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100" 70mm EDF U-2 Dragon Lady

Zephyr1

Well-known member
#1
I worked on a MiG-21 for a while and that had a really high wing loading so I want to try something in the opposite direction. The U-2 is one of only five planes in service with the USAF for over 50 years and was designed back in the 1950s by Skunk Works. I'm really excited to attempt an airplane with this large of a wingspan, everything I've made in the past has stopped at around 6 feet in width. With a wing this long, do you guys think a more heavily reinforced spar will be needed? I've built the nose section and it took an entire sheet of foamboard. This is going to be an exciting build.
U-2 Nose.JPG U-2 3 View.gif
 

Namactual

Well-known member
#2
At the end of the day, weight vs lift and overall speed/g's is what is going to decide that question.

What is your overall weight expected to be? This is going to determine what kind of structure you will need.

With the information given, just using my gut, I would recommend something other than a foam spar.

If I was you, I would start with more than what you think you might need. With the wing span you are talking about a few extra grams is not going to hurt your flight performance. You do not have to use something exotic like carbon fiber tubes, wooden dowel at your local craft store would work just as well.

I can't wait to see this build!
 

Zephyr1

Well-known member
#3
Overall weight is probably going to be around 1800g (I'm high-balling it) and at the moment I am planning on using box spars with some paint stick reinforcement. How would i fit a dowel rod in? Along the bottom of the wing?
 

Namactual

Well-known member
#4
Here is what I use for my larger builds...
Dowel.jpg
It's cheap, it's local and it's plenty strong. It's just about the same size as two layers of foam so it's easy to build around.

That said, having these out just a second ago made me realize just how big you plan on making this wing. I would do some experiments first. That's a whole lot of wing.
 

Zephyr1

Well-known member
#9
Thanks! Regrettably, I painted it black and brought it to FFO where the added weight meant that it had a much harder time climbing to any altitude.