage so there's no room for a single-piece elevator to move down. I think I'll add some subtle taper to the tail section so I can raise the elevator up a bit, kind of like a T-tail but not all the way on top of the rudder.

595940eaa9cc530dcaafb2895b64d2b1.jpg


It's such a deceptively simple looking plane- it is by far the hardest plane I've ever designed.
 
#18
Today I got the BDF mounted and started glueing together the fuselage sections. I made a new tail section as well that has a better profile and sharper taper, it fits a bit tighter around around the aft end of the BDF and works better as a thrust tube. I also fitted the tailwheel, there's another wheel embedded in the nose.

IMG_20200427_142535.jpg


Unfortunately after I glued everything up I realized I had nowhere to run the servo wires from the tail so I'm having to do some creative thinking. My original plan was for a U2A, however the U2R has a convenient pod in the tail that could hide my wires just enough to run them past the BDF. This also solves my elevator issue.

U2C.jpg


The U2R is much longer than earlier models so I would have to extend the fuselage a bit to look right but I don't really mind this. It's not really easy to explain but it would actually make it easier to fit everything together. Alternatively I could just add a long sensor pod down the top of the fuselage like I've seen on some A and C models.

U-2-model-960_640.jpg

A quick shot of my landing gear:
IMG_20200427_142547.jpg